GROWTH OF FEO(OH) CRYSTALS ON SELF-ASSEMBLED MONOLAYERS ON GOLD

Surfaces composed of self-assembled monolayers (SAM) on gold were used to study the influence on the crystal growth of iron oxide-hydroxide [FeO(OH)]. The self-assembled monolayer formation on gold evaporated o n microscope glass slides was carried out with alpha,omega mercaptoalk ane acids. The in-situ growth of iron oxide-hydroxide crystals on the substrates was induced through the hydrolysis reaction of acidic aqueo us 2 mM Fe(NO3)(3) x 9H(2)O solutions at 20 degrees C. Kinetic measure ments of the alkylthiol monolayer formation on gold and the subsequent deposition of FeO(OH) on the monolayer surface was performed with sur face plasmon resonance spectroscopy (SPS). Atomic force microscopy (AF M) was used to study the structure and topography of the FeO(OH) nanoc rystals. The largest crystal growth was on bare gold surfaces followed by gold covered by a monolayer of sulfonic acid terminated thiols HS- (CH2)(10)SO3-Na+ (MDS) and HS(CH2)(3)SO3-Na+ (MPS). No surface growth of FeO(OH) occurred with gold covered by a self-assembled monolayer of HS(CH2)(15)COOH (MHA), HS(CH2)(11)OH (MUDO) or HS(CH2)(15)CH3 (MHD) o n gold. The FeO(OH) crystals are flat with an average size of 100 nm i n length, 30 nm in width and a height of 20 nm. (C) 1998 Elsevier Scie nce S.A. All rights reserved.