Enhanced Photoresponsive Ultrathin Graphitic-Phase C₃N₄ Nanosheets for Bioimaging

Two-dimensional nanosheets have attracted tremendous attention because of their promising practical application and theoretical values. The atomic-thick nanosheets are able to not only enhance the intrinsic properties of their bulk counterparts but also give birth to new promising properties. Herein, we highlight an available pathway to prepare the ultrathin graphitic-phase C3N4 (g-C3N4) nanosheets by a “green” liquid exfoliation route from bulk g-C3N4 in water for the first time. The as-obtained ultrathin g-C3N4 nanosheet solution is very stable in both the acidic and alkaline environment and shows pH-dependent photoluminenscence (PL). Compared to the bulk g-C3N4, ultrathin g-C3N4 nanosheets show enhanced intrinsic photoabsorption and photoresponse, which induce their extremely high PL quantum yield up to 19.6%. Thus, benefiting from the inherent blue light PL with high quantum yields and high stability, good biocompatibility, and nontoxicity, the water-soluble ultrathin g-C3N4 nanosheet is a brand-new but promising candidate for bioimaging application.