Photomodulated Spatially Confined Chemical Reactivity in a Single Silver Nanoprism

Abstract

Single-atom and single-particle catalysis is an area of considerable topical interest due to their potential in explaining important fundamental processes and applications across several areas. An interesting avenue in single-particle catalysis is spatial control of chemical reactivity within the particle by employing light as an external stimulus. To demonstrate this concept, we report galvanic replacement reactions (GRRs) as a spatial marker of subparticle chemical reactivity of a silver nanoprism with AuCl4 – ions under optical excitation. The location of a GRR within a single Ag nanoprism can be spatially controlled depending on the plasmon mode excited. This leads to chemomorphological transformation of Ag nanoprisms into interesting Ag–Au structures. This spatial biasing effect is attributed to localized hot electron injection from the tips and edges of the silver nanoprisms to the adjacent reactants that correlate with excitation of different surface plasmon modes. The study also employs low-energy-loss EELS mapping to additionally probe the spatially confined redox reaction within a silver nanoprism. The findings presented here allow the visualization of a plasmon-driven subparticle chemical transformation with high resolution. The selective optical excitation of surface plasmon eigenmodes of anisotropic nanoparticles offers opportunities to spatially modulate chemical transformations mediated by hot electron transfer.

Plasmonic Nanocrystals with Complex Shapes for Photocatalysis and Growth: Contrasting Anisotropic Hot‐Electron Generation with the Photothermal Effect

“…Indeed, hot-spot driven photoreactions and anisotropic growth are prominent phenomena observed in several impressive experiments, which also utilized local microscopies (such as TEM, SEM, etc.). [19,49,73] Figure 1h,j shows two examples of such experimental work.…”

Local Growth Mediated by Plasmonic Hot Carriers: Chirality from Achiral Nanocrystals Using Circularly Polarized Light

“… 66 Also, it can arise from the larger excitation rates of hot carriers at plasmonic hot spots, producing growth patterns centered on these regions, such as the example in Figure 1 d showing the results of the galvanic reduction of silver triangular nanoprisms on excitation at their plasmonic resonance. 53 Importantly, the growth pattern can also reflect the symmetry of the incoming illumination, such as that shown in Figure 1 e, where the chiral deposition of PbO 2 over nonchiral Au rods is achieved by illuminating them with circularly polarized light (CPL). 54 This experiment exemplifies a category of cases where a photocatalytic process can transform achiral plasmonic NCs in chiral systems when they are illuminated with circularly polarized light.…”

“… 52 (d) Diagram and TEM image of a silver nanoprism after growth through galvanic replacement at its corners on illumination at its main plasmonic resonance by unpolarized light. 53 (e) TEM images of Au@PbO 2 chiral structures successfully photogrown by using circularly polarized illumination over nonchiral Au rods. Scale bars: 100 nm.…”

“…Copyright 2020 American Chemical Society. (d) was reproduced with permission from ref ( 53 ). Copyright 2020 American Chemical Society.…”

A minireview on the synthesis of single atom catalysts

“…Galvanic replacement is a technique which takes the advantage of the reduction potential differences between a metal in a template and metal ions in a solution. 112,113 Given proper potential differences, the galvanic replacement reactions could occur spontaneously, with the metal atoms in the template being oxidized and dissolved into the solution while the metal ions in the solution being reduced and plated on the surface of the metal template (Fig. 11).…”