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Liu H.,State Key Laboratory of Silicon Materials | Wang X.,State Key Laboratory of Silicon Materials | Wang X.,Zhejiang University | Liu Y.,State Key Laboratory of Silicon Materials | And 4 more authors.
Journal of Physical Chemistry C | Year: 2014

Niobium fluoride (NbF5) is introduced into the MgH2 + 1/4AlH3 hydride composite by ball milling to improve the hydrogen desorption properties of the Mg-Al-H system. It is found that after being ball milled with 1 mol % of NbF5, AlH3 in the composite has almost fully decomposed and forms metallic Al, which indicates that NbF 5 can significantly destabilize AlH3. DSC results show that NbF5 addition also helps reduce the peak desorption temperature of MgH2 in the composite from 324 to 280 °C. Isothermal desorption measurements demonstrate that MgH2 in the doped composite can rapidly release 98% of its hydrogen after desorption at 300 °C for 1 h, while the valued is only 46% for the undoped composite. The activation energy for hydrogen desorption of MgH2 in the doped composite is calculated to be 104.5 kJ/mol, much lower than that in the undoped composite (127.4 kJ/mol). These results suggest that NbF5 addition dramatically improves the hydrogen desorption kinetics of the MgH2 + 1/4AlH 3 composite. Dehydrogenation-hydrogenation measurements reveal that the hydrogen desorption kinetics of the undoped composite declines with cycle number, whereas the NbF5-doped composite maintains good cycling stability. Microstructure studies indicate that the decline of the kinetics is attributed to the grain growth and particle agglomeration of MgH2 during hydrogen sorption cycling. However, NbF5 addition can suppress this grain growth through the formation of Nb/NbH layers surrounding the particles of MgH2 and acting both as the impediment to grain growth of Mg/MgH2 and as the gateway for hydrogen diffusion. Finally, the role that AlH3 plays in the hydrogen desorption process of the Mg-Al-H composites is discussed. © 2014 American Chemical Society.

He H.,City University of Hong Kong | He H.,State Key Laboratory of Silicon Materials | Lin S.,State Key Laboratory of Silicon Materials | Lin S.,Zhejiang University | And 7 more authors.
Journal of Physical Chemistry C | Year: 2011

The p-type doping of ZnO is the key to ZnO-based light-emitting devices and has proven to be difficult. ZnO nanowires (NWs) are an ideal platform for the study of p-type doping due to their high crystal quality and easy growth. In this Article, we demonstrate an innovative approach via the combination of thin-film and nano techniques to fabricate single-crystal p-type ZnO and ZnMgO NWs. Using undoped ZnO NWs as templates, Na-doped ZnO and ZnMgO layers are deposited by pulsed laser deposition, forming core-shell NWs. Single NW field effect transistors are fabricated to testify the p-type conductivity. It is found that postannealing is crucial to activate the Na acceptor. The present method offers better controllability and reproducibility for fabricating p-type ZnO layers, which are advantageous for optoelectronic applications. © 2011 American Chemical Society.

Shi L.,State Key Laboratory of Silicon Materials | Huang H.,State Key Laboratory of Silicon Materials | Sun L.,State Key Laboratory of Silicon Materials | Lu Y.,Zhejiang University | And 7 more authors.
Dalton Transactions | Year: 2013

[Fe(CN)6]4- decorated mesoporous gelatin films, acting as colorimetric sensors and sorbents for heavy metal ions, were prepared by incorporating [Fe(CN)6]4- ions into the mesoporous gelatin films through electrostatic interaction. Gelatin-Prussian blue (PB) and gelatin-PB analogue composite films were successfully synthesized by immersing the [Fe(CN)6]4- decorated gelatin films into aqueous solutions of metal ions, such as Fe3+, Cu2+, Co 2+, Pb2+ and Cd2+ (all as nitrates). The in situ formation process of PB or its analogues in the films was investigated using quartz crystal microbalance (QCM) measurements. According to the different colors of the PB nanoparticles and its analogues, the [Fe(CN)6] 4- decorated mesoporous gelatin films demonstrated colorimetric sensor abilities for detecting the corresponding metal ions by the naked eye with sufficient sensitivity at 1 ppm level and a quite short response time of 5 minutes. Moreover, due to the [Fe(CN)6]4- functionality and other functional groups of gelatin itself, this [Fe(CN)6] 4- decorated mesoporous gelatin film shows a tens times higher adsorption ability for heavy metal ions in water than that of activated carbon. Due to both the efficient detection and high adsorption ability for heavy metal ions, this film has wide potential applications for the detection and purification of heavy metal ions from polluted water. This journal is © 2013 The Royal Society of Chemistry.

Niu W.,Zhejiang University | Xu H.,Zhejiang University | Guo Y.,State Key Laboratory of Silicon Materials | Li Y.,Zhejiang University | And 2 more authors.
Physical Chemistry Chemical Physics | Year: 2015

P-type sulphur-nitrogen (S-N) co-doped ZnO thin films are deposited and the effect of sulphur on the electrical properties is discussed. First-principles calculations indicate that the structure is most stable when the S atom is close to the N atom in the (0002) plane, implying that dual-doped ZnO is relatively feasible to approach. The partial density of states of S-N co-doped ZnO shows that the S impurity plays a vital role in forming the p-type conductivity. This journal is © the Owner Societies.

Wang L.,Beijing University of Technology | Zhang Z.,Beijing University of Technology | Zhang Z.,State Key Laboratory of Silicon Materials | Han X.,Beijing University of Technology
NPG Asia Materials | Year: 2013

Sub-micron and nanostructured materials exhibit high strength, ultra-large elasticity and unusual plastic deformation behaviors. These properties are important for their applications as building blocks for the fabrication of nano- and micro-devices as well as for their use as components for composite materials, high-strength structural and novel functional materials. These nano-related deformation and mechanical behaviors, which are derived from possible size and dimensional effects and the low density of defects, are considerably different from their conventional bulk counterparts. The atomic-scale understanding of the microstructural evolution process of nanomaterials when they are subjected to external stress is crucial for understanding these 'unusual' phenomena and is important for designing new materials, novel structures and applications. This review presents the recent developments in the methods, techniques, instrumentation and scientific progress for atomic-scale in situ deformation dynamics on nanomaterials, including nanowires, nanotubes, nanocrystals, nanofilms and polycrystalline nanomaterials. The unusual dislocation initiation, partial-full dislocation transition, crystalline-amorphous transitions and fracture phenomena related to the experimental mechanics of the nanomaterials are reviewed. Current limitations and future aspects using in situ high-resolution transmission electron microscopy of nanomaterials are also discussed. A new research field of in situ experimental mechanics at the atomic scale is thus expected. © 2013 Nature Japan K.K. All rights reserved.

Zuo L.,University of Washington | Zuo L.,State Key Laboratory of Silicon Materials | Chang C.-Y.,University of Washington | Chueh C.-C.,University of Washington | And 4 more authors.
Journal of Materials Chemistry A | Year: 2016

Series-connected tandem organic photovoltaic devices (SCTOPVs) have been shown to provide higher power conversion efficiencies (PCEs) than the single junction devices due to the improved light harvesting. To achieve the optimal device performance of SCTOPVs, balancing the photocurrents generated from the sub-cells is critical according to the Kirchhoff law. In this work, we demonstrate that the out-of-cell capping layer of an ITO-free microcavity SCTOPV plays an important role in manipulating the optical field distribution in the constituent sub-cells for achieving balanced photocurrents and optimal photovoltaic performance. Two mirror-like electrodes, a semi-transparent ultrathin Ag capped with a dielectric TeO2 layer and a thick Ag electrode were used to construct an ITO-free top-illuminated microcavity configuration, in which certain frequencies of solar irradiance can resonate between the reflective surfaces. As a result, a top-illuminated ITO-free SCTOPV with a comparable performance (7.4%) to the ITO-based counterpart (7.5%) was demonstrated despite the inferior transmittance of the ultra-thin Ag relative to ITO. © The Royal Society of Chemistry 2016.

Huang H.,State Key Laboratory of Silicon Materials | Zhang L.,State Key Laboratory of Silicon Materials | Wu K.,State Key Laboratory of Silicon Materials | Yu Q.,State Key Laboratory of Silicon Materials | And 6 more authors.
Nanoscale | Year: 2012

A controllable synthesis of various morphologies of CuO nanostructures with tuning by hetero-metal cations has been developed in aqueous solution at room temperature. The morphologies of CuO can be engineered from nanosheets to nanoparticles with different length ratios of the long axis to the short axis. The formation of many metal-ion complexes plays an important role in slowing the release rate of OH- and affects the reaction kinetics further. We found that the effect of hetero-metal cations on the final morphology of the CuO nanostructures was the same as that of the cooling temperature. A series of temperature-controlled experiments demonstrated this. Furthermore, among all the synthesized CuO nanostructures, the fascinating colloidal mesoporous CuO quasi-monocrystalline nanosheets prepared at 25°C with a thickness of ca. 10 nm and large specific surface area of 80.32 m2 g-1 is investigated intensively. These CuO nanosheets demonstrate a superior catalytic activity for CO oxidation, with features of high CO conversion efficiency (47.77 mmolCO g-1 CuO h-1 at 200°C), which is close to that reported for previously investigated supported-CuO catalysts, and a low apparent activation energy Ea (53.3 kJ mol -1). This journal is © 2012 The Royal Society of Chemistry.

Ying P.,State Key Laboratory of Silicon Materials | Liu X.,State Key Laboratory of Silicon Materials | Fu C.,State Key Laboratory of Silicon Materials | Yue X.,State Key Laboratory of Silicon Materials | And 6 more authors.
Chemistry of Materials | Year: 2015

Bi2Te3 based alloys have long been the best and most unique thermoelectric materials for power generation below 550 K. Their substitutes with abundantly available elements are highly desirable due to the scarcity of Te element. In this work the band structure calculation of the α-MgAgSb compound shows a narrow gap characteristic. Highly pure α-MgAgSb is obtained by carefully controlled processing. The samples exhibit an intrinsically low thermal conductivity due to the unique crystal structure. A high zT of ∼1.1 at 525 K is achieved in the In doped α-MgAgSb with the optimal carrier concentration of 8-9 × 1019 cm-3, comparable to that of Bi2Te3 based alloys. Considering the abundantly available constituent elements, the present results demonstrate that α-MgAgSb is a promising candidate for low-temperature (RT-550 K) power generation. © 2015 American Chemical Society.

Song H.,Zhejiang University | Song H.,State Key Laboratory of Silicon Materials | Zhu L.,Zhejiang University | Zhu L.,State Key Laboratory of Silicon Materials | And 8 more authors.
Journal of Materials Chemistry A | Year: 2015

ZnFe2O4 is a promising visible-light-driven photocatalyst with high energy level CBM for hydrogen generation. However, it could only be synthesized in the bulk form and its photocatalytic activities are limited by the rapid recombination of photo-generated carriers. Here, we report the preparation of a ZnFe2O4 nanostructure in ultrathin hollow sphere morphology with a 10 nm thick shell, which could shorten the diffusion distance of photo-generated carriers to minimize their interior recombination. Furthermore, ZnFe2O4/ZnO nanoheterostructures, containing 15 nm size heterojunctions, could be synthesized facilely. We have found that this unique structure endows ZnFe2O4/ZnO with a large separation of photo-generated carriers. The hydrogen generation rate of ZnFe2O4/ZnO nanoheterostructures without co-catalysts is up to 2.15 mmol h-1 g-1 under visible light irradiation (λ > 420 nm), which is 45 times higher than the best yields ever reported for ZnFe2O4-based photocatalysts. These research results provide a general and effective route to synthesize other nanoheterostructures for a variety of applications. © The Royal Society of Chemistry 2015.

Hu X.,State Key Laboratory of Silicon Materials | Shi M.,State Key Laboratory of Silicon Materials | Zuo L.,State Key Laboratory of Silicon Materials | Fu L.,State Key Laboratory of Silicon Materials | And 2 more authors.
Acta Chimica Sinica | Year: 2011

A series of perylene diimide derivatives 2a~2d with the substitutions of secondary amino groups at bay positions, were synthesized via simple Ullmann reaction, and their energy levels were characterized. From the UV-vis absorption spectra, it was found that, after the introduction of secondary amino into the bay position, the band gaps of perylene diimides became narrower, and the maximum absorption peaks were significantly red-shifted while compared to non-substituted parent compound. Thus, their absorption bands extended to the near-IR range. Through cyclic voltammetry, it was disclosed that 2a, 2c, and 2d exhibited both reversible reduction and oxidation processes, and their HOMO energy levels increased greatly, indicating bipolar semiconductive characteristics. Preliminary investigation of the application of bis-morpholine substituted perylene diimide 2d in organic photovoltaic devices was performed, and the results demonstrated that 2d could be used as both electron acceptor and electron donor.

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