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Title: Electronic interactions between gold nanoclusters in constrainedgeometries

Abstract

No abstract prepared.

Authors:
; ; ; ;
Publication Date:
Research Org.:
Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
Sponsoring Org.:
USDOE Director. Office of Science. Basic EnergySciences
OSTI Identifier:
924791
Report Number(s):
LBNL-58997
R&D Project: 517950; BnR: KC0203010; TRN: US200809%%340
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review B; Journal Volume: 73; Journal Issue: 1; Related Information: Journal Publication Date: 04/2006
Country of Publication:
United States
Language:
English
Subject:
36; GOLD; NANOSTRUCTURES; MOLECULAR CLUSTERS; INTERACTIONS; ELECTRONIC STRUCTURE

Citation Formats

Kim, Sang Hoon, Hwang, S., Shon, Young-Seok, Ogletree, D. Frank, and Salmeron, Miquel. Electronic interactions between gold nanoclusters in constrainedgeometries. United States: N. p., 2005. Web.
Kim, Sang Hoon, Hwang, S., Shon, Young-Seok, Ogletree, D. Frank, & Salmeron, Miquel. Electronic interactions between gold nanoclusters in constrainedgeometries. United States.
Kim, Sang Hoon, Hwang, S., Shon, Young-Seok, Ogletree, D. Frank, and Salmeron, Miquel. Fri . "Electronic interactions between gold nanoclusters in constrainedgeometries". United States. doi:. https://www.osti.gov/servlets/purl/924791.
@article{osti_924791,
title = {Electronic interactions between gold nanoclusters in constrainedgeometries},
author = {Kim, Sang Hoon and Hwang, S. and Shon, Young-Seok and Ogletree, D. Frank and Salmeron, Miquel},
abstractNote = {No abstract prepared.},
doi = {},
journal = {Physical Review B},
number = 1,
volume = 73,
place = {United States},
year = {Fri Dec 09 00:00:00 EST 2005},
month = {Fri Dec 09 00:00:00 EST 2005}
}
  • With the recent successful synthesis of an increasing number of atomically precise thiolate–gold nanoclusters (NCs), there are growing demands for a better understanding of their atomic structures and structure–property relationships in response to composition change. Herein, we present X-ray experimental results on structural and electronic properties of a recently synthesized gold–thiolate nanocluster, Au 19(SR) 13, in comparison with the structurally well-known Au 25(SR) 18 reference. The atomic structure of Au 19(SR) 13 was first probed with extended X-ray absorption fine structure (EXAFS). A multishell EXAFS fitting method (consisting of one Au–S and three Au–Au shells) allowed for a detailed structuralmore » comparison of the two nanoclusters, which revealed a sizable increase of the bond distances between the surface–surface and surface–staple Au atoms upon the decrease of Au atoms in the nanocluster. X-ray photoemission experiments and ab initio calculations further demonstrated the sensitive change of electronic properties of the nanoclusters when the cluster composition was varied, that is, the Au 19(SR) 13 nanocluster has a differently shaped and positively shifted Au 5d band relative to Au 25(SR) 18. These experimental findings highlight the sensitivity of the local structure and electronic properties of thiolate-gold nanoclusters to even a small change of the metal core from Au 13 to Au 11.« less
  • The electronic d-band properties are important factors for the emerging catalytic activity of Au nanoclusters of sub-5-nm size. We analyzed the d-band properties of Au nanoclusters grown on amorphous carbon supports by photoelectron spectroscopy using synchrotron-radiation light coupled with high-resolution ion scattering spectrometry which enables us to estimate the size and shape of Au nanoclusters. The d-band width (W{sub d}), d-band center position (E{sub d}), and apparent 5d{sub 3/2}-d{sub 5/2} spin-orbit splitting (E{sub SO}) were determined as a function of a number of Au atoms per cluster (n{sub A}) and an average coordination number (n{sub C}) in a wide rangemore » (11<n{sub A}<1600). The W{sub d} and E{sub SO} values decrease steeply with decreasing n{sub A} below {approx}150 owing to band narrowing which is caused by hybridization of fewer wave functions of the valence electrons. However, E{sub d} shifts to the higher binding energy side with decreasing cluster size. The rapid movement of E{sub d} is attributed to the dynamic final-state effect, which results in higher binding energy shifts of core and valence states due to a positive hole created after photoelectron emission. We have estimated the contribution from the final-state effect and derived the approximated initial-state spectra. Modified data, however, still show a slight movement of the d-band center away from the Fermi level (E{sub F}) although the E{sub d} values for Au nanoclusters are closer to E{sub F} compared to the bulk value. This behavior is ascribed to the contraction of average Au-Au bond length with decreasing cluster size.« less
  • Ultra-small gold nanoclusters were synthesized via a ligand exchange method and deposited onto different TiO2 supports to study their properties. STM imaging revealed that the as-synthesized gold nanoclusters had 2-D morphology consisting of monolayers of gold atoms. In conclusion, subsequent XPS, XAFS, and CO oxidation TPD results indicated that heat treatments of gold clusters at different temperatures significantly altered their electronic and catalytic properties due to ligand deprotection and cluster agglomeration.
  • Gold nanoclusters were synthesized by a bottom-up synergistic approach of in-situ oligomerization of the monomer, N-vinyl pyrrolidone (NVP) and simultaneous weak reduction of Au-NVP complexes in the absence of any other external energy sources, thereby making these tiny gold clusters as the most elemental building blocks to construct further novel nano/microstructures with application potentials. It is well-known that metal clusters with less than 2 nm size do not show the usual surface plasmon band, because of the presence of a band-gap at the fermi level. Nevertheless, our present oligomer coated gold clusters show a discrete intense band at around 630 nm, whichmore » could very well be attributed to the charge transfer between the oligomer chain and the surface Au atoms. Such kind of sacrificial plasmon induced charge transfer interaction, observed for the very first time to the best of our knowledge, were also strongly corroborated through the enhancement / shifting of specific vibrational / rotational peaks as observed from the FTIR and Raman measurements as a function of the metal oxidation states, thus representing a new prototype for an efficient solar energy conversion probe.« less
  • A new organic salt, ..beta..-(ET)/sub 2/AuCl/sub 2/, was synthesized, and its structure and physical properties were determined. Here ET refers to bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET). ..beta..-(ET)/sub 2/AuCl/sub 2/ is isostructural with ..beta..-(ET)/sub 2/ICl/sub 2/ and contains the shortest anion, AuCl/sub 2//sup -/, among the ..beta..-(ET)/sub 2/X salts with linear anions, X/sup -/, known so far. Crystal data for ..beta..-(ET)/sub 2/AuCl/sub 2/ are as follows: triclinic, P anti 1, 298 K/120 K, a = 6.651 (1)/6.627 (2) A, b = 9.761 (2)/9.595 (3) A, c = 12.734 (3)/12.662 (4) A, ..cap alpha.. = 86.12 (2)/85.15 (2)/sup 0/, ..beta.. = 100.70 (2)/101.40more » (2)/sup 0/, ..gamma.. = 99.41 (2)/98.24 (2)/sup 0/, and V/sub c/ = 800.7 (4)/779.8 (5) A/sup 3/. The electrical conductivities of type I ..beta..-(ET)/sub 2/X salts (i.e., those with short anions X/sup -/ = AuCl/sub 2//sup -/, ICl/sub 2//sup -/) measured by the four-probe technique show that they are semiconductors with thermal activation energy of 0.10 eV. The valence band (i.e., the highest occupied band) of ..beta..-(ET)/sub 2/AuCl/sub 2/, which is half-filled, is calculated to be one-dimensional in character as in the case of ..beta..-(ET)/sub 2/ICl/sub 2/. ESR data of ..beta..-(ET)/sub 2/AuCl/sub 2/ reveal the presence of a phase transition at approx. 33 K, which is somewhat higher than the corresponding temperature (22 K) of ..beta..-(ET)/sub 2/ICl/sub 2/. The ET molecule pairs of type I ..beta..-(ET)/sub 2/X salts are significantly more dimerized than those of type II ..beta..-(ET)/sub 2/X salts (i.e., those with long anions X/sup -/ = IBr/sub 2//sup -/, AuI/sub 2//sup -/, I/sub 3//sup -/).« less