Preparation and Thermal Conductivity Enhancement of Boron Nitride Nano-Material PiG Composite.

With the improvement of the conversion efficiency of LED chip and fluorescent material and the increasing demand for high-brightness light sources, LED technology has begun to move toward the direction of high-power. However, there is a huge problem that high-power LED must face with a large amount of heat generated by high power causing a high temperature thermal decay or even thermal quenching of the fluorescent material in the device, resulting in a reduction of the luminous efficiency, color coordinates, color rendering index, light uniformity, and service life of LED. In order to solve this problem, fluorescent materials with high thermal stability and better heat dissipation were prepared to enhance their performance in high-power LED environments. A variety of boron nitride nanomaterials were prepared by the solid phase-gas phase method. By adjusting the ratio of boric acid to urea in the raw material, different BN nanoparticles and nanosheets were obtained. Moreover, the control of catalyst amount and synthesis temperature can be used to synthesize boron nitride nanotubes with various morphologies. By adding different morphologies and quantities of BN material in PiG (phosphor in glass), the mechanical strength, heat dissipation, and luminescent properties of the sheet can be effectively controlled. PiG prepared by adding the right number of nanotubes and nanosheets has higher quantum efficiency and better heat dissipation after being excited by high power LED.

Remarkable Pyro-Catalysis of g-C3N4 Nanosheets for Dye Decoloration under Room-Temperature Cold-Hot Cycle Excitation.

Pyroelectric materials have the ability to convert the environmental cold-hot thermal energy such as day-night temperature alternation into electrical energy. The novel pyro-catalysis technology can be designed and realized on the basis of the product coupling between pyroelectric and electrochemical redox effects, which is helpful for the actual dye decomposition. The organic two-dimensional (2D) graphic carbon nitride (g-C3N4), as an analogue of graphite, has attracted considerable interest in the field of material science; however, its pyroelectric effect has rarely been reported. In this work, the remarkable pyro-catalytic performance was achieved in the 2D organic g-C3N4 nanosheet catalyst materials under the continuous room-temperature cold-hot thermal cycling excitation from 25 °C to 60 °C. The pyro-catalytic RhB dye decoloration efficiency of the 2D organic g-C3N4 can reach ~92.6%. Active species such as the superoxide radicals and hydroxyl radicals are observed as the intermediate products in the pyro-catalysis process of the 2D organic g-C3N4 nanosheets. The pyro-catalysis of the 2D organic g-C3N4 nanosheets provides efficient technology for wastewater treatment applications, utilizing the ambient cold-hot alternation temperature variations in future.

2D Heterostructure of Amorphous CoFeB Coating Black Phosphorus Nanosheets with Optimal Oxygen Intermediate Absorption for Improved Electrocatalytic Water Oxidation.

The oxygen evolution reaction (OER) plays a paramount role in a variety of electrochemical energy conversion devices, and the exploration of highly active, stable, and low-cost electrocatalysts is one of the most important topics in this field. The exfoliated black phosphorus (EBP) nanosheet with a two-dimensional (2D) layered structure has high carrier mobility but is limited by excessive oxygen-containing intermediate absorption and fast deterioration in air. We here report the fabrication of nanohybrids of amorphous CoFeB nanosheets on EBP nanosheets (EBP/CoFeB). The 2D/2D heterostructure, thanks to the electronic interactions and oxygen affinity difference between EBP and CoFeB nanosheets, is capable of balancing the oxygen-containing intermediate absorption to an optimal status for facilitating the OER process. While the crystalline EBP contributes to the improved conductivity, the amorphous coating protects EBP and thus ensures the catalytic stability. The EBP/CoFeB electrocatalyst shows excellent OER performance with an ultralow overpotential of 227 mV at 10 mA cm-2 with an ultrasmall Tafel slope of 36.7 mV dec-1 with excellent stability. This study may inspire more researches to develop heterostructured nanohybrid electrocatalysts for a diversity of electrochemical reactions.

In situ growth of Z-scheme CuS/CuSCN heterojunction to passivate surface defects and enhance charge transport.

Copper thiocyanate (CuSCN) has been considered as a promising hole transport material (HTMs), attributing to its inherent stability, low-cost, and suitable energy levels. To make it more attractive in practical applications, the drawbacks of CuSCN in poor charge transport and serious defect recombination are bottlenecks that need to be overcome. In this work, we propose an effective strategy of in-situ decorating CuSCN with copper sulfide quantum dots (CuS QDs), a simple one-step electrochemical deposition process, to solve these issues. Compared with the pristine CuSCN, the constructed Z-Scheme heterojunction of CuS QDs/CuSCN can significantly promote charge transport and restrict recombination. In addition, the decorated CuS QDs can not only passivate defects of CuSCN, but also provide more contacting sites to facilitate hole injection when employing as HTM. As a result, the average bulk charge lifetime was improved from 0.37 ms to 0.47 ms, and the surface recombination rate constant was suppressed. We believe that the excellent performances will pave it toward practical device applications, including solar cells, photocatalysis, photoelectrochemical sensors, and light-emitting diodes.

Recent Progress and Development in Inorganic Halide Perovskite Quantum Dots for Photoelectrochemical Applications.

Inorganic halide perovskite quantum dots (IHPQDs) have recently emerged as a new class of optoelectronic nanomaterials that can outperform the existing hybrid organometallic halide perovskite (OHP), II-VI and III-V groups semiconductor nanocrystals, mainly due to their relatively high stability, excellent photophysical properties, and promising applications in wide-ranging and diverse fields. In particular, IHPQDs have attracted much recent attention in the field of photoelectrochemistry, with the potential to harness their superb optical and charge transport properties as well as spectacular characteristics of quantum confinement effect for opening up new opportunities in next-generation photoelectrochemical (PEC) systems. Over the past few years, numerous efforts have been made to design and prepare IHPQD-based materials for a wide range of applications in photoelectrochemistry, ranging from photocatalytic degradation, photocatalytic CO2 reduction and PEC sensing, to photovoltaic devices. In this review, the recent advances in the development of IHPQD-based materials are summarized from the standpoint of photoelectrochemistry. The prospects and further developments of IHPQDs in this exciting field are also discussed.

Hydrogenated ZnIn2S4 microspheres: boosting photocatalytic hydrogen evolution by sulfur vacancy engineering and mechanism insight.

In some oxide photocatalysts, changing their surface structure rather than crystal structure by introducing some defects (such as oxygen vacancies) has been proven to be effective in enhancing the separation efficiency of photogenerated carriers and thus photocatalytic activity. To the best of our knowledge, however, such a surface defect engineering strategy for sulfide photocatalysts has rarely been verified. The present work shows the first case of employing pressure hydrogenation to prepare hydrogenated ZnIn2S4 (H-ZIS) microspheres with surface-deficient porous structures, which are favorable for furnishing sufficient surface sulfur vacancies to realize excellent photocatalytic hydrogen evolution reactions. The hydrogen evolution rate (HER) of H-ZIS is as high as 1.9 mmol h-1 g-1 (nearly 8.6 times that of the pristine ZIS sample), which rivals or exceeds those of previously-reported ZIS-based photocatalysts under visible light irradiation. Meanwhile, the inherent correlation between surface sulfur vacancies and photocatalytic activities of H-ZIS is also explored. Thus, this work demonstrates the feasibility of enhancing the hydrogen evolution capability of sulfide photocatalysts by the formation of sulfur vacancies through a pressure hydrogenation process.

Graphene quantum dots decorated graphitic carbon nitride nanorods for photocatalytic removal of antibiotics.

The over-use of antibiotics has resulted in seriously environmental pollution. Metal-free photocatalysts have received tremendous attentions due to their environmental friendliness. Meanwhile, morphology and structure of photocatalysts have significant influence on their photocatalytic performance. Herein, we report a metal-free composite photocatalyst of 0-dimensional (0D) graphene quantum dots (GQDs) decorated graphitic carbon nitride nanorods (g-CNNR) that was obtained by a hydrothermal treatment. Characterizations of physicochemical properties demonstrate that this GQDs/g-CNNR photocatalyst has a high crystallization level, enhanced visible light absorption and a staggered band alignment, which can promote the formation, the transportation and the separation of photo-excited electrons and holes. These prominent advantages bring improved photocatalytic activity of the GQDs/g-CNNR for efficient removal of antibiotics. Its photocatalytic reaction rate is 3.46 and 2.03 times higher than those of the pristine graphitic carbon nitride (g-C3N4) and the g-CNNR, respectively. Furthermore, this composite photocatalyst has good application universality for decomposing other antibiotics, and also possesses excellent stability and reusability. We further proved that photo-induced holes and superoxide radicals are main active species in the photocatalytic process. Our findings suggest that efficient g-C3N4 based photocatalysts can be well fabricated by structural regulation of g-C3N4 and formation of tightly contacted interface between g-C3N4 and GQDs.

Enhanced Transparency of Rough Surface Sapphire by Surface Vitrifaction Process.

A novel, simple, and low-cost in situ surface vitrification method has been effectively developed to enhance the optical transparency of rough surface sapphire at UV-visible-IR regions. This method is to obtain a glass layer on the sapphire surface through vitrifaction process. The thickness, refractive index, components and transition temperature of the glass layer have been investigated and discussed respectively by XRD, DSC, SEM and EDS elemental analysis. The experimental results show that the vitrified sapphire has high transparency even after 1000 °C annealing at UV-visible-IR regions.

Oxygen vacancies induced by zirconium doping in bismuth ferrite nanoparticles for enhanced photocatalytic performance.

Doping with certain foreign metal ions in a photocatalyst might introduce surface defects (such as extrinsic oxygen vacancies), which can probably play an important role in the photocatalytic performance. In this work, oxygen vacancies were for the first time introduced into bismuth ferrite (BiFeO3, denoted as BFO) nanoparticles by zirconium (Zr) doping, and the relationship between oxygen vacancies and the photocatalytic activity of Zr-doped BFO was investigated. It was found that the optical properties and the photocatalytic activities of Zr-doped BFO photocatalysts were significantly affected by the Zr doping amount. The Zr-doped BFO photocatalysts showed much higher photocatalytic activities for methyl orange degradation or Cr(VI) reduction than the pristine BFO. When the Zr doping content was 2mol%, the highest photocatalytic efficiency was achieved, which was more than two times that of the pristine BFO. The boosted photocatalytic performance of Zr-doped BFO was mainly attributed to the presence of surface oxygen vacancies induced by Zr doping, which could act as electron traps and active sites to promote the efficient separation and migration of photogenerated charge carriers, as verified by the trapping experiments and the photoelectrochemical measurements. Thus, the present work provides a simple approach to introduce oxygen vacancies in semiconductor photocatalysts through metal ion doping with a great potential for development of efficient visible light photocatalysts, and also enlarges the understanding of surface-defect dependence of photocatalytic performance for environmental remediation.

Crystal Structure, Magnetic and Optical Properties of Mn-Doped BiFeO3 by Hydrothermal Synthesis.

In this paper, Mn doped BiFeO3 were firstly synthesized by hydrothermal process. The influence of Mn doping on structural, optical and magnetic properties of BiFeO3 was studied. The different amounts of Mn doping in BiFeO3 were characterized by X-ray diffraction, Scanning Electron Microscope, Energy Dispersive X-ray Spectroscope, UV-Vis diffuse reflectance spectroscopy and magnetic measurements. The X-ray diffraction (XRD) patterns confirmed the formation of pure phase rhombohedral structure in BiFe(1−x) Mn (x) O3 (x = 0.01, 0.03, 0.05, 0.07) samples. The morphologies and chemical compositions of as-prepared samples could be observed by Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscope (EDS). A relative large saturated magnetization (Ms) of 0.53 emu/g for x = 0.07 sample was obtained at room temperature, which is considered to be Mn ions doping. UV-Vis diffuse reflectance spectroscopy showed strong absorption of light in the range of 200­1000 nm, indicating the optical band gap in the visible region for these samples. This implied that BiFe(1−x) Mn(x)O3 may be a potential photocatalyst for utilizing solar energy.

Enhanced visible light photocatalytic activity of Gd-doped BiFeO3 nanoparticles and mechanism insight.

To investigate the effect of Gd doping on photocatalytic activity of BiFeO3 (BFO), Gd-doped BFO nanoparticles containing different Gd doping contents (Bi(1-x)GdxFeO3, x = 0.00, 0.01, 0.03, 0.05) were synthesized using a facile sol-gel route. The obtained products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectra, and ultraviolet-visible diffuse reflectance spectroscopy, and their photocatalytic activities were evaluated by photocatalytic decomposition of Rhodamine B in aqueous solution under visible light irradiation. It was found that the Gd doping content could significantly affect the photocatalytic activity of as-prepared Gd-doped BFO, and the photocatalytic activity increased with increasing the Gd doping content up to the optimal value and then decreased with further enhancing Gd doping content. To elucidate the enhanced photocatalytic mechanism of Gd-doped BFO, the trapping experiments, photoluminescence, photocurrent and electrochemical impedance measurements were performed. On the basis of these experimental results, the enhanced photocatalytic activities of Gd-doped BFO could be ascribed to the increased optical absorption, the efficient separation and migration of photogenerated charge carriers as well as the decreased recombination probability of electron-hole pairs derived from the Gd doping effect. Meanwhile, the possible photocatalytic mechanism of Gd-doped BFO was critically discussed.

Hydrothermal Synthesis of BiFeO3 Nanoparticles for Visible Light Photocatalytic Applications.

Bismuth ferrite is a promising material for visible light response photocatalytic applications due to its narrow band gap. In this work, single crystalline BiFeO3 nanoparticles were prepared by a modified hydrothermal process. The effects of hydrothermal temperature, reaction time and precursor xerogel amoumt on the as-prepared BiFeO3 particle size and morphology were investigated by XRD, TEM and HRTEM. The XRD analysis reveals that single crystalline BiFeO3 particles can be obtained when the hydrothermal temperature is kept below 220 degrees C. TEM observation showed that the as-formed BFO particles are in a square or rectangle-like shape and that the particle size is increased with increasing hydrothermal temperature. The hydrothermal reaction time and the amount of xerogel could also influence the as-formed BFO particle morphology and size. The band gap of the as-prepared BFO nanoparticles was identified by UV-vis diffuse reflectance spectrum. The measurement of photodegradation of methyl orange dye in an aqueous solution revealed that the as-prepared BFO nanoparticles exhibit photocatalytic activity under visible light irradiation.

An organic photochromic compound: (2S)-2'-ethoxy-1,3,3-trimethyl-6'-(piperidin-1-yl)spiro[indoline-2,3'-3'H-naphtho[2,1-b][1,4]oxazine].

In the course of our synthesis of hybrid photochromic compounds, the unexpected new organic photochromic title compound, C(29)H(33)N(3)O(2), (I), was obtained. It is a derivative of the parent spirooxazine 1,3,3-trimethyl-6'-(piperidin-1-yl)spiro[indoline-2,3'-3'H-naphtho[2,1-b][1,4]oxazine], (II). The 2'-ethoxy group gives (I) different photochromic properties from its parent spirooxazine (II).

Two-dimensional dysprosium(III) triiodate(V) dihydrate, Dy(IO(3))(3)(H(2)O)·H(2)O.

During our research into novel nonlinear optical materials using 1,10-phenanthroline as an appending ligand on lanthanide iodates, crystals of an infinite layered Dy(III) iodate compound, Dy(IO(3))(3)(H(2)O)·H(2)O, were obtained under hydro-thermal conditions. The Dy(III) cation has a dicapped trigonal prismatic coordination environment consisting of one water O atom and seven other O atoms from seven iodate anions. These iodate anions bridge the Dy(III) cations into a two-dimensional structure. Through O-H⋯O hydrogen bonds, all of these layers stack along [111], giving a supra-molecular channel, with the solvent water mol-ecules filling the voids.