ULTRASTRUCTURAL CHARACTERIZATION OF COLLOIDAL METAL-FILMS FOR BIOANALYTICAL APPLICATIONS BY SCANNING FORCE MICROSCOPY

Colloidal metal films (CMFs) are prepared by the attachment of silver, gold, or platinum (or other metal) particles to a glass slide modifie d by silanization with 3-mercaptopropyl silane. The covalent attachmen t of the metal particles occurs through the metal-sulfur bond. In thes e samples the local electromagnetic field is enhanced near the surface of the CMF due to excitation of plasmon resonances. This phenomenon c an be used for a variety of analytical applications. Because the optic al properties are strongly dependent on the morphology of the him, its structural characterization becomes of great importance. To further c haracterize CMFs we have used scanning force microscopy (SFM). Initial studies revealed lateral dimensions of the particles as well as the p article density. Height measurements were made using the three-dimensi onal topographic image of the surface yielded by SFM, and were used to evaluate the selective deposition of a silica spacer layer onto the m etal particles. Comparative FM measurements in water and air using dif ferent imaging modes were performed to investigate the mechanical stab ility of CMFs against the forces exerted by the scanning tip. (C) 1996 American Vacuum Society.