Dr. A. Zarbakhsh BSc MSc PhD(Sheffield)

Lecturer in PhysicalChemistry

School of Biological & Chemical Sciences
Queen Mary, University of London
Walter Besant Building, Mile End Road
London
E1 4NS
Tel: +44 (0) 20 7882 3259
Fax: +44 (0) 20 7882 7427
email: A.Zarbakhsh@qmul.ac.uk

Research Interests
Structural study of polymeric and biological systems using X-ray and neutron scattering techniques; reflectivity, in-plane diffraction and small angle scattering. Vibrational sum frequency spectroscopy, ellipsometry and atomic force microscopy.

Dr Zarbakhsh has four main areas of research achievement and development:

The structure and the transport properties of membranes. Knowledge of the structure and the transport properties of membranes have a direct influence on our understanding of how cell membranes function. As a means of furthering this knowledge, the work concern the development and application the technique of neutron reflectivity to resolve the structure of membranes at liquid-liquid interfaces for the first time.

Development of experimental protocol to resolve orientation and atomic structural details at buried fluid-fluid interfaces. Recent measurements of aqueous surfaces and interfaces using sum-frequency spectroscopy (SFS) have revealed interesting ordering behaviour of water molecules at room temperature. Evidence has been found suggesting that the structure of water is more ice-like (extensively hydrogen-bonded) at a bare oil/water interface than at its free surface. We have observed this unusual phenomenon (manuscript is in preparation) in the first direct experimental observation. This is a part of ongoing work in developing the technique of in-plane X-ray diffraction for the first time at fluid-fluid interfaces. This will be applied in resolving orientation and structural details of polymers and biological membrane at buried interfaces. This work will be extended towards template- Self-assembled Inorganic Materials and nano-composite.

Study of wetting phenomenon. Wetting is an important phenomenon both from a fundamental point of view and because of its diverse applicability in everyday life. For example, wetting behaviour governs the spreading and adhesion of paints and glues to solid surfaces and is important for the action of cosmetic creams on human skin. Friction and lubrication are intimately coupled to wettability. The wettability of one medium by another is controlled by both long-range interactions such as dispersion forces, and by more localised, short-range interactions between molecules at the interface between the two media. Long-range dispersion interactions are ubiquitous and can in some cases explain wetting behaviour on their own, i.e. as in the wetting of many solids by simple, non-polar liquids. However, short-range interactions are of critical importance in many systems. This can be illustrated by considering how the presence of a self-assembled, hydrophobic monolayer on a silicon substrate dramatically alters the silicon’s wettability, changing it from hydrophilic to hydrophobic, even though the long-range dispersion interactions are only marginally different with the two types of surface. This area of a work will concentrate on phase transition and the structural study of wetting films at solid surface

The study of entrap biomolecules. The immobilisation of the biomolecules (glucose oxidase) on the transducer surface is an important step in the fabrication of the biosensor. One of the more popular methods for immobilisation is to entrap the biomolecules, together with other reagents, in a thin film, which is attached directly to the surface of the transducer. Consequently, the aim of this project is to study of the composition of this film, so that the stability and function of the biomolecules can be understood. Also the regeneration of the enzymes which are trapped within the film requires that charge transport extends throughout the bulk of the film, and is not limited to the electrode-film interface. Another objective of this project is the fundamental study of the movements of charged molecules in these films.We utilised the contrast match variation of the aqueous subphase to obtain information with regard to subtle structural changes in the Nafion membrane. We gain unambiguous models for Nafion films with and without entrapped glucose oxidase. The result will provide a better understanding of the stability and function of the entrapped biomolecules in biosensors.

Useful links:
• ISIS pulsed neutron source at Oxfordshire, England.
• European Synchrotron Radiation Facility , Grenoble, France.
• Hahn-Meitner-Institut , Berlin, Germany.

Completed and Ongoing Research Grants EPSRC Grant, GR/L50754 (£420,214), 1 postdoc. End of project report has been submitted and reviewed [Link].

Selected Recent Presentations

• "Structural studies of amphiphiles adsorbed at liquid-liquid interfaces using neutron reflectometry" Ali Zarbakhsh * and Aránzazu Querol, James Bowers and John Webster. Farady Discussion, RSC, 129, 155-167., 2005.

• "Adsorption from alkane + perfluoroalkane mixtures at fluorophobic andfluorophilic surfaces: Non-critical adsorption profiles II." J. Bowers, A. Zarbakhsh, H.K. Christenson, I.A. McLure, R. Cubitt, J. Chem.Phys, Vol. 121, No. 18. 2004.

• “Study of calcium Carbonate Precipitation under a series of Fatty Acid Langmuir
  Monolayers Using Brewster Angle Microscopy.” E. Loste, A. zarbakhsh and F.C. Meldrum, Langmuir, American Chemical Society, No 7, 2003.

• “Adsorption from alkane + perfluoroalkane mixtures at fluorophobic and
  fluorophilic surfaces: Non-critical adsorption profiles.”
  J. Bowers, A. Zarbakhsh, H.K. Christenson, I.A. McLure, R. Cubitt, J. Chem.
  Phys. 119, 11917, 2003.

• “Structure of a spread film of a PB-PEO linear diblock copolymer at the air-water interface as determined by neutron reflectometry”
  J. Bowers, A. Zarbakhsh*, J R P Webster, L.R. Hutchings and R.W. Richards
  Langmuir, American Chemical Society, No. 1, pp 131-139, 2001.

• “Neutron reflectivity studies at liquid-liquid interfaces: methodology and analysis”,
  J. Bowers, A. Zarbakhsh*, J R P Webster, L.R. Hutchings and R.W. Richards
  Langmuir, American Chemical Society, No. 1, pp 140-145, 2001.

  
  

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