Spin-Orbit Coupling Effects in Au 4f Core-Level Electronic Structures in Supported Low-Dimensional Gold Nanoparticles.

Smruti R Sahoo,Shyue-Chu Ke

doi:10.3390/nano11020554

Abstract

Despite their many advantages, issues remain unresolved over the variability in catalytic activities in supported gold nanoparticle (AuNP)-based catalysts, which requires precise characterization to unravel the presence of any fine features. Herein, upon analyzing the Au 4f core-level spin-orbit components in many as-synthesized AuNP-based catalysts, we observed that like deviations in the Au 4f7/2 binding energy positions, both the Au 4f7/2-to-Au 4f5/2 peak intensity and linewidth ratios varied largely from the standard statistical bulk reference values. These deviations were observed in all the as-synthesized supported AuNPs irrespective of different synthesis conditions, variations in size, shape or morphology of the gold nanoparticles, and different support materials. On the other hand, the spin-orbit-splitting values remained almost unchanged and did not show any appreciable deviations from the atomic or bulk standard gold values. These deviations could originate due to alterations in the electronic band structures in the supported AuNPs and might be present in other NP-based catalyst systems as well, which could be the subject of future research interest.

Highlights

Progress in synthesis methods and advances in sophisticated characterization techniques have made it possible to engineer the surface morphology of various types of low-dimensional nanostructures
It is reported that the lengths, widths, and aspect ratios of the as-synthesized supported gold nanorods (AuNRs) can be varied upon variation in the respective contents present in the growth solution, namely the concentration of seeds, silver ions, and ascorbic acid or by addition of suitable additives to the growth solution, respectively [33]
Au 4f core-level spin-orbit components from a set of gold nanoparticle catalysts supported on different substrate materials were analyzed carefully

Summary

Introduction

Progress in synthesis methods and advances in sophisticated characterization techniques have made it possible to engineer the surface morphology of various types of low-dimensional nanostructures. Recent interest has focused more on the application, postprocessing, and anchoring of nanoparticles (NPs) with different morphologies on different dielectric matrices in order to exploit the synergistic effects from both the nanoparticle surface and the underlying substrate materials [3,4] These modifications result in novel structural, optical, electronic, and catalytic properties [5,6]. Unlike chemically inert bulk gold, gold nanoparticles (AuNPs), when supported on various substrates, become catalytically active toward various organic reaction transformations and fuel-cell conversion-related applications [7,8,9] In such cases, apart from the agglomeration minimization and stabilization of gold nanoparticles, it has been observed that the selection of suitable support materials often plays a dominant role in dictating the rate of CO oxidation, water–gas shift reactions [8,10,11], and selective oxidation or hydrogenation reactions [12]. Catalytic activity and selectivity are highly influenced by an interplay

Methods

Results

Conclusion