Wiring proton gradients for energy conversion.

Area of Science:

• Photochemistry
• Materials Science
• Electrochemistry

Background:

• Merocyanine photoacids are light-sensitive molecules with potential applications in energy harvesting.
• Controlling their properties in solution is crucial for developing functional devices.
• Existing methods for pH control and energy conversion often lack precision and longevity.

Purpose of the Study:

• To investigate light-switchable buffer solutions based on merocyanine photoacids for photoenergy harvesting.
• To tune the photoacidity, relaxation kinetics, and solubility of merocyanine photoacids.
• To generate persistent pH gradients and electrical voltages using asymmetric light irradiation.

Main Methods:

• Utilized merocyanine photoacids in water-methanol mixtures to create tunable buffer solutions.
• Investigated the effect of solvation environment on photoacid properties.
• Interfaced solutions between two electrodes and applied asymmetric light irradiation (500 nm) to induce photoactivation and measure voltages.

Main Results:

• Achieved persistent pH gradients of approximately 4 pH units under 500 nm light.
• Generated open circuit voltages as high as 240 mV.
• Observed that generated voltages can persist for hours under steady-state irradiation.

Conclusions:

• Light-switchable buffer solutions based on merocyanine photoacids offer an efficient photoenergy harvesting system.
• Tuning the solvation environment allows precise control over photoacid properties and pH gradient formation.
• The generated electrical output rivals the performance of biological transmembrane proton pumps.