Photosensitive films incorporating molecular photoacid generators compartmentalized within a silica-surfactant mesophase were prepared by an evaporation-induced self-assembly process. Ultraviolet exposure promoted localized acid-catalyzed siloxane condensation, which can be used for selective etching of unexposed regions; for "gray-scale" patterning of refractive index, pore size, surface area, and wetting behavior; and for optically defining a mesophase transformation (from hexagonal to tetragonal) within the film. The ability to optically define and continuously control both structure and function on the macro- and mesoscales is of interest for sensor arrays, nanoreactors, photonic and fluidic devices, and low-dielectric-constant films.

Carboxylic acid (HORc)-modified Ti(OR)4 products were used to study the effect that similarly ligated species with substantially varied structures have on the final densification of the resultant ceramic (in this case TiO2). The 1:1 stoichiometric products isolated from the reactions of [Ti(μ-ONep)(ONep)3]2 (1, ONep = OCH2CMe3) and a variety of sterically hindered carboxylic acids [HORc:  HOFc (HO2CH), HOAc (HO2CCH3), HOPc (HO2CCHMe2), HOBc (HO2CCMe3), or HONc (HO2CCH2CMe3)] were identified by single-crystal X-ray diffraction and solid-state 13C MAS NMR spectroscopy as Ti3(μ3-O)(OFc)2(ONep)8 (2), Ti3(μ3-O)(OAc)2(ONep)8 (3), Ti6(μ3-O)6(OPc)6(ONep)6 (4), Ti2(μ-OBc)2(ONep)6 (5), and Ti3(μ3-O)(ONc)2(ONep)8 (6). Compounds 2, 3, and 6 adopt a triangular arrangement of Ti atoms linked by a μ3-oxide moiety with ORc and ONep ligands supporting the basic framework. Compound 4 adopts a distorted, hexagon-prism geometry of two offset [Ti−O−]3 rings with each six-coordinated metal possessing a terminal ONep and two monodentate OPc ligands. The unique, nonesterified product 5 is dimeric with two μ-ONep, two unidentate bridging OBc, and two terminal ONep ligands. The solution behaviors of 2−6 were investigated by NMR experiments and were found to retain the solid-state structure in solution with a great deal of ligand rearrangement. Films of TiO2 were made from redissolved crystals of 2−6. The highest density TiO2 thin films were derived from the partially hydrolyzed, trinuclear, low-carbon-containing ONep complexes 2 and 3, as determined from ellipsometric data.

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We have performed experiments to characterize permanent laser-induced darkening in CdS..,Se1-.2: semiconductor-doped glasses with picosecond pulses as a function of fluence, repetition rate, and pulse width. We find that the darkening occurs by means of a nonlinear process that exhibits an anomalous dependence on pulse width. Transmission spectra show that the induced darkening is uniform over the spectral range from the absorption edge out to 820 J.Lm. Darkening in a number of different glasses is compared. On the basis of our results we propose a mechanism that involves photoassisted trapping of electrons from the semiconductor microcrystallites into states within the glass host material.