A 'turn-off' fluorescence sensor for selective Hg(II) based on phenothiazine derivative

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Materials Science

Background:

• Heavy metal contamination, particularly mercury (Hg(II)), poses significant risks to environmental safety and human health.
• Developing sensitive and selective detection methods for Hg(II) is critical for environmental monitoring and remediation.

Purpose of the Study:

• To synthesize and characterize a novel fluorescence 'on-off' sensor, (E)-2-((10-octyl-10H-phenothiazin-3-yl)methylene)hydrazine-1-carbothioamide (PTZHC).
• To evaluate the sensor's efficacy in detecting Hg(II) ions in the presence of other metal ions.

Main Methods:

• Synthesis of PTZHC and its characterization using FTIR and 1H-NMR spectroscopy.
• Fluorescence spectroscopy to monitor the 'on-off' sensing mechanism upon Hg(II) coordination.
• Job's plot analysis to determine the binding stoichiometry between PTZHC and Hg(II).
• Computational studies including DFT and TD-DFT to understand the electronic and geometric properties.

Main Results:

• PTZHC was successfully synthesized and characterized.
• The sensor exhibited selective fluorescence quenching in the presence of Hg(II) ions, even with interfering metal ions.
• A low limit of detection (2.5 × 10^-8 M) was achieved.
• Job's plot analysis indicated a 1:1 binding stoichiometry between PTZHC and Hg(II) in a CH3CN/H2O mixture.

Conclusions:

• PTZHC is a promising fluorescent sensor for the sensitive and selective detection of Hg(II) ions.
• The study provides insights into the sensing mechanism and binding interactions at a molecular level.
• This work contributes to the development of advanced tools for environmental heavy metal monitoring.