Adsorption of Mixed Peptide/Thiol Adlayers on InAs: Assessment of Different Functionalization Strategies Using X-ray Photoelectron Spectroscopy
Date of this Version7-28-2011
Mixed adlayers are commonly used to create surfaces with multiple functional groups or molecular gradients. The resulting surfaces are designed to have the combined effects of each adsorbed functional group. In this work, we combine the passivation ability of a thiol with the functionality of a peptide by assembling mixed peptide/thiol adlayers on InAs. Both sequential (insertion) and simultaneous (co-assembly) methods are used to functionalize InAs and are analyzed by contact angle measurements and X-ray photoelectron spectroscopy (XPS). Peptide coverage, thiol coverage, and oxide layer thicknesses are estimated from XPS data. For each method, oxide layer thicknesses were significantly lower than the oxide thicknesses for as-received samples. Surfaces functionalized using the insertion methods had lower oxide layer thicknesses than peptide only samples, indicating that the addition of the thiol helped block oxide regrowth. Functionalization with the thiol followed by the peptide yielded surfaces with the highest peptide coverage and most likely formed a layered peptide/thiol structure. Functionalization with the peptide followed by the thiol produced surfaces with a lower peptide coverage and most likely consisted of peptide clusters surrounded by adsorbed thiol. Surfaces functionalized by the co-assembly method were predicted to form a disordered peptide/thiol adlayer.
Nanoscience and Nanotechnology
J. Phys. Chem. C, 2011, 115 (29), pp 14244–14252 DOI: 10.1021/jp203203x