Monitoring Cobalt-Oxide Single Particle Electrochemistry with Subdiffraction Accuracy

Abstract

By partially overcoming the diffraction limit, superlocalization techniques have extended the applicability of optical techniques down to the nanometer size-range. Herein, cobalt oxide-based nanoparticles are electrochemically grown onto carbon nanoelectrodes and their individual catalytic properties are evaluated through a combined electrochemical-optical approach. Using dark-field white light illumination, edges superlocalization techniques are applied to quantify changes in particle size during electrochemical activation with down to 20 nm precision. It allows the monitoring of (i) the anodic electrodeposition of cobalt hydroxide material and (ii) the large and reversible volume expansion experienced by the cobalt hydroxide particle during its oxidation. Meanwhile, the particle light scattering provides chemical information such as the Co redox state transformation, which complements both the particle size and the recorded electrochemical current and provides in operando mechanistic information on particle electrocatalytic properties.

Revealing the sub-50 ms electrochemical conversion of silver halide nanocolloids by stochastic electrochemistry and optical microscopy

“…Different mechanistic insights can be gathered from the change in optical properties of single NPs associated to their electrochemistry, ranging from double layer charging at Au NPs, 16 Au oxide formation, 17 reductive growth of Ag NPs, 18 their oxidative dissolution or oxidation into pseudo-halides 19 or the growth, electrocatalysis and doping of Co oxide particles. 20,21 They also have the advantage of being able to monitor in situ both type of configurations (Brownian and adsorbed NPs).…”

Single LiBH4 nanocrystal stochastic impacts at a micro water|ionic liquid interface

“…IL samples were deposited on the BALM substrate with the help of a micropipette and were imaged under atmospheric conditions. Darkfield optical microscopy was carried out with an Olympus IX71 inverted microscope equipped with a Sony XCD-X710 CCD camera and darkfield condenser along with 10×, 40×, and 60× objectives, NA = 0.3, 0.60, and 0.70, respectively, as described in detail elsewhere [44].…”

“…[31] Herein, we expand this technique to the w|IL one, where the Galvani potential difference across the interface, − IL = ∆ IL , is controlled by electrodes immersed in either phase, allowing control and quantification of charge transfer across the LLI. Transmission electron microscopy (TEM) and stochastic impacts were used to provide NC sizing, while optical microscopies (back absorbing layer, BALM [42,43], and darkfield [28,[44][45][46]) provided in situ visualisation of the reactivity of such NCs in solution. The latter have emerged as powerful techniques for imaging objects in situ below the diffraction limit of classical bright-field optical microscopies (<500nm) and have been used effectively for NP sizing as well as for monitoring the transport, electrochemical transformation or growth of NPs at nano/microelectrodes or pipettes [28,42,[47][48][49][50][51].…”

Nanopipette‐based electrochemical SERS platforms: Using electrodeposition to produce versatile and adaptable plasmonic substrates

“…The final particle geometry can be further investigated by imaging the particle geometry. While analyzing details of the surface morphology require electronic imaging (Figures 1b and S4), the average size can be readily estimated from DF microscopy images, provided that the diameter is above to the diffraction limit [ 39 ] (∼ λ /2 NA ). A comparison between particle size estimations using DF microscopy and SEM is shown in Figure S5.…”