A novel thiourea-based fluorescent turn-on sensor for rapidly detecting hypochlorite through a desulfurization reaction

Excess hypochlorite (ClO⁻) is harmful to living organisms and can cause various oxidative diseases in the human body. Owing to the toxicity of ClO⁻, the development of efficient fluorescence sensors to track ClO⁻ is necessary. In this work, we report a novel thiourea-based fluorescent turn-on sensor 1-(9-ethyl-9H-carbazol-3-yl)-3-(naphthalen-1-yl)thiourea (ECNT) for recognizing ClO⁻. ECNT can detect ClO⁻ with high selectivity, relatively low interference with other analytes, and a significantly fast response time (<1 s) through a desulfurization reaction. The detection limit of ECNT for ClO⁻ is calculated as 5.59 μM. Of note, ECNT is a chemosensor that reacts the fastest with ClO⁻ among the reported thiourea-based fluorescence turn-on sensors for detecting ClO⁻. The response mechanism of ECNT to ClO⁻ is demonstrated through ¹H NMR titration, ESI mass, and density functional theory calculations.