Mesoporous aminopropyl-functionalized hybrid thin films with modulable surface and environment-responsive behavior.

A. CALVO, P.C. ANGELOMÉ, V. M. SÁNCHEZ, D. A. SCHERLIS F. J. WILLIAMS, G.J.A.A. SOLER-ILLIA

CHEMISTRY OF MATERIALS

AMER CHEMICAL SOC

Año: 2008 p. 4661 - 4668

0897-4756

A first study of the behavior of amino functions in mesoporous hybrid thin films M1–x(Si-(CH2)3NH2)xO2-x/2 (M=Si, Ti, Zr; 0.05 x 0.2) with accessible Im3m- or Fm3m-derivedpore mesostructures is presented. An XPS study of surface nitrogen species shows twodifferent sites corresponding to amino and ammonium groups. The ratio of these specieschanges with pH, and is related to the nature of M, suggesting that the interaction between theorganic functions and the surface M-OH groups can be tailored to tune the surface acid-basebehaviour. Density Functional Theory (DFT) calculations were used to rationalize the XPSobservations showing that –NH3+ functions irreversibly transfer a proton to neighboring M-Osurface groups. The acid-base surface properties can be further modified by adding aphosphonate “capping” on the M surface sites. Our findings have a series of interestingimplications in surface functionalization: attachment of biomolecules to surfaces, design ofperm-selective or philicity-selective membranes, or design of catalysts that show a welldefinedorganic reactive function near surface hydroxyl groups.