FORMATION AND CHARACTERIZATION OF GOLD AND SILVER NANOPARTICLES ON SILICA NANOSPHERES P.-T. Miclea Institute of Materials Science, Department of Electrical and Information Engineering, University of Wuppertal, Wuppertal, D-42097, Germany H. Hofmeister Max Planck Institute of Microstructure Physics, Halle (Saale), D-06120, Germany Novel optical effects are expected by appropriately arranging metal nanoparti- cles on the surface of spherical insulating materials. Optical resonances of this nanostructures from near infrared to the visible range may be tuned by adjust- ing the oxide size, size of the metal particles and the filling factor. For a better control of the optical properties of such composite materials the best choice as oxide material is the monodisperse oxide particles. Water-soluble metal pre- cursor complexes hydrogentetrachloroaurate and silver acetate have been employed. The optical properties of these materials correspond to their overall structure of nanoparticulate composites having a very low filling factor of the metal phase. INTRODUCTION Small metal particles exhibit in the visible range optical properties different from those of the bulk material due to their size and shape [1]. At the beginning of the last century the study of color changes of various types of glasses [2,3] triggered this research area. Moreover, another area of inter- est was to find new materials with a dielectric function different from that of the bulk material that firstly were applied to improve photovoltaic con- version [4,5]. In order to study the properties of nanoparticles on oxide surfaces from the optical point of view in this work the Mie theory and also Address correspondence to P.-T Miclea, Institute of Materials Science, Department of Elec- trical and Information Engineering, University of Wuppertal, Wuppertal, D-42097, Germany. E-mail: miclea@uni-wuppertal.de 135=[619] Mol. Cryst. Liq. Cryst., Vol. 417, pp. 135=[619]–147=[631], 2004 Copyright # Taylor & Francis Inc. ISSN: 1542-1406 print=1563-5287 online DOI: 10.1080=15421400490478579