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

Area of Science:

• Chemical Sensing
• Analytical Chemistry
• Materials Science

Background:

• Mercury ions (Hg2+) pose significant environmental and health risks.
• Development of selective and sensitive detection methods for Hg2+ is crucial.
• Colorimetric sensors offer a simple and rapid approach for ion detection.

Purpose of the Study:

• To synthesize and characterize a novel colorimetric sensor (L1) for mercury ion detection.
• To evaluate the selectivity and sensitivity of sensor L1 towards Hg2+ in various solutions.
• To elucidate the recognition mechanism of the sensor for Hg2+.

Main Methods:

• Synthesis of a colorimetric sensor (L1) incorporating thiosemicarbazide and nitrophenyl moieties.
• Colorimetric and UV-vis spectrophotometric analysis for Hg2+ detection.
• Investigation of interference from other metal cations.
• Evaluation of the recognition mechanism using UV-vis and 1H NMR spectroscopy.

Main Results:

• Sensor L1 demonstrated high selectivity and sensitivity for Hg2+ in DMSO and DMSO/H2O solutions.
• A distinct color change from brown to colorless was observed upon Hg2+ addition.
• No significant interference was observed from common metal cations (Ca2+, Mg2+, Cd2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Pb2+, Ag+, Cr3+).
• Detection limits were determined to be 5.0 × 10(-6) M (visual) and 1.0 × 10(-7) M (UV-vis).
• The sensor selectively binds Hg2+ via CS and CO groups, forming a 1:1 complex and inducing an ICT transition.

Conclusions:

• The synthesized sensor L1 is a promising tool for the selective and sensitive colorimetric detection of mercury ions.
• The sensor's mechanism involves the formation of a stable complex with Hg2+, leading to a visual color change.
• This sensor holds potential for environmental monitoring and analytical applications requiring Hg2+ quantification.