Ligand-Mediated Control of the Surface Oxidation States of Copper Nanoparticles Produced by Laser Ablation.

We report on studies that demonstrate how the chemical composition of the surface of copper nanoparticles (CuNPs) - in terms of percentage copper(I/II) oxides - can be varied by the presence of N-donor ligands during their formation via laser ablation. Changing the chemical composition thus allows systematic tuning of the surface plasmon resonance (SPR) transition. The trialed ligands include pyridines, tetrazoles, and alkylated tetrazoles.

Atomically thin heavy-metal-free ZnTe nanoplatelets formed from magic-size nanoclusters.

Atomically thin colloidal quasi-two-dimensional (2D) semiconductor nanoplatelets (NPLs) have attracted tremendous attention due to their excellent properties and stimulating applications. Although some advances have been achieved in Cd- and Pb-based semiconductor NPLs, research into heavy-metal-free NPLs has been reported less due to the difficulties in the synthesis and the knowledge gap in the understanding of the growth mechanism. Herein wurtzite ZnTe NPLs with an atomic thickness of about 1.

Influence of cationic surfactants on the formation and surface oxidation states of gold nanoparticles produced via laser ablation.

We report on the time evolution of gold nanoparticles produced by laser ablation in the presence of the cationic surfactants cetyltrimethylammonium bromide (CTAB) and cetyltrimethylammonium chloride (CTAC) in aqueous solution. The broader applicability of a laser-induced nanoparticle formation kinetic model previously developed by us for the case of anionic surfactants in aqueous solution [ J. Phys.

Anion-π interactions of hexaaryl[3]radialenes.

Coordination polymers and discrete metallo-supramolecular assemblies of hexaaryl[3]radialene compounds exhibit intriguing structures with short anion to π-centroid distances in the solid-state. Furthermore, these [3]radialene compounds display useful photophysical and electrochemical properties that make them ideal as potential platforms for anion receptors. In this study, hexafluoro[3]radialene was optimized to the MP2/aug-cc-pVTZ level of theory, and its complexes with halide anions were optimized to HF/6-31G++(d,p), MP2/6-31G++(d,p), M06-2X/6-31G++(d,p), and M06-2X/6-311G++(d,p) levels of theory.

Translational and rotational energy content of benzene molecules IR-desorbed from an in vacuo liquid surface.

Benzene molecules were desorbed from an in vacuo aqueous liquid beam by direct irradiation of the beam with an IR laser tuned to the 2.85 μm absorption band of water. Spectroscopic interrogation of the desorbed benzene molecules was performed via 1 + 1 Resonance-Enhanced Multi-photon Ionisation (REMPI).

Photoreduction kinetics of sodium tetrachloroaurate under synchrotron soft X-ray exposure.

We report on the time evolution of the sodium tetrachloroaurate (NaAuCl(4)) chemical properties as a function of soft X-ray exposure in a dried sample on a silicon surface using X-ray photoelectron spectroscopy (XPS). Our investigations provide mechanistic insight into the photoreduction kinetics from Au(III) to Au(I) and then Au(I) to Au(0). We unambiguously show that XPS photoreduction occurs in stepwise fashion via the Au(I) state.

Study of the isomers of isoelectronic C(4), (C(3)B)(-), and (C(3)N)(+): rearrangements through cyclic isomers.

Optimized structures of the isoelectronic cumulenes (CCCB)(-), CCCC, and (CCCN)(+) and of their isomers formed by rearrangement have been calculated at the B3LYP/6-311+ G(3df) level of theory with relative energies and electronic states determined at the CCSD(T)/aug-cc-pVTZ level of theory. The ground states of CCCC and (CCCN)(+) are triplets, whereas the ground state of (CCCB)(-) is a quasi-linear singlet structure that is only 0.6 kcal mol(-1) more negative in energy than the linear triplet.

Onset of carbon-carbon bonding in the Nb(5)C(y) (y = 0-6) clusters: a threshold photo-ionisation and density functional theory study.

We have used photo-ionisation efficiency spectroscopy to determine the ionisation potentials (IPs) of the niobium-carbide clusters, Nb(5)C(y) (y = 0-6). Of these clusters Nb(5)C(2) and Nb(5)C(3) exhibit the lowest IPs. Complementary density functional theory calculations have been performed to locate the lowest energy isomers for each cluster.

Photoionization efficiency spectroscopy and density functional theory investigations of RhHo2O(n) (n = 0-2) clusters.

The experimental and theoretical adiabatic ionization energies (IEs) of the rhodium-holmium bimetallic clusters RhHo(2)O(n) (n=0-2) have been determined using photoionization efficiency spectroscopy and density functional theory (DFT) calculations. Both sets of data show the IE of RhHo(2)O to be significantly lower than the values for RhHo(2) and RhHo(2)O(2), which are found to be similar. This indicates that there are significant changes in electronic properties upon sequential addition of oxygen atoms to RhHo(2).

Threshold photoionization and density functional theory studies of the niobium carbide clusters Nb3C(n) (n = 1-4) and Nb4C(n) (n = 1-6).

We have used photoionization efficiency spectroscopy to determine ionization potentials (IP) of the niobium-carbide clusters, Nb3C(n) (n = 1-4) and Nb4C(n) (n = 1-6). The Nb3C2 and Nb4C4 clusters exhibit the lowest IPs for the two series, respectively. For clusters containing up to four carbon atoms, excellent agreement is found with relative IPs calculated using density functional theory.

Surface movement in water of splendipherin, the aquatic male sex pheromone of the tree frog Litoria splendida.

The aquatic sex pheromone splendipherin (GLVSSIGKALGGLLADVVKSKGQPA-OH) of the male green tree frog Litoria splendida moves across the surface of water to reach the female. Surface pressure and X-ray reflectometry measurements confirm that splendipherin is a surface-active molecule, and are consistent with it having an ordered structure, whereby the hydrophilic portion of the peptide interacts with the underlying water and the hydrophobic region is adjacent to the vapour phase. The movement of splendipherin over the surface of water is caused by a surface pressure gradient.

Associative versus dissociative binding of CO to 4d transition metal trimers: A density functional study.

Density functional calculations were performed to determine equilibrium geometrical structures, transition states and relative energies for M(3) clusters (M = Nb, Mo, Tc, Ru, Rh, Pd, Ag) reacting with CO, leading to proposed reaction pathways. For the Nb(3), Mo(3), and Tc(3) clusters, the lowest energy structure correlates to dissociated CO, with the C and O atoms bound on opposite sides of the metal triangle. For all other trimers, the lowest energy structures maintain the CO moiety.

BFW: a density functional for transition metal clusters.

Ionization potentials (IPs) or electron affinities (EAs) for transition metal clusters are an important property that can be used to identify and differentiate between clusters. Accurate calculation of these values is therefore vital. Previous attempts using a variety of DFT models have correctly predicted trends, but have relied on the use of scaling factors to compare to experimental IPs.

Ionization potentials of tantalum-carbide clusters: an experimental and density functional theory study.

We have used photoionization efficiency spectroscopy to determine the ionization potentials (IP) of the tantalum-carbide clusters, Ta3Cn (n = 1-3) and Ta4Cn (n = 1-4). The ionization potentials follow an overall reduction as the number of carbon atoms increases; however, the trend is not steady as expected from a simple electrostatic argument. Instead, an oscillatory behavior is observed such that clusters with an odd number of carbon atoms have higher IPs and clusters with an even number of carbon atoms have lower IPs, with the Ta4C4 cluster exhibiting the lowest IP.

Cyclodextrin and modified cyclodextrin complexes of E-4-tert-butylphenyl-4'-oxyazobenzene: UV-visible, 1H NMR and ab initio studies.

alpha-Cyclodextrin, beta-cyclodextrin, N-(6(A)-deoxy-alpha-cyclodextrin-6(A)-yl)-N'6(A)-deoxy-beta-cyclodextrin-6(A)-yl)urea and N,N-bis(6(A)-deoxy-beta-cyclodextrin-6(A)-yl)urea (alphaCD, betaCD, 1 and 2) form inclusion complexes with E-4-tert-butylphenyl-4'-oxyazobenzene, E-3(-). In aqueous solution at pH 10.0, 298.

Ab initio calculations of stationary points on the benzene-Ar and p-difluorobenzene-Ar potential energy surfaces: barriers to bound orbiting states.

The potential energy surfaces of the van der Waals complexes benzene-Ar and p-difluorobenzene-Ar have been investigated at the second-order Møller-Plesset (MP2) level of theory with the aug-cc-pVDZ basis set. Calculations were performed with unconstrained geometry optimization for all stationary points. This study has been performed to elucidate the nature of a conflict between experimental results from dispersed fluorescence and velocity map imaging (VMI).

Photoionization of NbCO and Nb(CO): Is CO Molecularly or Dissociatively Adsorbed on Niobium?

The photoionization efficiency spectra of gas-phase NbCO and Nb(CO) have been acquired using a laser-ablation, photoionization mass spectrometer. The adiabatic ionization energies of the species are 5.82 ± 0.

Metal Ion Dependent Molecular Inclusion Chemistry: Inclusion of p-Toluenesulfonate and p-Nitrophenolate within the Structure of Coordinated 1,4,7,10-Tetrakis((S)-2-hydroxy-3-phenoxypropyl)-1,4,7,10-tetraazacyclododecane.

The pendant donor macrocyclic ligand 1,4,7,10-tetrakis((S)-2-hydroxy-3-phenoxypropyl)-1,4,7,10-tetraazacyclododecane ((S)-thphpc12) has been synthesized in quantitative yield from cyclen (1,4,7,10-tetraazacyclododecane) and (2S)-(+)-3-phenoxy-1,2-epoxypropane. An X-ray diffraction study supports the result of molecular orbital calculations in showing that complexation with hydrated cadmium(II) diperchlorate produces an approximately square-antiprismatic complex in which the metal ion is located between a plane containing the four nitrogen atoms and a plane containing the four oxygen atoms. As a consequence of this the four phenoxymethyl moieties, each attached to one of the four N-O chelate rings, juxtapose to form a substantial empty cavity allowing the complex to act as a molecular receptor.