Academic Staff - Professor Robin Clark CNZM FRS - Inorganic Chemistry - Sir William Ramsay Professor Emeritus of Chemistry

Transition metal chemistry Infrared, Raman and electronic spectroscopy Pigment studies in Art and Archaeology

tel: +44 (0)20 7679 7457 fax: +44 (0)20 7679 7463 internal phone: 27457 email: r.j.h.clark@ucl.ac.uk

Robin Clark has been awarded the prestigious Bakerian Lecture for 2008 -
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Robin Clark has been awarded the inaugural biennial Franklin-Lavoisier Prize for 2008 -
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Robin Clark is the winner of the Sir George Stokes Award for 2009 -
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Transition Metal Chemistry

Synthetic, spectroscopic and structural studies on a wide variety of transition-metal complexes have been investigated in order to establish structure/spectroscopy relationships. Notable are studies of mixed-valence compounds at the inorganic chemistry/materials science borderline, many new compounds with highly anisotropic spectroscopic properties and conductivities having been synthesised 1. Extensive studies of metal-metal bonded species such as [Re₂Cl₈]^2-, Rh₂(O₂CCH₃)₄, [Mo₂(CN)₈]^4- and oxalate-bridged and perfluorophthalate-bridged complexes of dimolybdenum and ditungsten have been carried out 2.

Infrared, Raman and Resonance Raman Spectroscopy

Irradiation of a complex within the contour of an allowed electronic transition may yield very intense Raman spectra and long overtone progressions in totally symmetric modes, from which the geometry of the irradiated species in the resonant excited state can be established 3. Spectroscopic studies on radicals, i.e. S₂^-, S₃^-, Se₂^- in host lattices, e.g. sodalite, have involved the identification of the chromophores in various ultramarines and in a host of other inorganic compounds. Other studies have included the characterisation of reactive molecules and ions using matrix isolation spectroscopy and the in situ study of electrochemically generated species by electronic, infrared, and Raman spectroscopy using OTTLE and IRRAS cells 4.

The Raman characterisation of semiconductors 5, doped carbon nanotubes and related materials has been achieved 6, as has the deposition of micrometre-thick anatase, which is photoactive, and related materials on glass, leading to self-cleaning properties of plate glass 7.

Raman Microscopy and the Arts/Science Interface

The characterisation by Raman microscopy and other techniques of the pigments used to illuminate medieval manuscripts, paintings, ceramics, frescos, papyri, icons and other artefacts has been pioneered. These critical studies have a major international profile and are widely recognised for the insight that they give on the characterisation, conservation, restoration, authentication and dating of artwork and the characterisation of ceramics and archaeological artefacts. 8,9,10,11,12,13,14,15. Specific studies have been made of of anatase as a date marker in neolithic Chinese ceramics 16 and as a photocatalytic nanoparticulate material of high surface area 17.

Recent Grant Reports

Final Report on Grant GR/M 82592/01 (PDF - 154kb)

Raman Microscopy: I dentification and Study of Pigments, Dyes and Thin Films on Glass Substrates
Professor RJH Clark and Professor IP Parkin.
Publications for this report can be viewed here.

IGR Report on Grants GR/M95059/01 (PDF - 2.72 MB)

Self Cleaning Coatings - Tungsten Substituted Titania Prof.
I. P. Parkin and Prof. R. J. H. Clark, Department of Chemistry, University College London; Prof. A. Mills, Department of Chemistry, University of Strathclyde and Dr K. Sanderson and Mr S. Hurst, Pilkington Glass.

Selected Publications

1. R. J. H. Clark, The chemistry and spectroscopy of mixed-valence complexes, Chem. Soc. Rev., 1984, 13, 219; Synthesis, structure, and spectroscopy of metal-metal dimers, linear chains, and dimer chains. Chem. Soc. Rev., 1990, 19, 107; P. Day, N.S. Hush and R.J.H. Clark, Phil. Trans. Roy. Soc. A, 2008, 366, 5.
2. B. E. Bursten, M. H. Chisholm, R. J. H. Clark, S. Firth et al., Oxalate-bridged complexes of dimolybdenum and ditungsten supported by dipivalate Ligands, J. Am. Chem. Soc., 2002, 124, 3050; Perfluorophthalate-bridged complexes with M-M quadruple bonds, J. Am. Chem. Soc., 2002, 124, 12244.
3. R. J. H. Clark and T. J. Dines. Resonance Raman spectroscopy and its application to inorganic chemistry. Angew. Chem., Intl. Ed. Engl., 1986, 25, 131.
4. R. J. H. Clark and D. G. Humphrey. Redox behaviour of edge-shared bioctahedral [Re₂(mu-NCS)₂(NCS)₈]^2- and its relationship to the direct metal-metal bonded ion [Re₂(NCS)₈]^2-. Inorg. Chem., 1996, 35, 2053.
5. R. Sherwin, R.J.H. Clark, R. Lauck, M. Cardona. Effect of isotope substitution and doping on the Raman spectrum of galena (PbS). Solid State Comm. 2005, 134, 56; P.G. Etchegoin, M. Cardona, R. Lauck, R.J.H. Clark and A.H. Romero, Temperature-dependent Raman scattering of natural and isotopically labelled PbS. Phys. Stat. Sol. B, 2008, 245, 1125.
6. S. Firth, R. J. H. Clark, H. W. Kroto et al., Boron doping effects in carbon nanotubes, J. Mater. Chem., 2000, 10, 1425.
7. A. Mills, N. Elliot, I.P. Parkin, S.A. O'Neill and R.J.H. Clark, Novel TiO2 CVD films for semiconductor photocatalysis, J. Photochem. Photobiol. Chem., 2002, 151, 171.
8. R. J. H. Clark, Raman microscopy: application to the identification of pigments on medieval manuscripts. Chem. Soc. Rev., 1995, 24, 187; C. R. Chimie, 2002, 5, 7; Raman microscopy in the identification of pigments on artwork. In "Scientific Examination of Art", National Academies, Washington, D.C., 2005, pp.162-185.
9. L. Burgio, R. J. H. Clark, D. Anglos et al., Pigment identification in painted artworks by laser-induced breakdown spectroscopy and Raman microscopy. Appl. Spectrosc., 2000, 54, 463.
10. L. Burgio, R.J.H. Clark, L. Sheldon, G.D. Smith, Pigment identification by spectroscopic means: evidence consistent with the attribution of the painting "Young Woman Seated at a Virginal" to Vermeer. Anal. Chem. 2005, 77, 126.
11. T.D. Chaplin, R.J.H. Clark, D. Jacobs, K. Jensen, G.D. Smith. The Gutenberg Bibles: analysis of the illustrations and inks by Raman microscopy. Anal. Chem. 2005, 77, 3611.
12. A.M. Correia, R.J.H. Clark, M.I.M. Ribeiro and M.L.T.S. Duarte, Pigment study by Raman microscopy of 23 paintings by the Portuguese artist Henrique Pousao. J. Raman Spectrosc., 2007, 38, 1390.
13. R.J.H. Clark, The scientific investigation of artwork and archaeological artefacts: Raman microscopy as a structural, analytical and forensic tool, Appl. Phys. A, 2007, 89, 833.
14. L. Burgio, R.J.H. Clark, R.R. Hark, M.S. Rumsey and C. Zannini, Spectroscopic investigations of Bourdichon miniatures: masterpieces of light and colour, Appl. Spectrosc., 2009, 63, 611.
15. G.D. Smith and R.J.H.Clark, Raman spectroscopy in archaeological science, J. Archaeol. Sci., 2004, 31, 1137.
16. R.J.H. Clark, Q. Wang and A. Correia, Can the Raman spectum of anatase in artwork and archaeology be used as a date marker? J. Archaeol Sci., 2007, 34, 1787.
17. Z. Zhang et al., Direct continuous hydrothermal synthesis of high surface area nanosized titania, J. Alloys and Compounds, 2009, 476, 451.

This page last modified 20 October, 2009