Dr Gerry Swiegers (Adjunct Fellow)

Qualifications

BSc Hons cum laude
PhD Chemistry (Connecticut)

Biographical Statement

Gerry Swiegers is Vice-President R&D at Datatrace-DNA P/L, a company formed from his research in 2005, and an Adjunct Fellow in the Intelligent Polymer Research Centre. He actively collaborates with various members of the ARC Centre of Excellence for Electromaterial Science, including Prof Gordon Wallace, Prof Leone Spiccia, and Dr Jun Chen. He was previously leader of the Security Devices research group at CSIRO Molecular and Health Technologies in Melbourne.

Research Interests and Activities

“Mechanical” (Machine-like) Catalysts:
Chemical reactions may be controlled by either: (1) the minimum threshold energy that must be overcome during collisions between reactant molecules / atoms (the Activation Energy, Ea), or: (2) the rate at which reactant collisions occur (the Collision Frequency, A) (for reactions with low Ea,). Reactions of type (2) are governed by the physical, mechanical interaction of the reactants. Such mechanical processes are unusual, but not unknown in molecular catalysts. The nature of the action in several abiological mechanical catalysts can be shown to be machine-like in that it depends on synchronized, dynamic interactions driven by a mechanical impulse, which is, in this case, conformational flexing of the catalyst molecule.
Many Enzymes are Mechanical Catalysts:
In recent years, we have found that many enzymes appear to employ a mechanical mode of action. In such species the catalytic process is driven by the vigor and regularity of conformational fluctuations in the molecular framework of the catalyst, and not by an inherent predilection for catalysis on the part of the catalytic functional groups (as is normally the case). These conformational changes lead to reactive collisions between the bound reactants. The catalytic action is therefore unique in being controlled by the mechanics of reactant encounter rather than by its thermodynamics. Moreover, the catalysts act like molecular "machines", taking in reactants and transforming them into products in an action that is fundamentally driven by the mechanical impulse of conformational flexing.
A Connection with Complex Systems Science:
Catalysts that act like molecular "machines" are complex in their actions and provide examples of complex systems. This is because they involve multiple components interacting cooperatively in a synchronized, time-dependent manner. In the absence of the necessary synchronization, each individual component within a machine is unable to achieve a useful effect and is therefore quite useless.
H2-Generating Mechanical Catalysts: (with Prof G. G. Wallace, Dr J. Chen (Wollongong University))
We have recently illuminated the action of a [1.1]ferrocenophane molecular catalyst that appears to employ a mechanical action to generate H2 from acidic H2O. When coated on the Pt surface in a normal hydrogen electrode, this catalyst or its FeSO4 analogue, accelerates the rate of H2 generation by ca. 7-fold (Figure 1). Under illumination by sunlight, when deposited on p-type Si, this catalyst has previously been shown to generate, continuously, over 5 days of testing, 5 molecules H2 s-1 catalyst-1.
O2-Generating Mechanical Catalysts: (with Prof G. C. Dismukes (Princeton University), Prof L. Spiccia (Monash University)
We have developed a model of the Photosystem II Water Oxidizing Complex (Figure 2,3) found in all photosynthetic organisms, that spontaneously oxidizes water when illuminated with light under a bias of 1.00 V (vs. Ag/AgCl). This catalyst, which generates O2 continuously from H2O over at least 65 h of testing, achieves average turnover frequencies of 24 molecules O2 h-1 catalyst-1 and peak turnover frequencies of 270 molecules O2 h-1 catalyst-1.
A Water-Splitting Solar Cell: (with Prof G. C. Dismukes (Princeton University), Prof L. Spiccia (Monash University)
Recent work has shown that the above O2-generating catalyst readily redox couples with Ru(bipyridyl) dyes of the type used in Dye-Sensitized Solar Cells, such as the Graetzel cell. This has allowed us to build and demonstrate a free-standing, self-contained Dye-Sensitized Solar Cell (DSSC) that spontaneously splits water into hydrogen and oxygen when illuminated with sunlight. No external bias is required as the DSSC generates its own electrical current and voltage upon illumination. An electrolyte of distilled water, or even seawater, can be used. The oxygen generating electrode of this cell mimics, in principle, the organization and operation of the Photosystem II Water-Oxidizing Complex.

Significant recent publications

Mechanical Catalysis. Methods of Homogeneous, Heterogeneous, and Enzymatic Catalysis, Swiegers, G. F. (Ed), John Wiley and Sons, New York, 2008 (ISBN 978-0-470-26202-3)
Homogeneous Catalysts with a Mechanical (“Machine-like”) Action. Swiegers, G. F.; Huang, J.; Brimblecombe, R.; Chen, J.; Dismukes, G. C.; Mueller-Westerhoff, U. T.; Spiccia, L.; Wallace, G. G. Chemistry, A European Journal 2009, 15, 4746
Sustained Water Oxidation Catalysis by a Bio-Inspired Molecular Cluster. Brimblecombe, R.; Swiegers, G. F.; Dismukes, G. C.; Spiccia, L. Angewandte Chemie, International Edition 2008, 47, 7335 (“Hot” Paper; Top few percent of papers published in Angewandte Chemie)
Nano Pt-Modified, Flexible, Aligned Carbon Nanotubes are Efficient, Robust, High Surface Area Electrocatalysts. Chen, J.; Zhang, W.; Swiegers, G. F.; Too, C. O.; Wallace, G. G. Chemistry of Materials 2008, 20, 2603
An Efficient Bifunctional Catalyst of Methanol Oxidation. Chen, J.; Swiegers, G. F.; Wallace, G. G.
Organometallics. 2007, 26, 4860.
A Readily-Prepared, Convergent, Oxygen Reduction Electrocatalyst. Chen, J.; Zhang, W.; Officer, D.; Swiegers, G. F.; Wallace, G. G. Chemical Communications 2007, 3353
A readily-prepared electrocatalytic coating that is more active than Pt for hydrogen generation in 1 M strong acid. Chen, J.; Huang, J.; Swiegers, G. F.; Too, C. O.; Wallace, G. G. Chemical Commuications. 2004, 308 (“Hot” Paper; Top 10% of papers published in Chemical Communications)