FORMATION AND NAPHTHOYL DERIVATIZATION OF AROMATIC AMINOSILANE SELF-ASSEMBLED MONOLAYERS - CHARACTERIZATION BY ATOMIC-FORCE MICROSCOPY AND ULTRAVIOLET SPECTROSCOPY

Self-assembled monolayers (SAMs) prepared from short chain aminoalkyl- and aromatic aminoalkysilanes have recently proven valuable in contro lling the adhesive properties of silica substrates for chemical, biolo gical, and microelectronic applications. To gain insight to the struct ure and amine reactivity of these films, we have studied the formation of SAMs formed on silica surfaces from ((((aminoethyl) amino)methyl) phenethyl) trimethoxysilane (PEDA), and their modification with 2-naph thoyl chloride (NAP-C1). Atomic force microscopy was used to demonstra te that PEDA and PEDA-NAP SAMs do not pack in a periodic or regular ar ray on the surface but in fact are highly disordered relative to surfa ce-deposited Langmuir-Blodgett (LB) phospholipid films, organothiol SA Ms on gold, and at least one perfluorinated alkyl monochlorosilane SAM . In contrast to chromophores in well-ordered monolayers, the UV absor bance lineshapes and ratio of peaks corresponding to the (1)A-B-1(b) a nd (1)A-(1)L(a) transitions of the NAP chromophore remain relatively u nchanged after immobilization. A simple first-order model, used to est imate molecular densities and reaction stoichiometries, suggests that in reaction-site-limited PEDA SAMs, the amine reactivity is limited by the maximum packing density of the NAP chromophore.