Cation substitution is a promising strategy for modulating the structural properties and optimizing the electrochemical performance of spinel cobalt oxide (Co3O4); however, the underlying mechanism of this action induced by different cation substitutions has not yet been clearly addressed.

Arrays of pivoted GaN microdisks have been fabricated on a GaN / Si material by a combination of dry and wet etching. The Si material beneath the GaN microdisks is removed by wet etching, leaving behind a fine pillar to support the disks. Raman spectroscopy reveals substantial strain relaxation in these structures. Resonant modes, corresponding to whispering gallery modes, are observed in the photoluminescence spectra. Stimulated emission is achieved at higher optical pumping intensities.

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A vertical cavity structure composing of an in situ grown bottom Al x Ga 1−x N / Al y Ga 1−y N distributed Bragg reflector and a top SiO 2 / HfO 2 dielectric mirror for ultraviolet ͑UV͒ emission has been demonstrated. Close-packed nanopillars with diameters of around 500 nm have been achieved by the route of nanosphere lithography combined with inductively-coupled plasma etching. Optically-pumped UV lasing at a wavelength of 343.7 nm ͑3.608 eV͒ was observed at room temperature, with a threshold excitation density of 0.52 MW/ cm 2. The mechanism of the lasing action is discussed in detail. Our investigation indicates promising possibilities in nitride-based resonant cavity devices, particularly toward realizing the UV nitride-based vertical-cavity surface-emitting laser.

Simultaneously enhancing the reaction kinetics, mass transport, and gas release during alkaline hydrogen evolution reaction (HER) is critical to minimizing the reaction polarization resistance, but remains a big challenge. Through rational design of a hierarchical multiheterogeneous three-dimensionally (3D) ordered macroporous Mo 2 C-embedded nitrogen-doped carbon with ultrafine Ru nanoclusters anchored on its surface (OMS Mo 2 C/NC-Ru), we realize both electronic and morphologic engineering of the catalyst to maximize the electrocatalysis performance.The formed Ru-NC heterostructure shows regulative electronic states and optimized adsorption energy with the intermediate H*, and the Mo 2 C-NC heterostructure accelerates the Volmer reaction due to the strong water dissociation ability as confirmed by theoretical calculations. Consequently, superior HER activity in alkaline solution with an extremely low overpotential of 15.5 mV at 10 mA cm −2 with the mass activity more than 17 times higher than that of the benchmark Pt/C, an ultrasmall Tafel slope of 22.7 mV dec −1 , and excellent electrocatalytic durability were achieved, attributing to the enhanced mass transport and favorable gas release process endowed from the unique OMS Mo 2 C/NC-Ru structure.By oxidizing OMS Mo 2 C/NC-Ru into OMS MoO 3 -RuO 2 catalyst, it can also be applied as efficient oxygen evolution electrocatalyst, enabling the

Nanoflake bismuth ferrite thin film was synthesized by means of electrodeposition technique at room temperature. The morphology and phase evaluation of the synthesized electrode were analyzed using scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and surface wettability techniques. Specifically, the bismuth ferrite nanoflake electrode exhibited high specific capacitance of 72.2 F g -1 at a current density of 1 A g -1 , and high rate capability with 37 % retention of capacitance even up to 20A g -1 , and excellent cycling stability with 82.8 % retention of the initial capacitance after 1500 charge/discharge cycles, supporting that the bismuth ferrite thin-film electrode could be a potential candidate for supercapacitor application.

Conventional polymer binder in a lithium−sulfur (Li−S) battery, poly(vinylidene fluoride) (PVDF), suffers from insufficient ion conductivity, poor polysulfide-trapping ability, weak mechanical property, and requirement of organic solvents, which significantly encumber the industrial application of Li−S battery. Herein, a water-soluble binder with trifunctions, covalently cross-linked quaternary ammonium cationic starch (c-QACS), is developed to confront these issues. Similar to the poly(ethylene oxide) solid electrolytes, the c-QACS binder remarkably improves Li + ion transfer capacity. The abundant O actives endow the c-QACS binder with admirable lithium polysulfide-trapping capability to retard the shuttle effect. In addition, the formed 3D network effectively maintains the electrode integrity during cycling. Benefiting from the above merits, the sulfur cathode with the c-QACS binder demonstrates a performance improvement of 300 and 150% compared with sulfur cathode with PVDF and bulk QACS binder after 100 cycles at 0.2C.

The efficiency of green organic electroluminescent devices have been improved by cohosting the electron dominant complex, 4,7-diphenyl-1,10-phenanthroline into the traditional electron transporting layer of tris (8-hydroxyquinoline) aluminum. In this cohost strategy, we demonstrate that the luminous efficiency is enhanced by >20% while the driving voltage can be reduced by ∼30% in a uniformly mixed composition as compared to the traditional device configuration. The corresponding device lifetime under atmospheric condition is extended by a factor of ∼1.8, attributed to the reduction of the accumulated positive charges near the electron-hole recombination regime. Results indicate that the knowledge of bulk conductivity engineering of organic n-type transporters is essential in enhancing organic light-emitting devices.