Strategies for Spatially Separating Molecules in Mesostructured Sol-Gel Silicate Films

Abstract

Three strategies for placing molecules in designated regions of mesostructured thin films made by the sol-gel dip-coating technique are demonstrated. These strategies all involve one-step syntheses where all of the components are present in the sol from which the substrate is pulled. Silicate films templated by ionic surfactants contain three spatially-separated regions: a silicate framework, an organic region formed by the hydrocarbon tails of the surfactants, and an intervening ionic interface formed by the charged surfactant head groups. The first method exploits lipophilic interactions between the molecule and the micelle to place it in the organic region. The second method uses chemical bonding of multiple trialkoxysilane groups in a three dimensional array on the molecule to place it in the silica framework. The third method uses multiple functionality at opposite sides of the molecule to enable it to span two regions. Luminescent molecules are used, and spectroscopy monitors the formation.