Cailei Yuan

Numerous efforts in improving the hydrogen evolution reaction (HER) performance of transition metal dichalcogenides mostly focus on active sites exposing, vacancy engineering, and phase engineering. However, little room is left for improvement in these approaches. It should be noted that efficient electron transfer also plays a crucial role in catalytic activity. In this work, by employment of an external vertical magnetic field, ferromagnetic bowl-like MoS2 flakes can afford electrons transmitting easily from a glassy carbon electrode to active sites to drive HER, and thus perform magnetic HER enhancement. The ferromagnetic bowl-like MoS2 flakes with an external vertical magnetic field can provide a roughly doubled current density compared to that without an external vertical magnetic field at a constant overpotential of -150 mV. Our work may provide a new pathway to break the bottleneck for further improvement of HER performance and also paves the way to utilize the magnetic enhancement in widely catalytic application.

Abstract Eddy current is a magnetic field effect generated in alternating magnetic field (AMF), which could trigger continuous local heating, reducing the energy consumption without impairing the life of the catalyst or reactor. Unfortunately, the investigation of eddy current effect on transition metal disulfides (TMDs) electrocatalysis is still in its infancy, and its actual electrocatalytic applications has been impeded by the multilayered structure of traditional layered TMDs. Typically, the step pyramid MoS 2 , with a layer‐by‐layer stacking structure just like the silicon steel plate in the transformer, showing an inevitable interlayer potential barrier will suppress the generation of eddy current and cause low efficiency of magnetic heating. In this work, the designed screw pyramid MoS 2 can facilitate the formation of micro eddy current and maximize utilization of magnetic heating to boost electrocatalytic activity, benefiting from its eliminated interlayer potential barrier. This work provides a new thinking for the design of field‐assisted electrocatalytic reactions and development of the advanced catalyst technology.

Confining dual atoms (DAs) within the van der Waals gap of 2D layered materials is expected to expedite the kinetic and energetic strength in catalytic process, yet is a huge challenge in atomic-scale precise assembling DAs within two adjacent layers in the 2D limit. Here, an ingenious approach is proposed to assemble DAs of Ni and Fe into the interlayer of MoS2 . While inheriting the exceptional merits of diatomic species, this interlayer-confined structure arms itself with confinement effect, displaying the more favorable adsorption strength on the confined metal active center and higher catalytic activity towards acidic water splitting, as verified by intensive research efforts of theoretical calculations and experimental measurements. Moreover, the interlayer-confined structure also renders metal DAs a protective shelter to survive in harsh acidic environment. The findings embodied the confinement effects at the atom level, and interlayer-confined assembling of multiple species highlights a general pathway to advance interlayer-confined DAs catalysts within various 2D materials.

Coupling graphene-based materials with SiC nanostructures is one of the most feasible strategies to improve the photocatalytic CO2 reduction performance. Here, we synthesized the vertical graphene (VG) sheets on the SiC nanowires achieved from rice husks to form the [email protected]/C composite, in which the VG sheets possess high surface area, excellent electrical conductivity, and chemical stability, and the SiC nanowires have a suitable bandgap for sunlight absorption. The resulting [email protected]/C composite provides an enhanced photocatalytic reduction of CO2 to CO and CH4, yielding CO and CH4 evolution yields of 25.5 and 2.3 μmol g−1 h−1, respectively. The achieved CO yield is maximal so far among the SiC-based photocatalysts. The defective VG sheets promote the absorption of sunlight, enhance the CO2 adsorption and activation, increase the separation of photogenerated electron-hole pairs, improve the activity of photocatalyst, and thereby prompt the photocatalytic reduction of CO2 to CO with high yield and selectivity.

A MoS2 moiré superlattice with a twisted angle of θ ≈ 7.3° via a facile method instead of a conventional mechanical stacking method is successfully fabricated. With reduced interlayer potential barriers demonstrated by first-principles calculations and ultralow frequency Raman spectra, electrons can transfer easily from a conductive substrate to active sites in this MoS2 superlattice, thus leading to good hydrogen evolution reaction (HER) activities. By using an electrochemical microcell technique, improved catalytic performance in the MoS2 moiré superlattice is validated, with a current density of −10 mA/cm2 at an overpotential of −153 mV and a Tafel slope of 73 mV/dec. A strategy to boost the electrocatalytic performance by reducing the interlayer potential barriers is successfully achieved by employing a MoS2 moiré superlattice. The work paves a new pathway to break the bottleneck for further improvement of HER performance and also opens interesting possibilities for implementing moiré superlattices in catalysis, energy storage, and 2D functional devices.

Anatase hierarchical TiO2 with innovative designs (hollow microspheres with exposed high-energy {001} crystal facets, hollow microspheres without {001} crystal facets, and solid microspheres without {001} crystal facets) were synthesized via a one-pot hydrothermal method and characterized. Based on these materials, gas sensors were fabricated and used for gas-sensing tests. It was found that the sensor based on hierarchical TiO2 hollow microspheres with exposed high-energy {001} crystal facets exhibited enhanced acetone sensing properties compared to the sensors based on the other two materials due to the exposing of high-energy {001} crystal facets and special hierarchical hollow structure. First-principle calculations were performed to illustrate the sensing mechanism, which suggested that the adsorption process of acetone molecule on TiO2 surface was spontaneous, and the adsorption on high-energy {001} crystal facets would be more stable than that on the normally exposed {101} crystal facets. Further characterization indicated that the {001} surface was highly reactive for the adsorption of active oxygen species, which was also responsible for the enhanced sensing performance. The present studies revealed the crystal-facets-dependent gas-sensing properties of TiO2 and provided a new insight into improving the gas sensing performance by designing hierarchical hollow structure with special-crystal-facets exposure.

Array-based sensors are considered as potential candidates for gas detection due to their low cost and great miniaturization potential. However, the fabrication process of array-based sensors is complex and time-consuming since it usually contains the formation and growth processes of seed layers on the surface of alumina substrates. In addition, the gas-sensing materials for the fabrication of array-based sensors are mainly confined to n-type semiconductors such as ZnO, TiO2 and WO3. In this work, a kind of p-type heterostructures arrays composed of NiMoO4 nanosheets and Co3O4 nanowire (Co3O4@NiMoO4) was fabricated in-situ on flat alumina substrates via a simple hydrothermal method without seed layers. SEM and TEM characterizations revealed that the Co3O4 nanowire arrays were fully covered with NiMoO4 nanosheets. The gas-sensing measurements revealed that the Co3O4@NiMoO4 composite arrays showed the highest response (Rg/Ra = 17.12) towards 100 ppm trimethylamine at its optimal operating temperature of 250 °C. This response value was 3.91 times higher than that of Co3O4 arrays (Rg/Ra = 4.39) and 9.25 times higher than that of NiMoO4 nanosheets (Rg/Ra = 1.85) at their optimal operating temperatures of 250 and 350 °C, respectively. Meanwhile, the enhanced sensing mechanism of the Co3O4@NiMoO4 composite arrays was also discussed. It could be explained by the special heterojunction structure of the Co3O4@NiMoO4 composite arrays, which offered a high surface area and an additional modulation in resistance. Our studies shed a new light to design p-type heterostructure arrays in-situ for fabricating sensing device by a facile method. Moreover, the as-designed Co3O4@NiMoO4 composite arrays are potential candidates in the fabricating of high performance trimethylamine sensors.

Here we report the synthesis of two-dimensional (2D) ultra-thin WO3 nanosheets (∼4.9 nm) with dominant {002} crystal facets through a facile surfactant-induced self-assembly method. It was found that the ultra-thin WO3 nanosheets showed remarkably enhanced xylene sensing performance and methyl orange photocatalytic degradation performance, which could be ascribed to the high percentage of reactive {002} crystal facets (>90%) and high specific surface area (121 m2/g). The mechanism of gas sensing and photocatalysis was systematically studied. This work will be intriguing for designing high-performance metal oxides-based gas sensing and photocatalytic materials through 2D structural modulation and crystal facets engineering, which is important to promote their practical applications in environmental issues.

Transition metal chalcogenides with high theoretical capacity are promising conversion-type anode materials for sodium ion batteries (SIBs), but often suffer from unsatisfied cycling stability (hundreds of cycles) caused by structural collapse and agglomerate. Herein, a rational strategy of tunable surface selenization on highly crystalline MoO2 -based carbon substrate is designed, where the sheet-like MoSe2 can be coated on the surface of bundle-like N-doped carbon/granular MoO2 substrate, realizing partial transformation from MoO2 to MoSe2 , and creating b-NC/g-MoO2 @s-MoSe2 -10 with robust hierarchical MoO2 @MoSe2 heterostructures and strong chemical couplings (MoC and MoN). Such well-designed architecture can provide signally improved reaction kinetics and reinforced structural integrity for fast and stable sodium-ion storage, as confirmed by the ex situ results and kinetic analyses as well as the density functional theory calculations. As expected, the b-NC/g-MoO2 @s-MoSe2 -10 delivers splendid rate capability and ultralong cycling stability (254.2 mAh g-1 reversible capacity at 5.0 A g-1 after 6000 cycles with ≈89.0% capacity retention). Therefore, the tunable surface strategy can provide new insights for designing and constructing heterostructures of transition metal chalcogenides toward high-performance SIBs.

Ferromagnetic (FM) electrocatalysts have been demonstrated to reduce the kinetic barrier of oxygen evolution reaction (OER) by spin-dependent kinetics and thus enhance the efficiency fundamentally. Accordingly, FM two-dimensional (2D) materials with unique physicochemical properties are expected to be promising oxygen-evolution catalysts; however, related research is yet to be reported due to their air-instabilities and low Curie temperatures (TC). Here, based on the synthesis of 2D air-stable FM Cr2Te3 nanosheets with a low TC around 200 K, room-temperature ferromagnetism is achieved in Cr2Te3 by proximity to an antiferromagnetic (AFM) CrOOH, demonstrating the accomplishment of long-ranged FM ordering in Cr2Te3 because the magnetic proximity effect stems from paramagnetic (PM)/AFM heterostructure. Therefore, the OER performance can be permanently promoted (without applied magnetic field due to nonvolatile nature of spin) after magnetization. This work demonstrates that a representative PM/AFM 2D heterostructure, Cr2Te3/CrOOH, is expected to be a high-efficient magnetic heterostructure catalysts for oxygen-evolution.

Alternating magnetic field (AMF) is a promising methodology for further improving magnetic single-atom catalyst (SAC) activity toward oxygen evolution reaction (OER). Herein, the anchoring of Co single atoms on MoS2 support (Co@MoS2), leading to the appearance of in-plane room-temperature ferromagnetic properties, is favorable for the parallel spin arrangement of oxygen atoms when a magnetic field is applied. Moreover, field-assisted electrocatalytic experiments confirmed that the spin direction of Co@MoS2 is changing with the applied magnetic field. On this basis, under AMF, the active sites in ferromagnetic Co@MoS2 were heated by exploiting the magnetic heating generated from spin polarization flip of these SACs to further expedite OER efficiency, with overpotential at 10 mA cm-2 reduced from 317 mV to 250 mV. This work introduces a feasible and efficient approach to enhance the OER performance of Co@MoS2 by AMF, shedding some light on the further development of magnetic SACs for energy conversion.

Owing to tip effect can introduce localized enhanced electric field and reduce interfacial energy barrier, design of atomic tip structure in single-atom catalysts (SACs) may be a fascinating strategy to further improve its electrocatalytic activity. However, conventional synthesis methods, such as defect-trapping or substitution, only lead to the formation of planar geometry of SACs without tip atoms. Good conductive 1T-TMDs with electrocatalytically active basal plane can provide platform to directly stabilize single atoms (SAs) on the top sites of its surface to form atomic tip structure. Herein, a universal Laser-molecular beam epitaxy (L-MBE) method for precisely controlling non-noble metal SAs directly immobilizing on the Cr top site of 1T-CrS2 metallic basal plane is developed. In case of Mo, the Mo [email protected]2 with single-atom tip structure can exhibit enhanced electric field surrounding Mo atoms and an almost zero hydrogen adsorption free energy, resulting in superior HER performance together with high stability. This work provides a general way to design varieties of SACs in widely catalytic application.

In this work, we study the chemical vapor deposition growth of Sb2Se3 nanotubes and investigate their novel applications in polarization-sensitive near-infrared photodetectors. The grown Sb2Se3 nanotubes present a high crystal quality with an average length of 23.96 µm, an average width of 0.99 µm, and an average height of 315 nm. The fabricated singular Sb2Se3 nanotube-based photodetector exhibits a wide spectral response, ranging from visible to near-infrared light regions (400–980 nm), as well as a peak photo-response under the illumination of near-infrared (830 nm) light. At room temperature and standard atmospheric pressure, the Sb2Se3 nanotube photodetector presents a large photocurrent on/off ratio of 364, a high responsivity of 4.39 A W−1, a good specific detectivity of 9.63 × 1010 Jones, and a high external quantum efficiency of 655% under the illumination of 830 nm light. The identified performance can be attributed to intrinsic characteristics of this compound coupled with a highly uniform Sb2Se3 nanotube crystalline structure. The Sb2Se3 nanotube photodetector also exhibits excellent stability after> 200 photo-switching cycles. Most notably, the Sb2Se3 nanotube photodetector presents a large linear dichroic ratio of 3.95 under the illumination of 830 nm light, revealing its great potential in near-infrared polarized photodetection applications.

Resistive gas sensors based on metal oxides have aroused great interest in the sensing of NO₂ gas due to their low cost, good stability, and easy fabrication.

Hierarchical porous (HP) nanostructures of p-type metal oxide have attracted great attention in gas-sensing application due to their less agglomerated configurations and the advantages for gas diffusion. However, the contacts between grain boundaries around pores of HP nanostructures are usually too fragile to resist the shear force caused by ultrasonic treatment during sensor fabrication processes and the thermal stress produced from high operating temperature. To solve this problem, uniform Co3O4 microspheres assembled by single-crystalline porous nanosheets were synthesized by an ethylene glycol (EG) mediated solvothermal method with the co-assistant of water and polyvinyl pyrrolidone (PVP). Due to the structural stability of single-crystalline nanosheets, the as-synthesized HP Co3O4 is well kept during the sensor fabrication processes. Moreover, the Co3O4 shows a high response (Rg/Ra = 74.5–100 ppm) to xylene at the optimized temperature (150 °C), which is almost 4 times larger than that of commercial Co3O4 (19.1). It also exhibits excellent long-term stability with small deviations (less than 6%) for two months, which can be ascribed to the structural stability of single-crystalline nanosheets. Combined with their high selectivity and low detection limit, the as-prepared HP Co3O4 microspheres assembled by single-crystalline porous nanosheets are highly promising gas-sensing materials for xylene detection.

As an emerging two-dimensional (2D) material, Bi2Te3 has exhibited great potential for the applications in electronic and optoelectronic devices due to its unique features as topological insulator and thus high electron mobility. However, the application of 2D Bi2Te3 nanostructures in flexible NIR (near infrared) photodetectors has barely been investigated. In this work, we present a study on NIR photodetectors based on 2D Bi2Te3 nanoplates, which are grown on mica substrates by Van der Waals epitaxy (vdWe) method. The vertical thickness of the Bi2Te3 nanoplates is as small as 12 nm, while the lateral size is as large as 18 μm. The flexible NIR photodetectors based on the 2D Bi2Te3 nanoplates present excellent device performance, including photoresponsivity, specific detectivity and photoconductive gain. Under the illumination of a NIR laser (an emission wavelength of 850 nm), the photoresponsivity, specific detectivity and photoconductive gain are determined to be up to 55.06 mA/W, 8.05 × 10−2 and 5.92 × 107 Jones, respectively. In addition, the device performance (photoresponsivity, detectivity, rising time and decay time) of the Bi2Te3 nanoplate photodetectors shows no obvious degradation after bending for 100 times and 300 times, indicating the great flexibility of the photodetectors based on Bi2Te3 nanoplates. These findings indicate that Bi2Te3 nanoplates have great potential for fabricating flexible NIR detectors with high detectivity and photoresponsivity.

In this paper, novel flower-like Co3O4 structures have been fabricated by an ethylene glycol (EG) mediated solvothermal with the co-assistant of water and polyvinyl pyrrolidone (PVP). It was found that the water and PVP played a key role in the formation process. The structure and morphology of the as-prepared products were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscope (TEM). The results revealed that the flower-like Co3O4 was assembled by single-crystalline porous nanosheets. Due to the structural stability of single-crystalline nanosheets, the flower-like hierarchical porous structures can be well kept during the sensor-fabrication processed. Notably, gas-sensing tests revealed that the flower-like Co3O4 showed a high response (Rg/Ra = 79.8–100 ppm) to xylene at its optimized temperature (150 °C), which was 4 times higher than that of commercial Co3O4 (Rg/Ra = 19.1). Moreover, the flower-like Co3O4 also exhibited excellent long-term stability with small deviations (3.1%) for two months. The enhanced gas-sensing performances of flower-like Co3O4 were mainly attributed to the structural stability of single-crystalline porous nanosheets as building blocks. Combined with its high selectivity and low detection limit, the as-prepared novel flower-like Co3O4 assembled by single-crystalline porous nanosheets is a highly promising gas-sensing material for xylene detection.

Monolayer MoS2 films with substantial sulfur vacancies are obtained using the laser molecular beam epitaxy (L-MBE) technique benefitted by high substrate temperature and ultrahigh vacuum growth conditions. The intrinsic sulfur vacancies present an excellent opportunity for varying the work function of monolayer MoS2 films by nitrogen doping. The in-plane doping of nitrogen atoms on L-MBE-synthesized monolayer MoS2 films is realized on the basis of rapid thermal annealing in a nitrogen environment. The as-grown and nitrogen-doped monolayer MoS2 films are evaluated by using Raman and photoluminescence spectroscopies. In accordance with the X-ray photoelectron spectroscopy results, the ultraviolet photoelectron spectroscopy investigation shows that the work function of the monolayer MoS2 films increases by 0.29 eV after covalent nitrogen doping. Nitrogen doping on monolayer MoS2 is further treated theoretically using first-principles calculations. Based on theoretical calculations and experimental validations, it is illustrated that nitrogen is a promising in-plane heteroatom dopant for work function variation of monolayer MoS2.

Developing high-efficiency electrocatalysts based on non-precious transition metal compounds alternative to noble metal for oxygen evolution reaction (OER) is crucial for renewable energy storage technologies. Herein we designed a novel OER electrocatalyst by incorporating transition metal oxide (TMO) and sulfide (TMS) into a hierarchical nanoporous structure. Hierarchical porous Co3O4 nanosheet-assembled microspheres (HPMS Co3O4) were fabricated by a facile solvothermal method followed by an annealing process, and the Co3O4/CoS2 composite was easily obtained by a simple subsequent sulfurization process, which maintained the HPMS structure. Due to rapid surface diffusion and mass transfer, increased active sites, improved conductivity and strong synergetic coupling effects, the prepared HPMS Co3O4/CoS2 composite showed significantly enhanced electrocatalytic OER activities with a current density of 10 mA cm−2 at a low overpotential of 280 mV, a small Tafel slope of about 63 mV dec−1 and satisfactory stability at 20 mA cm−2. Notablely, it was non-durable at high current density. We expect that more active TMS functionalized hierarchical porous TMO will open a new avenue to innovate non-precious OER electrocatalysts.

In the present study, by a simple template method, biomass waste (gelatin) acting as precursor and mesoporous SBA-15 (highly ordered hexagonal mesoporous silica structure) serving as hard template, novel nitrogen-doped ordered mesoporous carbon (NOMC) was prepared. The NOMC serves as anode material for sodium-ion batteries, exhibiting a high reversible discharge capacity of 173.8 mAh g−1 after 150 cycles at 50 mA g−1. Moreover, even at 1000 mA g−1, prominent long-term cycling stability reaching 2000 cycles is also observed. According to the results, the electrochemical performance of NOMC electrode is remarkable (high reversible capacity, prominent rate performance, and superior cycling stability). Synergy effect between the N-doping and the ordered mesoporous structure most probably lead to the prominent electrochemical properties of NOMC electrode, the N-doping can improve the electrical conductivity and capacity of the carbonaceous anodes, and the ordered mesoporous structure can be fully contacted with the electrolyte to achieve better transportation of sodium ion/electrons.

As one of the promising low-cost and high-efficiency catalysts for the electrochemical hydrogen evolution reaction (HER), it is well-known that there are both tiny exposed catalytic active edge sites and large-area inert basal planes in two-dimensional MoS2 structures. For enhancing its HER activity, extensive work has been done to activate the inert basal plane of MoS2. In this article, wafer-scale (2 in.) continuous monolayer MoS2 films with substantial in situ generated sulfur vacancies are fabricated by employing the laser molecular beam epitaxy process benefitting from ultrahigh vacuum growth condition and high substrate temperature. The intrinsic sulfur vacancies throughout the wafer-scale basal plane present an ideal electrocatalytic platform for massive hydrogen production. The fabricated vacancy-rich monolayer MoS2 can achieve a current density of −10 mA/cm2 at an overpotential of −256 mV. The wafer-scale fabrications of sulfur vacancy-rich monolayer MoS2 provide great leaps forward in the practical application of MoS2 for massive hydrogen production.

Two-dimensional (2D) nanostructures, bismuth telluride (Bi2Te3), as represented by one of the topological insulators (TI) materials, have attracted tremendous interests from world-wide scientists due to their potential applications in electronic devices. However, the growth mechanism especially chemical vapour deposition (CVD) and the optoelectronic device applications of these Bi2Te3 nanostructures have barely been investigated and reported. In this work, we present a detailed study on the controlled CVD growth of 2D Bi2Te3 nanostructures and explore their applications in high performance visible photodetectors. With increasing the precursor material temperature from 470 °C to 510 °C, it is observed that the lateral size of Bi2Te3 nanoplates first increases and then becomes saturated when the precursor material temperature over 490 °C, which is mainly due to the competition between the transportation and diffusion of precursor molecules onto the substrate surface and the reaction consumption of precursor atoms on the substrate surface. In addition, it is also observed that the lateral size of Bi2Te3 nanoplates decreases with increasing the total inner tube pressure as a result of the reduced diffusion rate of Bi2Te3 precursor molecules. 2D Bi2Te3 nanoplates with a lateral size over 10 μm can be obtained with applying proper precursor material temperature and total inner tube pressure. Furthermore, a visible photodetector is fabricated using few-layered 2D Bi2Te3 nanoplates grown in this work. This visible photodetector demonstrates a high responsivity of 23.43 AW−1 and a high detectivity of 1.54 × 1010 Jones, outperforming some visible detectors based on traditional 2D nanomaterials. Tche intensity-dependent photo-responsivity measurements show stable photoswitching behavior. This 2D Bi2Te3 nanoplate photodetector also presents high flexibility by showing no obvious performance degradation after being bent for 50 times. The results presented in this work will not only contribute to a comprehensive understanding of the CVD growth mechanism of Bi2Te3 nanostructures, but open up novel optoelectronic device applications for 2D Bi2Te3 nanostructures.

For the development and utilization of renewable energy, it is impending but still a big challenge to develop cost-effective and stable electrocatalysts with feasible synthetic strategies towards hydrogen evolution reaction (HER). Herein, we have proposed a facile and simple strategy for the preparation of non-precious nanoporous FeP cubes within 35 min by acid etching the electrodeposited Fe/FeOOH/FeP precursors at room temperature. The FeP cubes materials possessed unique nanoporous structures on the surface and inside, which were beneficial to expose more active sites and effectively accelerate the mass transfer. Therefore, the as-synthesized nanoporous FeP cubes exhibited favourable catalytic HER activity with low overpotential to approach 10 mA cm−2 in both acid and alkaline media, as well as long-term stability in acid solution. We expect that this facile synthetic strategy of nanoporous FeP cubes will provide a promising prospect for boosting the development of non-precious HER electrocatalysts.

Novel one-dimensional shish-kebab structures composed of active (110)-faceted α-MnO2 nanowires as backbones and (111)-faceted Co3O4 nanocrystals as shells were prepared by a hydrothermal method followed by an in-situ epitaxial attachment growth strategy. A series of characterization revealed the formation of Co3O4@MnO2 heterostructures with closely integrated hetero-interfaces. The growth mechanism study suggested that the multiple functions of hexamethylenetetramine were crucial for the the successful growth of the Co3O4@MnO2 heterostructures. The gas sensing performance of the Co3O4@MnO2 heterostructures was studied for the first time. It was shown that the Co3O4@MnO2 heterostructures exhibited obvious enhanced triethylamine sensing performance compared with bare MnO2 nanowires and Co3O4 nanocrystals, suggesting a strong synergistic effect. The unique one-dimensional shish-kebab structures, increased surface active oxygen species and closely-attached hetero-interface were the key factors to improve the triethylamine sensing performance. The work not only provide an in-situ strategy for the synthesis of one-dimensional heterostructures, but also provide an effective way to improve the inherently low gas response of α-MnO2 through comprehensive design of morphology, crystal facet and hetero-interface. Moreover, thanks to the unique morphology, surface and interface characteristics of the Co3O4@MnO2 heterostructures, they are expected to be used in more fields, such as batteries, supercapacitor and catalysis.

Array-based sensors have been regarded as excellent candidates for the gas-sensing elements owing to their low-cost preparation, great miniaturization potential as well as stable performance. However, it still remains a great challenge to prepare porous arrays and regulate their porosity to increase pores for gas transport and active sites for surface reactions. To solve this problem, the porosity of metal oxide arrays (Co3O4) that had grown directly in-situ on the surface of ceramic substrates was regulated by the constructing and oxidizing of MOFs (ZIF-67) that coated on the surface cobalt-containing precursor arrays. It was found that the porosity and surface area of Co3O4 nanowire arrays increased with the content of ZIF-67. The porous Co3O arrays with the highest porosity and surface area exhibited the highest response value (Rg/Ra = 16.7), the lowest optimal operating temperature (200 °C) as well as the fastest response/recovery time (4/39 s) towards acetone. These porous Co3O4 arrays are thus promising gas-sensing materials for acetone detection with excellent performances. This novel strategy to enhance the porosity of arrays can pave a new way to improve the gas-sensing properties of array film-based sensors.

Abstract Although (oxy)hydroxides generated by electrochemical reconstruction (EC‐reconstruction) of transition‐metal catalysts exhibit highly catalytic activities, the amorphous nature fundamentally impedes the electrochemical kinetics due to its poor electrical conductivity. Here, EC‐reconstructed NiFe/NiFeOOH core/shell nanoparticles in highly conductive carbon matrix based on the pulsed laser deposition prepared NiFe nanoparticles is successfully confined. Electrochemical characterizations and first‐principles calculations demonstrate that the reconstructed NiFe/NiFeOOH core/shell nanoparticles exhibit high oxygen evolution reaction (OER) electrocatalytic activity (a low overpotential of 342.2 mV for 10 mA cm −2 ) and remarkable durability due to the efficient charge transfer in the highly conductive confined heterostructure. More importantly, benefit from the superparamagnetic nature of the reconstructed NiFe/NiFeOOH core/shell nanoparticles, a large OER improvement is achieved (an ultralow overpotential of 209.2 mV for 10 mA cm −2 ) with an alternating magnetic field stimulation. Such OER improvement can be attributed to the Néel relaxation related magnetic heating effect functionalized superparamagnetic NiFe cores, which are generally underutilized in reconstructed core/shell nanoparticles. This work demonstrates that the designed superparamagnetic core/shell nanoparticles, combined with the large improvement by magnetic heating effect, are expected to be highly efficient OER catalysts along with the confined structure guaranteed high conductivity and catalytic stability.

Abstract This work presents a study on the optical applications of chemical vapor deposition‐grown Sb 2 Se 3 nanowires in polarized single nanowire photodetectors. High‐quality Sb 2 Se 3 nanowires are obtained with diameters as small as ≈15 nm, which is the first report for ultrathin Sb 2 Se 3 nanowires. The fabricated Sb 2 Se 3 nanowire‐based photodetector presents a low shot noise of ≈ 9 × 10 –16 A Hz –1/2 , a large signal/noise ratio of 1436.55, a high responsivity of 3.61 A W –1 , and a high specific detectivity of 2.36 × 10 11 Jones, which can be attributed to the high‐quality crystalline nanowires obtained. More interestingly, the Sb 2 Se 3 nanowire‐based photodetectors exhibit broadband polarized photoresponse to incident light with wavelengths ranging from visible to near‐infrared (532 – 830 nm). A linearly dichroic ratio of 1.71 is obtained for the 830 nm light illumination. The Sb 2 Se 3 nanowire detectors also present appropriate polarimetric imaging quality, revealing the potential of Sb 2 Se 3 nanowires for polarimetric imaging applications.

The formation of p–n junctions has attracted much attention for improving the gas-sensing performances in the field of gas detection. Although the p–n heterojunctions with a defined interfacial contact are crucial in investigating their roles on gas-sensing properties, the design of such well-defined p–n heterojunctions has been sparse until now. Herein, a p–n heterostructure composed of well-defined {001}-faceted Co3O4 as backbones and Fe2O3 nanorods as shells was synthesized using a simple hydrothermal method without the requirement of seed crystals. During the reaction, it was demonstrated that the acetic acid holds the key to the epitaxial growth of Fe2O3 nanorods on the surface of Co3O4 nanocubes. The response of this as-designed Fe2O3@Co3O4 composite (Ra/Rg = 134.9) toward 100 ppm triethylamine was about 6 times higher than that of pristine Co3O4 (Ra/Rg = 23.1) and 5 times higher than that of pristine Fe2O3 (Ra/Rg = 28.9). The highly boosted gas-sensing performances were attributed to the positive effects of the heterointerface on the gas adsorption process that were revealed through the first-principles method based on the defined heterointerfacial contacts, as well as the enlarged signal of gas–solid reactions through the heterojunctions. This work not only provides a strategy to improve gas-sensing performances but also provides guidance for the investigation of the effects of p–n heterojunctions on gas-sensing properties by designing interfacial contact with defined crystal facets.

Light assistance and construction of heterojunctions are both promising means to improve the room temperature gas sensing performance of MoS2 recently. However, enhancing the separation efficiency of photo-generated carriers at interface and adsorption ability of surface have become the bottleneck problem to further improve the room temperature gas sensing performance of MoS2-based heterojunctions under light assistance. In the present study, a novel direct Z-scheme MoS2/SnO2 heterojunction was designed through crystal facets engineering and its room temperature gas sensing properties under light assistance was studied. It was found that the heterojunction showed outstanding room temperature NO2 sensing performance with a high response of 208.66 toward 10 ppm NO2, together with excellent recovery characteristics and selectivity. The gas sensing mechanism study suggested that high-energy {221} crystal facets of SnO2 and MoS2 directly formed Z-scheme heterojunction, which could greatly improve the separation efficiency of photo-generated carriers with high redox capacity. Moreover, {221} facets greatly enhanced adsorption ability towards NO2. This work not only opens up the application of Z-scheme heterojunctions in gas sensing, which will greatly promotes the development of room temperature light-assisted gas sensors, but also provides a new idea for the construction of direct Z-scheme heterojunctions through crystal facets engineering.

Introduction of alternating magnetic field (AMF) to electrocatalytic process has been proved an effective strategy for significantly enhancing catalytic performance of magnetic nanoparticles (NPs) electrocatalysts. Coupling AMF with currently highly promising monodispersed NPs electrocatalysts could be an interesting tactics. However, magnetic heating effect under AMF may cause agglomeration and even falloff of NPs, and how to efficiently and stably utilize AMF in monodispersed NPs electrocatalysts to enhance the catalytic performance is an urgent issue. In this work, room-temperature ferromagnetism is introduced into NiSe2−X nanoparticle by vacancy engineering, and proposes a feasible design to confine monodispersed ultra-small NiSe2−X NPs in an amorphous carbon matrix. Under AMF, the spin flips of the magnetic domains in confined NiSe2−X NPs generate magnetic heating related to Néel relaxation, which achieve rapid local heating of NiSe2−X NPs electrocatalyst and greatly improves hydrogen evolution reaction performance (a significantly increase of current density by ∼400 %). This work provides new ideas for the preparation of ultra-small monodispersed NPs electrocatalysts that can utilize AMF to enhance catalytic performance, and has an important significance in accelerating clean energy production.

Polycrystalline ordered double perovskite Sr2FeMoO6 bulk samples with grain size in the range of 29–45 nm have been synthesized at temperatures from 900 to 1000 °C, using a sol-gel method. We find that the intergrain magnetoresistance is closely correlated with the grain size. The sample with the grain size of 29 nm shows large magnetoresistance Δρ/ρ0, 30%–20% at a low magnetic field of 4 kG over a wide temperature range from 20 to 300 K. The results can be explained in terms of spin-dependent intergrain tunneling model.

Effective functionalization of magnetic properties through substitutional doping may extend the spintronic applications of two-dimensional (2D) semiconductor MoS2. Here, the magnetoelectric properties of nitrogen-doped monolayer MoS2 are investigated by first-principles calculations, revealing that the N-p and S-p states are strongly hybridized with the Mo-d states, thus leading to the appearance of magnetism as verified experimentally. We demonstrate in situ doping of monolayer MoS2 with nitrogen via a convenient chemical vapor deposition method. Incorporation of nitrogen into MoS2, leading to the evolution of magnetism, is evidenced by combining x-ray photoelectron spectroscopy and vibrating sample magnetometer measurements. By comparison with pristine monolayer MoS2, the distinct ferromagnetism behaviors of nitrogen-doped monolayer MoS2 are observed up to room temperature, while the semiconducting nature persists. Our work introduces an efficient and feasible approach to realize magnetism in the 2D limit and explores potential applications in semiconductor spintronics.

Atomic heating on single atoms (SAs) to maximize the catalytic efficiency of each active site would be a fascinating solution to break the bottleneck for the performance improvement of single-atom catalysts (SACs) but highly challenging task. Here, based on the Gd@MoS2 SACs synthesized by a facile laser molecular beam epitaxy method, high-frequency alternating magnetic field (AMF) technology is employed to induce atomic magnetic heating on Gd SAs that is meanwhile demonstrated to be the catalytic active center. Significant improvement in catalytic kinetics under AMF excitation (3.9 mT) is achieved, yielding a remarkable enhancement of hydrogen evolution reaction magnetothermal-current by ≈924%. Through theoretical calculations and spin-related electrochemical experiments, such promotion in catalyst activity can be attributed to spin flip (or canting) in Gd SAs leading to the atomic magnetic heating effect on catalytic active center. Together with the embodied high stability, the implement of AMF to the SAs field is demonstrated in this work, and the precisely atomic magnetic heating on specific SAs offers unprecedented thinking for further improvement of SACs performance in the future.

Herein, Fe-doped CoP nanoparticles (Fe-CoP NPs) encapsulated in porous N-doped carbon (PNC)/carbon nanotubes (CNTs) have been successfully synthesized. The Fe doping and confined structures resulted in enhanced charge transfer and improved active sites for intermediates adsorption. The obtained Fe-CoP@PNC/CNTs materials exhibited superefficient OER performance.

Low conductivity of metal-organic frameworks limits their applications in electrochemical energy storage and conversion. To overcome this shortcoming, we synthesized the zeolitic imidazolate framework-67 on the vertical graphene (VG) surface with abundant defects grown on carbon cloth (ZIF-67-VG-CC). Based on "one-for-two" strategy, the Co3O4 nanoparticles (Co3O4-VG-CC) and nanoporous carbon (NC-VG-CC) can be derived from ZIF-67-VG-CC via selective pyrolysis in the controlled atmospheres. In the hierarchically structured Co3O4-VG-CC and NC-VG-CC, the Co3O4 nanoparticles with a size of 20 nm and N-doped porous carbons were uniformly dispersed on the VG surface, as confirmed by electron microscopies. Both the Co3O4-VG-CC and NC-VG-CC yield high specific capacitance and excellent rate capability. After assembling these two electrodes to make an asymmetric supercapacitor, the Co3O4-VG-CC//NC-VG-CC delivered a maximum energy density of 43.75 Wh/kg at a power density of 5.2 kW/kg as well as excellent cycling stability with 91.5 % specific capacitance retained after 20,000 charge-discharge cycles. All these results should be ascribed to that the VG sheets possess their high electrical conductivity and 3D network structure, and provide the hierarchical supports for the uniform distribution of the ZIF-67-dervied Co3O4 nanoparticles and NC materials, which are beneficial to the fast electron and ion transfer in the electrodes.

Vertical graphene (VG) sheets, which consist of few-layer graphene vertically aligned on the substrate with three-dimensionally interconnected porous network, make them become one of the most promising energy storage electrodes, especially for SCs. Nevertheless, the intrinsic hydrophobic nature of pristine VG sheets severely limited its application in aqueous SCs. Here, electrochemical oxidation strategy is adopted to increase the hydrophilicity of VG sheets by introducing oxygen functional groups so that the aqueous electrolyte can fully be in contact with the VG sheets to improve charge storage performance. Our work demonstrated that the introduction of oxygen functional groups not only greatly improved the hydrophilicity but also generated a pseudocapacitance to increase the specific capacitance. The resulting capacitance of electrochemically oxidized VG for 7 min (denoted as EOVG-7) exhibited three orders of magnitude higher (1605 mF/cm2) compared to pristine VG sheets. Through assembled two EOVG-7 electrodes, a symmetric supercapacitor demonstrated high specific capacitance of 307.5 mF/cm2, high energy density of 138.3 μWh/cm2 as well as excellent cyclic stability (84% capacitance retention after 10000 cycles). This strategy provides a promising way for designing and engineering carbon-based aqueous supercapacitors with high performance.

Amorphous materials have been recognized as highly active electrocatalysts due to their abundant active sites stems from unsaturated chemical bonds. In addition, the application of alternating magnetic fields (AMF) to achieve magnetic heating effect has gradually become an important means to improve the performance of magnetic catalysts. Here, we have successfully realized the surfacial amorphization of confined Ni3C nanoparticles by using interfacial strain engineering. As expected, the surfacial amorphized Ni3C nanoparticles exhibit remarkable properties in electrochemical water-splitting. More importantly, magnetic measurements show that the surfacial amorphized Ni3C nanoparticles have room temperature ferromagnetism, which is consistent with our theoretical calculation results. Accordingly, under AMF stimulation, its overall water-splitting performance is further greatly improved as the result of magnetic heating effect associated with Néel relaxation. This work provides a new strategy for the development of highly efficient surfacial amorphized catalysts, and promotes the application of magnetothermal technology in amorphous catalysis.

Low-pressure chemical vapor deposition of SiC on carbonized Si from the single-source organosilane precursor silacyclobutane (c-C3H6SiH2,SCB) has been investigated from 800 to 1200 °C. On atmospheric pressure-carbonized (100)Si, SiC films grown at 900 °C and above exhibit a transmission electron diffraction pattern consisting only of sharp spots with cubic symmetry. X-ray diffraction (XRD) of these films exhibit primarily the (200) and (400) SiC lines. XRD of films grown at 900 °C on Si(111) exhibits only an extremely large SiC(111) peak with a full width at half-maximum of 450 arcsec. Using a SCB flow rate of 1 sccm, a SiC growth rate of 4–5 μm/h was obtained on Si at 900 °C. Crystalline SiC films have also been grown by SCB at a temperature of 800 °C.

Controllable crystal facets exposing is an efficient approach for enhancing gas sensing performances of semiconductor nanomaterials. In order to study the crystal-facets-dependent gas-sensing properties of TiO2 systematically and exactly, a series of anatase TiO2 nanocrystals with different percentage of high-energy {001} crystal facets exposure (from 6% to 91%) were designed and synthesized by a simple hydrofluoric acid-assisted hydrothermal method. Gas sensing tests suggested that gas response of the TiO2 nanocrystals increased with the percentage of high-energy {001} crystal facets, although the specific surface areas gradually decreased. The results unquestionably confirmed the enhanced gas sensing activity of anatase TiO2 high-energy {001} crystal facets. Moreover, it was found that surface fluorination of high-energy {001} crystal facets played a negative role on the gas sensing activity. The relevant sensing mechanism was discussed in detail based on combination of experimental characterization and first-principle calculations, which showed that gas adsorption properties made a great contribution to gas sensing performance. By providing a comprehensive understanding of the crystal-facets-dependent gas-sensing properties of TiO2, the present work will be helpful for the designing of TiO2-based gas-sensing materials.

The MoS2 flakes are directly prepared on SiO2/Si substrates with chemical vapor deposition (CVD) in varied carried gas flow rate. It can be found that the monolayer and dendritic morphologies MoS2 flakes can be formed with different Ar flow rate, respectively. It demonstrates that the carrier gas flow rate has strong influence on the structure and morphology of CVD-grown MoS2 flakes, and consequently tailors the optical properties of MoS2 flakes significantly. These results pave the way for the development of CVD method with controlled growth parameters and opens up new venues for the synthesis of macroscopically uniform monolayer MoS2.

Nanocomposite materials with excellent receptor and transducer functions are promising in ameliorating their gas sensing properties. However, due to the abrupt changes of receptor and transducer functions when different components are combined together, structural engineering that considers both the receptor and transducer functions to design such desirable sensing materials still remains a great challenge. Here, a nanocomposite material composed of 1D ZnO nanorods and 3D Co3O4 microspheres assembled by single-crystalline porous nanosheets has been designed, which was inspired by the high-efficiency receptor-transducer-response structure of venus flytraps. The as-designed ZnO/Co3O4 composite exhibited high response (Ra/Rg = 125 to 100 ppm ethanol) which was 84 times and 8 times higher than those of Co3O4 (Rg/Ra = 1.43) and ZnO (Ra/Rg = 15). The excellent sensing properties are ascribed to the as-designed flytrap-like structure which possesses a super receptor function from 1D ZnO with a large surface area, p-n heterojunctions with an amplified response signal, as well as excellent transducer functions from single-crystalline porous Co3O4 with fast charge transport channels. This strategy provides us with new guidance on the exploration of high-performance gas sensors which could further extend to other bio-structures that are abundant in nature.

Design and control of crystal facets is a promising way to optimize the gas sensing activity of metal oxides semiconductors. To study the crystal facets effects on the gas sensing properties, a series of anatase TiO2 with designed crystal facets were synthesized by hydrothermal routes. The gas sensing properties of the three most important low-index crystal facets ({010}, {001} and {101} facets) of anatase TiO2 were systematically studied and compared for the first time. It was found that {010} facets exhibited a surprisingly higher sensing activity in comparison with that of {101} facets and {001} facets, and the gas sensing activity order were determined to be {010} facets >{001} facets >{101} facets. The crystal facets-dependent gas sensing mechanism was investigated based on theory calculations from the atomic and electronic scale. It was found that the excellent gas adsorption properties and electron transfer properties both facilitated the gas response of {010} facets. The present results not only provide a new way to improve the gas response of TiO2 by exposing of {010} facets, but also deepen the understanding of crystal facets-dependent gas sensing properties of TiO2, which will be useful for the design of metal oxides gas sensing materials.

α-MoO₃@NiO nanocomposite with well-defined core@shell P–N heterojunction nanobelts was prepared which exhibited heterointerface-determined acetone sensing characteristics.

Crystal plane engineering is considered to be an effective means to improve the surface activity of catalysts recently. Nevertheless, study related to crystal plane dependent electrocatalytic activity for hydrogen evolution reaction (HER) is still scarce. Here, two NiS2 nanocrystals with different crystal planes ({1 1 1} planes and {1 0 0} planes) were designed and controllably prepared. It was demonstrated that the NiS2 nanocrystals with {1 1 1} planes showed an enhanced HER activity (an overpotential of 138 mV to achieve a current density of 10 mA/cm2) compared with the NiS2 nanocrystals with {1 0 0} planes (an overpotential of 302 mV to achieve a current density of 10 mA/cm2). Through first-principles calculation based on density functional theory, mechanism of the crystal plane dependent electrocatalytic activity was studied in detail. It was found that the {1 1 1} planes of NiS2 had much higher surface energy and better H adsorption capacity compared with that of {1 0 0} planes, which both contributed to the enhanced HER activity. The present study provides a typical case for crystal plane dependent HER electrocatalytic activity, which is of great significance for deep understanding the HER mechanism and accurate designing of high efficiency HER electrocatalysts.

Binding and trapping of lithium polysulfide (LPS) are being conceived as the most effective strategies to improve lithium-sulfur (Li-S) battery performance. Therefore, exploiting a simple but cost-effective approach for the absorption and conversion of LPS and the transfer of electrons and Li+ ions is of paramount importance. Herein, sandwich structure MWCNTs@N-doped-C@CoS2 integrated with multiple nanostructures of zero-dimensional (0D) CoS2 nanoparticles, 1D carbon nanotubes (CNTs), and 2D N-doped amorphous carbon layer was obtained, where MWCNTs was firstly uniformly attached with a polydopamine (PDA) of excellent adhesion, followed by hydrothermal method, the Co2+ nanoparticles were in-situ grown on the PDA by the formation of complex compound of Co2+ and N atoms in PDA, and then the CoS2 nanoparticles were in-situ grown on CNTs in a point-surface contact way by a bridging of N-doped amorphous carbon layer derived from the carbonization of attached PDA after the vulcanization at 500 °C under Ar atmosphere. The multifunction synergism of absorption, conductivity, and the kinetics of LPS redox is significantly improved, consequently effectively suppressing the shuttle effect and tremendously increasing the utilization rate of active substance. For the Li-S battery assembled with MWCNTs@N-doped-C@CoS2-modified separator, its rate capacity and cycling performance can be greatly enhanced. It can exhibit a high initial discharge capacity of 1590 mAh g-1 at 0.1 C, a stable long-term cycling performance with a relatively low capacity decay of 0.07% per cycle during 500 cycles at 1 C, and a reversible capacity of 772 mAh g-1 and a capacity decay of 0.04% per cycle during 250 cycles at 2 C. Even at a large current density of 4 C, an initial specific discharge capacity of 634 mAh g-1 can still be delivered. With a high sulfur loading of 5.0 mg cm-2, additionally, an outstanding cycling stability can also be well maintained at 685 mAh g-1 at 0.1 C after 50 cycles. This work provides a novel and simple but effective strategy to develop such sandwich hybrid materials comprised of polar metal sulfides and conductive networks via an effective bridging to help realize durable and stable Li-S battery.

Nanoclusters are ideal electrocatalysts due to their high surface activity. However, their high activities also lead to serious agglomeration and performance attenuation during the catalytic process. Here, highly dispersed Ni nanoclusters (∼3 nm) confined in an amorphous carbon matrix are successfully fabricated by pulsed laser deposition, followed by rapid temperature annealing treatment. Then, the Ni nanoclusters are further doped with nitrogen element through a clean N2 radio frequency plasma technology. It is found that the nitrogen-doped Ni nanoclusters obtained under optimized conditions showed superior OER performance with a very low overpotential of 240 mV at a current density of 10 mA/cm2, together with good stability. The excellent OER performance of the nanoclusters can be attributed to the unique confined structure and nitrogen doping, which not only provide more active sites but also improve the conductivity. Our work provides a controllable method for the construction of a novel confined structure with controllable nitrogen doping, which can be used as a high-efficiency OER electrocatalyst.

Lithium sulfur (Li-S) batteries are regarded as one of the most promising future energy storage candidates on account of high theoretical specific capacity of 1675 mAh g-1 and energy density of 2600 Wh kg-1. However, their practical application is seriously hindered due to the poor conductivity and volume expansion of sulfur, the weak redox kinetics of lithium polysulfide (LPS), and the severe shuttle effect of LPS. Herein, V2O3@N,Ni-C nanostructures, multiply integrated with zero-dimensional (0D) V2O3 nanoparticles, 1D carbon nanotubes, 2D carbon coating layers and graphene, 3D hollow spheres, and doped N and Ni heteroatoms, were synthesized via a solvothermal method followed by chemical vapor deposition. After being used as a modifier for traditional commercial separator of Li-S batteries, the shuttle effect of LPS can be effectively suppressed owing to the abundant active physical and chemical adsorption sites derived from large specific surface area, rich porosity, and tremendous polarity of the V2O3 nanoparticles with multiple secondary nanostructure integration. Meanwhile, the transfer of Li+ ions and electrons can be effectively enhanced by the highly conductive 2D carbon network, and the kinetics of redox reaction (Li2Sn ↔ Li2S) can be accelerated by the doped N and Ni heteroatoms, leading to a synergistic promotion on the reutilization of the adsorbed LPS. Additionally, the unique 3D hollow structure can not only enhance the penetration of electrolyte, but also buffer the volume expansion of sulfur to some extent. Therefore, the rate capacity and cycling performance can be significantly enhanced by the multifunction synergism of adsorption, conductivity, catalysis, and volume buffering. An initial discharge capacity of 1590.4 mAh g-1can be achieved at 0.1C, and the discharge capacity of 803.5 mAh g-1can be still exhibited when increasing to 2C. After a long period of 500 cycles, additionally, the discharge specific capacity of 1142.2 mAh g-1 and capacity attenuation of 0.0617% per cycle can be obtained at 1C.

Further uprating the catalytic activities of diatomic active sites while maintaining the atomic loading and diatomic coordination by external stimulation is a promising way to break the bottleneck in the improvement of diatomic site catalysts (DASCs). Herein, the as-prepared NiFe@MoS2 DASCs treated by external high-frequency alternating magnetic field (AMF) further expedite the alkaline water electrolysis process with a superior cell voltage of 1.576 V to afford a current density of 10 mA cm−2 than that treated without AMF (1.652 V). Theoretical simulation by COMSOL Multiphysics helps visualize the increase in temperature locally around the diatomic active sites, qualitatively revealing the magnetic heating effect that originates from the anchored magnetic Ni and Fe atoms. The selective magnetic heating of bifunctional diatomic active site proposed in this work can broaden horizons and endow another dimension in the design of highly efficient catalysts toward various complicated energy-related reactions.

The development of non-noble metal-based bifunctional electrocatalysts toward overall water splitting is urgent recently. However, their catalytic activity is still limited by the insufficient active sites and unsatisfactory adsorption toward reaction intermediates. Here, a self-supported rare earth Ce-doped Ni5P4 porous nanosheets array is designed as an efficient bifunctional electrocatalyst, which requires a competitive overall water splitting potential of 1.56 V to drive the current density of 10 mA/cm2 under alkaline condition. It is shown that the introduction of Ce can greatly reduce the charge transfer resistance and increase the active sites of Ni5P4, which promotes fast charge transfer and facilitates the kinetics to maintain high catalytic activity. Especially, systematic DFT theoretical calculation is further conducted to study the electrocatalytic process, and it is shown that Ce doping can regulate the center of the d band and adsorption of reaction intermediates, thus reducing the overall speed-decisive step of water splitting reaction. This work demonstrates an efficient strategy for enhancing the overall water splitting properties of bifunctional electrocatalysts through rare earth Ce doping, which also has guiding significance for the study of electrocatalytic mechanism in atomic scale.

In this work, porous NiCo2O4 nanosheets anchored on the surface of 1D WO3 nanofibers were synthesized via a hydrothermal route followed by a facile chemical deposition treatment. The as-obtained products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Brunauer-Emmett-Teller analysis. The porous NiCo2O4 nanosheets grew on the surface of WO3 nanofibers with an intimate contact between their interfaces, leading to the formation of p-n heterojunctions and an increase of surface area. Compared with the pristine WO3 nanofibers and NiCo2O4 nanosheets, the NiCo2O4/1D WO3 nanocomposite exhibited the highest response to xylene (Rg/Ra = 15.69 toward 100 ppm). Moreover, the NiCo2O4/1D WO3 nanocomposite also demonstrated outstanding selectivity, excellent stability and low detection limitation (~ 5 ppm) to xylene vapor. The main mechanism for the enhanced gas-sensing properties of NiCo2O4/1D WO3 nanocomposite was attributed to the unique porous structures and p-n heterojunctions between NiCo2O4 nanosheets and WO3 nanofibers. The excellent gas-sensing properties of NiCo2O4/1D WO3 nanocomposite make it a good candidate as a gas-sensing material for the practical application in xylene detection.

Anatase TiO2 hierarchical microspheres were synthesized by a facile hydrothermal method. Characterization results indicated that the microspheres were consisted of massively aggregative nanothorns with truncated tips, which had exposed {001} and {101} crystal facets, and there were abundant mesoporous structures in the microspheres. A possible growth model of the TiO2 hierarchical microspheres was put forward based on a series of experimental analysis. When used for gas sensing, it was found that the TiO2 hierarchical microspheres showed a distinct high sensitivity towards acetone, the optimal response to 100 ppm acetone was 14.6, which was much higher than that of other materials reported in previous works. Moreover, the TiO2 hierarchical microspheres exhibited a fast response/recovery speeds (<10 s), a low detection limit (the response still reaches 6.1 even at a low acetone concentration of 10 ppm) and an excellent selectivity. Through systematical analysis, it can be concluded that the enhancement of gas sensing performance of the TiO2 hierarchical microspheres was ascribed to its unique structural features (perfect hierarchical mesoporous structure as well as specific crystal facets exposing), which could be described as structurally enhanced gas sensing performance. The present results encourage us to further investigate crystal facets-dependent gas sensing properties of TiO2 for the designing of conductometric gas sensors with better sensing performance.

The good thermoelectric performance of some half-Heusler (HH) alloys has been stimulating substantial efforts in searching for more materials with similar crystal structures but better properties.

The development of efficient hydrogen evolution reaction (HER) catalysts based on non-precious metal alternative to noble metal is significant for booming energy conversion/storage systems. Here, we report a facile strategy to design a novel hierarchical nanoporous (HNP) HER electrocatalyst by incorporating transition metal oxide (TMO) NiO and complex phosphide (TMP) NiCoP. With the HNP NiCo2O4 products via a facile solvothermal and annealing method, the NiO/NiCoP composite was easily obtained through a simple subsequent phosphorization process at the optimized temperature. Owing to various factors such as the strong synergetic coupling effects between TMO and TMP, electron interaction between TMPs, unique HNP structure features and increased active sites, the resulting HNP NiO/NiCoP composite demonstrated significantly enhanced electrocatalytic HER activities with a current density of 10 mAcm−2 at a small overpotential of 112 mV, a low Tafel slope of about 56 mV dec−1 and satisfactory stability. We expect that this facile synthetic strategy of active binary TMPs functionalized hierarchical porous TMOs will provide a promising prospect for the development of non-precious HER electrocatalysts.

Gas-sensing properties of metal-oxide nanocomposites are largely depended on their structures and compositions. It remains great challenges to design well-defined heterostructures to improve gas-sensing properties and establish the relationship between these properties with heterostructures. In this paper, an extremely sensitive ethanol sensing material via decoration of NiCo2O4 nanosheets onto 1D α-MoO3 nanorods by a facile chemical deposition method was developed. The structures and compositions of the as-prepared sensing materials were characterized by XRD (X-ray diffraction), SEM (scanning electron microscopy) and TEM (transmission electron microscopy). It was revealed that uniform porous NiCo2O4 nanosheets grown on the surface of α-MoO3 nanorods backbones with a low lattice mismatch at the interface of heterostructures. Gas-sensing tests showed that this novel NiCo2O4/α-MoO3 nanocomposite exhibited superior sensing performances for ethanol with high response, negligible cross-responses to other interfering gases and excellent stability. The response to 1 ppm ethanol was about 20 (Rg/Ra), whereas pure NiCo2O4 and α-MoO3 showed almost no response. Notably, the detection limit for ethanol was as low as 50 ppb (Rg/Ra = 2.7). The enhanced sensing properties were attributed to the unique structures and heterojunctions between NiCo2O4 nanosheets and α-MoO3 nanorods. The results above indicated the potential of this as-designed NiCo2O4/α-MoO3 nanocomposite to detect sub-ppm level ethanol in a highly sensitive manner.

Conversion-type anode materials possess high theoretical capacity for sodium-ion batteries (SIBs), owing to multi-electron transmission (2-6 electrons). Mo-based chalcogenides are a class of great promise, high-capacity host materials, but their development still undergoes serious volume changes and low transport kinetics during the cycling process. Here, MoO2 nanoparticles anchored on N-doped carbon nanorod bundles (N-CNRBs/MoO2) are synthesized by a facile self-polymerized route and a following annealing. After hydrothermal sulfuration, N-CNRBs/MoO2 composites are encapsulated by surface growth of ultrathin MoS2 nanosheets, acquiring hierarchical N-CNRBs/MoO2@MoS2 composites. Serving as the SIB anode, the N-CNRBs/MoO2@MoS2 electrode exhibits significantly improved sodium-ion storage properties. The reversible capacity is up to 554.4 mA h g-1 at 0.05 A g-1 and maintains 249.3 mA h g-1 even at 10.0 A g-1. During 5000 cycles, no obvious capacity decay is observed and the reversible capacities retain 334.8 mA h g-1 at 3.0 A g-1 and 301.4 mA h g-1 at 5.0 A g-1. These properties could be ascribed to the vertical encapsulation of MoS2 nanosheets on high-crystalline N-CNRBs/MoO2 substrates. The hierarchical architecture and unique heterostructure between MoO2 and MoS2 synergistically facilitate sodium-ion diffusion, relieve volume changes, and boost pseudocapacitive charge storage of N-CNRBs/MoO2@MoS2 electrode. Therefore, the rational growth of nanosheets on complex substrates shows promising potential to construct anode materials for high-performance batteries.

The van der Waals (vdW) gaps in layered transition-metal dichalcogenides (TMDs) with an interlayer poor charge transport are considered the bottleneck for higher hydrogen evolution reaction (HER) performance of TMDs. Filling the vdW gap of TMDs materials with intercalants is considered a good way to generate new interesting properties. However, postsynthesis intercalation with foreign atoms may bring extra crystalline imperfections and low yields. In this work, to overcome the interlayer potential barriers of TMDs, CrS2–Cr1/3–CrS2 is produced by naturally self-intercalating native Cr1/3 atom plane into the vdW layered CrS2. The CrS2–Cr1/3–CrS2 exhibits strong chemical bonds and high electrical conductivity, which can provide excellent HER electrocatalytic performance. Moreover, based on the first-principles calculations and experimental verification, the intercalated Cr atoms exhibit a Gibbs free energy of the adsorbed hydrogen close to zero and could further improve the electrocatalytic HER performance. Our work provides a new view in self-intercalation for electrocatalysis applications.

The development of high-performance carbon-based anodes for Na-ion batteries is highly desired but still remains challenging because of carbon materials with a low reversible capacity and poor cyclic performance. Herein, novel S-doped carbon nanosheets (SCNs) were prepared by a hydrothermal self-assembly process in the presence of graphene oxide (GO) as the matrix, starch as the carbon source, and dibenzyl disulfide as the sulfur source. The obtained SCNs with hierarchical pores and a sandwich-like structure were utilized as anode materials for Na-ion batteries, exhibiting a high reversible discharging capacity of 207.3 mAh g–1 after 100 cycles at 50 mA g–1. When the current density is up to 1 A g–1, a reversible discharge capacity of 118.8 mAh g–1 can also be acquired. Moreover, the prominent long-term cycling stability of more than 500 cycles can be obtained at 200 mA g–1. The outstanding electrochemical property (high reversible capacity, high rate performance, and long-term cycling stability) of the SCN electrode may be due to the synergistic effect of S doping, hierarchical pores, and the sandwich-like structure. Furthermore, electrochemical kinetic analysis also confirmed that the sodium storage mechanism of the SCN electrode reinforced pseudocapacitive-control behavior. The present study not only shows a high-performance anode material for Na-ion batteries but also provides a new method to prepare S-doped carbon materials for various applications.

Light excitation has been developed as an economical way to realize room-temperature gas sensing recently. However, the high recombination rate of photogenerated carriers in semiconductor gas sensing materials leads to very limited carriers that can effectively take part in sensing reactions, which greatly restricts the further performance improvement of gas sensing under light excitation. Here, a hierarchical Z-scheme heterostructure microsphere of MoS2/SnO2 is designed and prepared. The heterostructure demonstrates an outstanding NO2 sensing performance at room temperature with the excitation of a low-power LED light (0.06 W), which exhibits an ultrahigh sensitivity of 264.2 to 10 ppm of NO2 along with acceptable response/recovery properties. The physical mechanism of NO2 sensing is analyzed. The results suggest that the construction of the Z-scheme heterostructure between MoS2 and SnO2 can greatly promote the separation of photogenerated carriers so that more photogenerated carriers can take part in the NO2 sensing reaction. Furthermore, the designing of a hierarchically porous structure can provide abundant active sites for gas sensing reactions. The work not only expands the development of Z-scheme heterostructures in gas sensing but also provides a strategy to promote the performance of light-excited gas sensors by designing a Z-scheme heterostructure with a hierarchically porous structure.

Due to the special three-dimensional structures and excellent physicochemical properties, vertical graphene (VG) has been extensively investigated as potential material for supercapacitors. However, achieving VG-based supercapacitors with high-energy density and high-power density is a still tremendous challenge. Here we attempt to synthesize large-scale VG films on flexible substrates and design a novel battery-like supercapacitor (BSCs) with the VG on Ni foil (VG@Ni) as a binder-free electrode operating in the KOH electrolyte with the redox additives of K3Fe(CN)6 and/or K4Fe(CN)6. The VG@Ni electrodes demonstrate an ultrahigh areal capacitance of 1453 mF cm−2 at 5 mA cm−2 in 1 M KOH electrolyte with adding 0.07 M K3Fe(CN)6 and 0.07 M K4Fe(CN)6, coulombic efficiency greater than 90%, and long-life cycling stability (capacitance retention is 99.3% after 20000 charge-discharge cycles). The BSCs, which are assembled with two identical VG@Ni electrodes, deliver the areal capacitance of 231 mF cm−2 with energy density of 32 μWh cm−2 and power density of 2498 μW cm−2 at 1 mA cm−2. These outstanding performances can be ascribed to the special feature and excellent properties of VG materials, high electronic conductivity of binder-free VG@Ni electrode, faradaic properties of redox electrolyte, and synergistic effects between the VG film and redox electrolyte.

Light irradiation has emerged as a promising strategy to promote room temperature sensing of resistive-type semiconductor gas sensors recently. However, high recombination rate of photo-generated carriers and poor visible light response of conventional semiconductor sensing materials have greatly limited the further performance improvement. It is urgent to develop gas sensing materials with high photo-generated carrier separation efficiency and excellent visible light response. Herein, a novel direct Z-scheme NiO/Bi2MoO6 heterostructure arrays were designed and in-situ constructed on alumina flat substrate to form thin film sensors, which realized excellent room temperature gas response towards ether under irradiation of visible light for the first time, together with excellent stability and selectivity. Based on density functional theory calculation and experimental characterization, it was demonstrated that the construction of Z-scheme heterostructure could greatly promote the separation of photo-generated carriers and adsorption of ether. Moreover, the excellent visible light response characteristics of NiO/Bi2MoO6 could improve the utilization of visible light. In addition, the in-situ construction of array structure could avoid a series of problems caused by the conventional thick film devices. The work not only provides a promising guideline for Z-scheme heterostructure arrays in promoting the room temperature sensing performance of semiconductors gas sensors under visible light irradiation, but also clarifies the gas sensing mechanism of Z-scheme heterostructure at the atomic and electronic level.

The crystal structure and magnetoresistance of the polycrystalline La1−xLixMnO3 (x=0.10, 0.15, 0.20, 0.30) are investigated. The result of the Rietveld refinement of x-ray powder diffraction shows that the room temperature structural transition from rhombohedral (R3̄C) to orthorhombic (Pbnm) symmetry occurs at the Li-doped level x⩾0.2. Accompanying the occurrence of the structural transition, the lattice distortion and the bending of the Mn–O–Mn bond increase and the ferromagnetic transition temperature TC decreases. For x=0.10 and 0.15 samples, double metal–insulator (M–I) transitions accompanying a single ferromagnetic transition and a negative magnetoresistance as high as 26% in a magnetic field of 0.8 T are observed. For x=0.20 and 0.30, the samples manifest nonmetallic behavior throughout the measured temperature range. We suggest that the double M–I transitions phenomena of low Li-doped samples originate from the magnetic inhomogeneity due to the formations of the Mn3+ and Mn4+-rich regions induced by partial substitution of the monovalent Li1+ ions for the trivalent La3+ ions. The transport property of high Li-doped samples (x=0.20 and 0.30) can be explained according to the additional localization of eg electrons induced by a static coherent Jahn–Teller distortion of the MnO6 octahedra stemming from the structural transition from rhombohedral (R3̄C) to orthorhombic (Pbnm) and the reduced bandwidth of eg electrons due to the increased bending of the Mn–O–Mn bond.

Ni/NiO core/shell nanoparticles embedded in an amorphous Al2O3 matrix were fabricated by pulsed laser deposition. The core/shell nanoparticles consist of a single-crystal Ni core and polycrystalline NiO shell. High coercivity at room temperature was achieved in the sample with Ni/NiO nanoparticles, which can be attributed to the interfacial interaction between the ferromagnetic Ni core and the antiferromagnetic NiO shell. These results indicate that the formed Ni/NiO core/shell structure is favorable for the large coercivity application.

Confining ZnO quantum dots (QDs) into a solid state matrix to form nanocomposite materials is an important mean to design nonlinear optical devices. In this paper, ZnO confined in Al2O3 matrix are synthesized by pulsed laser deposition method and rapid thermal annealing technique. The substantial oxygen vacancies are generated in the N2-annealed ZnO QDs. Magnetic measurements illustrate that the ferromagnetic nature of ZnO QDs confined in Al2O3 matrix can be due to the oxygen vacancies. The determined two-photon absorption in N2-annealed ZnO QDs is an instantaneous nonlinear process and is enhanced almost 2 times compared to that of O2-annealed ZnO QDs. The enhancement of optical nonlinearities achieved in confined ZnO QDs with substantial oxygen vacancies is important for the practical applications of ZnO nanostructures in such as optical limiting devices and all-optical switching elements.

Developing high-performance anode materials is a crucial research target of sodium-ion batteries (SIBs). Transition metal oxides (TMOs) have attracted great interest as potential anodes, but their applications are still hindered by slow reaction kinetics and large volume changes. Herein, Mo-aniline nanorods (Mo-ANRs) are prepared as precursors by a simple self-polymerized method in acid condition. After the in-situ phase transformation during annealing, multistage composites ([email protected]2) are formed, with N-doped carbon nanorods (N-CNRs) converted from polymeric aniline ligands, on which granular molybdenum dioxide (g-MoO2) are uniformly precipitated and residual MoO2 nanodots are remained. As anode materials for SIBs, [email protected]2 electrode is benefited from the shortened ion/electron diffusion length caused by steady g-MoO2 and residual nanodots, and the enhanced electrical conductivity and relieved volume changes introduced by N-CNRs and unique architecture. Thus, [email protected]2 electrode delivers high discharge capacity (497.5 mAh g−1 at 0.05 A g−1), excellent rate performance and ultra-long cycling stability (165.6 mAh g−1 at 10.0 A g−1 after 12000 cycles), and 122% capacity retention is obtained at 1.0 A g−1 over 500 cycles even after the rate test. The significant enhancements in sodium-ion storage are mainly attributed to the multistage architecture and synergistic advantages among MoO2 nanodots, N-CNRs and g-MoO2. These results indicate that the in-situ phase transformation route has great potential in constructing novel composites with unique architecture for high-performance SIBs.

The studies of nonlinear optical properties of alloyed AgCu nanoparticles embedded in Al2O3 film with Ag to Cu atomic ratio of 1:1 are presented. To enhance nonlinear optical properties of alloyed AgCu nanoparticles, glassy nanoparticles are synthesized by adjusting the parameters of rapid thermal annealing. The nonlinear optical absorption coefficient of AgCu glassy nanoparticles is found to be twice than that of AgCu crystalline nanoparticles. In addition to conventional morphology modulation, this provides another dimension for modifying the nonlinear optical properties of metallic nanostructures. The optical nonlinear enhancement can be achieved by realizing the growth of glassy nanoparticles, which is of great significance for the application of nanostructures in optical limiting devices and all-optical switching devices.

The high recombination rate of photoinduced electron–hole pairs limits the hydrogen production efficiency of the MoS2 catalyst in photoelectrochemical (PEC) water splitting. The strategy of prolonging the lifetime of photoinduced carriers is of great significance to the promotion of photoelectrocatalytic hydrogen production. An ideal approach is to utilize edge defects, which can capture photoinduced electrons and thus slow down the recombination rate. However, for two-dimensional MoS2, most of the surface areas are inert basal planes. Here, a simple method for preparing one-dimensional MoS2 nanoribbons with abundant inherent edges is proposed. The MoS2 nanoribbon-based device has a good spectral response in the range of 400–500 nm and has a longer lifetime of photoinduced carriers than other MoS2 nanostructure-based photodetectors. An improved PEC catalytic performance of these MoS2 nanoribbons is also experimentally verified under the illumination of 405 nm by using the electrochemical microcell technique. This work provides a new strategy to prolong the lifetime of photoinduced carriers for further improvement of PEC activity, and the evaluation of photoelectric performance provides a feasible way for transition-metal dichalcogenides to be widely used in the energy field.

Crystal facet engineering and graphene modification are both effective means to improve the gas sensing performance of metal oxide semiconductors (MOSs) currently. However, research on the crystal facet effect and synergistic effect of graphene modification of p-type MOS sensors is relatively lacking. Here, p-type Co3O4 nanocrystals with controlled crystal facets ({112} and {100}) were in situ wrapped in the two-dimensional (2D) nanosheet network of graphene. It was found that bare {112} facets showed a significantly higher triethylamine sensing performance than {100} facets, implying a strong crystal facet effect. Interestingly, the triethylamine sensing performance of {112} facets was significantly improved after rGO modification, while the performance improvement of Co3O4 {100} was limited after rGO modification. Further study suggested that {112} facets contained more active Co3+ species and chemically adsorbed oxygen species than {100} facets, which promoted the adsorption of triethylamine and the subsequent sensing reaction. In addition, the strong electronic interaction between Co3O4 {112} crystal facets and rGO promoted efficient charge exchange through the heterogeneous interface. This work provides a new way to improve the gas sensing performance of Co3O4 through the synergistic effect of crystal facet engineering and graphene modification.

Chemical vapor deposition of SiC on Si (111) from silacyclobutane (c-C3H6SiH2, SCB) has been carried out on propane carbonized and on virgin Si substrates. The carbonization was performed at 760 Torr and the SiC growth at 5 Torr. Transmission electron diffraction (TED) and x-ray diffraction were used to determine the crystallinity of the resulting films. The minimum temperature for obtaining crystalline films, as indicated by a TED pattern consisting of sharp spots with (111) SiC crystal hexagonal symmetry, was lower with carbonization (∼800–900 °C) than without (∼1000 °C). However, the carbonization process creates voids in the Si just below the SiC/Si interface, while SCB growth without carbonization produces a very smooth and void-free interface. Fourier-transform infrared measurements of SiC films grown at 1200 °C without carbonization exhibit a sharp (full width at half-maximum=30 cm−1) Si-C absorption peak at 794 cm−1.

We describe a single step route for the synthesis of MoS₂ wires using a chemical vapour deposition (CVD) method.

The strain effect on graphene-encapsulated Au nanoparticles is investigated. A finite-element calculation is performed to simulate the strain distribution and morphology of the monolayer and multilayer graphene-encapsulated Au nanoparticles, respectively. It can be found that the inhomogeneous strain and deformation are enhanced with the increasing shrinkage of the graphene shell. Moreover, the strain distribution and deformation are very sensitive to the layer number of the graphene shell. Especially, the inhomogeneous strain at the interface between the graphene shell and encapsulated Au nanoparticles is strongly tuned by the graphene thickness. For the mono- and bilayer graphene-encapsulated Au nanoparticles, the dramatic shape transformation can be observed. However, with increasing the graphene thickness further, there is hardly deformation for the encapsulated Au nanoparticles. These simulated results indicate that the strain and deformation can be designed by the graphene layer thickness, which provides an opportunity to engineer the structure and morphology of the graphene-encapsulated nanoparticles.

NiO nanosheets were successfully exfoliated from the paired metal Ni wires by one-step electrochemical process in blank NaOH electrolyte. The nanosheets were composed of agglomerated nanoparticles, with the thickness of the nanoscale, nano/micro size, and abundant lacerated edges. The NiO nanosheets modified glass carbon electrode demonstrated excellent electrocatalytic activities and performance in sensing glucose with high sensitivity (838.09 μA mM−1 cm−2), wide linear concentration range (500 nM to 2.31 mM), low detection limit (0.145 μM), good anti-interference, and reproducibility, which was further applied to detect glucose in a serum sample.

In this paper, 1D ZnO nanofibers were selected as the backbones, which were prepared by a hydrothermal route. Afterward, porous NiCo2O4 nanosheets with large surface area were further grown on the surface of single-crystal ZnO nanofibers via a chemical bath deposition. The structures and compositions of the as-prepared gas-sensing materials were characterized. It was found that uniform porous NiCo2O4 nanosheets were anchored on the surface of ZnO nanofibers backbones with a low lattice mismatch at the interface of heterostructures. Gas-sensing tests showed that this novel [email protected]2O4-shell nanocomposite exhibited improved gas-sensing performances towards methanol, such as high response, low detection limit and excellent stability. The response to 5 ppm methanol was about 1.96 (Rg/Ra), whereas pristine NiCo2O4 and ZnO showed negligible response. The enhanced gas-sensing properties were attributed to the unique core-shell heterojunctions between NiCo2O4 nanosheets and ZnO nanofibers resulting in an improved receptor function as well as transducer function.

<italic>In situ</italic> hybridized composites of mono-faceted WO_3−x nanorods in N-doped carbon nanosheets (WO_3−x NRs/N-CNSs) were developed for ultra-fast/stable sodium-ion storage.

Experimental results have shown that the quaternary compound Cu2ZnSnSe4 is an excellent thermoelectric material. This inspires us to seek the other quaternary compounds with similar chemical formula to Cu2ZnSnSe4 as thermoelectric materials. In this paper, we use the first-principle method to systematically explore the electronic and phonon structures, mechanical, thermal and thermoelectric properties of p- and n-type Ag2XYSe4 (X=Ba, Sr; Y=Sn, Ge). It is found that the ZT maximum for n-type Ag2SrGeSe4 can reach up to 1.22 at 900 K, and those for p-type Ag2SrSnSe4, Ag2SrGeSe4 and Ag2BaSnSe4 can reach up to 1.20, 1.13 and 1.12, respectively. Our work not only shows that Ag2XYSe4 (X=Ba, Sr; Y=Sn, Ge) are a kind of potential thermoelectric materials, but also can inspire more theoretical and experimental researches on thermoelectric properties of quaternary compounds.

Laminated bilayer MoS₂ structures are prepared with MoS₂ nanoparticles trapped between two individual MoS₂ layers which can prevent the formation of a true stacking structure held together by van der Waals interaction.

Iron phosphide (FeP) is a promising alternative catalyst for electrocatalytic hydrogen evolution reaction (HER) due to its low price, highly active catalytic sites and long-term anti-acid corrosion. Herein, we report a very facile strategy to fabricate novel FeP nanosheets as a HER electrocatalyst. Three-dimensional interconnected nanosheet structures of Fe2O3 (3D Fe2O3 NS) were directly exfoliated from metal Fe wires by alternating current (AC) voltage disturbance, and a simple subsequent phosphorization process could easily convert γ-Fe2O3 into FeP phase, which also maintained the 3D NS structure. Importantly, increasing the AC voltage resulted in the evolution of iron-containing nanostructures from nanoparticles to 2D nanosheets until the formation of 3D NS structure. Owing to the large specific surface area, enriched active sites and abundant hierarchical porous channels, as-prepared 3D FeP NS has exhibited significantly enhanced electrocatalytic HER activities such as a cathode current density of 10 mA cm−2 at a small overpotential of 88 mV, low Tafel slope (47.7 mV dec−1) and satisfactory long-term stability in acidic electrolyte. We expect that this simple and green synthetic strategy of transition metal phosphides will provide a promising prospect to innovate nonprecious HER electrocatalysts.

This work presents a study on the controlled growth and the growth mechanism of vapour-phase deposited two-dimensional Bi2Te3 nanostructures by investigating the influence of growth conditions on the morphology of Bi2Te3 nanostructures. The formation of a hexagonal plate geometry for Bi2Te3 nanostructures is a consequence of the large difference in growth rate between crystal facets along 〈0001〉 and 〈112¯0〉 directions. Under low Ar carrier gas flow rates (60–100 sccm), the growth of Bi2Te3 nanoplates occurs in the mass-transport limited regime, whereas under high carrier gas flow rates (130 sccm), the growth of Bi2Te3 nanoplates is in the surface-reaction limited regime. This leads to an increase in the lateral size of Bi2Te3 nanoplates with increasing the Ar carrier gas flow rate from 60 to 100 sccm, and a decrease in size for a flow rate of 130 sccm. In addition, the lateral size of Bi2Te3 nanoplates was found to increase with increasing growth time due to the kinetic characteristics of material growth. The proposed growth model provides an effective guide for achieving controlled growth of Bi2Te3 nanoplates, as well as other two dimensional nanomaterials.

Proper morphology, surface and interface structure designing are required to obtain efficient gas sensing and photocatalytic materials. In the present work, ultra-thin NiO single-crystalline porous nanosheets with dominant {1 1 1} crystal facets (denoted as SP-NiO) and hierarchical NiO porous microspheres (denoted as HP-NiO) supported highly dispersed Pt nanoparticles with controllable sizes were designed and synthesized. Their gas sensing and photocatalytic performance were investigated. It was found that both the formaldehyde sensing and methyl orange photocatalytic degradation performance were greatly enhanced by decorating Pt nanoparticles on SP-NiO, while Pt nanoparticles decoration contributed little to the improved photocatalytic performance of HP-NiO. The results indicated that surface structure of the NiO support could also produce significant impact on the activity of Pt/NiO heterojunctions. Moreover, Pt decorated SP-NiO with stable structure showed a marked long-term stability with negligible attenuation of gas sensitivity (less than 5%) for 45 days, while Pt decorated HP-NiO exhibited obvious attenuation of gas sensitivity (more than 30%) due to the structural collapse. The work not only offers promising materials for gas sensing and photocatalytic application, but also brings new dawn for the designing of efficient p-type metal oxides gas sensing and photocatalytic materials through the synergistic effect of single-crystalline porous structures modulation, crystal facets engineering and facet-selective deposition of highly-dispersed Pt nanoparticles.

As the core of an electrocatalyst, the active site is critical to determine its catalytic performance in the hydrogen evolution reaction (HER). In this work, porous N-doped carbon-encapsulated CoP nanoparticles on both sides of graphene (CoP@NC/GR) are derived from a bimetallic metal-organic framework (MOF)@graphene oxide composite. Through active site engineering by tailoring the environment around CoP and engineering the structure, the HER activity of CoP@NC/GR heterostructures is significantly enhanced. Both X-ray photoelectron spectroscopy (XPS) results and density functional theory (DFT) calculations manifest that the electronic structure of CoP can be modulated by the carbon matrix of NC/GR, resulting in electron redistribution and a reduction in the adsorption energy of hydrogen (ΔGH*) from -0.53 to 0.04 eV. By engineering the sandwich-like structure, active sites in CoP@NC/GR are further increased by optimizing the Zn/Co ratio in the bimetallic MOF. Benefiting from this active site engineering, the CoP@NC/GR electrocatalyst exhibits small overpotentials of 105 mV in 0.5 M H2SO4 (or 125 mV in 1 M KOH) to 10 mA cm-2, accelerated HER kinetics with a low Tafel slope of 47.5 mV dec-1, and remarkable structural and HER stability.

layers produced on Si substrates by rapid thermal chemical vapor deposition have been transferred onto oxidized Si substrates by bonding and etchback. For films with a mean surface roughness of about 20 Å room temperature bonding to smooth oxidized Si wafers is possible under the influence of an external force. For 4 in. diam substrates, bonding of ∼85% of the area was obtained. Sections of the layer of the bonded pair peeled off when the Si substrate of the layer is thinned down to ∼150 μm and below. This is probably caused by the low interface fracture energy due to trapped air at the bonding interface and by outgassing from the thermal oxide of in addition to the film stress. Multistep annealing at 1100°C between etches of the Si substrate can enhance the interface fracture energy of the bonded pairs. A densification step of the thermal oxide after dry oxidation helps to reduce the trapped gas in the oxide. Auger and transmission electron microscopy results have verified that the transferred layer retains its original properties.

The electrical, magnetic, and transport properties of Cu-doped polycrystalline samples Sr2Fe1−xCuxMoO6 with ordered double perovskite structure have been investigated systematically. Analysis of the x-ray powder diffraction pattern based on the Rietveld analysis indicates that the substitution of Fe3+ ions by Cu2+ ions enhances the site location order of Fe, Cu, and Mo on the B site for the high-doping-level samples (x=0.20, 0.25, 0.30). With increasing doping level, a transition from semiconductor to metal behavior was also found to occur. Furthermore, the transition temperature was found to decrease either by the application of a magnetic field or by increasing the doping level. It can be concluded that the existence of Cu2+ ions induces the occurrence of Fe3+δ ions and the double exchange interaction in Fe3+–O–Mo–O–Fe3+δ. The transport mechanism in these samples can be attributed to the competition between the metal phase and the semiconductor phase arising from the doping of Cu2+ ions. Both the semiconductor-to-metal transition and the magnetoresistive behavior can be explained by the percolation threshold model.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation Cailei Yuan, Shuangli Ye, Bo Xu, Wen Lei; Strain induced tetragonal SrTiO3 nanoparticles at room temperature. Appl. Phys. Lett. 13 August 2012; 101 (7): 071909. https://doi.org/10.1063/1.4747204 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioApplied Physics Letters Search Advanced Search |Citation Search

The influence of compressive strain on the deformation of GaAs nanoparticles embedded in different host matrices is investigated. The simulation results indicate that it can be easier to deform GaAs nanoparticles grown in an Al2O3 film than those in an SiO2 film. The deformation induced by the applied compressive strain has significant influence on the shape, size and microstructure of GaAs nanoparticles. Most significantly, these simulated results have a good agreement with HRTEM experimental results.

The growth of nanoparticles embedded in a host matrix can lead to substantial strain. Strain can have a substantial influence on the properties of nanoparticles. In this work, Si nanoparticles embedded in an amorphous Al2O3 matrix were fabricated using pulsed laser deposition and rapid thermal annealing. The strain-induced structural transition from the cubic phase to the hexagonal phase was observed during the rapid thermal annealing process and led to the decrease of the band gap caused by the hexagonal crystalline phase. It was found that the microstructures and photoluminescence of Si nanoparticles are closely related to strain. Thus, strain engineering is an effective tool for tailoring the optical properties of Si nanoparticles.

We observed the regular morphology evolution of chemical vapor deposition (CVD) grown MoS2 nanorods along the gas flow direction on the SiO2/Si substrate. It can be attributed to the concentration gradient of the gas phase MoO3 along the gas flow direction, which impacts the average growing rate of the MoS2 crystals. The MoS2 domains experience a regular morphology transformation as well as a size change as the deposition location moves closer to the MoO3 powder. It paves the way for the development of CVD method with controlled growth parameters and opens up new venues for the tunable morphology evolution of MoS2 nanorods.

Crystal facets engineering and graphene hybridizing have been proved to be effective means to improve the photocatalytic activities of semiconductor photocatalysts in recent years. However, most of these efforts are concentrated in metal oxides. In the present study, crystal facets effect on the photocatalytic activity of metal sulfide NiS2 was studied for the first time. It was found that the {111}-faceted NiS2 nanocrystals showed improved photocatalytic activity in the degradation of various typical pollutants in water compared with {100}-faceted NiS2 nanocrystals. Moreover, through hybridizing with rGO nanosheets, the photocatalytic activity of the {111}-faceted NiS2 nanocrystals can be further improved, resulting in the complete degradation of heavy metal hexavalent chromium and organic dyes. The photocatalytic mechanism was studied in detail through theory calculation and experimental characterization. It was found that both the surface energies of Ni-terminated and S-terminated {111} facets were much higher than that of {100} facets, indicating that {111} facets were more active. Besides, rGO hybridizing can realize the effective separation of photogenerated electrons and holes. The results provide important guidance for the further development of efficient metal sulfide photocatalysts.

By a combination of the first-principles calculations and climbing image nudged elastic band method (ciNEB) we investigate structure stabilities and hydrogen evolution reaction (HER) performance of monolayer 2H-CrS2. The results suggest the free energy for the Volmer reaction in the monolayer 2H-CrS2 with S vacancy is 0.07 eV, comparable with Pt-based catalyst, and HER on the surface of the monolayer is prone to the Volmer-Heyrovsky mechanism with no energy barrier. We propose that high HER performance stems from the reduction of the energy level of d-band center. Additionally, the S vacancy leads to defect states in the middle of electronic bandgap and the reduction of potential barrier between the S atom layer and the vacuum, which is conducive to improve HER performance.

One-dimensional NiS2 nanotube arrays and nanorod arrays are controllably grown on Ni foam surface. The electrocatalytic test shows that the NiS2 nanotube arrays require competitive overpotentials of 209 mV for HER and 367 mV for OER (to achieve a current density of 50 mA/cm2), respectively, which are much lower than the NiS2 nanorod arrays and other NiS2 nanostructures reported before. Specifically, the NiS2 nanotube arrays can be employed as an efficient bi-functional catalyst for overall water splitting, with a low cell voltage (1.58 V) to deliver a current density of 10 mA/cm2. The outstanding performance can be attributed to the special structural characteristics of nanotubes, which have high specific surface areas along with abundant active sites. The present study not only enriches the morphology of NiS2 nanostructures for highly efficient electrocatalytic reaction, but also provides an interesting self-assembly path for the synthesis of one-dimensional NiS2 nanostructures.

Lead sulfide (PbS) is a significant short-wave infrared (1 to 3 μm) sensitive direct-bandgap semiconductor which has been broadly applied as the sensitizer in infrared detector and solar cell, yet low-cost preparation of high-quality PbS thin film remains challenging. Herein, we propose an epitaxial mechanism for preparing centimeter-scale and highly-oriented PbS polycrystalline thin films via convenient low-pressure chemical vapor deposition (LPCVD) technology. The crystallinity of PbS thin film can be remarkably improved by initial nucleation density conditions that can be modulated by substrate temperature. Furthermore, we discover that PbS thin film detectors of high crystallinity is fast responsive (80 μs) to short-wave infrared (0.98, 2.3 μm) due to its low density of structure defects originating from grain boundaries. Our work reinvents a traditional infrared semiconductor thin film with highly-crystalline nature and large area via low-cost thermal evaporation method. Together with fast response and room-temperature high sensitivity (NEP = 4.32 nW/Hz1/2), the as-grown PbS thin films open a new avenue towards large format infrared imaging.

Co-based phosphides are considered to be highly promising electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). However, their electrocatalytic efficiencies are greatly limited by the weak water dissociation process and unsatisfactory adsorption ability toward reaction intermediates. Herein, novel Mn-doped CoP/Ni(PO3)2 heterostructure array electrocatalysts which are composed of highly dispersed Ni(PO3)2 nanoclusters that are tightly wrapped on Mn-doped CoP nanowire arrays are designed. An electrocatalytic performance test suggested that the heterostructure arrays exhibited competitive electrocatalytic performance toward both HER and OER, which needed overpotentials of 116 and 245 mV to drive a current of 10 mA/cm2, respectively. Encouragingly, a symmetric two electrode water splitting system constructed by the heterostructure arrays required an ultralow cell voltage, suggesting the potential in overall water splitting. First-principles calculations combined with experimental characterization were further performed to clarify the electrocatalytic mechanism. On the one hand, effective doping of Mn atoms could optimize the surface electronic structure of CoP and promote the intrinsic activity. On the other hand, the compact and abundant heterogeneous interface between Ni(PO3)2 and CoP not only made more active sites exposed but also promoted the effective adsorption of intermediate reaction species on the catalyst surface. This work provides a new strategy to improve electrocatalytic performance of Co-based phosphides through the synergistic coupling of metal-doping and phosphate surface decoration, which will greatly promote the development of highly efficient electrocatalysts for overall water splitting.

As a clean and effective approach, the introduction of external magnetic fields to improve the performance of catalysts has attracted extensive attention. Owing to its room-temperature ferromagnetism, chemical stability, and earth abundance, VSe2 is expected to be a promising and cost-effective ferromagnetic electrocatalyst for the accomplishment of high-efficient spin-related OER kinetics. In this work, a facile pulsed laser deposition (PLD) method combined with rapid thermal annealing (RTA) treatment is used to successfully confine monodispersed 1T-VSe2 nanoparticles in amorphous carbon matrix. As expected, with external magnetic fields of 800 mT stimulation, the confined 1T-VSe2 nanoparticles exhibit highly efficient oxygen evolution reaction (OER) catalytic activity with an overpotential of 228 mV for 10 mA cm-2 and remarkable durability without deactivation after >100 h OER operation. The experimental results together with theoretical calculations illustrate that magnetic fields can facilitate the surface charge transfer dynamics of 1T-VSe2 , and modify the adsorption-free energy of *OOH, thus finally improving the intrinsic activity of the catalysts. This work realizes the application of ferromagnetic VSe2 electrocatalyst in highly efficient spin-dependent OER kinetics, which is expected to promote the application of transition metal chalcogenides (TMCs) in external magnetic field-assisted electrocatalysis.

Advanced MaterialsVolume 35, Issue 32 2370227 FrontispieceFree Access Interlayer-Confined NiFe Dual Atoms within MoS2 Electrocatalyst for Ultra-Efficient Acidic Overall Water Splitting (Adv. Mater. 32/2023) Zhenzhen Jiang, Zhenzhen Jiang Jiangxi Key Laboratory of Nanomaterials and Sensors, School of Physics, Communication and Electronics, Jiangxi Normal University, 99 Ziyang Avenue, Nanchang, Jiangxi, 330022 ChinaSearch for more papers by this authorWenda Zhou, Wenda Zhou School of Materials Science and Engineering, Anhui University, 111 Jiulong Road, Hefei, Anhui, 230601 ChinaSearch for more papers by this authorCe Hu, Ce Hu Jiangxi Key Laboratory of Nanomaterials and Sensors, School of Physics, Communication and Electronics, Jiangxi Normal University, 99 Ziyang Avenue, Nanchang, Jiangxi, 330022 ChinaSearch for more papers by this authorXingfang Luo, Xingfang Luo Jiangxi Key Laboratory of Nanomaterials and Sensors, School of Physics, Communication and Electronics, Jiangxi Normal University, 99 Ziyang Avenue, Nanchang, Jiangxi, 330022 ChinaSearch for more papers by this authorWei Zeng, Wei Zeng Jiangxi Key Laboratory of Nanomaterials and Sensors, School of Physics, Communication and Electronics, Jiangxi Normal University, 99 Ziyang Avenue, Nanchang, Jiangxi, 330022 ChinaSearch for more papers by this authorXunguo Gong, Xunguo Gong Jiangxi Key Laboratory of Nanomaterials and Sensors, School of Physics, Communication and Electronics, Jiangxi Normal University, 99 Ziyang Avenue, Nanchang, Jiangxi, 330022 ChinaSearch for more papers by this authorYong Yang, Yong Yang Jiangxi Key Laboratory of Nanomaterials and Sensors, School of Physics, Communication and Electronics, Jiangxi Normal University, 99 Ziyang Avenue, Nanchang, Jiangxi, 330022 ChinaSearch for more papers by this authorTing Yu, Ting Yu Jiangxi Key Laboratory of Nanomaterials and Sensors, School of Physics, Communication and Electronics, Jiangxi Normal University, 99 Ziyang Avenue, Nanchang, Jiangxi, 330022 ChinaSearch for more papers by this authorWen Lei, Wen Lei Department of Electrical, Electronic and Computer Engineering, The University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009 AustraliaSearch for more papers by this authorCailei Yuan, Cailei Yuan Jiangxi Key Laboratory of Nanomaterials and Sensors, School of Physics, Communication and Electronics, Jiangxi Normal University, 99 Ziyang Avenue, Nanchang, Jiangxi, 330022 ChinaSearch for more papers by this author Zhenzhen Jiang, Zhenzhen Jiang Jiangxi Key Laboratory of Nanomaterials and Sensors, School of Physics, Communication and Electronics, Jiangxi Normal University, 99 Ziyang Avenue, Nanchang, Jiangxi, 330022 ChinaSearch for more papers by this authorWenda Zhou, Wenda Zhou School of Materials Science and Engineering, Anhui University, 111 Jiulong Road, Hefei, Anhui, 230601 ChinaSearch for more papers by this authorCe Hu, Ce Hu Jiangxi Key Laboratory of Nanomaterials and Sensors, School of Physics, Communication and Electronics, Jiangxi Normal University, 99 Ziyang Avenue, Nanchang, Jiangxi, 330022 ChinaSearch for more papers by this authorXingfang Luo, Xingfang Luo Jiangxi Key Laboratory of Nanomaterials and Sensors, School of Physics, Communication and Electronics, Jiangxi Normal University, 99 Ziyang Avenue, Nanchang, Jiangxi, 330022 ChinaSearch for more papers by this authorWei Zeng, Wei Zeng Jiangxi Key Laboratory of Nanomaterials and Sensors, School of Physics, Communication and Electronics, Jiangxi Normal University, 99 Ziyang Avenue, Nanchang, Jiangxi, 330022 ChinaSearch for more papers by this authorXunguo Gong, Xunguo Gong Jiangxi Key Laboratory of Nanomaterials and Sensors, School of Physics, Communication and Electronics, Jiangxi Normal University, 99 Ziyang Avenue, Nanchang, Jiangxi, 330022 ChinaSearch for more papers by this authorYong Yang, Yong Yang Jiangxi Key Laboratory of Nanomaterials and Sensors, School of Physics, Communication and Electronics, Jiangxi Normal University, 99 Ziyang Avenue, Nanchang, Jiangxi, 330022 ChinaSearch for more papers by this authorTing Yu, Ting Yu Jiangxi Key Laboratory of Nanomaterials and Sensors, School of Physics, Communication and Electronics, Jiangxi Normal University, 99 Ziyang Avenue, Nanchang, Jiangxi, 330022 ChinaSearch for more papers by this authorWen Lei, Wen Lei Department of Electrical, Electronic and Computer Engineering, The University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009 AustraliaSearch for more papers by this authorCailei Yuan, Cailei Yuan Jiangxi Key Laboratory of Nanomaterials and Sensors, School of Physics, Communication and Electronics, Jiangxi Normal University, 99 Ziyang Avenue, Nanchang, Jiangxi, 330022 ChinaSearch for more papers by this author First published: 10 August 2023 https://doi.org/10.1002/adma.202370227AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Graphical Abstract Water Splitting In article number 2300505, Cailei Yuan and co-workers report an ingenious approach to assemble Ni and Fe dual atoms into the interlayer of MoS2. The interlayer-confined structure provides a microenvironment highly boosting the catalytic process, and meanwhile a protective “shelter” for active metal atoms away from acid corrosion, agglomeration, and detachment. The interlayer-confined strategy provides a new direction for single-atom catalysts development in the future. Volume35, Issue32August 10, 20232370227 RelatedInformation

Engineering heterointerfaces between metal and alloy to facilitate charge transfer would be an attractive strategy for superefficient electrocatalysis. Herein, a simple xerogel-pyrolysis strategy has been designed to prepare an advanced bifunctional electrocatalyst, Co/Co7Fe3 confined by a porous N-doped carbon nanosheets/CNTs composite (Co/Co7Fe3@PNCC). The formative Co/Co7Fe3 heterostructure promoted the charge transfers from metal Co to active alloy Co7Fe3, thus reducing the energy barrier of the oxygen reduction reaction and improving the catalytic kinetics and active surface area for the oxygen evolution reaction. The PNCC provided monodispersed confined space for Co/Co7Fe3 particles, which also owned a high specific surface area for ions/gases diffusion. Therefore, Co/Co7Fe3@PNCC exhibited excellent bifunctional oxygen catalysis activities and durability with an ultralow polarization gap (ΔE) of only 0.64 V. When practically adopted as an air electrode in ZAB, a large open-circuit voltage of 1.534 V, a maximum power density of 211.82 mW cm–2, an ultrahigh specific capacity of 807.33 mAh g–1, and superior durability over 800 h were obtained. This catalyst design concept offers a facile strategy toward modulating electronic structure to achieve efficient bifunctional electrocatalysts for ZAB.

Carbon-based materials are the most advantageous candidates for anode in sodium-ion batteries (SIBs). Nevertheless, their practical utilization has been hampered by their low reversible capacity and poor cyclic performance. In this study, novel double-shell and hierarchical porous N-doped carbon nanocages (DHNCNs) were prepared by a soft template-assisted strategy in the presence of ZIF-8 as the matrix, dopamine hydrochloride as the nitrogen and carbon source, and F127/TMB as the soft template. The study found that the carbonization temperature has a significant impact on the surface area, pore volume, interlayer distance, defect concentration, and N content of DHNCNs, thereby altering their electrochemical performance. The DHNCNs-900 synthesized at 900 °C exhibit the best sodium-ion storage performance, including high discharge capacity of 235.5 mAh g−1 after 100 cycles at 50 mA g−1, outstanding rate performance of 209.4 mAh g−1 at 2.0 A g−1, and excellent long-term cycling stability of 171.3 mAh g−1 after 900 cycles at 500 mA g−1. The exceptional electrochemical performance of the DHNCNs-900 electrode is induced by synergistic effects of the double-shell, hierarchical porous, N-doped, and hollow structure. Additionally, the electrochemical kinetic analysis indicates that DHNCNs-900 electrode possesses a reinforced sodium-ion storage mechanism by the pseudo-capacitive-control behavior. In conclusion, this study presents a superior anode material for SIBs and exhibits a simple method for synthesizing N-doped carbon nanocage materials, holding promise for advanced energy storage systems.

This work presents a study on controlled growth of Sb2Te3 nanoplates via chemical vapor deposition and their potential applications in near-infrared photodetectors. The lateral size of the nanoplates is investigated by studying two main growth parameters: argon carrier gas flow rate and growth temperature. As the argon gas flow rate increases from 20 sccm to 60 sccm, the average lateral size of Sb2Te3 nanoplates gradually increases from 3.68 μm to 10.31 μm as the growth of Sb2Te3 nanoplate under lower argon gas flow rate is limited by the Sb2Te3 molecules delivered onto the substrate surface. In contrast, at a higher argon gas flow rate of 80 sccm, the average lateral size decreases to 8.77 μm due to the combined effect of a saturated substrate surface reaction rate and increased heat loss by convection. Similarly, the average lateral size of Sb2Te3 nanoplates progressively increases from 4.21 μm at a growth temperature of 400 °C to 10.31 μm at 410 °C, which could be ascribed to the limited reaction rate of active Sb2Te3 molecules/atoms on the substrate surface at lower growth temperature. The average size then saturates at 10.06 μm at 415 °C upon further increasing the growth temperature as the growth of Sb2Te3 nanoplates is limited by the amount of vaporized Sb2Te3 molecules delivered onto the substrate surface. The fabricated photodetector based on Sb2Te3 nanoplates presents a wide spectral response from 400 to 980 nm, with a maximum photo-response observed at 850 nm. Notably, the photo-response time of the Sb2Te3 nanoplate photodetector is measured as small as 64 μs, indicating its ultrafast photo-response characteristics. The photodetector also exhibits good performance with a responsivity of 155.6 mA W−1 and a specific detectivity of 1.68 × 109 Jones at 850 nm with a light power intensity of 130.0 mW cm−2.

The delineation of tumor target and organs-at-risk is critical in the radiotherapy treatment planning. Automatic segmentation can be used to reduce the physician workload and improve the consistency. However, the quality assurance of the automatic segmentation is still an unmet need in clinical practice. The patient data used in our study was a standardized dataset from AAPM Thoracic Auto-Segmentation Challenge. The OARs included were left and right lungs, heart, esophagus, and spinal cord. Two groups of OARs were generated, the benchmark dataset manually contoured by experienced physicians and the test dataset automatically created using a software AccuContour. A resnet-152 network was performed as feature extractor, and one-class support vector classifier was used to determine the high or low quality. We evaluate the model performance with balanced accuracy, F-score, sensitivity, specificity and the area under the receiving operator characteristic curve. We randomly generated contour errors to assess the generalization of our method, explored the detection limit, and evaluated the correlations between detection limit and various metrics such as volume, Dice similarity coefficient, Hausdorff distance, and mean surface distance. The proposed one-class classifier outperformed in metrics such as balanced accuracy, AUC, and others. The proposed method showed significant improvement over binary classifiers in handling various types of errors. Our proposed model, which introduces residual network and attention mechanism in the one-class classification framework, was able to detect the various types of OAR contour errors with high accuracy. The proposed method can significantly reduce the burden of physician review for contour delineation.

Purpose: We aims to examine the impact of different head tilt angles on the dose distribution in the whole-brain target area and organs at risk. It also aims to determine the head tilt angle to achieve optimal radiation therapy outcomes. Methods: CT images were collected from 8 brain metastases patients at 5 different groups of head tilt angle. The treatment plans were designed using the volumetric modulated arc therapy (VMAT) technique. The 5 groups of tilt angle were as follows: [0,10), [10,20), [20,30), [30,40), and [40,45]. The analysis involved assessing parameters such as the uniformity index, conformity index, average dose delivered to the target, dose coverage of the target, hot spots within the target area, maximum dose, and average dose received by organs at risk. Additionally, the study evaluated the correlation between hippocampal dose and other factors and established linear regression models. Results: Significant differences in dosimetric results were observed between the [40,45] and [0,10) head tilt angles. The [40,45] angle showed significant differences compared to the [0,10) angle in the average dose in the target area, dose uniformity, hotspots in the target area, maximum hippocampal dose, maximum dose in the lens, and average dose in the lens. There is a moderate correlation between the maximum dose in the hippocampi and the PTV length. Likewise, the mean dose in the hippocampi is significantly correlated with the hippocampi length. Conclusion: The VMAT plan with a head tilt angle of [40,45] met all dose constraints and demonstrated improved uniformity of the target area while reducing the dose to organs at risk. Furthermore, the linear regression models suggest that increasing the head tilt angle within the current range of [0,45] is likely to lead to a decrease in the average hippocampal dose.

The electronic and magnetic properties of Cu-doped perovskite La0.7Ca0.3Mn1−xCuxO3 obtained by doping Cu on its Mn sites have been studied. The perovskite structure was found to remain intact up to the highest doping level of x=0.20. At low Cu concentration (x=0.05) the temperature-dependence of resistivity of the material exhibited up to two peaks corresponding to the magnetic transitions from the PM to the FM phase, and from the FM to the AFM phase. In general, the doping level was found to suppress the ferromagnetic ordering of the material, increase its resistivity, and produce large values of magnetoresistance near the resistivity peak. These results were explained as due to the formation of the antiferromagnetic phase.

Ge/GeO2 core/shell nanoparticles embedded in an Al2O3 gate dielectrics matrix were fabricated. The core/shell nanoparticles consist of a single-crystal Ge core and a tiny GeO2 nanocrystallites shell. The high percentage of defects located at the shell surfaces and the grain boundaries between the Ge/GeO2 nanocrystals or disorderly arranged areas in the GeO2 shell induce a significant phonon localization effect, which leads to enhanced radiative recombination and thus it enhances the photoluminescence intensity. We believe that the findings presented here provide physical insight and offer useful guidelines to controllably modify the optical properties of indirect semiconductors through defect engineering.

Uniform hierarchical micro/nanostructured TiO2 microspheres (MTS) composed of well-crystallized anatase phase nanoparticles were first fabricated by a fast and facile microwave-assisted hydrothermal method, then Ag nanoparticles were further decorated onto MTS by a simple polyvinylpyrrolidone-assisted reduction method (the product was denoted as Ag-MTS). The characterization data indicated that the Ag-MTS sample had a high specific surface area (121 m2 g−1) and abundant mesopores with Ag nanoparticles homogeneously dispersed among the TiO2 nanoparticles. The photocatalytic performance of Ag-MTS for the removal of organic dye methyl orange was evaluated. It was found that Ag-MTS showed an enhanced photocatalytic activity when compared to MTS and commercially available nano-sized TiO2 Degussa P25. The hierarchical micro/nanostructure (high specific surface area and abundant mesopores properties) together with Ag decoration contributed to the enhanced photocatalytic activity. In addition, Ag-MTS showed easy recovery feature in the recovery process and high durability in the recycling test, which was expected to be a practical photocatalyst used for wastewater treatment.