Materials chemistry: Structures and properties of organic self-assembled monolayers on gold surfaces.

摘要

I describe here how the structures and properties of organic self-assembled monolayers (SAMs) on gold surfaces can be determined and measured by grazing angle surface fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV), and atomic force microscope (AFM). Emphases are being focused on three monolayer systems.;First, the synthesis of a photolabile linker, its two-step sequential attachment to a gold surface prefunctionalized with an adamantane-based anchor, and its photocleavage on the surface were carried out. FTIR measurements confirmed the existence of the reaction products on the surface. Second, in the comparison of two types of ferrocene-terminated short chain ( 6 CH2) SAMs, i.e., one with a small thiolate anchoring head group and the other with a bulky trithiaadamantane group, the structural features regarding carbonyl orientation, hydrogen bonding formation and ferrocene moiety orientation relative to the surfaces were elucidated from FTIR spectra. Their electrochemical behavior shown by CV indicates a remarkable electrochemical stability for the latter. Based on the combined structural and electrochemical information, a model for the decay mechanism is proposed to explain the difference in the stability. Thirdly, a SAM terminated with ferrocene sulfonic acid groups was subjected to AFM measurements to address the issue of counterion binding rates at the charged SAM/liquid interface. The experimental results show that the ion-binding rate (∼97%) remains relatively constant and independent of electrode surface charge change.