A practical graphitic carbon nitride (g-C₃N₄)based fluorescence sensor for the competitive detection of trithiocyanuric acid and mercury ions

A fluorescent sensor for the detection of trithiocyanuric acid (TCA)and Hg²⁺ was developed based on competitive interactions: non-covalent stacking between g-C₃N₄ and TCA vs coordinative interaction between TCA and Hg²⁺. Electrostatic simulations were used to evaluate the interactions and help describe the detection mechanism. Moreover, normalized 2D fluorescence contour plots have been used to understand the fluorescence phenomenon. When TCA was added into a g-C₃N₄ nanosheet solution free of Hg²⁺, TCA interacted with g-C₃N₄ nanosheets via hydrogen bonding and π-π interactions, resulting in fluorescence quenching of the g-C₃N₄ nanosheets. However, upon the addition of Hg²⁺, the fluorescence of the TCA-g-C₃N₄ nanosheet hybrid system was restored, due to coordination of Hg²⁺ with TCA through the S atoms, breaking the TCA-g-C₃N₄ stacking interaction. Our results provide a new approach for the design of multifunctional nanosensors suitable for the detection of environmental pollutants.