All-Optical Electrochemiluminescence by Light Downconversion at BiVO₄ Photoanodes

Area of Science:

• Electrochemistry and Analytical Chemistry
• Materials Science for Sensors
• Photochemistry and Luminescence

Background:

• Electrochemiluminescence (ECL) is a powerful analytical technique but requires external power supplies, limiting portability.
• Existing all-optical ECL (AO-ECL) systems often use complex fabrication and are limited to upconversion processes (excitation wavelength > emission wavelength).
• There is a need for simpler, more portable ECL systems, particularly those operating via downconversion (excitation wavelength < emission wavelength).

Purpose of the Study:

• To develop a new sensing scheme based on all-optical ECL (AO-ECL) that eliminates the need for external electrical devices.
• To demonstrate the first AO-ECL downconversion process using a cost-effective and easily fabricated bismuth vanadate (BiVO4) electrode.
• To evaluate the system's performance for detecting hydrogen peroxide (H2O2) and cadmium ions (Cd2+).

Main Methods:

• Fabrication of a bismuth vanadate (BiVO4) electrode for AO-ECL applications.
• Utilizing the photovoltage generated by BiVO4 under light excitation to drive ECL reactions.
• Investigating the AO-ECL response of the luminol-H2O2 system using the BiVO4 electrode, including spectral analysis and potential-dependent measurements.

Main Results:

• Successfully demonstrated an AO-ECL downconversion process (excitation < emission) with BiVO4, emitting light at 510 nm.
• Observed a significant shift in ECL onset potential for H2O2 detection (from +0.3 V to -0.3 V vs Ag/AgCl) and a 2.6-fold intensity enhancement.
• Achieved a 2.2-fold increase in AO-ECL intensity for cadmium ion (Cd2+) detection, demonstrating the platform's versatility.

Conclusions:

• The developed BiVO4-based downconversion AO-ECL system offers a simplified, portable, and cost-effective alternative to traditional ECL instrumentation.
• The system exhibits strong responsiveness to H2O2 and Cd2+, indicating its potential for sensitive bioanalytical sensing.
• This technology holds promise for future development in portable bioanalytical sensors and wireless bioimaging applications.