AVS 53rd International Symposium
    Biomaterial Interfaces Thursday Sessions
       Session BI-ThM

Paper BI-ThM1
Light Exposure Affects the Adsorption of Colloidal Gold onto Monolayers of 3-Mercaptopropyltrymethoxysilane

Thursday, November 16, 2006, 8:00 am, Room 2014

Session: Plasmonic Methods and Sub-micron Structures for Biology and Medicine
Presenter: V.H. Perez-Luna, Illinois Institute of Technology
Authors: K. Pandya, Illinois Institute of Technology
O. Ogunsanwo, Illinois Institute of Technology
V.H. Perez-Luna, Illinois Institute of Technology
Correspondent: Click to Email
Light exposure affects the capability of thiol-terminated monolayers to adsorb colloidal gold particles. This effect was determined by forming monolayers of 3-mercaptopropyltrimethoxysilane (MPTMS) on silica surfaces in the presence of white light, red light (635 nm) and under dark conditions. Surface characterization by means of wettability, ellipsometry and FTIR spectroscopy was carried out to determine differences in surface properties for the different preparation methods. Monolayers prepared under different conditions of light exposure (white light, red light and absence of light) were exposed to colloidal gold solutions in order to study the adsorption of gold nanoparticles. The adsorbed colloidal gold monolayers were characterized by optical absorption spectroscopy. In spite of the strong affinity of the thiol group for gold, samples that were exposed to white light did not adsorb gold nanoparticles to a significant extent. In contrast, monolayers prepared using red light or under dark conditions were capable of adsorbing gold nanoparticles at levels comparable to amine-functionalized surfaces. These findings may offer some insights as to differing literature reports on adsorption of colloidal gold to thiol-functionalized surfaces. The thiol groups may undergo oxidation in the presence of oxygen and white light to from sulfonate groups that do not promote adsorption of gold nanoparticles. Hence MPTMS monolayers exposed to light may not present sufficient thiol groups for subsequent attachment of gold. Surface analysis of samples exposed to white and red light and those kept in the dark verify this hypothesis.