How Structure-Directing Agents Control Nanocrystal Shape: Polyvinylpyrrolidone-Mediated Growth of Ag Nanocubes

Abstract

The importance of structure-directing agents (SDAs) in the shape-selective synthesis of colloidal nanostructures has been well documented. However, the mechanisms by which SDAs actuate shape control are poorly understood. In the polyvinylpyrrolidone (PVP)-mediated growth of {100}-faceted Ag nanocrystals, this capability has been attributed to preferential binding of PVP to Ag(100). We use molecular dynamics simulations to probe the mechanisms by which Ag atoms add to Ag(100) and Ag(111) in ethylene glycol solution with PVP. We find that PVP induces kinetic Ag nanocrystal shapes by regulating the relative Ag fluxes to these facets. Stronger PVP binding to Ag(100) leads to a larger Ag flux to Ag(111) and cubic nanostructures through two mechanisms: enhanced Ag trapping by more extended PVP films on Ag(111) and a reduced free-energy barrier for Ag to cross lower-density films on Ag(111). These flux-regulating capabilities depend on PVP concentration and chain length, consistent with experiment.

Ligand‐Guided Growth of Alloyed Shells on Intermetallic Seeds as a Route toward Multimetallic Nanocatalysts with Shape‐Control

“…Controlling the shape of multimetallic nanoparticles (NPs) through colloidal synthesis has attracted significant attention as shape‐control defines what facets are expressed and available to facilitate catalysis while multimetallic compositions provide unique and composition‐dependent surface electronics. In the synthesis of metal NPs, shape is often controlled by the use of capping agents, which are reagents ( e. g., small molecules, polymers, surfactants, and even ions) that adsorb onto the surfaces of the growing NPs and provide stability . Through the selection of capping agents with greater affinity for one surface‐type over another, controlled overgrowth is possible and enables selective facet expression and shape‐control .…”

Controlled Molybdenum Disulfide Assembly inside Carbon Nanofiber by Boudouard Reaction Inspired Selective Carbon Oxidation

“…Conventional bulk metallurgy continues to provide insight into many intriguing nanoscale phenomena. For example, the Kirkendall effect (hollow structures), Ostwald ripening (size control), Wulff construction (facet formation), and spinodal decomposition (phase separation) contribute core principles in the area of nanomaterial synthesis. Herein, we have explored the possibility of using the Boudouard reaction at the nanoscale for synthesis and assembly of molybdenum disulfide (MoS 2 ).…”

Polyvinylpyrrolidone (PVP)‐Capped Pt Nanocubes with Superior Peroxidase‐Like Activity

“…As shown in Table , the values of K cat‐specific for different PVP‐capped cubes increased in the order of: PVP 10 ‐capped Pt cubes<PVP 55 ‐capped Pt cubes<PVP 360 ‐capped Pt cubes. This trend of K cat‐specific might be related to the packing density of PVP on Pt cube surfaces. Specifically, the packing densities of PVP 10 , PVP 55 , and PVP 360 were estimated to be 1.30, 1.19, and 0.87 nm −2 , respectively (see Figure S8 and Table S1 for details), according to TGA analysis .…”