Gold sensing with rhodamine immobilized hydrogel-based colorimetric sensor

Area of Science:

• Materials Science
• Analytical Chemistry
• Chemical Sensing

Background:

• Gold ions (Au³⁺) are significant in various fields, necessitating accurate detection methods.
• Existing methods for Au³⁺ detection can be complex or lack selectivity.
• Development of novel optical sensors is crucial for efficient ion monitoring.

Purpose of the Study:

• To synthesize a highly sensitive and selective optical membrane sensor for Au³⁺ detection.
• To immobilize a rhodamine derivative onto an agarose hydrogel matrix.
• To investigate the sensing mechanism and performance of the developed sensor.

Main Methods:

• Synthesis of a rhodamine derivative via solvatochromism and rhodamine lactone-zwitterion equilibrium.
• Immobilization of the rhodamine derivative onto an agarose hydrogel.
• Characterization using UV-vis spectroscopy, SEM, TGA, and ATR-FTIR.
• Evaluation of sensor selectivity and sensitivity for Au³⁺ detection.
• Density Functional Theory (DFT) calculations to understand interaction mechanisms.

Main Results:

• Successful incorporation of rhodamine-lactone (RhoL) into the agarose hydrogel was confirmed.
• The sensor demonstrated high selectivity for Au³⁺ over other common metal ions.
• DFT calculations indicated stable complex formation between the sensor and Au³⁺ via cation-dipole and ion-ion interactions.
• The limit of detection (LOD) for Au³⁺ was determined to be 5 µM.

Conclusions:

• A novel optical membrane sensor for Au³⁺ detection based on a rhodamine derivative immobilized on agarose hydrogel was successfully developed.
• The sensor exhibits excellent sensitivity, selectivity, and a low limit of detection.
• This approach provides a promising, easily measurable method for Au³⁺ determination in environmental and biological applications.