It is now well-known that the size, shape, and composition of nanomaterials can dramatically affect their physical and chemical properties, and that technologies based on nanoscale materials have the potential to revolutionize fields ranging from catalysis to medicine. Among these materials, anisotropic particles are particularly interesting because the decreased symmetry of such particles often leads to new and unusual chemical and physical behavior. Within this class of particles, triangular Au and Ag nanoprisms stand out due to their structure- and environment-dependent optical features, their anisotropic surface energetics, and the emergence of reliable synthetic methods for producing them in bulk quantities with control over their edge lengths and thickness. This Review will describe a variety of solution-based methods for synthesizing Au and Ag triangular prismatic structures, and will address and discuss proposed mechanisms for their formation.

Colloidal Gold and Silver Triangular Nanoprisms

Underpotential deposition at single crystal surfaces of Au, Pt, Ag and other materials

The Colloid Chemical Approach to Nanostructured Materials

Ordered anion adlayers on metal electrode surfaces.

Electrochemical reduction of CO2 was studied using single-crystal electrodes, Cu(111), Cu(100), Cu(S)-[n(100) × (111)], and Cu(S)-[n(100) × (110)] at a constant current density 5 mA cm-2 in 0.1 M KHCO3 aqueous solution. Copper single crystals were prepared from 99.999% copper metal in graphite crucibles by the Bridgeman method. The crystal orientation was determined by the X-ray back reflection method. The Cu(111) electrode yields mainly CH4 from CO2, and the Cu(100) favorably gives C2H4. Introduction of (111) steps to Cu(100) basal plane, leading to Cu(S)-[n(100) × (111)] orientations, significantly promoted C2H4 formation and suppressed CH4 formation. The selectivity ratio C2H4/CH4 on Cu(711) (n = 4) amounted to 14, 2 orders of magnitude higher than that on Cu(111).

Selective Formation of C2 Compounds from Electrochemical Reduction of CO2 at a Series of Copper Single Crystal Electrodes

In situ scanning tunneling microscopy (STM) of the dissolution of a Cu(100) electrode in aqueous chloride media (HC1) was employed to find the mechanism of reaction at the atomic level. Imaging the surface at potentials where no dissolution occurred resulted in a clear ( 4 2 x 42)R45' C1 structure with an observed C1-C1 distance of 0.35 f 0.02 nm, in agreement with previous ultrahigh vaccum surface analytical lowenergy electron diffraction and Auger electron analysis studies of Cu(100) surfaces dosed with chlorine or aqueous C1-. Images acquired at potentials where dissolution was modest showed the preferred reaction sites were step edges with edges always retreating along the Cu(100) ( 100) direction. At still higher potentials, the rate increased and the reaction sites were still mainly the step edges. This work compares well with a previous STM study of Cu(ll1) electrodes under similar conditions, where the dissolution of the Cu( 11 1) caused reaction along (21 l} step edges, which are very similar to the Cu(100) { 100) step edges.

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Scanning Tunneling Microscopic Study with Atomic Resolution of the Dissolution of Cu(100) Electrodes in Aqueous Chloride Media

In this paper the method of electrochemical atomic layer epitaxy (ECALE) is described. It involves the alternated electrochemical deposition of atomic layers of elements to form compound semiconductors. It is being investigated as a method for forming epitaxial thin films. Presently, it appears that the method is applicable to a wide range of compound semiconductors composed of a metal and one of the following main group elements: S, Se, Te, As, Sb, or Br. Initial studies have involved CdTe deposition. Factors controlling deposit structure and composition are discussed here. Preliminary results which show that ordered electrodeposits of CdTe can be formed by the ECALE method are also presented. Results reported here were obtained with both a polycrystalline Au thin-layer electrochemical cell and a single-crystal Au electrode with faces oriented to the (111), (110), and (100) planes. The single-crystal electrode was contained in a UHV surface analysis instrument with an integral electrochemical cell. Deposits were examined without their exposure to air using LEED and Auger electron spectroscopy. Coverages were determined using coulometry in the thin-layer electrochemical cell.

Conditions for the Deposition of CdTe by Electrochemical Atomic Layer Epitaxy

The oxidative chemisorption and cathodic stripping reductive desorption of iodine have been compared at smooth polycrystalline and well-defined Au(111) single-crystal electrodes. Experimental measurements were based upon cyclic voltammetry, thin-layer coulometry, X-ray photoelectron spectroscopy, Auger electron spectroscopy, and low-energy electron diffraction. The results indicate that iodide is oxidatively adsorbed as zerovalent atomic iodine at potentials between −0.4 V and +0.4 V (Ag/AgCl reference); at lower potentials, surface iodine is reductively desorbed as aqueous iodide, while at considerably more positive potentials, it is oxidized to aqueous iodate

Anodic underpotential deposition and cathodic stripping of iodine at polycrystalline and single-crystal gold: studies by LEED, AES, XPS, and electrochemistry

D. Wayne Suggs

Papers

Scanning Tunneling Microscopic Study with Atomic Resolution of the Dissolution of Cu(100) Electrodes in Aqueous Chloride Media

Conditions for the Deposition of CdTe by Electrochemical Atomic Layer Epitaxy

Anodic underpotential deposition and cathodic stripping of iodine at polycrystalline and single-crystal gold: studies by LEED, AES, XPS, and electrochemistry

Formation of and phase transitions in electrodeposited tellurium atomic layers on Au(1 1 1)

Studies of the surface structures formed by the alternated electrodeposition of Cd and Te on the low-index planes of Au: II. STM studies