STM image (25nm) of low coverage of MoO3 on Fe3O4
The topic for the Faraday discussion in Berlin this year is the formation and chemistry of nanoparticles on surfaces. Discussion has been very lively and a number of interesting points have arisen. One is the way in which the ligands associated with a deposited nanoparticle can be critical to its behaviour, something that alot of the surface science studies do not consider. Gold on TiO2 remains a topic of huge interest but I am reminded by one of Graham Hutching’s contributions to the discussion that CO oxidation may not be the best reaction to study since there is clear evidence that it involves at least three different mechanisms dependent on temperature and conditions. My contributed talk on the formation of Molybdenum oxide films is available on Slideshare.
Presentation to SURCAT’s Dennis Dowden Commemoration meeting in Durham on 3-4th April 2013. The talk describes our recent work on the local etching of graphite surfaces by weak acids and their influence on the deposition of gold.
Slides now available on Slideshare
Posted in Catalysis, Nanoparticles
Tagged AFM, catalysis, delamination, Dowden, gold, graphene, Graphite, HOPG, STM, XPS
My presentation on Hatem’s recent work on HCl reactions on the different oxygen phases on Cu(100) is available to view on slideshare
The picture here shows STM images of the missing row O(a) structure as it reacts with HCl at room temperature.
See the Prezi which I presented at UCL today, the lecture discussed both our work on amine/oxygen interactions of a few years ago and our newest work on the treatment of carbon surfaces with acid.
Gold deposition on HCl treated graphite
Rob presented the first results of the EPSRC grant: EP/I038748/1 at the RSC Postgraduate Symposium on Nanotechnology in Birmingham
This figure is from the talk and shows how graphite surfaces are modified by treatment with acid. The work has been submitted to Carbon for publication.
Carbon catalyst supports are usually treated with acid before the adsorption of the active phase and often reactivated with a similar treatement. But what effect does the acid treatement have on the carbon and how does it influence the adsorption of the active phase? Highly oriented pyrolytic graphite (HOPG) samples were treated with dilute HCl and HNO3 under ambient conditions and examined with AFM, STM and XPS to explore this issue. Raised features were formed on the HOPG surface after acid treatment. These protrusions were typically 4-20 nm in height and between 10 to 100 nm in width, covering 5% to 20% of the substrate for acid concentrations between 0.01 and 0.5 M. Both width and surface density of the features increases with acid concentration but the heights are not affected. STM images show that the graphite lattice extends over the protrusions indicating that the features are “blisters” on the surface rather than deposited material, a view that is supported by the XPS. We propose that penetration of the acid at defective sites leads to a decrease in the interplanar van der Waals forces and a local delamination. Deposition of Au onto the acid treated surfaces showed fundamental differences in the way Au is adsorbed depending on which acid is used. AFM showed that HCl pre-treatment facilitates the formation of significant independent Au clusters on top of the delamination sites whereas HNO3 pre-treatment results in rather larger less dispersed structures. XPS revealed that HCl enables greater Au deposition thanHNO3, and also increases the presence of Au0 state on the surface
Dave, Rob & Phil provide a stand for the launch of the Science Strategy for Wales. For 45 minutes before the presentation by Prof Harries we were bombarded with interested experts & non experts.
Dave explaining the STM to an interested visitor
Prof. Harries gave an impassioned plea for the academic community in Wales to work together to try to match Scotland’s achievements. The headline catching part of his presentation is the £50m to bring in top scientists but will they stay and what is he going to do to build up the ground level workers to support them. PhD students are the bedrock of chemisty and EPSRC’s policies are having a dramatic effect on the number of PhD places situated in Wales.
Professor John Harries, the Chief Scientific Adviser for Wales, at 5.45pm for 6.30pm, Julian Hodge Building, Colum Road, Cardiff CF10 3EU.
Thursday, 15 March 2012, Julian Hodge Building, Colum Drive, Cardiff CF10 3EU
The ability to design the structure of particles at the nanoscale is a key requirement to making this technology work for us in practical ways. In the latest ACS nano, Yang et al. have reported a way of creating gold nanorods tipped with silver. The method involves preparing Au@Ag core-shell rods and then selectively etching away the silver in the middle section of the rod with FeCl2. Etching commences in the middle of the rods and if stopped at the right time leaves them gold centres and silver coated ends. The catalytic activity of the rods towards the reduction of p-nitrophenol at room temperature appears to be enhanced.
Selective etching of Au@Ag nanorods
Lateral Etching of Core–Shell Au@Metal Nanorods to Metal-Tipped Au Nanorods with Improved Catalytic Activity – ACS Nano ACS Publications.
ACS Nano, 2012, 6 (2), pp 1165–1175