Single Nanoparticle Growth from Nanoparticle Tracking Analysis: From Monte Carlo Simulations to Nanoparticle Electrogeneration

Nanoimpact Electrochemistry to Quantify the Transformation and Electrocatalytic Activity of Ni(OH)2 Nanoparticles: Toward the Size-Activity Relationship at High Throughput

The fast establishment of structure-reactivity relationships is crucial to identifying the most appropriate nanoparticles (NPs) for a given application. This requires the development of methodologies allowing, simultaneously, the unraveling of the NPs geometry and the screening of their reactivity. Herein, nanoimpact electrochemistry (NIE) allows for quantifying the transformation and measuring the electrocatalytic activity for the oxygen evolution reaction (OER) of >100 Ni(OH)₂ NPs of a wide range of size (NP radii from 25 to 100 nm). This is achieved by scanning electrochemical microscopy in a generation/collection-like mode, with one electrode being used to electrogenerate by local precipitation colloidal Ni(OH)₂ NPs and the second one being used to collect them by NIE. It allows (i) quantifying the reductive and oxidative conversion of the Ni(OH)₂ NPs and (ii) separating the electrochemical conversion and the OER electrocatalysis, leading to the evaluation of a structure-activity relationship.

Effect of the driving force on nanoparticles growth and shape: an opto-electrochemical study

Most protocols developed to synthesize nanoparticles (NPs) and to control their shape are inspired from nucleation and growth theories. However, to rationalize the mechanisms of the shape-selective synthesis of NPs, experimental strategies allowing to probe in situ the growth of NPs are needed. Herein, metal Au or Ag nanoparticles (NPs) are produced by reaction of a metallic ion precursor with a reversible redox reducer. The process is explored by an oxidative electrosynthesis strategy using a sacrificial Au or Ag ultramicroelectrode to both trigger the metallic ion generation and control the local concentrations of the different reactants. The effect of the driving force for the metallic ion reduction over metal NP growth dynamics is inspected in situ and in real time at the single NP level by high-resolution optical microscopy from the tracking of the Brownian trajectories of the growing NPs in solution. The NP reductive growth/oxidative etching thermodynamics, and consequently the NP shape, are shown to be controlled electrochemically by the reversible redox couple, while the intervention of an Au(i) intermediate ion is suggested to account for the formation of gold nanocubes.