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 alkanethiols, namely (1-mercaptoundec-11-yl)hexa(ethylene glycol) (HS(CH2)(11)(OCH2CH2)(6)OH) and 1-dodecanethiol (HS(CH2)(11)CH3), on the surface of planar gold films and on colloidal gold particles. A quantitative method for studying the physical adsorption of SAM-modified gold colloids onto the planar SAMs was developed. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to measure the composition of planar SAMs and to quantify the extent of colloidal adsorption, respectively. Results confirm that the colloids studied adsorb from the aqueous solution more extensively to hydrophobic surfaces, that the extent of adsorption increases with particle hydrophobicity, and that oligo(ethylene glycol) surfaces are resistant to colloidal adsorption. Colloidal gold particles and flat gold substrates modified with SAMs form a convenient and versatile model system for examining existing theoretical models associated with the adsorption of colloids and proteins, and cellular attachment and adhesion at solid surfaces.