Detecting solution pH changes using poly (N-isopropylacrylamide)-co-acrylic acid microgel-based etalon modified...

Area of Science:

• Materials Science
• Chemical Engineering
• Biomedical Engineering

Background:

• Poly (N-isopropylacrylamide)-co-acrylic acid (pNIPAm-co-AAc) microgel etalons exhibit tunable optical properties based on temperature and pH.
• These microgels undergo a volume phase transition around 32°C, affecting their swelling state.

Purpose of the Study:

• To fabricate pNIPAm-co-AAc microgel-based etalons on a quartz crystal microbalance (QCM).
• To investigate the resonant frequency changes of the QCM as a function of temperature and pH.
• To determine the sensitivity and detection limit of the system for pH sensing.

Main Methods:

• Fabrication of pNIPAm-co-AAc microgel etalons on a gold-coated QCM electrode.
• Monitoring QCM resonant frequency at varying temperatures (pH 3.0) and pH levels (constant temperatures).
• Analysis of frequency shifts attributed to microgel swelling/deswelling.

Main Results:

• Resonant frequency was lower at pH 3.0 compared to pH 7.0 below the microgel collapse transition temperature.
• The magnitude of resonant frequency change increased as temperature approached the microgel collapse transition.
• Achieved a sensitivity of 1.3×10(-8)M [H(+)]Hz(-1) with a theoretical detection limit of 390nM.

Conclusions:

• The pNIPAm-co-AAc microgel-based QCM system effectively responds to pH changes.
• The observed sensitivity and detection limit indicate potential for future biosensing applications.
• The temperature-dependent swelling behavior of microgels is crucial for sensor performance.