Abstract

Organosilane compounds, such as octadecyltrichlorosilane (OTS), are commonly used in the formation of thin films for microelectronic, biosensor or chromatographic applications. In this paper, self-assembled OTS monolayer films were characterized by atomic force microscope (AFM) imaging and Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy. Conditions to provide a monolayer free of OTS aggregates were established. These films were then exposed to aqueous solutions of benzo[k]fluoranthene (B[k]F), a carcinogenic polycyclic aromatic hydrocarbon (PAH) that is often present in both aqueous and terrestrial environments. Through the B[k]F associations with these OTS monolayer films, it was possible to obtain a film–solution partition coefficient (log K_fs) value of 7.0 ± 0.1 using fluorescence detection; this value is similar to partition coefficients previously observed in octanol–water systems. Using AFM images and fluorescence spectroscopy measurements, a maximum surface coverage of 9 (±1) × 10⁻⁴ molecules of B[k]F per Ų was measured within these films. An upper limit to B[k]F concentration in solution was found, above which aggregates of B[k]F molecules were formed on the surface.