Regioselective magnetization in semiconducting nanorods.

Chirality-the property of an object wherein it is distinguishable from its mirror image-is of widespread interest in chemistry and biology1-6. Regioselective magnetization of one-dimensional semiconductors enables anisotropic magnetism at room temperature, as well as the manipulation of spin polarization-the properties essential for spintronics and quantum computing technology7. To enable oriented magneto-optical functionalities, the growth of magnetic units has to be achieved at targeted locations on a parent nanorod. However, this challenge is yet to be addressed in the case of materials with a large lattice mismatch. Here, we report the regioselective magnetization of nanorods independent of lattice mismatch via buffer intermediate catalytic layers that modify interfacial energetics and promote regioselective growth of otherwise incompatible materials. Using this strategy, we combine materials with distinct lattices, chemical compositions and magnetic properties, that is, a magnetic component (Fe3O4) and a series of semiconducting nanorods absorbing across the ultraviolet and visible spectrum at specific locations. The resulting heteronanorods exhibit optical activity as induced by the location-specific magnetic field. The regioselective magnetization strategy presented here enables a path to designing optically active nanomaterials for chirality and spintronics.

Mechanism of photocatalytic activity improvement of AgNPs/TiO2 by oxygen plasma irradiation.

Plasmonic metal Ag nanoparticles (AgNPs) on TiO2 thin films (AgNPs/TiO2) are a kind of excellent photocatalyst of high efficiency under visible light, and thus draw great interest nowadays. Further improvement of their photocatalytic activity (PA) is difficult but is of high importance for their applications. In this paper, oxygen plasma was taken to partially oxidize AgNPs deposited on the surface of TiO2 to form a structure with the configuration of a p-type semiconductor/plasmonic metal/n-type semiconductor (Ag2O/AgNPs/TiO2). The localized surface plasmon resonance (LSPR) of the AgNPs was strongly damped after oxygen plasma irradiation (OPI) but the photocatalytic activity was improved. The mechanisms of the photocatalytic activity improvement under UV and visible light were explored based on charge kinetics.

Microwave-assisted synthesis of silver indium tungsten oxide mesocrystals and their selective photocatalytic properties.

A new kind of silver indium tungsten oxide (AgIn(WO(4))(2)) mesocrystals with high hierarchy can be synthesized by a microwave-assisted approach, which shows high and selective photocatalytic activity for the degradation of different organic dyes under UV and visible light irradiation.

UV-light induced fabrication of CdCl2 nanotubes through CdSe/Te nanocrystals based on dimension and configuration control.

Since the discovery of WS2 nanotubes in 1992 ( Nature 1992, 360, 444), there have been significant research efforts to synthesize nanotubes and fullerene-like hollow nanoparticles (HNPs) of inorganic materials ( Nat. Nanotechnol. 2006, 1, 103) due to their potential applications as solid lubrications ( J. Mater. Chem. 2005, 15, 1782), chemical sensing ( Adv. Funct. Mater. 2006, 16, 371), drug delivering ( J. Am. Chem. Soc. 2005, 127, 7316), catalysis ( Adv. Mater. 2006, 18, 2561), or quantum harvesting ( Acc. Chem. Res. 2006, 39, 239). Nanotubes can be produced either by rolling up directly from layer compounds ( Nature 2001, 410, 168) or through other mechanisms ( Adv. Mater. 2004, 16, 1497) such as template growth ( Nature 2003, 422, 599) and decomposition ( J. Am. Chem. Soc. 2001, 123, 4841). The Kirkendall effect, a classical phenomenon in metallurgy ( Trans. AIME 1947, 171, 130), was recently exploited to fabricate hollow 0-D nanocrystals ( Science 2004, 304, 711) as well as 1-D nanotubes ( Nat. Mater. 2006, 5, 627). Although the dimension of resulting hollow nanostructures depends on precursors, the hollow nanomaterials can also be organized into various dimensional nanostructures spontaneously or induced by an external field. In this letter, we report, for the first time, the UV-light induced fabrication of the ends-closed 1-D CdCl2 nanotubes from 0-D CdSe solid nanocrystals through the Kirkendall effect and the head-to-end assembled process. Our results demonstrate the possibility to control the dimension (0-D to 1-D) and the configuration (solid to hollow) of nanostructures simultaneously and have implications in fabricating hollow nano-objects from zero-dimensional to multidimensional.

Carbothermal chemical vapor deposition route to Se one-dimensional nanostructures and their optical properties.

A simple and practical carbothermal chemical vapor deposition route has been developed for the growth of trigonal phase selenium nanowires and nanoribbons. In detail, the mixture of active carbon and selenium was heated for the chemical reaction to occur, followed by thermal evaporation and decomposition into elemental selenium. The as-prepared sample was characterized by X-ray diffraction, transmission electron microscopy, high-resolution electron microscopy, UV-vis absorption, and photoluminescence. The results show that trigonal Se nanowires have uniform diameters ranging from 20 to 60 nm and grow along the [001] direction, with the same growth direction found for nanoribbons. Spectral measurements suggest a large blue shift and two types of electron transition activity. The influences of experimental conditions on morphologies and growth processes are also discussed. This synthetic method should be able to be extended to grow other one-dimensional chalcogens and chalcogenides nanostructures.

Synthesis of aligned zinc sulfide nanostructures and the influence of experimental conditions on their morphologies and phase.

A novel aligned flower-like array and single-crystal nanosheets composed of ZnS quantum wires were fabricated via a simple solution route. In the method, ZnCl2 chemicals reacted with Na2S in 50 ml of ethylenediamine (en) solution containing different amounts of hydrochloric acid (HCl) at 70-80 degrees C. After annealing at 500 degrees C for 1.5 h, wurtzite phase ZnS nanoscaled materials were synthesized. When the amount of HCl was 2 ml and 3 ml, respectively, flower-like structure and nanosheets were obtained. The products were characterized by X-ray diffraction, transmission electron microscopy, high-resolution electron microscopy (HREM), and electron diffraction (ED). The influences of concentration, temperature, and reaction time on the morphologies and phase of ZnS nanostructures were also studied. The photoluminescence peaks are located at approximately 308 nm and approximately 410 nm. The formation mechanism is also discussed here.