Potential‐Controlled (R)Evolution: Electrochemical Synthesis of Nanoparticles with Well‐Defined Shapes

Abstract

To enable the rational design of synthetic approaches for producing precisely defined nanomaterials, a detailed mechanistic understanding needs to be established. Colloidal approaches to nanoparticle growth have been used to produce many novel shape‐ and composition‐controlled nanoparticles with various important target applications. Concurrently, electrochemical approaches to nanoparticle synthesis have also been developed, though at present this field is less expansive than colloidal synthesis. This review covers recent progress in the synthesis of shaped metal, metal oxide, and alloyed nanoparticles via electrochemical methods that use specific control of potential or current in combination with tailoring of the chemical growth solution environment. These approaches have produced nanoparticles with compositions and architectures that were inaccessible via standard colloidal approaches. Importantly, electrochemical nanoparticle synthesis can also serve as a powerful tool for understanding fundamental mechanisms of colloidal nanoparticle growth. We highlight multiple promising opportunities in this growing research area.

Direct Bottom-UpIn SituGrowth: A Paradigm Shift for Studies in Wet-Chemical Synthesis of Gold Nanoparticles

“…There are three basic elements in the colloidal wet-chemical synthesis of gold nanoparticles: ( i ) the gold salt, the source of gold ions, usually HAuCl 4 , NaHAuCl 4 , or KAuCl 4 , ( ii ) a capping ligand, usually a surfactant, to stabilize the particles in colloidal suspension via Coulombic and/or steric repulsion, and ( iii ) a reducing agent to reduce the Au 3+ ions. Although there exist approaches where electrochemical reduction , and/or light , are used in place of a chemical reductant, we will not focus on these approaches here and instead direct readers to recent comprehensive reviews. − …”

Nanomaterials Synthesis Discovery via Parallel Electrochemical Deposition

“…Electrochemical nanomaterials synthesis (i.e., electrodeposition) expands available synthetic handles to include both electrochemical and chemical parameters . Specifically, electrodeposition affords additional variation of physicochemical processes, such as electrochemical potentials and mass transport, through control of the potential or current at the electrode/solution interface.…”

“…Specifically, electrodeposition affords additional variation of physicochemical processes, such as electrochemical potentials and mass transport, through control of the potential or current at the electrode/solution interface. Ultimately, this influences precursor reduction and nanoparticle growth, thus providing control of synthetic parameters that are not typically accessed in colloidal nanoparticle synthesis. − For example, an oscillating square wave potential can be applied in which growth conditions switch from deposition (more reducing potentials) to dissolution (more oxidizing potentials), affording an opportunity to electrochemically anneal particles at the electrode interface. − Reaction potentials can also be fine-tuned over the time course of a nanoparticle growth process to modulate reduction kinetics at key points in the nanoparticle shape development . In addition, electrochemistry can provide quantitative information about the dynamic chemical environment during nanoparticle growth, thereby guiding synthetic design from fundamental principles. , However, a drawback of electrochemical materials synthesis is the inherently serial nature of the approaches typically taken.…”

Bridging colloidal and electrochemical syntheses of metal nanocrystals with seeded electrodeposition for tracking single nanocrystal growth

“…Unlike colloidal syntheses which require a molecular reducing agent to nucleate metal NCs from metal salts, electrochemical syntheses use a potentiostat to set the working electrode's potential where metal deposition occurs from metal salts, providing different kinetic pathways to metal NCs compared to colloidal syntheses. 11,12 Interest in such syntheses grew when Sun and co-workers demonstrated electrochemical syntheses of Pt and Pd NCs with high-index facets by applying a squarewave potential to a glassy carbon electrode (GCE) with a metal salt growth solution. [13][14][15] As we will show, electrochemical syntheses offer the possibility of tracking NCs as they are created or modified on a GCE exposed to the growth solution.…”