Search

Mesostructured SiO2 films functionalized with the azo-chromophore Disperse Red 1 were synthesized by sol-gel method. The mesostructured long-range order in the films was determined by X-Ray Diffraction. The azo-chromophores in the films work as nano-impellers through their photo-induced trans-cis reversible isomerization. When the films are doped, they are able to control the release of the dopant by all-optical processes. We used the dye laser Rhodamine 6G as dopant, its very distinctive luminescence around 550 nm allows to follow the release. Polarized green and infrared laser light were used as pump sources to direct the movement of the nano-impellers. 299 nm light was used as a probe to induce the Rhodamine 6G luminescence, which was measured as function of the pumping time with a photomultiplier coupled to a monochromator. The results corresponding to the green and to the infrared pumping sources are compared in order to determine the feasibility to photo-control the nano-impellers movement through a two-photon absorption process.

Films made of Polymethylmetacrylate (PMMA) and doped with dipolar second order nonlinear optical chromophores were studied by UV-visible spectroscopy and transmitted resonant Second Harmonic Generation technique. The chromophores were non-centrosymmetrically oriented by a Corona poling field. The UV-visible spectra were measured in poled films at normal incidence as function of their poling temperatures (60, 80 and 100°C) and they were analyzed in terms of the Second Order Parameter (A2). The Second Harmonic Generation (SHG) signals in the films were measured in-situ as function of the poling time at several incidence angles for each poling temperature. The stability of the SHG signal was also determined, by turning off the Corona field but leaving the films at their original poling temperature. The films were of two different kinds: amorphous and nanostructured. All the films doped simultaneously with chromophores and surfactants showed long-range ordered nanostructures. Two kinds of surfactants were used during the synthesis of the films: ionic and neutral, both of them induced long-range order in the structure of the PMMA, but only some of the nanostructured films exhibited enough large SHG signals. The second order nonlinear optical response of the nanostructured films was compared with the corresponding response of the amorphous films. The long-range order in the films was detected by X-Ray Diffraction (XRD).

The kinetics of the orientation of Disperse Red 1 (DR1) molecules embedded in nanostructured Polymethylmetacrylate (PMMA) films was studied under the effect of an intense constant electric poling field. The changes in the orientation distribution of the DR1 molecules were followed by Second Harmonic Generation (SHG) measurements. The SHG signal was recorded as function of time at three different temperatures. We focused on both, the signal increases under the presence of the poling field and the signal decays without the poling field. The studied PMMA films were nanostructured by the incorporation of ionic surfactants as the Sodium Dodecyl Sulfate (SDS) and the Cetyl Trimethyl Ammonium Bromide (CTAB) during their preparation. The kinds of nanostructures obtained in the films were determined by means of X-ray diffraction (XRD) measurements. Substantial differences in signal intensity and in growth and decay rates between amorphous and nanostructured films were found.

Mesostructured SiO2 films functionalized with the azo-chromophore Disperse Red 1 were synthesized by sol-gel method. The mesostructured long-range order in the films was determined by X-Ray Diffraction. The azo-chromophores in the films work as nano-impellers through their photo-induced trans-cis reversible isomerization. When the films are doped, they are able to control the release of the dopant by all-optical processes. We used the dye laser Rhodamine 6G as dopant, its very distinctive luminescence around 550 nm allows to follow the release. Polarized green and infrared laser light were used as pump sources to direct the movement of the nano-impellers. 299 nm light was used as a probe to induce the Rhodamine 6G luminescence, which was measured as function of the pumping time with a photomultiplier coupled to a monochromator. The results corresponding to the green and to the infrared pumping sources are compared in order to determine the feasibility to photo-control the nano-impellers movement through a two-photon absorption process.