Professor Gerry Swiegers
BSc Hons cum laude
Gerry Swiegers is a Professor in the Intelligent Polymer Research Institute (IPRI). He is also an Adjunct Fellow of the ARC Centre of Excellence for Electromaterials Science (ACES). He actively collaborates with various members of ACES, including Professor Gordon Wallace, Professor Doug MacFarlane, and Dr Jun Chen. Gerry was previously leader of a 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 appear to be 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 regular, repeated 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.
Hydrogen-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 hydrogen from acidic water. When coated on the platinum surface in a normal hydrogen electrode, this catalyst or its FeSO4 analogue, accelerates the rate of H2 generation by ca. 7-fold. 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.
Oxygen-Generating Mechanical Catalysts: (with Prof G. C. Dismukes (Princeton and Rutgers Universities), Prof L. Spiccia (Monash University))
We have developed a model of the Photosystem II Water Oxidizing Complex 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 and Rutgers University), Prof L. Spiccia (Monash University))
Recent work has shown that the above O2-generating catalyst readily redox couples with Ru(bipyridyl)3 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)
- Solar Driven Water Oxidation by a Manganese Molecular Catalyst Inspired by Photosystem II. Brimblecombe, R.; Koo, A.; Dismukes, G. C.; Swiegers, G. F.; Spiccia, L. Journal of the American Chemical Society 2010, 132, 2892
- 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
- Lessons from Photosystem II for the Development of Abiological Mn-oxo Water Oxidation Catalysts. Dismukes, G. C.; Brimblecombe, R.; Felton, G. A. N.; Pryadun, R. S.; Spiccia, L.; Swiegers, G. F. Accounts of Chemical Research 2009, 42, 1935
- 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)
- 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)
phone (direct line): +61-2-4221-5577
phone (secretary): +61-2-4221-3127