Nanostructures and Photomolecular Systems  
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Prof. David L Andrews

David Andrews is Chair of the SPIE Nanotechnology Technical Group. At UEA his theory group conducts fundamental and applied research on optical forces, energy transport between molecules and within macromolecules, molecular photophysics and a range of nonlinear and quantum optical phenomena. The studies on optical forces focus primarily on the laser manipulation of nanoparticles such as carbon nanotubes, and the effect known as ‘optical binding’; the research on energy transport centres on energy harvesting in nanoscale photosystems, both natural and synthetic.

The group has recently developed theory for optically nonlinear behaviour (multiphoton resonance energy transfer and energy pooling) in a variety of light harvesting materials, mostly multichromophore arrays such as dendrimers which mimic the molecular structures operative in natural photosynthesis. Exploiting such principles, a new basis for a new form of optical switching has also recently been identified. The group has strong international links - particularly with groups in Canada, the United States, New Zealand and Lithuania. For information on other activities of the group in nonlinear optics and photonics click here.

Prof. Stephen R Meech

The group headed by Steve Meech is interested in the research applications of lasers and nonlinear optics to probe the chemistry and dynamics of the condensed phase and its interface, focussed on :

  1. Ultrafast dynamics in complex fluids. The optical Kerr effect is used to observe molecular motion in nanometre dispersed liquids, liquid crystal, polymers and liquid mixtures.
  2. Femtochemistry in fluorescent proteins. The excited state chemistry of the chromophore of the green fluorescent protein has been studied by ultrafast polarisation spectroscopy and femtosecond fluorescence up-conversion.
  3. Laser surface photochemistry. The photochemistry and photoelectron emission of surfaces prepared in ultra-high vacuum are studied by steady state and time-of-flight mass spectrometry. Studies of two-photon photoemission from ice surfaces doped with alkali metals aim to elucidate some of the chemistry associated with noctilucent clouds.
  4. Nonlinear optics for molecular structure. The group maintains a strong interest in applying nonlinear optics in bioimaging and surface structure determination. Recent results include a two-photon fluorescence microscopy study of mitosis. Also the use of second harmonic generation to probe interfaces and organised media and (at higher order) liquid dynamics have also been reported.

Prof. Thomas Nann

Thomas Nann's research is focused on the preparation, characterisation and application of nanomaterials in general and nanoparticles in particular.

  1. Colloidal nanoparticles of various types - noble metals, semiconductors or doped insulators - are synthesised with wet-chemical methods. The morphologies of the yielded particles range from spherical, rod- and wire-like to sophisticated three-dimensional structures. The resulting nanoparticles are further derivatised with additional inorganic surface layers like e.g. silica, or organic ligands.
  2. The unique structural, magnetic and optical properties of such nanoparticles are invesitgated by means of transmission electron microscopy (TEM), UV/vis/PL spectroscopy, electrochemical methods and others. The focus of interest is on mesoscopic properties of the nanomaterials.
  3. Potential applications of nanomaterials are examined in collaboration with industrial and academic partners in areas such as nanotechnology, biology and medicine.

Dr Stephen H Ashworth

Stephen Ashworth performs high resolution spectroscopy, and other spectroscopy applied to atmospheric chemistry, using a number of laser techniques. The high resolution spectroscopy concentrates on the detailed molecular and electronic structure of small transient species in the gas-phase. In collaboration with the School of Environmental Sciences, measurements are made of the speed of reactions involved in processing material in the atmosphere, particularly meteoric dust and halogens released from the sea and seashore.

Especially of interest are the reactions which turn the atoms formed from ablation (of meteors) and photolysis (of marine gases) into nanometer-sized aerosol particles. In another collaboration with Mike Cook’s synthetic group measurements are made on the properties of novel phthalocyanines. This class of molecules has application as photodynamic therapy (PDT) agents; their capacity to self-assemble on surfaces also makes them potential candidates for sensor applications.

Dr Yimin Chao

Yimin Chao’s research interest is in investigating nanostructured systems, from their basic physical and chemical mechanisms of synthesis, through their optical and electronic properties, to biological and medical applications.

  1. Functionalization and characterization of Si quantum dots (Si-QDs): Si-QDs prepared by electrochemical etching and coated with alkyl chains, characterized by means of AFM, STM, TEM, SAXS, and XPS, Raman spectroscopy, FTIR, UV/Vis / photoluminescence spectroscopy.
  2. Evaporation and deposition of Si-QDs in ultra-high-vacuum (UHV) at relatively low temperatures: intact sublimation is enabled by a combination of anomalously weak inter-particle interactions with the extremely high thermal stability of the alkyl-coated silicon nanoparticles.
  3. Biological and medical applications: size-selected Si-QDs can act as both luminescence probes (for spatial localisation) and Raman probes (to provide time-resolved biochemical information) inside living cells. With the observation of different signals between cancer cells and normal cells, this method could have potential application in diagnosis.
  4. Applications in memory devices: Silicon quantum dot memories, in which the SiO2 layer is replaced by a Si-QD monolayer, have attracted considerable attention in the last few years as one of the simplest evolutions of the standard flash technology, allowing for improved reliability and scaling perspectives.

Dr Nigel Clayden

Nigel Clayden’s interests lie in the structure and dynamics of chemical systems, ranging from zirconium phosphonate supports to the FMuF state. The unifying theme of his research is the use of magnetic resonance spectroscopy and relaxation. Two current projects exemplify this:

  1. Structure and dynamics in zirconium phosphonate supports (in collaboration with Professor M Bochmann).

    Multinuclear 13C, 31P and 1H MAS NMR are being used to characterise the structure of zirconium phosphonates with ionic liquids as catalyst supports. Incorporation of Pd is evident through the changes in the 13C CPMAS NMR spectra.

  2. Double resonance rf-μSR of the FMuF state in ionic fluorides.

    Radiofrequency techniques in μSR are being explored at ISIS, RAL. Double resonance, in particular, the combination of rf pulses on the muon and a nuclear spin has not been examined and its potential in μSR is unclear. In a recent experiment polarisation transfer was attempted using matched spin-locking rf fields of the FMuF state in a single crystal of CaF2 and powdered SrF2. Paradoxically despite the ubiquitous presence of the FMuF state in inorganic fluorides none was observed in the current CaF2 sample.

Dr Upali A Jayasooriya

Some of the current projects of Jayasooriya’s research group are:

  1. Application of muon spectroscopies to investigate the fundamental properties of the classic nanomaterial, DNA. For example this group has measured the excess electron conduction in DNA over a large temperature range, 2 to 300 K, recognising one- and two-dimensional conduction and identifying some of the mechanisms in operation. This is a collaboration with Dr Julea Butt at UEA.
  2. The group is also using radiation from synchrotron radiation facilities such as the European Synchrotron Radiation Facility in Grenoble, France, to conduct studies based on Nuclear Inelastic Scattering (NIS), an element-selective vibrational spectroscopy. Two sets of experiments, one with the prototype metallocene, ferrocene and another with iron-sulfur clusters that model such entities in protein structures illustrate the potential of this technique.

    This is a collaboration with Professor Chris Pickett and Dr Dave Evans at the John Innes Centre, Norwich Research Park.

Dr Andrew G Mayes

Research in Andrew Mayes’s group focuses on three main areas: embedded holograms in hydrogels; photo-switching hydrogels for microscale valves, pumps and actuators; surface engineering via photopolymerisation.

  1. Holograms provide a good method for probing the behaviour of hydrogel materials. Mayes’s research uses this as a method for developing low-cost chemical sensors with direct visual readout, also to follow the kinetics and thermodynamics of hydrogel swelling by a variety of mechanisms.
  2. Micro-analytical devices have developed rapidly during the last decade, but there are still significant problems to be overcome in interfacing the micro-separation and micro-detection steps with appropriate sample and reagent delivery technology. Photo-switching hydrogels are being investigated as a possible method to generate integrated pumps and valves for such applications.
  3. Mayes’s group is developing methods to create polymer patterns on gold and metal oxide surfaces. Polymerisation initiators are attached to the surfaces (uniformly or in patterns), and these are used to photo-initiate growth of polymer chains from the surface. This can be for surface patterning or to produce a variety of polymer architectures to engineer surface properties.

Dr David C Steytler

David Steytler’s research interests stem from a fascination with the unique ability of surfactants to self-assemble, both in solution and at interfaces. Through this process a rich variety of structures (micelles, microemulsions, vesicles, and liquid crystals) may be formed, often representative of those found in nature. Steytler’s research group is primarily concerned with the fundamental understanding of such systems and their application in chemical separation, synthesis and nanofabrication. A variety of specialised physical methods are employed including Small-Angle Neutron Scattering (SANS) for structural characterisation, and high pressure tensiometry. Projects include:

  1. The development of surfactants for application in near-critical CO2 and hydrofluorocarbon (HFC) systems.
  2. Applications of microemulsions, liquid crystal phases and vesicles to control structure in constrained polymerisation and materials fabrication.
  3. Communication and transport across the oil-water interface – microemulsions and nanoparticles.
  4. Structure and applications of frozen dispersions.
  5. The application of pressure waves in supercritical fluid recrystallisation.

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