ADSORPTION OF SURFACE-MODIFIED COLLOIDAL GOLD PARTICLES ONTO SELF-ASSEMBLED MONOLAYERS - A MODEL SYSTEM FOR THE STUDY OF INTERACTIONS OF COLLOIDAL PARTICLES AND ORGANIC-SURFACES

Self-assembled monolayers (SAMs) were formed from omega-substituted al kanethiols, namely (1-mercaptoundec-11-yl)hexa(ethylene glycol) (HS(CH 2)(11)(OCH2CH2)(6)OH) and 1-dodecanethiol (HS(CH2)(11)CH3), on the sur face of planar gold films and on colloidal gold particles. A quantitat ive method for studying the physical adsorption of SAM-modified gold c olloids onto the planar SAMs was developed. X-ray photoelectron spectr oscopy (XPS) and scanning electron microscopy (SEM) were used to measu re the composition of planar SAMs and to quantify the extent of colloi dal adsorption, respectively. Results confirm that the colloids studie d adsorb from the aqueous solution more extensively to hydrophobic sur faces, that the extent of adsorption increases with particle hydrophob icity, and that oligo(ethylene glycol) surfaces are resistant to collo idal adsorption. Colloidal gold particles and flat gold substrates mod ified with SAMs form a convenient and versatile model system for exami ning existing theoretical models associated with the adsorption of col loids and proteins, and cellular attachment and adhesion at solid surf aces.