We report on TiO 2 thin films with superior photocatalytic efficiency due to an increase in its exciton carrier generation induced by the plasmonic field of the underlying silver nanoparticles. TiO 2 thin films are deposited on supported silver nanoparticles and are separated from each other by a fine-tunable thickness of SiO 2 interlayer. The TiO 2 (15 nm)/SiO 2 /Ag nanoparticle architectures with systematic variation of SiO 2 interlayer thickness of 2, 5, 10, and 20 nm show systematic increase in photocatalytic efficiency with decrease in the SiO 2 thickness. The efficiency enhancement is shown to be caused by plasmonically enhanced carrier generation, which was confirmed through photocurrent measurements and Raman spectroscopy. With a 2 nm SiO 2 interlayer that exhibited the best photocatalytic performance, a 3 times increase in photocurrent density, and a 200 times increase in Raman signal intensity of TiO 2 is found. Atomic layer deposition was employed to achieve precise film thickness control of SiO 2 and TiO 2 layers.

Transparent, well-aligned TiO(2) nanotube arrays (NTAs) with controllable dimensions are grown on glass substrates via atomic layer deposition (ALD) of TiO(2) onto free-standing porous anodic alumina (PAA) templates. Photodegradation of aqueous methylene blue (MB) solution and solid stearic acid (SA) film using TiO(2) NTAs of various wall thicknesses are investigated. The Pd functionalized TiO(2) NTAs, with a wall thickness of 15 nm and height of 200 nm, has the highest photodegradation efficiency at 76% after 4 h of UV irradiation. These functionalized NTAs are able to photodegrade MB molecules completely as no obvious demethylated byproducts are observed during the process. It also demonstrates excellent photocatalytic activity for solid contaminants such as SA film. By using the ALD technique, the nanotube wall thickness can be precisely controlled so that it is sufficiently thin to be transparent while sufficiently thick for excellent photocatalytic performances. The transparent TiO(2) NTAs on glass substrates with excellent photocatalytic properties might have potential applications in self-cleaning coating, transparent electronics, and solar cells.

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We report that a very thin film of titania, with thickness controlled to the order of its Debye length, exhibits reversible on/off electrical switching effects upon hydrogen/air exposure at room temperature. Such extreme changes in electrical conduction are usually observed only in the "nanosensors" made of their nanoscaled counterparts. The nanofilm of titania with compact, "monograin-equivalent" film structure is fabricated by atomic layer deposition (ALD) with atomic layer control over its thickness. For the first time, the switching effects of the titania nanofilm capped with catalytic Pd nanoparticles are in situ observed with conducting atomic force microscopy (C-AFM) technique. We further demonstrate that the switching effects can be achieved only when the thickness of the nanofilm is reduced to less than 15 nm. In addition, arrays of TiO 2 nanowires are fabricated to demonstrate the compatibility of ALD with the planar technology.