Optical monitoring of the electrochemical nucleation and growth of silver nanoparticles on electrode: From single to ensemble nanoparticles inspection

Abstract

The electrochemical nucleation and growth of nanoparticles (NPs) on an electrode surface at a constant potential is traditionally followed by recording the resulting current density during the experiment. The obtained chronoamperometric transients are average measurements, making it difficult to separate individual NP behaviors and to study their cross-talks. Herein, the recently developed Backside Absorbing Layer Microscopy (BALM) is employed to monitor optically in situ and operando the electrodeposition of silver NPs. This latter technique exploits a pseudo-antireflective and metallic contrast layer and allows both subnanometer vertical and sub-micrometer spatial resolutions. The information from the recorded movies is readily exploited to study the NP electrodeposition at the single entity level. The image sequences allow quantifying the local electrodeposition of nanomaterials onto the electrode surface, probing the NP dynamics through the extraction of single optical NP growth transients, and analyzing the effect of the neighboring nuclei on the growth of individual NPs.

Hybrid scanning electrochemical cell microscopy-interference reflection microscopy (SECCM-IRM): tracking phase formation on surfaces in small volumes

“…Although previous studies of nucleation/growth of NPs with optical microscopy monitoring could optically isolate a single event, the electrochemical information (current) associated to such event was recorded for the entire electrode, averaged over the ensemble of NPs. [28][29][30]82 In contrast, with SECCM-IRM, the current is confined to the small SECCM meniscus, allowing the synchronous electrochemical monitoring and optical imaging of a single event. 83 Should SECCM allow isolation of a single nucleation event from the electrochemical transient, the question is: can IRM also visualize this individual event?…”

“…The optical detection principle has been detailed in previous works. 28,31,32 It is based on the reflection of the light wave at the ITO-electrolyte interface and its possible interference with light wave scattered by objects present on the ITO surface, which disturb the local optical conditions and are highlighted within the background, with the camera acting as an interferometric detector. Optical features can show either a negative contrast, the feature appearing darker than the background, or a positive contrast, where the feature appears brighter than the background.…”

“…Recently a hybrid approach, using interference reflection microscopy (IRM) coupled to electrochemistry, was used to visualise and study the growth of ensembles of nanoparticles at optically transparent electrodes, in situ, at different overpotentials. [28][29][30] As a surface sensitive technique, IRM is particularly suited to the investigation of phenomena at the electrode/electrolyte interface. [31][32][33][34] At optically transparent electrodes, such as indium tin oxide (ITO) immersed in solution, local phase formation and/or change at the electrode surface modify the refractive index, giving rise to a difference in contrast in the observed reflected light image.…”

Substrate mediated dissolution of redox active nanoparticles; electron transfer over long distances

“…properties [30][31][32][33][34][35][36]. Due to the ability to provide complementary information, recent work has focused on the coupling of optical and electrochemical techniques to facilitate the investigation of redox processes at the nanoscale [37][38][39][40][41][42][43][44][45][46][47][48][49].…”

Interactive Competition Between Individual Diffusion Layers during Cyclic Voltammetry at Random Arrays of Band and Disk Electrodes: A Thorough Analysis Based on Global Simulations

“…Indeed, the peculiar voltammetric behavior of any regular array of nano-active objects stems from the fact that as soon as the extent, d � ðpDRT=FvÞ 1=2 , of the diffusion layers generated by the individual activities of each of these objects becomes much larger than their mean separation distance, d, they collapse and merge together to generate a collective planar diffusion wave progressing towards the solution bulk, [1,12,18] as it has been established experimentally later by optical and ECL methods, including for application to electronucleation of nanoparticles. [19][20][21][22][23][24][25][26][27] Hence, each given regular array is intrinsically associated to a characteristic transition scan rate v trans ¼ ðpDRT=FÞ=d 2 , i. e., a transition time t trans ¼ d 2 =pD, around which the array shifts from an apparent behavior akin to a classical voltammetric one for planar electrode of identical surface area as that of the whole array ( v trans < v) towards that featuring the simple addition of the individual steady (disk-type arrays) or quasi-steady state (bandtype arrays) currents generated by each active object as if it was performing alone (v trans > v). [1,12,28] Since truly random arrays display a wide range of separation distances values, d, they necessarily exhibit a correspondingly even wider range of v trans values (note that v trans / d À 2 ) and, accordingly, should not exhibit any identifiable transition limit.…”