A highly selective colorimetric sensor for Hg²⁺ based on nitrophenyl-aminothiourea.

A simple and highly selective colorimetric sensor (L1) bearing thiosemicarbazide moiety as binding site and nitrophenyl moiety as signal group were synthesized. Sensor L1 showed great colorimetric single selectivity and high sensitivity for mercury cation in DMSO and DMSO/H(2)O binary solutions. When Hg(2+) was added to the DMSO solution of L1, dramatic color change from brown to colorless was observed. While the cations Ca(2+), Mg(2+), Cd(2+), Fe(3+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Pb(2+), Ag(+) and Cr(3+) could not cause any distinct interferer toward the recognition process for Hg(2+). The detection limit is allowable to 5.0 × 10(-6) and 1.0 × 10(-7)M level of Hg(2+) according to visual color change and UV-vis change, respectively. The recognition mechanism of the sensor toward mercury cation was evaluated in DMSO solutions by UV-vis and (1)H NMR. The sensor selectively sense Hg(2+)via the formation of a stable 1:1 complex through CS and CO group with Hg(2+). When these complex bonds formed, the sensor carried out an ICT transition induced color change.
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