Dingke Zhang

3D structured porous CoP3 nanoneedle arrays as an efficient bifunctional electrocatalyst for the evolution reaction of hydrogen and oxygen

Self-supported porous cobalt poly-phosphide nanoneedle arrays on carbon fiber paper (CoP3 NAs/CFP) are fabricated via topotactic phosphidation of the Co(OH)F/CFP precursor. The prepared CoP3 NAs/CFP, as a 3D structured electrocatalyst with a large specific surface area and high porosity, exhibits superior bifunctional electrocatalytic activity and durability for both the HER and OER.

Self-supported three-dimensional mesoporous semimetallic WP2 nanowire arrays on carbon cloth as a flexible cathode for efficient hydrogen evolution.

The design and development of high-efficiency and non-noble metal hydrogen evolution reaction (HER) electrocatalysts with optimized nanostructures for human clean and sustainable energy systems has attracted significant research interest over the past years. Herein, self-supported semimetallic tungsten diphosphide nanowire arrays on carbon cloth (WP2 NWs/CC) were topotactically fabricated by in situ phosphidation of a WO3 NWs/CC precursor. Such a binder-free flexible HER cathode with integrated three-dimensional nanostructures can not only provide a large surface area to expose abundant active sites, but also facilitate electrolyte penetration for electrons and electrolyte ions. The WP2 NWs/CC electrode exhibits superior catalytic performance, and it needs overpotentials of 109 and 160 mV with a small Tafel slope of 56 mV dec-1 to achieve current densities of 10 and 50 mA cm-2, respectively. High stability in acidic media is also observed for the catalyst for a duration of 20 hours at least. In addition, density functional theory (DFT) calculations indicate a low kinetic energy barrier for H atom adsorption on the WP2 surface which guarantees the excellent catalytic activity of the catalyst, and the influences of phosphidation temperature on the HER activity are also studied. The excellent electrocatalytic activity makes the present 3D structured WP2 NWs/CC a promising catalyst for large scale highly pure hydrogen evolution by electrochemical water splitting.

Facile preparation of semimetallic MoP2 as a novel visible light driven photocatalyst with high photocatalytic activity

The production of clean and renewable H2 by photocatalytic water splitting has attracted much attention due to the increasing energy crisis. In this work, semimetallic MoP2 nanoparticles are discovered as a new photocatalyst to efficiently degenerate methyl orange and produce H2 from water under visible light irradiation. MoP2 nanoparticles were prepared using a solid-state reaction route via a vacuum encapsulation technique followed by acid washing. Both first-principle band-structure calculations and experimental measurements reveal typical semimetallic characteristics for MoP2. The obtained MoP2 nanoparticles display superior photocatalytic performances for the degradation of methyl orange with a good stability and the reduction of water assisted by sacrificial elemental Pt under visible light. The detection of hydroxyl radicals in the solution in the presence of MoP2 with fluorescence spectroscopy confirmed its photodegradable activities. The present study points out a new direction for developing semimetallic photocatalysts for H2 production through water splitting.

Facile preparation of semimetallic WP2 as a novel photocatalyst with high photoactivity

Searching for inexpensive and earth-abundant photocatalysts with high activities has attracted considerable research in recent years. In this work, semimetallic tungsten diphosphide (WP2) micro-particles are explored as a novel photocatalyst for the first time. The WP2 particles were synthesized through a solid-state reaction route via vacuum encapsulation technique following by water washing. The first principle calculations and electric transport measurements show a semimetallic characteristic of WP2, however a strong absorption in the UV range is observed. The prepared WP2 particles exhibit an admirable photocatalytic activity towards oxidation of methyl orange and reduction of water for H2 evolution with the assistance of co-catalyst element Pt under UV light irradiation. Hydroxyl radicals detected by fluorescence spectroscopy in the solution in the presence of WP2 under UV light irradiation confirms the photoactivity. Furthermore, the photocatalyst shows a good photostability and reusability even after three successive experiment runs. Based on the experimental measurements and theoretical calculations, a possible photocatalytic mechanism is proposed for semimetallic WP2. The present study may provide a chance for practical applications of the semimetallic material WP2 in the field of photocatalysis.

Random lasing in human tissues embedded with organic dyes for cancer diagnosis

Various nanostructures found in biological organisms are often complex and they exhibit unique optical functions. This study surprisingly found that typical random lasing occurs in cancerous human tissues embedded with the nanotextured organic dye 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7- tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB). Hematoxylin and eosin stain images show that there are more laser resonators in cancerous tissues, caused by a large number of disordered scatters. It is also noteworthy that the random lasing thresholds were found to relate to the tumor malignancy grade. Consequently, the resulting typical random lasing resonators differ between cancerous tissues in different malignancy grades. Further studies are warranted to investigate tissue optical spectroscopy in the field of cancer diagnostics.

Fabrication of Phosphorus Nanostructures/TiO 2 Composite Photocatalyst with enhancing Photodegradation and Hydrogen Production from Water under Visible Light

As the world faces serious environmental pollution and energy shortage, developing Vis-light-driven photocatalysts for water splitting is highly attractive in clean energy utilization. Fabricating heterostructures has been proposed to be an efficient system to enhance the photocatalytic activity. However, synthesizing heterostructures with good contact and understanding charge transfer dynamics are still unresolved issues. In this work, a facile calcination approach was used to synthesize red phosphorus (RP) nanostructures/TiO2 heterostructured composites. The RP nanostructures were directly grown on the TiO2 nanoparticles with an intimate surface contact. By adjusting the molar ratio of amorphous RP to TiO2 and the synthesizing temperature, thin nanorod-like RP nanostructures with a large exposed surface and a good surface contacting with TiO2 were obtained. The synergetic effect of heterostructured RP/TiO2 composites leads to an enhanced charge separation and transfer, and a better utilization of visible-light. As expected, the RP/TiO2-700 °C composites exhibit good photocatalytic activity of degrading RhB and the optimal H2 evolution rate. This work not only provides a method to prepare earth abundant elemental phosphorus well-contacted heterostructures, expand the well-known UV-active TiO2 photocatalyst to visible active, but also deepens understanding of charge transfer dynamics in heterostructured photocatalyst.

Optimization of lasing in an inverted-opal titania photonic crystal cavity as an organic solid-state dye-doped laser

Lasing performance of a dye-doped laser by encapsulating orange fluorescent dye 4-(Dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM) with different concentrations in a highly ordered three-dimensional (3D) inverted-opal titania (TiO2) photonic crystal (PC) microcavity was studied. The lasing threshold and laser quality were improved by optimizing the concentration of the laser dye DCM. When the concentration of DCM is optimized to 10-4  mol/l, the photoluminescence (PL) efficiency of DCM is sufficient to achieve lasing emission and meanwhile no fluorescence quantum quenching occurs. Therefore, the emission spectrum was greatly narrowed and the threshold was significantly improved, which reached 0.8  mJ pulse-1 cm-2. Our findings are promising results toward the realization of fabricating a highly efficient low-threshold organic laser.

Amplified spontaneous emission from DCJTB encapsulated in mesostructured composite silica SBA-15

Amplified spontaneous emission (ASE) characteristics of a red dye 4-(Dicyanomethylene)-2-t-butyl-6-(1,1,7,7- etramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) encapsulated in a highly ordered mesoporous SBA-15 were studied. The mesoporous composite silica film loaded with organic dye has been successfully synthesized by a solgel reaction process and a simple postgrafting method at room temperature. The spectrum narrowing phenomena has been observed when the composite film is pumped at λp=532  nm by a Nd:YAG ed laser. There is a substantial reduction in the full width at half-maximum of the emitting light, which is one of the signatures of the presence of ASE. The ASE threshold and net gain, respectively, reached 0.03  mJ pulse-1 and 34.7  cm-1 for the DCJTB encapsulated in mesoporous SBA-15 film. The optimized ASE properties owe much to the effects of the better spatial confinement of the molecules in the ordered mesoporous structure of the host SBA-15.

A 3D porous WP 2 nanosheets@carbon cloth flexible electrode for efficient electrocatalytic hydrogen evolution

Self-standing porous WP2 nanosheet arrays on carbon fiber cloth (WP2 NSs/CC) were synthesized and used as a 3D flexible hydrogen evolution electrode. Because of its 3D porous nanoarray structure, the WP2 NSs/CC exhibits a remarkable catalytic activity and a high stability. By using the experimental measurements and first-principle calculations, the underlying reasons for the excellent catalytic activity were further explored. Our work makes the present WP2 NSs as a promising electrocatalyst for hydrogen evolution and provides a way to design and fabricate efficient hydrogen evolution electrodes through 3D porous nano-arrays architecture.

Molecular dynamics study on the thermal conductivity of multiple layers in semiconductor disk laser

Thermal properties of multiple layers including distributed Bragg reflector (DBR) and multiple quantum wells (MQWs) used in the semiconductor gain element are crucial for the performance of a semiconductor disk laser (SDL). For the purpose of more reasonable semiconductor wafer design, so to improve the thermal management of SDLs, accurate thermal conductivity value of a DBR is under considerable requirement. By the use of equilibrium molecular dynamics (EMD) method, thermal conductivities of AlAs/GaAs DBRs, which were widely employed in 1μm wavelength SDLs, were calculated, and simulated results were compared with reported data. Influences of the Al composition, and the layer thickness on the thermal conductivities were focused and analyzed.