The Chemical Adsorption Properties of Silanol to Metal-Oxide Surface Studied by Using Di(1-naphthyl)silanediol and Nano-porous Alumina Membranes

Abstract

Silanols have a high bonding ability to the surface of metal oxides by forming Si–O-metal bonds, and can produce functional properties which originate in the organic moieties of them to the metal-oxide surface. In order to tune and to emphasize the functional properties, it is important to control the degree of surface modification and to increase the amount of modifiers on the metal-oxide surface. In this work, the chemical surface modification of nano-porous alumina membranes (NPAMs), which possess a regular honeycombed structure with sub-micrometer pores and a high shape stability, with a typical silanol compound of di(1-naphthyl)silanediol, (Nap)2Si(OH)2, by immersing NPAMs into its solutions in order to obtain quantitative information on the reaction conditions for the efficient surface modification. The NPAMs having chemically modified surface with (Nap)2Si(OH)2 were prepared successfully by the immersing method, and the amount of (Nap)2Si(OH)2 adsorbed on the NPAM surface was estimated quantitatively by UV absorption of the NPAM. The effects of the solvent, temperature, and concentration of (Nap)2Si(OH)2 solutions on the efficiency in the chemical surface modification were investigated precisely, and almost complete surface modification with the covering ratio of the NPAM surface by (Nap)2Si(OH)2 of ∼100% was achieved by using the solutions with non-polar solvents, higher temperatures, and a concentration of ∼1 mM.