Characterising the infrared spectra of minerals through ab initio simulation

Dr. Marco De La Pierre

Department of Chemistry and Nanostructured Interfaces and Surfaces Centre of Excellence, Università degli Studi di Torino, Turin, Italy

Ab initio quantum-mechanical simulation has nowadays reached a high level of accuracy in the prediction of infrared (IR) properties, namely frequencies and intensities, of crystalline solids [1,2]. Two advanced case studies are here presented, involving the use of hybrid Hartree-Fock / Density Functional Hamiltonians and localized Gaussian-type basis sets.

A novel approach has recently been proposed [3,4], that makes large use of symmetry to reduce the computational cost for the simulation of disordered structures and mineral solid solutions, with potential applications in the fields of materials science and geochemistry. We here present the investigation of the infrared vibrational spectrum of the Andradite-Grossular garnet solid solution Ca₃Fe_xAl_2-xSi₃O₁₂ [5]. Relationships can be established between IR properties (frequencies and intensities) and variables such as structural parameters, chemical composition, short-range cation order. Effective comparisons with experimental observations are made possible.

Accurate IR data as obtained from ab initio simulation may represent the starting point for a synergistic approach to characterization of experimental IR reflectance spectra [6,7]. These spectra contain a high amount of information, which is accessible through the mathematical relations among reflectance spectrum, dielectric function and frequencies/intensities of the vibrational modes. Extraction of these data from the experimental spectra requires a delicate best-fit process involving a large number of parameters. Simulation here plays a crucial role, providing the full set of fundamental modes with accurate frequencies and intensities, which is the ideal starting guess for the best-fit. Low intensity fundamentals are identified, whereas peaks not corresponding to fundamental computed modes are recognized as combinations or overtones. Interpretation of almost all the spectral features of the spectra is enabled through a straightforward scheme.

References

[1] M. De La Pierre, R. Orlando, L. Maschio, K. Doll, P. Ugliengo, R. Dovesi (2011) J. Comput. Chem. 32, 1775-1784.
[2] R. Dovesi, M. De La Pierre, A. M. Ferrari, F. Pascale, L. Maschio, C. M. Zicovich-Wilson (2011) Am. Miner. 96, 1787-1798.
[3] S. Mustapha, Ph. D’Arco, M. De La Pierre, Y. Nöel, M. Ferrabone, R. Dovesi (2013) J. Phys.: Condens. Matter 25, 105401 (16 pp.).
[4] Ph. D’Arco, S. Mustapha, M. Ferrabone, Y. Noël, M. De La Pierre, R. Dovesi (2013) J. Phys.: Condens. Matter 25, 355401 (13 pp.).
[5] M. De La Pierre, Y. Nöel, S. Mustapha, A. Meyer, Ph. D’Arco, R. Dovesi (2013) Am. Miner. 98, 966-976.
[6] C. Carteret, M. De La Pierre, M. Dossot, F. Pascale, A. Erba, R. Dovesi (2013) J. Chem. Phys. 138, 014201 (12 pp.).
[7] M. De La Pierre, C. Carteret, R. Orlando, R. Dovesi (2013) J. Comput. Chem. 34, 1476–1485.

Development of bio-electrochemical fuel cells

Dr Paul Kavanagh

Biomolecular Electronic Research Laboratory, School of Chemistry, NUI Galway, Galway, Ireland

Electrochemical energy storage and conversion systems include batteries, capacitors and fuel cells. Fuel cells transform chemical reactivity into electricity by oxidising fuel at the anode and reducing oxidant at the cathode using noble metal catalysts, providing electrical power output for as long as sufficient fuel and oxidant are available. Bio-electrochemical fuel cells (BFCs) are low-temperature fuel cells that harness biological catalytic reactions, in place of metal catalysts in traditional low-temperature fuel cells, to generate electricity from electrolysis of fuel and oxidant. Due to nature’s versatility, BFCs are not limited to use of hydrogen or methanol as a fuel, and can derive electrical power from a wide range of organic substrates. BFCs can be classified into those which utilise living cells (bacteria, algae)^1,2 and those which utilise catalysts extracted from cells (enzymes, enzyme cascades and, more recently, mitochondria)^3-6 as biological catalysts. Biofilms of electro-active bacteria can facilitate proficient organic carbon removal from wastewater while producing biological renewable energy in the form of electricity.² Similarly, the utilisation of redox enzymes (oxidoreductases) as biocatalysts for the electro-catalytic oxidation (or reduction) of specific redox reactions at miniaturised electrodes permit in vivo power generation with the long-term objective of providing self-powered subcutaneously implantable biosensors.⁶

In this presentation, an overview of BFC development within the Biomolecular Electronic Research Laboratory, NUI Galway will be presented. Specific approaches to improve electrode current densities, cell voltages and operational stability of BFCs through various combinations of electrode materials, biocatalysts and redox mediators will be discussed. For example, loading of electroactive bacteria within three dimensional carbon nanotube-based scaffolds results in substantial current generation for oxidation of acetate, with electrodes producing a current density of 19 kA m⁻³ representing one of the highest volumetric current densities in microbial electrochemical systems reported to date. In addition, modification of electrode surfaces with chemical functional groups provides a route for increased stability of biofilms through greater retention of biocatalytic components at the electrode surface. Improvements in the design of the redox mediating species in terms of structure and redox potential can help to increase the biocatalytic output of BFCs, and our approach for preparation and screening of libraries of mediators from a theoretical and practical point of view will be included.

References

1. K. P. Katuri, P. Kavanagh, R. Saravanan, D. Leech, Chem. Comm. 2010, 46, 4758-4760.
2. T. Catal, P. Kavanagh, V. O’Flaherty, D. Leech, J. Power Sources 2011, 196, 2676-2681.
3. F. Barrière, P. Kavanagh, D. Leech, Electrochimica Acta, 2006, 51, 5187-5192.
4. P. Kavanagh, S. Boland, P. Jenkins, D. Leech, Fuel Cells 2009, 9, 79-84.
5. D. MacAodha, P. Ó Conghaile, B. Egan, P. Kavanagh, D. Leech, ChemPhysChem 2013 14, 2302-2307.
6. P. Kavanagh, D. Leech, Phys. Chem. Chem. Phys. 2013, 15, 4859-4869.

PDF flyer: http://blogs.curtin.edu.au/science-seminars/wp-content/uploads/sites/19/2013/09/PK-CU-seminar-abstract.pdf

Bentley Campus Map, Curtin University: http://properties.curtin.edu.au/maps/

Modelling molecular organic crystals: confessions of a reborn researcher

Prof Andrew Rohl

Department of Chemistry and Nanochemistry Research Institute, Curtin University, Perth WA

Bentley Campus Map, Curtin University: http://properties.curtin.edu.au/maps/

Use of researcher profiles to boost your academic career

Barbara Parnaby

Faculty Librarian, Science & Engineering | Research & Learning Services, Curtin University Library

Researcher profiles session – Find out what a researcher profile is, the keys tools available in different systems; their pros and cons, where to go to set yours up.  The aim of the session is alert researchers to the range of tools and the benefits of investing some time in maintaining your own profile, to save time later when tracking your research, preparing grant proposals, measuring your impact, etc.

PDF flyer: http://blogs.curtin.edu.au/science-seminars/wp-content/uploads/sites/19/2013/08/30-August-Library.pdf

Bentley Campus Map, Curtin University: http://properties.curtin.edu.au/maps/