Protonation of g-C3N4 and its temperature-sensing properties

Graphitic carbon nitride (g-C3N4) was obtained through heat treatment of melamine and the g-C3N4 flakers were then protonated with sulfuric acid. Their crystalline structure, microstructure, and optical properties were systematically studied. Our results show that protonation treatment did not change the crystal structure of g-C3N4 but mitigated the agglomeration problem (i.e., decrease of the particle size), and resulted in certain degree of exfoliation. A blue shift in the ultraviolet–visible absorption measurement was observed. Temperature-dependent photoluminescence measurements were carried out on the protonated g-C3N4 sample, where a linear temperature-dependent behavior was observed in a wide temperature range with a sensitivity of 0.83%K−1. Our results showed that the protonated g-C3N4 is a promising material for temperature sensors.