Harnessing Photoluminescent Properties of Carbon Nitride Nanosheets in a Hierarchical Matrix

Rapid screening of polycyclic aromatic hydrocarbons (PAHs), a large class of toxic and carcinogenic compounds, is highly desirable for environmental and food safety. In principle, a photoluminescent (PL) assay is a potential route, but demands highly efficient and stable, low cost, and environment‐friendly photoactive materials. 2D carbon nitride nanosheets (CNNS) that have triggered increasing interest may meet all these requirements. However, conventional applications of CNNS are restricted in aqueous solution, in which the long‐term dispersibility is difficult to be addressed. Here, the harnessing of unique PL properties of CNNS is reported by dispersing them in a hierarchical polymeric matrix, driven by electrostatic interactions. Such a configuration not only enables a solid‐state host to perpetually maintain homogeneous dispersibility of CNNS but also processes free channels for sufficient mass transfer. Moreover, the nanohybrid inherits the unique PL properties of CNNS. Further using β‐CD as the molecular recognition unit, an economic, highly selective and sensitive paper‐based PL sensor for PAHs is constructed via an inner‐filter effect. This work opens a new avenue in harnessing unique PL properties of CNNS in solid state with superior stability for a variety of potential sensing applications, especially for point‐of‐care testing and/or in developing countries. 2D metal‐free carbon nitride (CN) has drawn worldwide interest, for example, in the field of optical sensing. However, previous efforts have largely relied on CN dispersion in solutions, in which the long‐term dispersibility is challenging. Here, the photoluminescent properties of 2D CN nanosheets is unlocked by introducing CN into a solid‐state hierarchical matrix, which not only maintains perpetual dispersibility but also exhibits superior performance in polycyclic aromatic hydrocarbon photoluminescent sensing.