Rhodamine-based Hg2+-selective chemodosimeter in aqueous solution: fluorescent OFF-ON

Area of Science:

• Analytical Chemistry
• Environmental Science
• Materials Science

Background:

• Mercury (Hg2+) is a toxic heavy metal pollutant with significant environmental and health impacts.
• Developing selective and sensitive detection methods for Hg2+ is crucial for environmental monitoring.
• Fluorescent and colorimetric sensors offer advantages in sensitivity and visual detection.

Purpose of the Study:

• To develop a novel chemodosimeter for the selective detection of mercury ions (Hg2+).
• To achieve dual-mode detection (fluorescent and colorimetric) with a broad pH operating range.
• To investigate the sensing mechanism and selectivity of the developed chemodosimeter.

Main Methods:

• Synthesis of N-(Rhodamine-6G)lactam-N'-phenylthiourea-ethylenediamine (1).
• Spectroscopic analysis (UV-Vis absorption and fluorescence) in aqueous solutions.
• Testing selectivity against various competitive metal cations (Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Pb2+, Cd2+, Ca2+, Mg2+, K+, Na+).
• pH-dependent response studies.

Main Results:

• The chemodosimeter (1) exhibited high selectivity and sensitivity toward Hg2+.
• A broad pH operating range (pH 5-10) was demonstrated.
• Hg2+ induced a spirolactam ring opening and subsequent cyclic guanylation, leading to a dual "OFF-ON" chromogenic and fluorogenic response.
• No significant interference was observed from other tested metal ions.

Conclusions:

• N-(Rhodamine-6G)lactam-N'-phenylthiourea-ethylenediamine is an effective fluorescent and colorimetric chemodosimeter for Hg2+ detection.
• The sensor provides a reliable method for monitoring mercury in aqueous environments.
• The dual-mode detection and broad pH range enhance its practical applicability.