ORCID Profile
0000-0002-1459-8619
Current Organisation
University of Adelaide
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Publisher: AIP Publishing
Date: 02-07-2014
DOI: 10.1063/1.4884642
Abstract: Chemically made, atomically precise phosphine-stabilized clusters Au9(PPh3)8(NO3)3 were deposited on titania and silica from solutions at various concentrations and the s les heated under vacuum to remove the ligands. Metastable induced electron spectroscopy was used to determine the density of states at the surface, and X-ray photoelectron spectroscopy for analysing the composition of the surface. It was found for the Au9 cluster deposited on titania that the ligands react with the titania substrate. Based on analysis using the singular value decomposition algorithm, the series of MIE spectra can be described as a linear combination of 3 base spectra that are assigned to the spectra of the substrate, the phosphine ligands on the substrate, and the Au clusters anchored to titania after removal of the ligands. On silica, the Au clusters show significant agglomeration after heat treatment and no interaction of the ligands with the substrate can be identified.
Publisher: American Chemical Society (ACS)
Date: 23-04-2014
DOI: 10.1021/IC403040U
Abstract: High-quality far-IR absorption spectra for a series of ligated atomically precise clusters containing Ru3, Ru4, and AuRu3 metal cores have been observed using synchrotron radiation, the latter two for the first time. The experimental spectra are compared with predicted IR spectra obtained following complete geometric optimization of the full cluster, including all ligands, using DFT. We find strong correlations between the experimental and predicted transitions for the low-frequency, low-intensity metal core vibrations as well as the higher frequency and intensity metal-ligand vibrations. The metal core vibrational bands appear at 150 cm(-1) for Ru3(CO)12, and 153 and 170 cm(-1) for H4Ru4(CO)12, while for the bimetallic Ru3(μ-AuPPh3)(μ-Cl)(CO)10 cluster these are shifted to 177 and 299 cm(-1) as a result of significant restructuring of the metal core and changes in chemical composition. The computationally predicted IR spectra also reveal the expected atomic motions giving rise to the intense peaks of metal-ligand vibrations at ca. 590 cm(-1) for Ru3, 580 cm(-1) for Ru4, and 560 cm(-1) for AuRu3. The obtained correlations allow an unambiguous identification of the key vibrational modes in the experimental far-IR spectra of these clusters for the first time.
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3CP44005B
Abstract: Synchrotron XPS was used to investigate a series of chemically-synthesised, atomically-precise gold clusters Au(n)(PPh(3))(y) (n = 8, 9, 11 and 101, with y depending on cluster size) immobilized on titania nanoparticles. The gold clusters were washed with toluene at 100 °C or calcined at 200 °C to remove the organic ligand. From the position of the Au 4f(7/2) peak it is concluded that cluster size is not altered through the deposition. From the analysis of the phosphorous spectra, it can be concluded that the applied heat treatment removes the organic ligands. Washing and calcination leads to partial oxidation and partial agglomeration of the clusters. Oxidation of the clusters is most likely due to the interaction of the cluster core with the oxygen of the titania surface after removal of ligands. The position of the Au 4f(7/2) peak indicates that the size of the agglomerated clusters is still smaller than that of Au(101).
Publisher: American Chemical Society (ACS)
Date: 07-03-2012
DOI: 10.1021/JP212056S
Publisher: AIP Publishing
Date: 05-2017
DOI: 10.1063/1.4982350
Abstract: A high-temperature, high-pressure, pulsed-gas s ling and detection system has been developed for testing new catalytic and photocatalytic materials for the production of solar fuels. The reactor is fitted with a sapphire window to allow the irradiation of photocatalytic s les from a l or solar simulator light source. The reactor has a volume of only 3.80 ml allowing for the investigation of very small quantities of a catalytic material, down to 1 mg. The stainless steel construction allows the cell to be heated to 350 °C and can withstand pressures up to 27 bar, limited only by the sapphire window. High-pressure s ling is made possible by a computer controlled pulsed valve that delivers precise gas flow, enabling catalytic reactions to be monitored across a wide range of pressures. A residual gas analyser mass spectrometer forms a part of the detection system, which is able to provide a rapid, real-time analysis of the gas composition within the photocatalytic reaction chamber. This apparatus is ideal for investigating a number of industrially relevant reactions including photocatalytic water splitting and CO
Publisher: MDPI AG
Date: 22-11-2018
DOI: 10.3390/C4040064
Abstract: Degussa P25 is a benchmark form of TiO2 used worldwide in photocatalysis studies. Currently, no such benchmark exists for co-catalysts, which are essential for many photocatalytic reactions. Here, we present the preparation of Pt nanocluster co-catalysts on TiO2 using an unmodified commercial source and equipment that is commonly available. Transmission electron microscopy reveals that the procedure produces TiO2 decorated with Pt atoms and nanoclusters (1–5 atoms). Optical reflectance and X-ray diffraction measurements show that the procedure does not affect the TiO2 polymorph or ultraviolet-visible (UV-Vis) absorbance. Gas phase photocatalytic splitting of heavy water (D2O) shows that the Pt nanocluster-decorated TiO2 outperforms Pt nanoparticle (produced by photodeposition) decorated TiO2 in D2 production. Pt nanoclusters, produced directly from a commercial source, with high co-catalyst activity, are prime candidates to be used in benchmark photocatalytic reactions.
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3CP52497C
Abstract: Synchrotron XPS was used to investigate a series of chemically synthesised, atomically precise gold clusters Au(n)(PPh3)y (n = 8, 9 and 101, y depending on the cluster size) immobilized on anatase (titania) nanoparticles. Effects of post-deposition treatments were investigated by comparison of untreated s les with analogues that have been heat treated at 200 °C in O2, or in O2 followed by H2 atmosphere. XPS data shows that the phosphine ligands are oxidised upon heat treatment in O2. From the position of the Au 4f(7/2) peak it can be concluded that the clusters partially agglomerate immediately upon deposition. Heating in oxygen, and subsequently in hydrogen, leads to further agglomeration of the gold clusters. It is found that the pre-treatment plays a crucial role in the removal of ligands and agglomeration of the clusters.
Publisher: American Chemical Society (ACS)
Date: 03-2010
DOI: 10.1021/JP100118R
Abstract: We have used photoionization efficiency spectroscopy to determine ionization energies (IEs) of the gas-phase tantalum-carbide clusters Ta(5)C(y) (y = 0-6). The structures of the clusters observed in the experiment are assigned by comparing the experimental IEs with those of candidate isomers, calculated by density functional theory. Two competing geometries of the underlying Ta(5) cluster are found to be present in the assigned Ta(5)C(y) structures either a "prolate" or "distorted oblate" trigonal bipyramid geometry. The onset of carbon-carbon bonding in the Ta(5)C(y) series is proposed to occur at y = 6, with the structure of Ta(5)C(6) containing two molecular C(2) units.
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3RA44803G
Publisher: AIP Publishing
Date: 17-03-2016
DOI: 10.1063/1.4943203
Abstract: Triphenylphosphine ligand-protected Au9 clusters deposited onto titania nanosheets show three different atomic configurations as observed by scanning transmission electron microscopy. The configurations observed are a 3-dimensional structure, corresponding to the previously proposed Au9 core of the clusters, and two pseudo-2-dimensional (pseudo-2D) structures, newly found by this work. With the help of density functional theory (DFT) calculations, the observed pseudo-2D structures are attributed to the low energy, de-ligated structures formed through interaction with the substrate. The combination of scanning transmission electron microscopy with DFT calculations thus allows identifying whether or not the deposited Au9 clusters have been de-ligated in the deposition process.
Publisher: American Chemical Society (ACS)
Date: 31-03-2015
DOI: 10.1021/JP5119162
No related grants have been discovered for Jason Alvino.