Surface Capping Agents and Their Roles in Shape‐Controlled Synthesis of Colloidal Metal Nanocrystals

Abstract

Surface capping agents have been extensively used to control the evolution of seeds into nanocrystals with diverse but well‐controlled shapes. Here we offer a comprehensive review of these agents, with a focus on the mechanistic understanding of their roles in guiding the shape evolution of metal nanocrystals. We begin with a brief introduction to the early history of capping agents in electroplating and bulk crystal growth, followed by discussion of how they affect the thermodynamics and kinetics involved in a synthesis of metal nanocrystals. We then present representative examples to highlight the various capping agents, including their binding selectivity, molecular‐level interaction with a metal surface, and impacts on the growth of metal nanocrystals. We also showcase progress in leveraging capping agents to generate nanocrystals with complex structures and/or enhance their catalytic properties. Finally, we discuss various strategies for the exchange or removal of capping agents, together with perspectives on future directions.

Revitalizing silver nanocrystals as a redox catalyst by modifying their surface with an isocyanide-based compound

“…Although organic ligands are oen used to stabilize the particles during their colloidal synthesis, it has long been recognized that the organic ligands remaining on the surface could relentlessly "poison" catalytic particles by simply blocking the active sites. [21][22][23][24][25] Here we demonstrate that organic ligands can have a positive impact on the properties of catalytic particles. Specically, we discover that an isocyanide compound can adsorb on the surface of Ag nanocubes to enable the Agcatalyzed redox reaction between isocyanide and nitroaromatic molecules toward the production of an aromatic azo compound under ambient conditions.…”

Challenges and opportunities in the bottom-up mechanochemical synthesis of noble metal nanoparticles

“…At least in solution, the capping agent plays a pivotal role in the size and shape control. 85,86 This happens due to the manipulation of the growth kinetics along with preferential interaction with some crystallographic directions. 86 In mechanochemical systems it has to be present in a larger mass fraction compared to the metal load.…”

“…85,86 This happens due to the manipulation of the growth kinetics along with preferential interaction with some crystallographic directions. 86 In mechanochemical systems it has to be present in a larger mass fraction compared to the metal load. 87 Nonetheless, the use of common capping agents can be dismissed when the NPs are directly synthesized over a supporting material.…”

Editorial: Electrocatalysis on Shape-Controlled Nanoparticles

“…Among the factors that must be taken into consideration, the surface cleanliness is one of the most critical. Several synthetic approaches can produce shaped nanoparticles, but the use of surface capping agents under colloidal routes is one of the most effective ways to control the growth of nanoparticles so as to induce the formation of specific particle shapes (Xia et al, 2015;Yang et al, 2019). However, once nanoparticles are formed, the presence of these surface-regulating agents at the surface of the nanoparticles results in an obstacle; and it is mandatory to apply specific decontamination protocols to completely remove (without altering the initial surface structure of the nanoparticles) their presence from the surface of the nanoparticles (Monzó et al, 2012;Montiel et al, 2017;García-Cruz et al, 2019).…”