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Bothenhancing the excitons’ lifetime and ingeniously controllingthe spatial charge transfer are the key to the realization of efficientlyphotocatalytic and artificially photosynthetic devices. Nanostructuredmetal/metal-oxide interfaces often exhibit improved energy conversionefficiency. Understanding the surface potential changes of nano-objectsunder light illumination is crucial in photoelectrochemical cells.Under ultraviolet (UV) illumination, here, we directly observed thecharge separation phenomena at the Au-nanoparticle/TiO2-nanotube interfaces by using Kelvin probe force microscopy. Thesurface potential maps of TiO2nanotubes with and withoutAu nanoparticles were compared on the effect of different substrates.We observed that in a steady state, approximately 0.3 electron perAu particle of about 4 nm in diameter is effectively charged and consequentlyscreens the surface potential of the underlying TiO2nanotubes.Our observations should help design improved photoelectrochemicaldevices for energy conversion applications. [ABSTRACT FROM AUTHOR]

Atomic layer deposition (ALD) not only presents a direct way to prepare nanomaterials when combined with templates, but also allows surface engineering to fine-tune the properties of the material. Here, we review recent progress in the field of nanostructured materials and devices that have been fabricated by ALD. Various materials, including semiconducting, magnetic, noble metallic, and insulating materials, can be used to form three-dimensional (3D), complex nanostructures with controlled composition and physical properties. We begin this review with ALD nanomaterials that can be prepared from porous templates with a 2D pore arrangement, such as anodic aluminum oxide, and advance toward opal structures with a 3D pore arrangement. We also discuss surface engineering by ALD on existing nanowires/nanotubes, devices, and chemical patterns that has the potential for application in high-performance transistors, sensors, and green energy conversion. Finally, we provide perspectives for future device applications that could arise from ALD nanomaterials. [ABSTRACT FROM AUTHOR]

We report on the interplay between nanostructuring and defect activation in dense polycrystalline Bi2Te3 thin films in terms of the thermopower engineering. The Bi2Te3 thin films were prepared at relatively low temperatures (100–160 °C) by atomic layer deposition and their grains showed different sizes in the range of 50–200 nm according to the deposition temperatures. We monitored the conductivity, Seebeck coefficient, and power factor of all samples from the temperature of 50–400 K. By increasing the growth temperature, remarkably, we observed the gradual defect activation from the nominal p-type to n-type in our binary end compound, Bi2Te3 without any alloying. The present results give us an insight on the optimization of thermoelectric materials not only by nanostructuring (i.e., phonon engineering) but also by controlled defect activation (i.e., electron engineering). [ABSTRACT FROM AUTHOR]