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One-step solid-phase transformation from high-quality cadmium carbonate microcrystal into highly nanoporous cadmium oxide is demonstrated. The new approach is found to have good potential to prepare nanoporous material at a large scale by using perfect monolithic carbonate crystals, and is also useful to synthesize different nanoporous materials on metal-oxide-coated substrates.

The application of nitric oxide for switching the photoluminescence of nonfluorescent molecularly engineered quantum dots (QDs) is demonstrated. The energy transfer taking place between the excited QD and the surface bound iron(III) carbamates is shown to lead to the quenching of the fluorescence of these excited QDs.

Semiconductor nanostructures that can effectively serve as light-responsive photocatalysts have been of considerable interest over the past decade. This is because their use in light-induced photocatalysis can potentially address some of the most serious environmental and energy-related concerns facing the world today. One important application is photocatalytic hydrogen production from water under solar radiation. It is regarded as a clean and sustainable approach to hydrogen fuel generation because it makes use of renewable resources (i.e., sunlight and water), does not involve fossil fuel consumption, and does not result in environmental pollution or greenhouse gas emission. Another notable application is the photocatalytic degradation of nonbiodegradable dyes, which offers an effective way of ridding industrial wastewater of toxic organic pollutants prior to its release into the environment. Metal oxide semiconductors (e.g., TiO2) are the most widely studied class of semiconductor photocatalysts. Their nanostructured forms have been reported to efficiently generate hydrogen from water and effectively degrade organic dyes under ultraviolet-light irradiation. However, the wide band gap characteristic of most metal oxides precludes absorption of light in the visible region, which makes up a considerable portion of the solar radiation spectrum. Meanwhile, nanostructures of cadmium chalcogenide semiconductors (e.g., CdS), with their relatively narrow band gap that can be easily adjusted through size control and alloying, have displayed immense potential as visible-light-responsive photocatalysts, but the intrinsic toxicity of cadmium poses potential risks to human health and the environment. In developing new nanostructured semiconductors for light-driven photocatalysis, it is important to choose a semiconducting material that has a high absorption coefficient over a wide spectral range and is safe for use in real-world settings. Among the most promising candidates are the multinary chalcogenide semiconductors (MCSs), which include the ternary I-III-VI2 semiconductors (e.g., AgGaS2, CuInS2, and CuInSe2) and the quaternary I2-II-IV-VI4 semiconductors (e.g., Cu2 ZnGeS4, Cu2ZnSnS4, and Ag2 ZnSnS4). These inorganic compounds consist of environmentally benign elemental components, exhibit excellent light-harvesting properties, and possess band gap energies that are well-suited for solar photon absorption. Moreover, the band structures of these materials can be conveniently modified through alloying to boost their ability to harvest visible photons. In this Account, we provide a summary of recent research on the use of ternary I-III-VI2 and quaternary I2-II-IV-VI4 semiconductor nanostructures for light-induced photocatalytic applications, with focus on hydrogen production and organic dye degradation. We include a review of the solution-based methods that have been employed to prepare multinary chalcogenide semiconductor nanostructures of varying compositions, sizes, shapes, and crystal structures, which are factors that are known to have significant influence on the photocatalytic activity of semiconductor photocatalysts. The enhancement of photocatalytic performance through creation of hybrid nanoscale architectures is also presented. Lastly, views on the current challenges and future directions are discussed in the concluding section. [ABSTRACT FROM AUTHOR]

Site and size control of ordered arrays of semiconductor nanostructures in an efficient way has remained a large challenge and has thus attracted intensive research interest due to their potential applications inintegrated optoelectronics. In this work, we report an original approach to grow hexagonally ordered arrays of InGaAs/GaAs nanobars on the designed regions of GaAs substrate coated with silicon dioxide through nanospherelithography (NSL). To control the growth sites of the nanostructures, microsized wells are first fabricated on a thin silicon dioxide film deposited on the GaAs substrate by photolithography, and bilayers of hexagonally ordered polymer nanospheres are then self-assembled on the silicon dioxide films with two different thicknesses. Finally,an array of nanocavities is created by dry etching through the self-assembled nanospheres. By controlling the etching depth, the nanocavities areetched down to the GaAs substrate first in the wells, leading to epitaxial growth of InGaAs/GaAs nanobars only in the wells with one-step metal-organic chemical vapor deposition (MOCVD). To fabricate dual sized InGaAs/GaAs nanobars, combined etchants are used to etch not only the silicon dioxide but also the polymer; the etching front of nanocavities inside the microsized wells reaches the GaAs substrate first and is further widened when the etching front of the nanocavities outside the wells also reaches the bottom. This results in the formation of dual-sized nano openings of the silicon dioxide film on the GaAs substrate for the expitaxial growth of dual-sized InGaAs/GaAs nanobars by one-step MOCVD. [ABSTRACT FROM AUTHOR]