2012 Seminars

Our cells, the ones that join together to make our bodies, are fairly small.  Even smaller, sometimes much smaller, are the shapes that nanofabrication can provide.

The results of projects mixing these aspects are expected to impact strongly on health, both well-being and recovery from disease. Imaging methods, such as AFM produce 3-D information, at the nanoscale level, on the morphologies of pores through which cells release compounds that transmit messages from one tissue to another.

It appears that these messages are altered according to the physical environment of the cell. Polymers have been used to make moulds of cell populations as Bioimprints and these were used as substrates for other cells to grow on. Our results, indeed, indicate that both the topology of the substrate and its chemical nature affect cell activity.

The opposite perspective, of examining individual cells that are isolated from interactions with neighbours, is being approached by fabricating chips that allow study of cells with addresses that can be repeatedly revisited. Microfluidics is applied so artificial solutions flow around the cells.  It appears that poking cells or altering the micro- or nano-environment, and thus the mechanical forces at the surface, might lead to a cure for cancer, make injured muscles grow again, and direct cosmetic changes.

Hide-and-seek games in resonant Raman spectroscopy

Dr Baptiste Auguié
Victoria University of Wellington

A persistent challenge in Raman spectroscopy has always been the characterisation of resonant dye molecules, where an overwhelming fluorescence often masks the weak Raman signals, with an intensity ratio that can reach as much as 5 orders of magnitude.

A noise analysis performed on a standard Raman spectrometer demonstrates that a naïve averaging procedure – increasing of the number of acquisitions – is not sufficient to reveal the Raman peaks above the noise level. Our group recently investigated two practical techniques to overcome this issue and regain a signal-to-noise ratio only limited by the acquisition time (shot noise). I will describe these two techniques and illustrate their great potential in resonant Raman spectroscopy with our most recent experimental results. Furthermore, I will show that the second method is applicable to a much wider range of spectroscopic and/or imaging measurements, where a weak signal is swamped in an overwhelming background.

Fermi surface reconstruction and pseudogap asymmetry in the high-T_c cuprates

Dr James Storey
Industrial Research Limited

Twenty six years since their discovery the origin of superconductivity in the cuprate high-temperature superconductors remains a major outstanding challenge in physics and an active area of research in the MacDiarmid Institute.Their relatively simple layered two-dimensional crystal structure conceals an extremely rich electronic behaviour as a function of hole doping.

Recently, we have found that evidence from NMR of a two-component spin system is paralleled by similar evidence from the electronic entropy so that a two-component quasiparticle fluid is implicated. We propose that this two-component behaviour arises from reconstruction of the energy-momentum dispersion into two branches, giving rise to a particle-hole asymmetric pseudogap and small Fermi surface pockets. If correct then it follows that single-component electronic behavior will be recovered when the pseudogap closes in the overdoped regime.We illustrate this by calculating the spin susceptibility using a resonating valence bond spin liquid model, finding excellent agreement with the NMR results. The possible detection of electron-like Fermi surface pockets in the thermopower will also be presented.

Victoria University of Wellington, Room RB105
University of Otago, Teaching & Learning Facilities, AVC2
University of Auckland, 23 Symonds St, Rm 411, Chemistry Building 301
Massey University, Science Block, Room to be advised
Industrial Research Ltd – Gracefield Campus, C-Block Meeting Room
University of Canterbury – Kirkwood Village, KE06

Upcoming Seminars

Fishing for Chloride in Salty Waters using Photoactive Foldamers
Date:Thu 4^th October 2012 - 12:15pm - 1:00pm
Professor Amar H. Flood, Dept. of Chemistry, Indiana University, USA

Recent Seminars:

Gold, silver and copper
Date: Thu 6^th September
Dr Doreen Mollenhauer, Industrial Research Limited
Dr Nadia Grillet, University of Canterbury

The Future of Solar Technology as Clean Energy
Date: Thu 2^nd August 2012 - 12:15pm - 1:00pm
Professor Yoshitaka Okada, Research Center for Advanced Science and Technology, The University of Tokyo

Dr Bob Buckley, Industrial Research Limited

Resonant Raman Spectroscopy and Origins of Superconductivity
Date: Thu, 7 June 2012 - 12:15pm - 1:00pm
James Storey ,  Industrial Research Limited
Baptiste Auguie, Victoria University of Wellington

UV radiation in New Zealand: implications for health
Date: Thu, 3 May 2012 - 12:15pm - 1:00pm
Dr Richard McKenzie, Principal Scientist, NIWA

When the fairly small bits meet the tiny, tiny bits … different things will happen
Date: Thu, 5 April 2012 - 12:15pm - 1:00pm
John Evans, Christchurch School of Medicine, University of Otago, Christchurch

Terry L. Gustafson, Photon Factory, University of Auckland and Center for Chemical and Biophysical Dynamics, Ohio State University

Dr Volker Nock, Electrical and Computer Engineering, University of Canterbury

Venues:

• Victoria University of Wellington, RB105, Rankin Brown Building
• University of Otago, Teaching & Learning Facilities, AVC2
• University of Auckland, 23 Symonds St, Rm 411, Chemistry Building 301
• Massey University, Science Block, Room to be advised
• Industrial Research Ltd – Gracefield Campus, C-Block Meeting Room
• University of Canterbury – Kirkwood Village, KE06

If you are unable to attend at one of the above locations the seminar can be viewed via Scopia Desktop.

Dr Doreen Mollenhauer, Industrial Research Limited

Dr Nadia Grillet, University of Canterbury

Dr Doreen Mollenhauer
Industrial Research Limited

Towards the understanding of the chemical environment effect on small gold-containing clusters

Gold clusters and nanoparticles have attracted continuing attention due to interesting and important electronic, catalytic and optical properties [1,2]. The understanding of the effect of the chemical environment on these properties is essential for a complete and realistic picture. In order to demonstrate the influence of the ligand shell on the electronic properties, we will present various gold clusters surrounded by phosphine ligands. To describe the system accurately, we have performed benchmark calculations including coupled cluster, MP2 and DFT approaches, as well as considering medium and long range dispersion effects via a dispersion correction. The need for such studies has been shown for example in investigations of gold systems with carbon monoxide [3] or pyridine [4]. Furthermore as bimetallic gold-palladium catalysts have been found to have improved catalytic properties in various reactions in comparison to the monometallic clusters, the influence of the ligand shell on the mixed clusters was also analyzed.
 

[1]        M.-C. Daniel, D. Astruc, Chem. Rev., 104, 293 (2004).
[2]        M. Turner, V. B. Golovko, O. P. H. Vaughan, P. Abdulkin, A. Berenguer-Murcia, M. S. Tikhov, B. F. G. Johnson, R. M.  Lambert,     Nature, 454, 981 (2008).
[3]        P. Schwerdtfeger, M. Lein, R. P. Krawczyk, C. R. Jacob, J. Chem. Phys., 128, 124302 (2008).
[4]        D. Mollenhauer, J. Floß, H.-U. Reissig, E. Voloshina, and B. Paulus, J. Comput. Chem. 32, 1839 (2011).

Dr Nadia Grillet
University of Canterbury

Silver-copper nanoclusters: Structure and time evolution

There is currently a great deal of interest in bimetallic nanoclusters because of both fundamental scientific questions and their possible technological applications. Ag-Cu clusters are of particular interest for the production of nanoscale chips. In our case, the clusters are prepared by inert gas aggregation in an ultra high vacuum compatible magnetron sputtering system (1). The structures have been observed by bright field high resolution Transmission Electron Microscopy (TEM) and high-angle annular dark field (HAADF) scanning TEM (2) as a function of the alloy composition, the coverage of the sample and the size of the clusters. Fresh Ag-Cu clusters have shown a very complex structure but over time a progressive rearrangement occurs, finally yielding well-ordered structures.

[1]       R. Reichelet al., Journal of Nanoparticle Research 8, 405 (2006).
[2]       Z. Y. Liet al., Nature 451, 46 (2007).

Venues
Victoria University of Wellington, Room RB105
University of Otago, please use Scopia Desktop
University of Auckland, 23 Symonds St, Rm 411, Chemistry Building 301
Massey University, please use Scopia Desktop
Industrial Research Ltd – Gracefield Campus, C-Block Meeting Room
University of Canterbury – Kirkwood Village, KE06