The adsorption of benzo[k]fluoranthene on self assembled films of octadecyltrichlorosilane

Organosilane compounds, such as octadecyltrichlorosilane (OTS), are commonl y used in the formation of thin films for microelectronic, biosensor or chr omatographic applications. In this paper, self-assembled OTS monolayer film s were characterized by atomic force microscope (AFM) imaging and Fourier t ransform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy. Con ditions to provide a monolayer free of OTS aggregates were established. The se films were then exposed to aqueous solutions of benzo[k]fluoranthene (B[ k]F), a carcinogenic polycyclic aromatic hydrocarbon (PAH) that is often pr esent in both aqueous and terrestrial environments. Through the B[k]F assoc iations with these OTS monolayer films, it was possible to obtain a film-so lution partition coefficient (log K-fs) value of 7.0 +/- 0.1 using fluoresc ence detection, this value is :similar to partition coefficients previously observed in octanol-water systems. Using AFM images and fluorescence spect roscopy measurements, a maximum surface coverage or 9 (+/- 1) x 10(-4) mole cules of B[k]F per Angstrom (2) was measured within these films, An upper l imit to B[k]F concentration in solution was found, above which aggregates o f B[k]F molecules were formed on the surface.