Two novel fluorescence “turn on” probes based on pyrazolone and thiosemicarbazide for selective recognition of In3+†

Highly selective fluorescence “turn on” probes (PTSC and TSC) based on a conjugate of pyrazolone and thiosemicarbazide were devised and synthesized. The structure was verified by ¹H NMR, ¹³C NMR and HR-MS. The probe demonstrated effectiveness, high selectivity, and specificity to capture indium ions. The fluorescence intensity of the probe solution was significantly enhanced by the addition of In³⁺. The 1 : 1 complexation between In³⁺ and probe PTSC was confirmed by Job's plot, and the limit of detection (LOD) of PTSC for In³⁺ was calculated to be 2.01 × 10⁻⁷ M. Furthermore, PTSC was produced as test strips, which have enormous potential to detect In³⁺ ions in the environment.