Stimuli-responsive microgels with fluorescent and SERS activities for water and temperature sensing

Area of Science:

• Materials Science
• Analytical Chemistry
• Nanotechnology

Background:

• Stimulus-responsive microgels are emerging as promising materials for controllable sensing devices.
• Developing dual-responsive platforms for simultaneous detection of multiple analytes remains a challenge.

Purpose of the Study:

• To fabricate a dual-responsive microgel platform for on-spot fluorescence and SERS quantification of water and temperature.
• To investigate the sensing capabilities and stability of the developed microgel-based sensor.

Main Methods:

• In-situ encapsulation of 4,4'-dimercaptoazobenzene (DMAB), meso-formyl-1,3,5,7-tetramethyl pyrromethene fluoroborate (FPF) probe, and Ag nanoparticles (AgNPs) into polyvinyl alcohol (PVA) microgels.
• Utilizing fluorescence and surface-enhanced Raman scattering (SERS) for analyte detection.
• Evaluating the response to varying water concentrations and temperatures.

Main Results:

• The microgels demonstrated ultra-sensitive and reversible detection of water (detection limit 10^-4% v/v) via SERS.
• Water presence triggered FPF conversion, enabling visual water assay through enhanced fluorescence.
• SERS signals were precisely tuned by the thermo-sensitive microgel substrate for temperature monitoring (32-50 °C).
• The sensor exhibited fast response (2 min) and excellent stability for detecting water in organic solvents and pharmaceuticals.

Conclusions:

• The fabricated hybrid microgels serve as a smart, dual-responsive sensor for simultaneous water and temperature monitoring.
• This platform shows potential for point-of-care (POC) analysis and advanced molecular recognition applications.