One-step synthesis of high quality kesterite Cu2ZnSnS4nanocrystals: A hydrothermal approach

The present work demonstrates a systematic approach for the synthesis of pure kesterite-phase Cu2ZnSnS4 (CZTS) nanocrystals with a uniform size distribution by a one-step, thioglycolic acid (TGA)-assisted hydrothermal route. The formation mechanism and the role of TGA in the formation of CZTS compound were thoroughly studied. It has been found that TGA interacted with Cu2+ to form Cu+ at the initial reaction stage and controlled the crystal-growth of CZTS nanocrystals during the hydrothermal reaction. The consequence of the reduction of Cu2+ to Cu+ led to the formation Cu2−xS nuclei, which acted as the crystal framework for the formation of CZTS compound. CZTS was formed by the diffusion of Zn2+ and Sn4+ cations to the lattice of Cu2−xS during the hydrothermal reaction. The as-synthesized CZTS nanocrystals exhibited strong light absorption over the range of wavelength beyond 1000 nm. The band gap of the material was determined to be 1.51 eV, which is optimal for application in photoelectric energy conversion device.

One step synthesis of monoclinic VO2 (B) bundles of nanorods: Cathode for Li ion battery

One of the metastable phases of vanadium dioxide, VO2(B) bundles of nanorods and microspheres have been synthesized through a simple hydrothermal method by dispersing V2O5 in aqueous quinol. The obtained products were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and electrochemical discharge-charge test for lithium battery. It was found that the morphologies of the obtained VO2(B) can be tuned by manipulating the relative amount of quinol. The electrochemical test found that the bundles of nanorods exhibit an initial discharge capacity of 171 mAh g(-1) and its almost stabilized capacity was reached to 108 mAh g(-1) after 47 cycles at a current density of 0.1 mA g(-1). The formation mechanism of the VO2(B) bundles of nanorods and microspheres was also discussed. (C) 2012 Elsevier Inc. All rights reserved.

On the Two-Step Mechanism for Synthesis of Transition-Metal Nanoparticles

The two-step particle synthesis mechanism, also known as the Finke-Watzky (1997) mechanism, has emerged as a significant development in the field of nanoparticle synthesis. It explains a characteristic feature of the synthesis of transition metal nanoparticles, an induction period in precursor concentration followed by its rapid sigmoidal decrease. The classical LaMer theory (1950) of particle formation fails to capture this behavior. The two-step mechanism considers slow continuous nucleation and autocatalytic growth of particles directly from precursor as its two kinetic steps. In the present work, we test the two-step mechanism rigorously using population balance models. We find that it explains precursor consumption very well, but fails to explain particle synthesis. The effect of continued nucleation on particle synthesis is not suppressed sufficiently by the rapid autocatalytic growth of particles. The nucleation continues to increase breadth of size distributions to unexpectedly large values as compared to those observed experimentally. A number of variations of the original mechanism with additional reaction steps are investigated next. The simulations show that continued nucleation from the beginning of the synthesis leads to formation of highly polydisperse particles in all of the tested cases. A short nucleation window, realized with delayed onset of nucleation and its suppression soon after in one of the variations, appears as one way to explain all of the known experimental observations. The present investigations clearly establish the need to revisit the two-step particle synthesis mechanism.

One-step growth of ZnO from film to vertically well-aligned nanorods and the morphology-dependent Raman scattering

We observed a transition from film to vertically well-aligned nanorods for ZnO grown on sapphire (0001) substrates by metalorganic chemical vapor deposition. A growth mechanism was proposed to explain such a transition. Vertically well-aligned homogeneous nanorods with average diameters of similar to 30, 45, 60, and 70 nm were grown with the c-axis orientation. Raman scattering showed that the E-2 (high) mode shifted to high frequency with the decrease of nanorod diameters, which revealed the dependence of nanorod diameters on the stress state. This dependence suggests a stress-driven diameter-controlled mechanism for ZnO nanorod arrays grown on sapphire (0001) substrates. (c) 2005 American Institute of Physics.

Nanoporous In2O3 nanocrystal clusters: One-step synthesis, thermal stability and optical property

Nanoporous In2O3 nanocrystal clusters with high surface areas have been synthesized by a one-step solvent-thermal method at a relatively low temperature. On the basis of our experimental data and nanomaterial growth mechanism, a template-assistant dehydration accompanied by aggregation mechanism was proposed to explain their formation. Besides, the influence of the high-temperature treatment on their porous structure and optical properties were studied and compared by various technologies.

One-step synthesis of gold-polyaniline core-shell particles

A one-step method has been developed for synthesizing gold-polyaniline (Au@PANI) core-shell particles by using chlorauric acid (HAuCl4) to oxidize aniline in the presence of acetic acid and Tween 40 at room temperature. SEM images indicated that the resulting core-shell particles were composed of submicrometre-scale Au particles and PANI shells with an average thickness of 25 nm. Furthermore, a possible mechanism concerning the growth of Au@PANI particles was also proposed based on the results of control experiments.

Quantum cryptography - one step closer to reality

Most of cryptographic techniques today provide secure enough communications in society. However, none of them can provide unconditional security (except One-Time pad, which is the only such mechanism). They all have weaknesses. That is why they should be consistently updated and renovated along with changes in technology.

However, the quantum computers have potential to completely revolutionize cryptography. They would be so powerful that all complex computations and mathematical problems on which current cryptography rely, would become trivial. They would be able to solve them in a matter of seconds. At the same time quantum cryptography would offer perfectly secure communication.

This paper is brief introduction to quantum computing, quantum cryptography, and to existing quantum technology.

One-Step synthesis of the pine-shaped nanostructure of aluminum nitride and its photoluminescence properties

An array of pine-shaped nanostructures of aluminum nitride (AlN) was synthesized through direct reaction between Al vapor and nitrogen gas in direct current (DC) arc discharge plasma without any catalyst or template. The as-prepared nanostructure consists of many pine-needle-shaped leaves with conical shape tips. The structure, morphology, and optical property of the nanostructure have been characterized by X-ray powder diffraction, energy-dispersive X-ray spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, Raman spectroscopy, and photoluminescence. A possible growth mechanism of the pine-shaped nanostructure was discussed. Two factors were found to be essential for branched nanostructure growth, i.e., the reaction time and N2 pressure. The photoluminescence spectrum of the nanostructure of AlN revealed an intense emission band, suggesting that there may be potential applications in electronic and optoelectronic nanodevices.

"One-Step" alkynylation of adamantyl iodide with Silver(I) acetylides

Silver(I) acetylides allow one-step alkynylation of adamantyl iodide in yields ranging from 25 to 68%.

Surrogacy laws in Queensland: one step forward and two steps back?

This short article summarises some of the proposed reforms to surrogacy laws in Queensland, suggested by the Liberal National Party in 2012. The paper outlines some of the main objections that could be voiced in response to the proposed changes to the law.

One-step synthesis of titanium oxide with trilayer structure for dye-sensitized solar cells

Titanium oxide films with trilayer structure grown on fluorine doped tin oxide substrate were prepared from one-step hydrothermal process. The trilayer structure consists of microflowers, nanorod array and compact nanoparticulates, which is expected to possess the merits of good light harvesting, a high electron transport rate, while avoiding the issues of electron shunting. The photovoltaic performance was comprehensively studied and a 60% enhancement in short circuit photocurrent density was found from microflowers contribution as a light scattering layer. This unique trilayer structure exhibits great potential application in future dye-sensitized solar cells.