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Curtin University
Staff Profile

Dr Debbie Silvester-Dean

Dr Debbie Silvester-Dean Dr Debbie Silvester-Dean

MSci (Bristol, UK), DPhil (Oxford, UK)

Position Senior Research Fellow
Faculty Faculty of Science and Engineering
School School of Science
Department Department of Chemistry
Campus Bentley Campus
Location 500.4112
Phone 08 9266 7148
Email D.Silvester-Dean@curtin.edu.au
Twitter twitter.com/debbiesilvester
Website debbiesilvester.wordpress.com
Linked In linkedin.com/in/debbie-silvester-790b6536
ORCID orcid.org/0000-0002-7678-7482
ResearcherID www.researcherid.com/rid/D-4679-2013
Google Scholar scholar.google.com.au/citations?user=51P07a4AAAAJ&hl=en
Scopus Author Identifier www.scopus.com/authid/detail.url?authorId=14623139100

Brief Summary

Debbie Silvester’s research activities include understanding electrochemical processes with a focus on sensing. She is particularly interested in the role of room temperature ionic liquids (RTILs) as replacements for organic solvents in various electrochemical reactions. RTILs are a new and interesting class of solvent that possess several properties such as: negligible vapour pressure, intrinsic conductivity, wide electrochemical windows, high chemical and thermal stability, high polarity and the ability to dissolve a wide range of compounds.

Overview

Current interests include:

Electrochemical behaviour of toxic gases in RTILs. Before RTILs can be employed in sensor devices, the fundamental behaviour of gases in RTILs needs to be uncovered. We aim to investigate the electrochemical reactions and mechanisms of various toxic gases  in RTILs, and uncover information about various analytical parameters (e.g. sensitivity and selectivity towards a certain gas). The toxic gases under investigation include ammonia, chlorine, hydrogen chloride and methylamine, in addition to other gases such as oxygen and nitrous oxide. It is imperative to understand the reaction mechanisms of gases in RTILs, to determine if any follow-up chemical reactions may detramentally affect the sensor response. Additionally, since there are many different RTILs available for electrochemical experiments, it is also important to determine which RTIL is suitable for sensing any particular gas. For example, we recently showed that RTILs containing [BF4]- and [PF6]- ions are not suitable for the detection of HCl gas, due to the formation of HF.

Electrochemical behaviour and detection of explosives (e.g. TNT) in ionic liquids. Explosive compounds are increasingly being used by terrorists, and there is much interest in developing on-the-spot, low-cost, robust, portable and miniaturised gas sensors to detect trace concentrations of explosive materials in real samples. Redox-active explosive compounds such as TNT and DNT can be detected electrochemically through the reduction of the nitro groups present in the compounds. We have recently demonstrated that the reaction mechanism for TNT reduction in (aprotic) ionic liquids is very different to that in water. For example, a 6 electron reduction occurs at each nitro group in water (18 electrons total), but only a 1-electron reduction of the nitro groups is observed in ionic liquids. Interestingly, the radical anion of TNT was found to dimerise to produce azo or azoxy compounds, resulting in an electrochemically generated red solid. An overall EC2 reaction mechanism was proposed, based on the experimental observations and digital simulation of the cyclic voltammetry.  We aim to expand this work further by studying the detection of explosive compounds in real soil samples. This work is in collaboration with Prof. Simon Lewis at Curtin (Chemistry) and is currently being investigated by PhD student Holly Yu.

Planar electrode devices: SPEs, TFEs and MATFEs. Conventional three-electrode cells   employed in research laboratories are not suitable for real sensor devices due to their large size and inability to be miniaturised. Planar devices such as screen-printed electrodes (SPEs), thin-film electrodes (TFEs) and microarray thin-film electrodes (MATFEs) have become commercially available to researchers in the last few years, costing only a few $$ per device. Microarray electrodes have advantages over SPEs and TFEs due to the increased radial diffusion, lower Ohmic drop and higher current density. We are interested in employing these planar, low-cost devices for electrochemical experiments, particularly for sensing applications. However, since these surfaces are not as ‘ideal’ as conventional  metal electrodes (e.g. micro disk and macro disk), and cannot be easily polished, the behaviour of analytes on these surfaces needs to be studied. An example of where the behaviour is different to conventional solvents is oxygen reduction on Pt SPEs in ionic liquids containing the imidazolium cation. In imidazolium ionic liquids, a reaction of the superoxide with the C(2) proton was observed, catalysed by materials present in the screen-printed paste. Since the manufacturers do not readily disclose the nature of the inks used in their manufacture, the exact nature of the compounds in the paste are generally unknown, but can obviously be detrimental to the sensing response. We later showed that the response could return to more ‘ideal’ behaviour by simple mechanical polishing of the SPE device. The achievement of long-term real-time oxygen detection was achieved by polishing. We are also working with graphite SPEs with Prof. Craig Banks, to assess their suitability for gas sensing in ionic liquids. TFEs and MATFEs are made entirely of metal and have flat and smooth surfaces, and appear to be more promising for electroanalytical applications.

Spill-less gas sensors using gelled ionic liquids. When employing miniaturised membrane-free planar devices such as SPEs and TFEs for gas sensing, RTILs are highly advantageous due to their non-volatile nature. However, even a microlitre droplet of ionic liquid can be unstable (i.e. will flow) if the electrode device is tilted on its side or turned upside down. This leads to an instability in the voltammetric response. To overcome this issue, we have combined an ionic liquid with a polymer, poly(methyl methacrylate) (PMMA) to produce a gelled material that does not flow when placed in a vertical orientation. With the gelled electrolyte, the voltammetry is very stable and does not change when the electrode is tilted in different orientations. An added advantage is that we can use gelled electrolytes with MATFEs to achieve long-term oxygen sensing at high concentrations (up to 100 %), which is very difficult to achieve with other solvent/electrolyte combinations. PostDoc Junqiao Lee is currently working on this area of research.

Modification of electrode surfaces for enhanced sensing response. For highly toxic gases such as ammonia, a sensor device is required to detect and quantify very low (often sub ppm) concentrations. Often bare metal electrodes (e.g. platinum, gold, glassy carbon) with viscous RTIL solvents do not offer the sensitivity required at trace concentrations. In these cases, we will use surfaces modified with nano materials in order to achieve enhanced sensitivities and improved limits of detection. We are currently investigating the deposition of platinum nanoparticles and other platinum structures onto bare electrodes to enhance the sensitivity towards ammonia gas. Another strategy is to fill the holes of recessed microarray electrodes (e.g. MATFEs) to improve the radial diffusion characteristics of these electrodes, enabling the detection of lower concentrations. We use SEM and AFM (and occasionally XPS) to characterise the electrodeposited materials. PhD student Ghulam Hussain is currently working on this project.

Deposition of mesoporous materials for hydrogen storage and electroanalytical applications. The storage of hydrogen is one of the most important issues that remains to be solved before the mass implementation of hydrogen as an energy carrier becomes commercially viable. Our role is to investigate the kinetic and thermodynamic benefits of using mesoporous metal scaffolds as reactive containment vessels for hydrogen storage materials. The electrodeposition of different metals (e.g. aluminium/platinum) around inert polystyrene spheres (PSSs) of nanometre dimensions can afford porous metal scaffolds to be used for these applications. The results of this research will be used to tune hydrogen desorption temperatures and pressures of various light weight hydrogen storage materials to generate new materials attractive to the automobile industry. This work is in collaboration with Prof. Craig Buckley at Curtin (Physics), and is currently being investigated by PostDoc Dr. Veronica Sofianos and Honours student Caitlyn Gibson.

Ion sensing at water|RTIL interfaces. Electrochemistry at the liquid|liquid interface offers the possibility to detect ions that are cannot be detected at conventional solid|liquid interfaces (i.e. are not redox active). Conventional liquid|liquid ion sensing employs a water phase in contact with an immiscible organic solvent such as 1,2-dichloroethane or nitrobenzene. Recently, hydrophobic RTILs have also been explored at the liquid|liquid interface. We have demonstrated the transfer of simple ions (e.g. tetra alkyl ammonium cations, and tetrafluoroborate or hexaflurorphosphate anions) across the water|ionic liquid interface, and also extended this to the detection of biological molecules such as lysozyme. During this work, we also uncovered some unique behaviour of protons at the water|RTIL interface, that lead us to propose a “void-assisted” ion pairing interaction of protons with the RTIL anion ([FAP]-). Although the potential windows at these interfaces are smaller than for conventional solvent/electrolyte combinations, this shows scope for detection of ions using ionic liquids as the water-immiscible phase. This work is in collaboration with Prof. Damien Arrigan at Curtin (Chemistry).

Redox behaviour of dissolved metal complexes in RTILs. The fundamental investigation of redox processes in metal complexes is of major importance for the design of new multifunctional molecular materials such as molecular wires, switches, photoluminescence sensors and molecular logic operators to name a few. Cyclic voltammetry in ionic liquids offers a versatile system for this investigation, however there are not many studies available on this topic to date. We explore the electrochemistry of newly-synthesized metal complexes in ionic liquids to understand the electronic properties of these exciting materials. The results will generate vital information and new knowledge for the application of these complexes in a variety of fields such as biological labels, molecular materials or luminescent devices. This work is in collaboration with Dr. Max Massi at Curtin (Chemistry).

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Memberships, Awards and Training

Awards and Research Grants:

2014-17: ARC Discovery Project (DP) "Mesoporous Metal Scaffolds: Reactive Containment Vessels" with Prof. Craig Buckley and Dr. Drew Sheppard (Curtin Physics)

2013: AM Bond Medal for contributions to electrochemistry in Australia from a young researcher. Awarded by the electrochemical division of the RACI (Royal Australian Chemical Institute).

2013: Finalist for the Woodside Early Career Researcher of the Year (WA Science Awards).

2012-present: ARC Discovery Early Career Research Award (DECRA) "Electrochemical behaviour of toxic gases and explosives in room temperature ionic liquids"

2013: ARC LIEF with M. Massi and others "Western Australian advanced fluorescence and phosphorescence characterisation facility"

2013: ARC LIEF with M.I. Ogden and others "A facility for the nanoscale imaging and characterisation of materials"

2012: Pro-Vice Chancellors Researcher of the Year Award (Early Career), Faculty of Science and Engineering, Curtin University

2011: Electrochimica Acta Travel Award for Young Electrochemists to attend the 62nd Annual meeting of the International Society of Electrochemistry (ISE) in Niigata, Japan.

2011: Curtin Internal Research Grant (IRG) "Development of an Electrochemical Gas Sensor for the Detection of Toxic Gases and Explosives"

2009-2012: Curtin Research Fellowship "Investigation into the Fundamental and Applied Aspects of Electrochemical Sensors"

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Employment History

2015-present: Senior Research Fellow, Department of Chemistry, Curtin University

2012-present: Discovery Early Career Research Fellow, Department of Chemistry, Curtin University

2009-2012: Curtin Research Fellow, Department of Chemistry, Curtin University

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Teaching

2017 - Chemical Energetics and Kinetics 2000 - Thermodynamics

2013-2017 - Chemical Sensing and Measurement 3002 - Electrode Dynamics

2011-2012 Nanochemistry 341- Nanoscale Sensing

2012 Chemistry 401- Dynamic Electrochemistry

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Research Fields

Chemical Sciences

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Research Interests

Electrochemistry, sensors, room temperature ionic liquids, gas detection, solid/liquid interface, liquid/liquid interface, nanomaterials, functionalizing surfaces

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Publications

2016

Book Chapters (Research)

Journal Articles (Research)

2015

Journal Articles (Research)

2014

Journal Articles (Research)

2013

Journal Articles (Research)

2012

Journal Articles (Research)

2011

Journal Articles (Research)

2010

Journal Articles (Research)

2009

Journal Articles (Research)

2008

Book Chapters (Research)

Journal Articles (Research)

2007

Journal Articles (Research)

2006

Journal Articles (Research)

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Other Information

Invited presentations

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