One step preparation of proton-functionalized photoluminescent graphitic carbon nitride and its sensing applications

Graphitic carbon nitride (g-C3N4) has aroused extensive attention in the field of catalysis, sensing and bioimaging due to its unique structure and superior optical properties. Reported synthesis procedures for g-C3N4 usually need high reaction temperatures and long reaction times; in addition, the macro size and poor water solubility of bulk g-C3N4 significantly limit its practical applications. Herein, we report for the first time a fast one-step approach for the preparation of proton-functionalized g-C3N4 under microwave with thiourea and HNO3 as source materials. After ultrasonic stripping of the raw material for 4 h, well dispersed g-C3N4 nanosheets in solution are readily obtained. The g-C3N4 nanosheets are positively charged and ultrathin, with a planar size of ca. 60-90 nm and a thickness of 3.3 nm. The presence of hemin causes a significant quenching on the fluorescence of g-C3N4, and a sensitive and selective hemin sensing approach is thus developed, with a detection limit of 0.17 mu g mL(-1). The method is further utilized for the analysis of hemin in a series of biological samples.