Peter Trenton Bishop

Ultrafast Growth of Highly Branched Palladium Nanostructures for Catalysis

Palladium is widely used as a catalyst in pharmaceutical and chemical syntheses as well as in the reduction of harmful exhaust emissions. Therefore, the development of high performance palladium catalysts is an area of major concern. In this paper, we present the synthesis of highly branched palladium nanostructures in a simple solution phase reaction at room temperature. By varying the nature of the organic stabilizer system we demonstrate control over the reaction kinetics and hence the shape of the nanostructures. Investigations into the structural evolution of the nanostructures show that they form from multiply twinned face centered cubic (fcc) nanoparticle nuclei. Reaction kinetics then determine the resulting shape where ultrafast growth is shown to lead to the highly branched nanostructures. These results will contribute greatly to the understanding of complex nanoparticle growth from all fcc metals. The nanostructures then show excellent catalytic activity for the hydrogenation of nitrobenzene to aniline.

Synthesis, Alignment, and Magnetic Properties of Monodisperse Nickel Nanocubes

This Communication describes the synthesis of highly monodispersed 12 nm nickel nanocubes. The cubic shape was achieved by using trioctylphosphine and hexadecylamine surfactants under a reducing hydrogen atmosphere to favor thermodynamic growth and the stabilization of {100} facets. Varying the metal precursor to trioctylphosphine ratio was found to alter the nanoparticle size and shape from 5 nm spherical nanoparticles to 12 nm nanocubes. High-resolution transmission electron microscopy showed that the nanocubes are protected from further oxidation by a 1 nm NiO shell. Synchrotron-based X-ray diffraction techniques showed the nickel nanocubes order into [100] aligned arrays. Magnetic studies showed the nickel nanocubes have over 4 times enhancement in magnetic saturation compared to spherical superparamagnetic nickel nanoparticles.

Dithiocarbamate ligand stabilised gold nanoparticles

Dithiocarbamates are used as adsorbates for the preparation of gold nanoparticles. A range of mono- and tetrakis-functionalised dithiocarbamate ligands containing alkyl, benzyl and resorcinarene cavitand substituents are synthesised. Nanoparticles are prepared by a two-phase synthesis and are characterised by 1H NMR spectroscopy, UV-Visible spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX) and elemental analysis. The colloids are found to be stable over a number of months storage in air. The synthetic versatility of the dithiocarbamate ligand is further demonstrated by the synthesis of ruthenium(II) bipyridyl dithiocarbamate capped gold nanoparticles.

Engineering Preformed Cobalt-Doped Platinum Nanocatalysts For Ultraselective Hydrogenation

Bimetallic heterostructures are used as industrial catalysts for many important transformations. However, conventional catalysts are primarily prepared in cost-effective manners without much appreciation in metal size control and metal-metal interaction. By employing recent nanotechnology, Pt nanocrystals with tailored sizes can be decorated with Co atoms in a controlled manner in colloid solution as preformed nanocatalysts before they are applied on support materials. Thus, we show that the terminal CO hydrogenation can be achieved in high activity, while the undesirable hydrogenation of the CC group can be totally suppressed in the selective hydrogenation of alpha,beta-unsaturated aldehydes to unsaturated alcohols, when Co decorated Pt nanocrystals within a critical size range are used. This is achieved through blockage of unselective low coordination sites and the optimization in electronic influence of the Pt nanoparticle of appropriate size by the Co decoration. This work clearly demonstrates the advantage in engineering preformed nanoparticles via a bottom-up construction and illustrates that this route of catalyst design may lead to improved catalytic processes.

Interstitial modification of palladium nanoparticles with boron atoms as a green catalyst for selective hydrogenation

Lindlar catalysts comprising of palladium/calcium carbonate modified with lead acetate and quinoline are widely employed industrially for the partial hydrogenation of alkynes. However, their use is restricted, particularly for food, cosmetic and drug manufacture, due to the extremely toxic nature of lead, and the risk of its leaching from catalyst surface. In addition, the catalysts also exhibit poor selectivities in a number of cases. Here we report that a non-surface modification of palladium gives rise to the formation of an ultra-selective nanocatalyst. Boron atoms are found to take residence in palladium interstitial lattice sites with good chemical and thermal stability. This is favoured due to a strong host-guest electronic interaction when supported palladium nanoparticles are treated with a borane tetrahydrofuran solution. The adsorptive properties of palladium are modified by the subsurface boron atoms and display ultra-selectivity in a number of challenging alkyne hydrogenation reactions, which outclass the performance of Lindlar catalysts.

Printed gold for electronic applications

Molecular and nanoparticulate gold precursors for application in inkjet printing onto flexible substrates are discussed. The choice of stabilising ligands and the size of the nanoparticles influence the solution stability of the ink and their ability to form decorative or conductive functional films.

The use of gold mercaptides for decorative precious metal applications

An overview of the use of soluble gold mercaptide compounds as precursors in Decorative Precious Metal (DPM) ink formulations, for application onto ceramic, glass and plastic substrates, is given. Synthetic, thermal, structural and metallisation properties are highlighted, together with the advantages that these precursors show for DPM ink applications. The literature reviewed covers the period 1960 to 2001. Mechanistic studies are described and likely future trends indicated.

Atomic Resolution Observation of a Size-Dependent Change in the Ripening Modes of Mass-Selected Au Nanoclusters Involved in CO Oxidation

Identifying the ripening modes of supported metal nanoparticles used in heterogeneous catalysis can provide important insights into the mechanisms that lead to sintering. We report the observation of a crossover from Smoluchowski to Ostwald ripening, under realistic reaction conditions, for monomodal populations of precisely defined gold particles in the nanometer size range, as a function of decreasing particle size. We study the effects of the CO oxidation reaction on the size distributions and atomic structures of mass-selected Au(561±13), Au(923±20) and Au(2057±45) clusters supported on amorphous carbon films. Under the same conditions, Au(561±13) and Au(923±20) clusters are found to exhibit Ostwald ripening, whereas Au(2057±45) ripens through cluster diffusion and coalescence only (Smoluchowski ripening). The Ostwald ripening is not activated by thermal annealing or heating in O2 alone.

Functional thin film coatings incorporating gold nanoparticles in a transparent conducting fluorine doped tin oxide matrix

Noble nanoparticle–metal oxide composites attract research interest due to their unique combination of properties. We report the successful combination of gold nanoparticles (AuNPs) and F-doped SnO2 composites by layering, producing films that demonstrate unique and interesting optoelectronic properties – high visible transparency, electrical conductivity and with additional plasmonic effects. Both of the layers were deposited by aerosol assisted chemical vapour deposition (AACVD) onto heated glass substrates. Four distinctive sets of films were prepared and analysed consisting of: gold nanoparticles, F-doped SnO2 (FTO), a layer of gold nanoparticles on FTO and an FTO layer on gold nanoparticles. The sizes of the AuNPs were shown to depend on the precursor concentration used. Layered Au:FTO composite films have an attractive blue colouration from the surface plasmon resonance (SPR) of the AuNPs yet have high transparency in the visible region and are electrically conducting, comparable to commercial FTO.

Heteropolymetallic copper(II)-gold(III) dithiocarbamate [2]catenanes via magic ring synthesis

A rare class of mixed-metal [2]catenane has been assembled via magic ring synthesis of dinuclear copper(II) and gold(III) dithiocarbamate macrocycles.