ZnO materials with a range of different morphologies have been synthesized via a simple solvothermal method with different solvents. Zinc acetylacetonate was used as the zinc source in such solvothermal syntheses for the first time. XRD data showed that single-phase ZnO with the wurtzite crystal structure was obtained for all the solvents used. FE-SEM imaging showed that ZnO with cauliflower-like, truncated hexagonal conical, tubular and rodlike, hourglass-like, nanorods, and spherical shapes were produced when THF, decane, water, toluene, ethanol, and acetone were used as the solvent, respectively. The TEM data showed that the crystalline ZnO had different growth habits in the different solvents. The optical properties of the as-prepared ZnO materials were investigated by UV-vis absorption and room temperature photoluminescence. Photodegradation of phenol was used as a model reaction to test the photocatalytic activity of the ZnO samples. ZnO samples with different morphologies and crystal growth habits exhibited different activities to phenol degradation. The ZnO material prepared using THF as the solvent showed a nine-times enhancement of the kinetic rate constants over commercial ZnO (0.1496 min -1 vs 0.0182 min -1 ). The influence of the solvents on the morphology of ZnO samples and the effect of the morphologies on the photocatalytic activity are discussed.

Light-emitting diodes are becoming the alternative for future general lighting applications, with huge energy savings compared to conventional light sources owing to their high efficiency and reliability. Polarized light sources would largely enhance the efficiency in a number of applications, such as in liquid-crystal displays, and also greatly improve contrast in general illumination due to the reduction in indirect glare. Here, we demonstrate light-emitting diodes presenting high-brightness polarized light emission by combining the polarization-preserving and directional extraction properties of embedded photonic-crystals applied to non-polar gallium nitride. A directional enhancement of up to 1.8-fold was observed in the total polarized light emission together with a high polarization degree of 88.7% at 465 nm. We discuss the mechanisms of polarized light emission in non-polar gallium nitride and the photonic-crystal design rules to further increase the light-emitting diode brightness. This work could open the way to polarized white-light emitters through their association with polarization-preserving down-converting phosphors. INTRODUCTIONDue to a continuously improved performance, light-emitting diodes (LEDs) are not only the major contender for future general lighting sources, 1 but also play an important role in a growing number of other applications-from backlight for high-efficiency televisions and mobile phone displays, to car lights and headlights-replacing the classical white sources owing to their high efficiency, brightness, reliability and low operation cost. Polarized light sources would largely improve the efficiency of most of these applications: from general illumination, with an improved contrast due to reduced glare, 2 which also minimizes eye discomfort and ultimately eye strain, 3 to highefficiency displays which operate through the spatial modulation of polarized light 4 (for completeness, we also note that polarized light and other forms of artificial light could be harmful for the life of animals and other species relying on natural light cycles to live 5 ). However, common light sources are usually unpolarized, since the electric field of the light emitted has no preferred orientation. This is also the case for most of the nitride-based LEDs commercialized nowadays. A strongly linearly polarized source, however, is obtained in m-plane GaN LEDs where the asymmetric in-plane biaxial stress on the quantum wells (QWs) orients the light emitting dipoles preferentially along the in-plane a direction. Non-polar m-plane GaN LEDs were first developed and more intensively investigated due to the possible reduction of polarization-induced electric fields in the QWs, which for c-plane GaN LEDs degrade their radiative recombination rate as a result of quantum confined stark effects. 6,7 Today, the

Progress in metal-organic chemical vapor deposition of high quality ( ) 0001 ¯N-polar (Al, Ga, In)N films on sapphire, silicon carbide and silicon substrates is reviewed with focus on key process components such as utilization of vicinal substrates, conditions ensuring a high surface mobility of species participating in the growth process, and low impurity incorporation. The high quality of the fabricated films enabled the demonstration of N-polar (Al, Ga, In)N based devices with excellent performance for transistor applications. Challenges related to the growth of high quality N-polar InGaN films are also presented.

On the basis of the first-principles calculation, single transition-metal (TM) atoms of first and second transition series are anchored on the β 12 phase of the boron monolayer (BM) electrocatalyst for the sustainable production of ammonia (NH 3 ) by reducing nitrogen (N 2 ). We have found a new type of electrocatalyst, i.e., V atom support on the β 12 -BM (V/β 12 -BM), which has a low onset potential (0.28 V), low cost, high stability, high selectivity, and high efficiency under mild conditions. The difference charge density and local density of state further demonstrated that there is an "acceptance−donation" interaction between TM atom and N 2 , and the ionization of 1π orbital of N 2 can greatly elongate the N−N bond length, leading to the activity enhancement of N 2 . We also point out that the bonding orbital (1π) and antibonding orbital (1π*) of N 2 play a crucial role in increasing the activity of N 2 . Further, the climbing nudged elastic band method and molecular dynamics simulation indicate that V/β 12 -BM has high dynamic and thermodynamic stabilities. Moreover, V/β 12 -BM can also effectively suppress the hydrogen evolution reaction during the whole N 2 reduction reaction process. So, we propose V/β 12 -BM as an excellent and promising catalyst for N 2 reduction to NH 3 at ambient conditions.

InGaN/GaN multiple quantum well concentrator solar cells Appl. Phys. Lett. 97, 073115 (2010); 10.1063/1.3481424 Effect of indium fluctuation on the photovoltaic characteristics of InGaN/GaN multiple quantum well solar cells Appl. Phys. Lett. 96, 081103 (2010); 10.1063/1.3327331 Effects of In composition on ultraviolet emission efficiency in quaternary InAlGaN light-emitting diodes on freestanding GaN substrates and sapphire substrates