Optically Transparent Thin-Film Electrode Chip for Spectroelectrochemical Sensing

Area of Science:

• Electrochemistry
• Analytical Chemistry
• Materials Science

Background:

• Spectroelectrochemistry combines spectroscopy and electrochemistry for in-situ analysis.
• Existing methods can be limited by electrode stability and optical transparency.
• Development of novel electrode platforms is crucial for advancing analytical techniques.

Purpose of the Study:

• To develop and characterize a novel microfabricated optically transparent thin-film electrode chip.
• To evaluate the performance of the electrode chip for spectroelectrochemical applications.
• To demonstrate the utility of the chip for both absorption and fluorescence measurements.

Main Methods:

• Fabrication of a microelectrode chip with indium tin oxide (ITO) working electrode and platinum quasi-reference/auxiliary electrodes.
• Enhancement of quasi-reference electrode stability using a solid-state Ag/AgCl layer.
• Characterization using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS).
• Electrochemical performance evaluation via cyclic voltammetry and Randles-Sevcik analysis.
• Demonstration of absorption and fluorescence spectroelectrochemistry using an optically transparent thin-layer electrode (OTTLE) setup.

Main Results:

• The electrode chip demonstrated stable and comparable performance to standard electrochemical cells.
• Randles-Sevcik analysis yielded a diffusion coefficient of 1.59 × 10^-6 cm²/s for K₃[Fe(CN)₆].
• Successful spectroelectrochemical modulation was achieved for both [Fe(CN)₆]^3-/4- (absorption) and [Ru(bpy)₃]^2+/3+ (fluorescence).
• A detection limit of 36 nM was achieved for fluorescence-based determination of [Ru(bpy)₃]²⁺.

Conclusions:

• The developed microfabricated electrode chip is a viable platform for optically transparent thin-film spectroelectrochemistry.
• The chip offers improved stability and performance suitable for sensitive analytical measurements.
• This technology advances in-situ electrochemical and spectroscopic analysis, particularly for fluorescent and absorbing species.