Naveen Chopra

Pore architecture affects photocatalytic activity of periodic mesoporous nanocrystalline anatase thin films

We report the photocatalytic activity of periodic mesoporous nanocrystalline anatase thin films (denoted meso-nc-TiO2) using Methylene Blue (denoted MB) as a probe of pore architecture effects on reactivity. Specifically, 2D hexagonal and 3D cubic mesoporous nanocrystalline anatase thin films (denoted h-meso-nc-TiO2 and c-meso-nc-TiO2 respectively) annealed at different temperatures were investigated to reveal the effects of different pore architectures on the photocatalytic activity. The adsorption behavior of MB on the films annealed at the same temperature signaled that c-meso-nc-TiO2 has a larger accessible surface area but a lower adsorption surface affinity, compared to h-meso-nc-TiO2. In the case of the solid-state photodegradation of MB, the most efficacious photocatalyst was found to be c-meso-nc-TiO2 annealed at 450 °C. For MB in solution, a 400 °C annealed c-meso-nc-TiO2 was established to have the optimum photocatalytic activity among the samples investigated. The observed superior photocatalytic activity of c-meso-nc-TiO2 relative to both h-meso-nc-TiO2 and nc-TiO2 is believed to originate from the higher photoactivity of anatase nanocrystallites comprising the more open cubic framework. as well as geometrical advantages, such as a larger surface area and less obstructed 3D diffusion paths of guest molecules. It is concluded that the photocatalytic efficiency of periodic mesoporous nanocrystalline anatase thin films depends on the pore architecture.

Towards flexible inorganic ?mesomaterials?: one-pot low temperature synthesis of mesostructured nanocrystalline titaniaElectronic supplementary information (ESI) available: IR spectra and SEM image of mesoporous nanocrystalline titania. See http://www.rsc.org/suppdata/cc/b4/b403607g/

We hereby report a simple route for the low temperature synthesis of mesoporous nanocrystalline titania involving brief hydrothermal treatment of butanolic precursors and non-ionic tri-block-copolymer surfactant at 100 degrees C, followed by evaporation induced self assembly to make a crack-free flexible film. At no time in the film-forming process is a temperature of more than 120 degrees C reached, thereby permitting the use of substrates that are not stable to higher temperatures.

Amorphous Silicon Backplane with Polymer MEMS Structures for Electrophoretic Displays

The development of electronic paper has been a desire since a long time and electrophoretic displays are a promising candidate for this application. Apart from developing the electrophoretic display medium there are important issues to solve regarding the overall system. The importance of the electronic addressing method increases with the demand for arbitrary images or text. We have developed and tested active-matrix backplanes based on amorphous silicon technology, as well as the driver electronics. The electrophoretic ink is combined with the backplane employing polymer MEMS cell structures. This system allows us to display highresolution images and it is a good test bed for investigating various parameters of the electrophoretic display medium and of the electronics.

Evolution of nanocrystallinity in periodic mesoporous anatase thin films

Herein we report the first kinetic study of the intrachannel wall phase-transition of amorphous titania to nanocrystalline anatase for periodic mesoporous titania thin films, monitored by time-resolved in situ high-temperature X-ray diffraction. Structural transformations associated with the phase transition are further probed by high-resolution scanning electron microscopy and transmission electron microscopy. The model found to be most consistent with the kinetic data involves 1D diffusion-controlled growth of nanocrystalline anatase within the spatial confines of the channel walls of the mesostructure. The observation of anisotropic, rod-shaped anatase nanocrystals preferentially aligned along the channel axis implies that the framework of the liquid-crystal-templated mesostructure guides the crystal growth.