Plasmonic Imaging of the Interfacial Potential Distribution on Bipolar Electrodes

Abstract

Bipolar electrochemistry is based on the gradient distribution of free-electron density along an electrically isolated electrode, which causes a positive electrode potential at one end and a negative potential at the other, allowing for wide applications in analytical chemistry and materials science. To take full advantage of its wireless and high-throughput features, various types of optical probes, such as pH indicators and fluorescence and electrochemiluminescence reagents, have often been used to indirectly monitor the interfacial electron transfer through chromogenic or fluorogenic reactions. Herein, we report the first probe-free imaging approach that can directly visualize the distribution of the interfacial potential in bipolar electrodes, providing essential information for the validation and development of the theory and applications of bipolar electrochemistry. This approach is based on the sensitive dependence of surface plasmon resonance imaging on the local electron density in the electrode, which enables the direct mapping of potential with a spatial resolution close to the optical diffraction limit, a temporal resolution of 50 ms, and a sensitivity of 10 mV. In addition, in contrast to previous optical readouts that relied on faradaic reactions, the present work achieved the impedance-based measurements under non-faradaic conditions. It is anticipated that this technique will greatly expand the application of bipolar electrochemistry as a platform for chemical and biosensing.

Combining Electrodeposition and Optical Microscopy for Probing Size‐Dependent Single‐Nanoparticle Electrochemistry

“…Such a situation, known as the electrochemical Ostwald ripening, is monitored in Figure but cannot be quantified from direct EC measurement as no overall current is exchanged with the exterior. Optical microscopies are able to detail its dynamic, as reported for Galvanic replacement or bipolar electrochemical systems …”

Combining Electrodeposition and Optical Microscopy for Probing Size‐Dependent Single‐Nanoparticle Electrochemistry

“…Indeed, Equation (7) suggests that conductive substrates structured with Ag NPs of different sizes are unstable.E ven in the absence of external polarization, when electrically contacted, as mall and an eighboring large NP create aG alvani corrosion cell;t he large NP growing at the expense of the small one.S uch as ituation, known as the electrochemical Ostwald ripening,i sm onitored in Figure 3 but cannot be quantified from direct EC measurement as no overall current is exchanged with the exterior.O ptical microscopies are able to detail its dynamic,a sr eported for Galvanic replacement [3f] or bipolar electrochemical systems. [17] An array of electrodeposited Ag NPs of various sizes was washed and exposed to ultra-pure water, while being monitored by BALM. The I BALM transients at various locations (NPs or background) were analyzed;n ormalized from the I BALM values at the same location on the first image they reflect local Ag material deposition/dissolution.…”

Simple One‐Step Fabrication of Semiconductive Lateral Heterostructures Using Bipolar Electrodeposition

“…The electric field is produced using two feeder electrodes connected to an external power supply which in turn causes an Ohmic drop in the solution. Therefore, an interfacial potential polarization appears between the metallic substrate and the solution that can promote electrochemical reactions at the edges of the bipolar electrode . The BPE has shown its capability for designing of chemical composition gradients over conductive substrates.…”