Plasmonic Imaging of Electrochemical Reactions of Single Nanoparticles

Abstract

Electrochemical reactions are involved in many natural phenomena, and are responsible for various applications, including energy conversion and storage, material processing and protection, and chemical detection and analysis. An electrochemical reaction is accompanied by electron transfer between a chemical species and an electrode. For this reason, it has been studied by measuring current, charge, or related electrical quantities. This approach has led to the development of various electrochemical methods, which have played an essential role in the understanding and applications of electrochemistry. While powerful, most of the traditional methods lack spatial and temporal resolutions desired for studying heterogeneous electrochemical reactions on electrode surfaces and in nanoscale materials. To overcome the limitations, scanning probe microscopes have been invented to map local electrochemical reactions with nanometer resolution. Examples include the scanning electrochemical microscope and scanning electrochemical cell microscope, which directly image local electrochemical reaction current using a scanning electrode or pipet. The use of a scanning probe in these microscopes provides high spatial resolution, but at the expense of temporal resolution and throughput. This Account discusses an alternative approach to study electrochemical reactions. Instead of measuring electron transfer electrically, it detects the accompanying changes in the reactant and product concentrations on the electrode surface optically via surface plasmon resonance (SPR). SPR is highly surface sensitive, and it provides quantitative information on the surface concentrations of reactants and products vs time and electrode potential, from which local reaction kinetics can be analyzed and quantified. The plasmonic approach allows imaging of local electrochemical reactions with high temporal resolution and sensitivity, making it attractive for studying electrochemical reactions in biological systems and nanoscale materials with high throughput. The plasmonic approach has two imaging modes: electrochemical current imaging and interfacial impedance imaging. The former images local electrochemical current associated with electrochemical reactions (faradic current), and the latter maps local interfacial impedance, including nonfaradic contributions (e.g., double layer charging). The plasmonic imaging technique can perform voltammetry (cyclic or square wave) in an analogous manner to the traditional electrochemical methods. It can also be integrated with bright field, dark field, and fluorescence imaging capabilities in one optical setup to provide additional capabilities. To date the plasmonic imaging technique has found various applications, including mapping of heterogeneous surface reactions, analysis of trace substances, detection of catalytic reactions, and measurement of graphene quantum capacitance. The plasmonic and other emerging optical imaging techniques (e.g., dark field and fluorescence microscopy), together with the scanning probe-...

Electrochemistry of CdSe Quantum Dots Studied by Single Molecule Spectroscopy

“…Single NP electrochemistry has been combined with several optical methods for gaining an experimental correlation between an electrochemically registered event and the localization of the NP at or near the electrode surface. So far, surface plasmon resonance, dark field scattering or Raman scattering were utilized for this purpose. Sun and co‐workers combined surface plasmon resonance (SPR) and simultaneous electrochemical recording to study the electrochemical events of single Ag NPs.…”

Active plasmonic nanoantenna: an emerging toolbox from photonics to neuroscience

“…In addition, they showed that the surface plasmon modes of the PNAs with elongated morphologies (plate or rod shape) exhibited higher oscillator strengths and therefore were more sensitive to surface charge perturbations with respect to PNAs with spherical shapes [202]. Faradaic charging arises from electrochemical reactions that take place at the interface between PNAs and their surrounding electrolyte [158,[209][210][211][212][213]. This process involves electron transfer between the chemical species and the plasmonic nanostructures.…”

The promise of antireflective gold electrodes for optically monitoring the electro-deposition of single silver nanoparticles

“…Several optical microscopy techniques have already been successfully coupled to electrochemistry. The groups of Tao and of his collaborators [12][13][14] used the surface plasmon resonance microscopy (SPRM) to image different electrochemical processes occurring at individual nano-domains or NPs. Particularly related to the present work, they demonstrated the ability to image the electro-dissolution of single silver NPs.…”