Peter Weightman and Trevor Farrell

Reflection Anisotropy Spectroscopy

Research in surface science began in the 1960's with the development of ultra high vacuum (UHV) techniques and enormous progress has been made in the understanding of surfaces and surface processes by making use of such techniques. However in my opinion it is timely for surface studies to move out of UHV and become concerned with real surfaces and in particular with the important surface processes that involve biological systems ranging from molecules to cells.

The study of biological systems requires techniques that can provide information on a liquid environment. My group are playing a leading role in developing the promising optical technique of RAS which, when combined with local expertise in electrochemistry, (C.I. Smith and R.J. Nichols), scanning probe microscopy (D.S. Martin) and synchrotron based surface x-ray diffraction techniques (C. Lucas) has great potential for the study of molecular assembly at metal/liquid interfaces.

RAS instruments are not commercially available and two instruments of the traditional Aspnes design have been completed in Liverpool with support from the EU ESPRIT programme (EPIOPTICS, 1989-92, EASI: 1992-95). In 1998 the Paul instrument fund of the Royal Society made an award to support the construction of a next generation instrument of novel design. This Rapid RAS instrument has recently been completed. The EPSRC has awarded grants to develop RAS as a probe of metal surfaces, to support the first application of RAS to the study of metal-liquid interfaces, to investigate DNA adsorbed at metal/liquid interfaces and to study interactions between nucleic acids in relation to biomedical implants. The BBSRC has awarded a grant to use RAS to monitor conformational change in proteins. De Beers are supporting research on the application of RAS to diamond surfaces and the programme is also supported by a Marie Curie Fellowship funded by the EU.

Scientific highlights of the programme in include;

1 The first application of RAS to a metal/liquid interface; Au(110)/electrolyte.

2 The demonstration that RAS is sensitive to the orientation of surface dimers.

3 The demonstration that RAS can reveal the three dimensional orientation of molecules adsorbed at metal / liquid interfaces.

4 Demonstrating that RAS can distinguish between single and double stranded DNA adsorbed on Au and Diamond surfaces and has potential as a fast, cheap and accurate method of genetic screening.

5 The monitoring of conformational change in proteins resulting from electron transfer in real time.