Intertwining Roles of Silver Ions, Surfactants, and Reducing Agents in Gold Nanorod Overgrowth: Pathway Switch between Silver Underpotential Deposition and Gold–Silver Codeposition

Abstract

The past two decades have witnessed great success achieved in the geometry-controlled synthesis of metallic nanoparticles using the seed-mediated nanocrystal growth method. Detailed mechanistic understanding of the synergy among multiple key structure-directing agents in the nanocrystal growth solutions, however, has long been lagging behind the development and optimization of the synthetic protocols. Here we investigate the foreign ion-and surfactant-coguided overgrowth of singlecrystalline Au nanorods as a model system to elucidate the intertwining roles of Ag + foreign ions, surface-capping surfactants, and reducing agents that underpin the intriguing structural evolution of Au nanocrystals. The geometry-controlled nanorod overgrowth involves two distinct underlying pathways, Ag underpotential deposition and Au-Ag electroless codeposition, which are interswitchable upon maneuvering the interplay of the Ag + ions, surfactants, and reducing agents. The pathway switch governs the geometric and compositional evolution of nanorods during their overgrowth, allowing the cylindrical Au nanorods to selectively transform into a series of anisotropic nanostructures with interesting geometric, compositional, and plasmonic characteristics. The insights gained from this work shed light on the mechanistic complexity of geometry-controlled nanocrystal growth and may guide the development of new synthetic approaches to metallic nanostructures with increasing architectural complexity, further enhancing our capabilities of fine-tuning the optical, electronic, and catalytic properties of the nanoparticles.

A general soft-enveloping strategy in the templating synthesis of mesoporous metal nanostructures

“…The four diffraction peaks are consistent with those of Au or Ag metals with a fcc structure that correspond to the (111), (200), (220), and (311) planes. Based on the HAADF-STEM, EDX, XPS, and XRD data, the controlled phase structure of bimetallic AuAg alloy NPs with a composition of ~12 wt% Ag can be obtained by adjusting the feeding ratio of AgNO 3 40 , 41 .…”

Effective removal of surface-bound cetyltrimethylammonium ions from thiol-monolayer-protected Au nanorods by treatment with dimethyl sulfoxide/citric acid

“…Surface analysis of PEG-AuNRs was performed using XPS, 18,19,[30][31][32] which conrmed the removal of residual CTA cations from PEG-AuNRs aer DMSO/Cit (100 mM) treatment. Fig.…”

Rational Component and Structure Design of Noble‐Metal Composites for Optical and Catalytic Applications

“…Under the control of the UPD mechanism, the presynthesized noble‐metal seeds can induce the reduction of fewer noble‐metal ions. [ 160 ] Under this UPD mechanism, various noble‐metal composites have been prepared, such as Cu–Au nanoparticles, [ 146 ] an Ag–Au(111) layer, [ 161,162 ] Ag–Au octahedra, [ 163 ] Ag–Au–Ag dogbone‐like nanorods, [ 164 ] tetrahexahedral Pd–Ag alloy nanocrystals, [ 160 ] Pd@Ru nanosheets, [ 165 ] PtCu nanodendrites, [ 166 ] and PbS nanorod–GO film. [ 167 ]…”