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Self-mosaic flower-like Cu 2 S nanocrystals with the diameter of about 2 μm have been fabricated via a two-step hydrothermal method for the first time without using any additives or surfactants. The crystal structures of self-mosaic Cu 2 S nanoflowers and original Cu 2 S nanoflowers are both highly crystalline cubic crystal systems with similar diffraction peak from XRD measurement. Because of the large quantities of small and thin edges, self-mosaic Cu 2 S nanostructure can serve as an efficient edge emitter for field emission (FE). FE properties of self-mosaic Cu 2 S nanoflowers were investigated and compared with original Cu 2 S nanoflowers. The results indicate that self-mosaic Cu 2 S nanostructure has enhanced field emission performance with turn-on field of about 4.4 V/μm and threshold field of about 7.6 V/μm on Si substrate. The results suggest that the self-mosaic flower-like Cu 2 S nanocrystal is a good candidate for effective and high performance FE devices.

Three different kinds of V2O5/ZnO heteronanorods were synthesized through a CVD process and oxidized in air at temperatures of 350, 420 and 500 °C. These 1D heteronanorods were formed from ZnO nanorods (NRs) coated with V2O5 nanoparticles (NPs). With the rise of oxidation temperature, the coated V2O5 NPs were found to be growing and their crystallinity gradually improved. Photoluminescence (PL) spectra for these V2O5/ZnO samples exhibited some novel characteristics, such as the appearance of new emission peaks, the variation in PL intensity, and the tremendously enhanced visible emission for the 500 °C sample. Photocatalysis investigation for all V2O5/ZnO samples showed enhanced photocatalytic activities compared to their single-component counterparts. Furthermore, their photocatalytic activities were also influenced by the oxidation temperature. The 350 °C sample showed the highest photocatalytic activity, and gradually decreased photocatalytic activities were observed for the other two samples. The novel PL properties and enhanced photocatalytic activities were attributed to the coupling between ZnO NRs and V2O5 NPs, and can be attributed to the collective effect of the V-doped ZnO layer near the interface, the decreased defect concentration in V2O5 NPs, and the improved particle crystallinity.

The collision of a single-walled carbon nanotube (SWCNT) with two graphitic patches has been simulated by the tight-binding molecular dynamics method. We found that it is possible that a close-ended SWCNT with a large diameter can be formed by this kind of collision. This is a possible route in which a SWCNT with a small radius can convert into a SWCNT with a larger radius.

Temperature dependence of the optical properties of InGaN/GaN single quantum well light-emitting diodes (LEDs) with different indium (In) contents is investigated by using the effective mass theory taking into account the band-gap shrinkage and lattice thermal expansion. The peak intensity of the spontaneous emission spectrum is decreased by 30.6%, 30.4%, and 30.3% for the violet, blue, and green LEDs in the temperature range 300 K?400?K, while the reductions of internal quantum efficiency (?) with temperature are ~0.13, ~0.11, and ~0.1 respectively at the injection current density of 100 A cm?2. Moreover, two different slopes for all the ??T curves are observed: a lower absolute value of the slopes at T??=??300?350?K; a larger absolute value of the slopes at T??=??350?400?K. The numerical results also indicate that the efficiency droop effect with increasing the temperature becomes more serious, especially for the InGaN/GaN LED structures with the lower In-content.

The effects of temperature on the optical properties of InGaN/GaN quantum well (QW) light-emitting diodes have been investigated by using the six-by-six K-P method taking into account the temperature dependence of band gaps, lattice constants, and elastic constants. The numerical results indicate that the increase of temperature leads to the decrease of the spontaneous emission rate at the same injection current density due to the redistribution of carrier density and the increase of the non-radiative recombination rate. The product of Fermi-Dirac distribution functions of electron f c n and hole ( 1 − f v U m ) for the transitions between the three lowest conduction subbands (c1–c3) and the top six valence subbands (v1–v6) is larger at the lower temperature, which indicates that there are more electron-hole pairs distributed on the energy levels. It should be noted that the optical matrix elements of the inter-band transitions slightly increase at the higher temperature. In addition, the internal quantum...

A ZnO photonic amorphous diamond nanostructure was successfully synthesised using a feather barb of the Rosy-Faced Lovebird as supporting template via a facile sol–gel process. Different from ordered structures, an isotropic PBG around 500 nm was evidenced from reflectance spectra and an optical metallurgical microscopy image, which overlaps with the visible emission peak of ZnO. As a result, the inhibition of visible emission inside the PBG and the enhancement of UV emission at the PBG edges have both been observed, which is independent from the incident angle. Moreover, the rapid thermal annealing can also help improve the crystallinity of ZnO and raise the UV/visible emission ratio without affecting the structure. These results can be very useful for the study of the modification of the optical emission properties of ZnO and other semiconductor materials as well as research on ZnO random lasing.

Bundlelike VO(2)(B) nanostructures were synthesized via a hydrothermal method, and VO(2)(M(1)/R) nanobundles were obtained after a heat-treatment process. Structural characterization shows that these nanobundles are self-assembled by VO(2) nanowires, and VO(2)(M(1)/R) nanobundles have better crystallinity. Temperature-dependent field-emission (FE) measurement indicates that FE properties of these two phases of nanobundles can both be improved by increasing the ambient temperature. Moreover, for the VO(2)(M(1)/R) nanobundles, their FE properties are also strongly dependent on the temperature-induced metal-insulator transitions process. Compared with poor FE properties found in the insulating phase, FE properties were significantly improved by increasing the temperature, and about a three-orders-of-magnitude increasing of the emission current density has been observed at a fixed field of 6 V/μm. Work function measurement and density-functional theory calculations indicated that the decrease of work function with temperature is the main reason that caused the improvement of FE properties. These characteristics make VO(2)(M(1)/R) a candidate material for application of new type of temperature-controlled field emitters, whose emission density can be adjusted by ambient temperature.

Cu2O–TiO2–ZnO ternary nano-heteroarchitectures were designed and successfully fabricated using titanium (IV) oxideacetylacetonate (TiO(acac)2) as a precursor and polyethyleneimine (PEI) as a binding agent. Field emission and photocatalytic activities of pure Cu2O nanopines, Cu2O–TiO2 core–shell nanopines and Cu2O–TiO2–ZnO ternary composites were investigated and compared. The results revealed that the as-prepared nano-heterojunctions and nanoparticles at the surface remarkably enhanced the field emission and photocatalytic activities of pure Cu2O nanopines. The as-prepared nano-heterojunctions induced interfacial states and energy band differentials, which caused electron transition and the inhibition of photo-induced electron–hole pair recombination. The nanoparticles at the surface formed thousands of surface nano-protrusions and active sites for photocatalytic chemical reactions.

A polyol method was first employed to synthesize MoS2@MWNT nano-flower composites. Due to their high conductivity, large aspect ratio and sharp edges, an excellent field emission performance was obtained relative to pure MoS2 with the turn-on field decreasing from 5.3 V μm−1 to 2.7 V μm−1 and the threshold field decreasing from 8.0 V μm−1 to 5.3 V μm−1. When used as anode materials for Li-ion batteries in an aqueous electrolyte, the composites exhibit a highest specific capacity of 1217 mA h g−1 at a current of 100 mA g−1, excellent cycling stability and high-rate capability, and a high specific capacity of 851 mA h g−1, which was still retained at a high current density of 1600 mA g−1.

A novel hierarchical three-dimensional (3D) Cu2S@ZnO heteroarchitecture was successfully synthesized by a facile three-step synthetic process. FESEM and TEM analyses revealed the formation of the hierarchical 3D structure of the as-prepared Cu2S@ZnO. The purity and crystalline phase of the individual component in the 3D Cu2S@ZnO were determined by a powder X-ray diffractogram. The formation of the hierarchical 3D structure of the as-prepared Cu2S@ZnO leads to multiple p–n junctions formed at p-Cu2S@n-ZnO interfaces, which promote the generation and separation of photoinduced electrons and holes and thus improves the photocatalytic efficiency tremendously. According to the data, after irradiation for 40 min, the remaining MB in solution is about 35% for Cu2S nanoflowers and 9% for Cu2S@ZnO binary nanoflowers. Also, the increases in the overall aspect ratio and the ZnO nanoparticles act as extra emission sites, which help to enhance the field emission properties. The turn-on fields and threshold fields for the Cu2S nanoflowers as well as the Cu2S@ZnO nanoflower hybrid emitters are 3.3 and 9.2 V μm−1, 2 and 6.3 V μm−1, respectively. Compared with the Cu2S nanoflowers, the Cu2S@ZnO hetero-nanoflowers show excellent improvements in both photocatalytic and field emission applications.

ZnO replicas with photonic structures were fabricated from Papilio paris butterfly wing scales and their tunable optical properties were studied. Through modification of the fabrication method, the reticular porous network structure was successfully replicated from dark black (DB) wing scales. The DB wing scale replicas exhibit a photonic band gap (PBG) in the visible region, which overlaps with the visible emission range of ZnO. Both DB and GB (greenish-blue) wing scale replicas can work as one-dimensional diffraction gratings in optical diffraction experiments, whose spot distances can be tuned by different periodic sizes of butterfly wing structure. Moreover, the ZnO DB wing scale replicas exhibit improved photoluminescence (PL) spectra with reduced visible emission and enhanced UV emission, which can both be attributed to the existence of a PBG produced by the reticular porous network structure in DB wing scales. These results can be very helpful in the research of applications of ZnO materials in UV lasing and optical diffraction devices.

Porous V2O5 micro/nano-tubes were synthesized via a modified chemical vapor deposition process and a possible growth mechanism was proposed. The micro/nano-tubes have large surface area because of their tubular structure with a porous wall. A humidity sensor based on a single porous V2O5 micro/nano-tube was constructed, and humidity sensing measurements indicated fast response/recovery. Due to the large surface area, the porous V2O5 micro/nano-tubes were used as a cathode material for lithium-ion batteries that exhibited great improvement of the electrochemical performance such as a high lithium-storage capacity of ∼290 mA h g−1, excellent cycling stability and reversibility. Further cyclic voltammetry measurements under different scanning rates confirmed that the intercalation/de-intercalation is of high efficiency and the kinetic performance of the battery is significantly improved. These characteristics of porous V2O5 micro/nano-tubes make them promising materials for application in gas detection and lithium-ion batteries.