Operando detection of dissolved oxygen in fluid solution using a submersible rapid scan EPR on a chip dipstick sensor

Area of Science:

• Analytical Chemistry
• Materials Science
• Physical Chemistry

Background:

• Electron Paramagnetic Resonance (EPR) is a powerful technique for studying unpaired electrons.
• Traditional EPR spectrometers are limited by resonator-based designs, restricting in-situ measurements.
• Developing portable and sensitive EPR devices is crucial for broader applications.

Purpose of the Study:

• To develop a microchip-integrated EPR spectrometer (EPRoC) for in-situ measurements.
• To enhance EPR sensitivity using rapid scan techniques (RS-EPRoC).
• To demonstrate the EPRoC device's capability for monitoring dissolved oxygen in aqueous solutions.

Main Methods:

• Integration of a voltage-controlled oscillator (VCO) coil as a simultaneous microwave source and detector on a microchip.
• Utilization of a dipstick EPRoC sensor combined with frequency-swept frequency modulated rapid scan EPR.
• Measurement of triarylmethyl (trityl, Ox071) oxygen-sensitive probes in aqueous solutions with varying oxygen concentrations.

Main Results:

• The EPRoC device successfully operated within the sample solution.
• Rapid scan EPR-on-a-chip (RS-EPRoC) demonstrated improved sensitivity.
• The device accurately monitored changes in dissolved oxygen concentration in real-time.

Conclusions:

• The EPR-on-a-chip (EPRoC) device overcomes limitations of traditional EPR spectrometers.
• RS-EPRoC significantly enhances sensitivity for EPR measurements.
• EPRoC is a viable technology for online monitoring of dissolved oxygen in fluid solutions.