Defining Rules for the Shape Evolution of Gold Nanoparticles

Abstract

The roles of silver ions and halides (chloride, bromide, and iodide) in the seed-mediated synthesis of gold nanostructures have been investigated, and their influence on the growth of 10 classes of nanoparticles that differ in shape has been determined. We systematically studied the effects that each chemical component has on the particle shape, on the rate of particle formation, and on the chemical composition of the particle surface. We demonstrate that halides can be used to (1) adjust the reduction potential of the gold ion species in solution and (2) passivate the gold nanoparticle surface, both of which control the reaction kinetics and thus enable the selective synthesis of a series of different particle shapes. We also show that silver ions can be used as an underpotential deposition agent to access a different set of particle shapes by controlling growth of the resulting gold nanoparticles through surface passivation (more so than kinetic effects). Importantly, we show that the density of silver coverage can be controlled by the amount and type of halide present in solution. This behavior arises from the decreasing stability of the underpotentially deposited silver layer in the presence of larger halides due to the relative strengths of the Ag(+)/Ag(0)-halide and Au(+)/Au(0)-halide interactions, as well as the passivation effects of the halides on the gold particle surface. We summarize this work by proposing a set of design considerations for controlling the growth and final shape of gold nanoparticles prepared by seed-mediated syntheses through the judicious use of halides and silver ions.

Engineering the architectural diversity of heterogeneous metallic nanocrystals

“…In this approach, UPD is used to reverse the order of the reduction potentials of the two metal precursors (Ag and Pd precursors). The precursor of the more reactive metal (Ag in this case) is quickly reduced to form a Ag UPD layer on the central NC [18][19][20][21][22][23] , which would otherwise be the less favourable metal for reduction without UPD ( Fig. 2i-ii).…”

Wafer-Scale Leaning Silver Nanopillars for Molecular Detection at Ultra-Low Concentrations

“…A broad variety of SERS substrates have been fabricated over the past decade, e.g. nanorods 8 , nanocubes 9 , nanostars 10 , various particle arrays [11][12][13][14][15][16] and silver dendrites 17 . Recently electric field (E-field) enhancement factors (EF) above 10 8 to even 10 10 have been reported.…”

Shape-dependent electrocatalytic activity of free gold nanoparticles toward glucose oxidation

“…Since these properties strongly depend on the shape, the size, the crystallinity and the surface structure of nanoparticles, significant progresses in synthesis methods emerged in recent years for controlling the particles' morphology [4][5][6][7][8][9][10]. Among the mentioned synthesis approaches in the literature, the template method, the electrochemical method, the microwave rapid heating, the laser ablation, and the seed-mediated growth methods have been undertaken to yield gold nanoparticles with uniform sizes and morphologies [5,9,[11][12][13][14]. The size and shape control in a wet chemical process has the advantages of low cost and easy scale-up over methods.…”