title: Probing the functionalization of gold surfaces and protein adsorption by PM-IRRAS.
abstract: The control of morphology and coating of metal surfaces is essential for a number of organic electronic devices including photovoltaic cells and sensors. In this study, we monitor the functionalization of gold surfaces with 11-mercaptoundecanoic acid (MUA, HS(CH(2) )(10) CO(2) H) and cysteamine, aiming at passivating the surfaces for application in surface plasmon resonance (SPR) biosensors. Using polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS), cyclic voltammetry, atomic force microscopy and quartz crystal microbalance, we observed a time-dependent organization process of the adsorbed MUA monolayer with alkyl chains perpendicular to the gold surface. Such optimized condition for surface passivation was obtained with a systematic search for experimental parameters leading to the lowest electrochemical signal of the functionalized gold electrode. The ability to build supramolecular architectures was also confirmed by detecting with PM-IRRAS the adsorption of streptavidin on the MUA-functionalized gold. As the approaches used for surface functionalization and its verification with PM-IRRAS are generic, one may now envisage monitoring the fabrication of tailored electrodes for a variety of applications.
authors.affiliation: Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, São Paulo, Brazil.
authors.forename: Rodrigo Marques
authors.initials: RM
authors.lastname: de Oliveira
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Ferreira
authors.forename: Marcos J L
authors.initials: MJ
authors.lastname: Santos
authors.forename: Roberto M
authors.initials: RM
authors.lastname: Faria
authors.forename: Osvaldo N
authors.initials: ON
authors.lastname: Oliveira
mesh_terms: D000327:Adsorption; D006046:Gold / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry*; D013054:Spectrophotometry, Atomic; D013055:Spectrophotometry, Infrared; D013499:Surface Properties
chemical_list: D011506:Proteins; D006046:Gold