In situ probing by fluorescence spectroscopy of the formation of continuous highly-ordered lamellar-phase mesostructured thin films

Continuous highly-ordered mesostructured lamellar-phase thin films are formed by a rapid dip-coating method. The films are made by a dip-coating process from a sol consisting of tetraethoxysilane and the surfactant sodium dodecyl sulfate (SDS). XRD patterns give sharp peaks extending to 14 orders, indicative of a highly-ordered structure. Film thickness is measured in real time by using interferometry; interference fringes remain constant in height above the sol on the continuously-moving silicon substrate. In situ fluorescence spectra of probe molecules were recorded to trace both the formation of the micelles and the solvent composition of the films as they are pulled in real time. Micelles are formed, break up, and re-form to produce the final structure in 12 s, and the water content smoothly increases from 2% to 60% in the same amount of time.