1. Department of Pharmaceutical Sciences, University of Nottingham, Nottingham NG7 2RD, U.K., Department of Chemistry and Physics, Trent University, Nottingham NG11 8NS, U.K., Centre for Surface and Materials Analysis, Armstrong House, Oxford Road, Manchester M1 7ED, U.K., Department of Chemistry, UMIST, P.O. Box 88, Manchester M60 1QD, U.K., and Department of Materials Science and Engineering, University of Surrey, Guildford GU2 5XH, U.K.