170 results on '"Fang, Wen"'
Search Results
2. Remanent solvent management engineering of perovskite films for PEDOT: PSS-based inverted solar cells
- Author
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Shenghou Zhou, Lin Du, Wenfeng Zhang, Rui Liu, Liuwen Tian, Fang Wen, Puan Lin, Changtao Peng, Taotao Hu, Xiangqing Zhou, Fu Zhang, Meng Zhang, and Yuelong Huang
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Materials science ,Photoluminescence ,Renewable Energy, Sustainability and the Environment ,Annealing (metallurgy) ,020209 energy ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Microstructure ,Evaporation (deposition) ,Solvent ,Chemical engineering ,PEDOT:PSS ,Yield (chemistry) ,0202 electrical engineering, electronic engineering, information engineering ,General Materials Science ,0210 nano-technology ,Perovskite (structure) - Abstract
Perovskite solar cells (PSCs) have been attracting tremendous attention due to ease of processing, flexibility, and high performance. Dimethyl sulfoxide (DMSO) and N, N-dimethylformamide (DMF) are the two most widely used solvents to dissolve perovskite precursors. Here, we investigate the impact of residual amount and evaporation rate of the DMSO inside the precursor films on the microstructure of the ultimate perovskite films. We decouple the DMSO and DMF solvents and demonstrate that DMSO component exhibits great and dominant influence on the final film morphology by using quasi in-situ photoluminescence (PL) measurement and X-ray diffraction (XRD) characterization of the wet films after spin-coating. Much more smooth and uniform perovskite films are obtained by careful management of remanent solvent, including decreasing residual amount by shelving the precursor films prior to heating and retarding the evaporation of the solvent via adopting a gradient annealing (GA) process. In consequence, the as-prepared PEDOT: PSS-based inverted PSCs yield a champion efficiency of 15.59% with high reproducibility. This work shows great potential in preparing high-quality perovskite films through a simple remanent solvent management engineering.
- Published
- 2021
3. Composite-pulse enhanced room-temperature diamond magnetometry
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Jing-Yan Xu, Yang Dong, Guanzhong Wang, Xiang-Dong Chen, Shao-Chun Zhang, Wei Zhu, Guang-Can Guo, Yu Zheng, and Fang-Wen Sun
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Materials science ,business.industry ,Magnetometer ,Quantum sensor ,Diamond ,General Medicine ,engineering.material ,Composite pulse ,law.invention ,law ,engineering ,Optoelectronics ,Sensitivity (control systems) ,Spin dephasing ,business ,Computer Science::Databases - Abstract
The sensitivity of practical solid quantum sensing can be boosted up by increasing the number of probes. However, the effects of spin dephasing caused by inhomogeneous broadening and imperfect quan...
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- 2021
4. Rising from the Ashes: Gaseous Therapy for Robust and Large-Area Perovskite Solar Cells
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Hua Yu, Puan Lin, Wenfeng Zhang, Xiangqing Zhou, Tao Chen, Xu Liu, Yuelong Huang, Shenghou Zhou, Meng Zhang, Fang Wen, Zhu Ma, Zhang Haichuan, Liuwen Tian, and Yutong Jiang
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Materials science ,Fabrication ,business.industry ,Photovoltaic system ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Maximum power point tracking ,0104 chemical sciences ,Optoelectronics ,General Materials Science ,Post treatment ,0210 nano-technology ,business ,Scaling ,Perovskite (structure) - Abstract
Scalable fabrication of perovskite solar cells (PSCs) with high reliability is one of the most pivotal concerns that must be addressed before they get into the photovoltaic (PV) market. Scaling large-area high-quality perovskite films is of great importance in this process. Here, gaseous therapy has been proposed for the post-treatment of perovskite films with high scalability and low cost. An inspiring evolvement from poor perovskite films to high quality ones is demonstrated under a joint treatment of methylamine gas and hot solvent vapors. The perovskite films are completely reconstructed and repaired regardless of the morphology of the original films. As a consequence, small-area (0.09 cm2) and large-area (4 cm2) PSCs based on the healed MAPbI3 films can afford J-V scanned efficiencies of 19.2 and 16.5% under a reverse sweep, respectively. Furthermore, stabilized power outputs of 18.5 and 15.2% are obtained from the small one and large one under continuous maximum power point tracking.
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- 2020
5. Low Turn-Off Loss 4H-SiC Insulated Gate Bipolar Transistor With a Trench Heterojunction Collector
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Ying Wang, Xue Wu, Xingji Li, Jian-Qun Yang, Fang-wen Su, Cheng-Hao Yu, and Hong-kai Mao
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4H-SiC ,Materials science ,heterojunction ,Condensed matter physics ,turn-off time ,turn-off loss ,Doping ,Heterojunction ,Insulated-gate bipolar transistor ,Electron ,breakdown voltage ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,chemistry ,Trench ,Silicon carbide ,Breakdown voltage ,Figure of merit ,insulated gate bipolar transistor (IGBT) ,lcsh:Electrical engineering. Electronics. Nuclear engineering ,Electrical and Electronic Engineering ,lcsh:TK1-9971 ,Biotechnology - Abstract
In this work, an improved 4H-SiC insulated gate bipolar transistor (IGBT), or CTH-IGBT, with a trench p-polySi/p-SiC heterojunction on the backside of the device is proposed to reduce the turn-off energy loss (Eoff) and turn-off time (Toff). The electrical properties of the proposed and contrast structures are all simulated using the ATLAS simulation software to research the working mechanism of this improved structure. For the static performance, the specific ON-resistance (Ron,sp) and the figure of merit (FOM = VBR2/Ron,sp) are not influenced much as compared to the traditional structure at the same breakdown voltage (VBR) of 12 kV. However, with a prominent electron current path formed by the heterojunction region of CTH-IGBT, a very available conduction path to discharge the electrons during turn-off process is proved in this article. The simulation results demonstrate that compared with the traditional structure, the turn-off energy loss of the CTH-IGBT is reduced by 76.4%, while the turn-off time is reduced by 85.0%.
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- 2020
6. Nitrogen-Stabilized Low-Valent Ni Motifs for Efficient CO2 Electrocatalysis
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Huai Qin Fu, Xin Yu Zhang, Chun Fang Wen, Yuanwei Liu, Peng Fei Liu, Fangxin Mao, Hua Gui Yang, and Lirong Zheng
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Materials science ,Field (physics) ,010405 organic chemistry ,Inorganic chemistry ,chemistry.chemical_element ,General Chemistry ,010402 general chemistry ,Electrocatalyst ,Electrochemistry ,01 natural sciences ,Nitrogen ,Redox ,Catalysis ,0104 chemical sciences ,chemistry - Abstract
Single-atom catalysts have found considerable applications in the field of electrochemical CO2 reduction reaction (CO2RR) due to their unique coordination environments. However, during the preparat...
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- 2019
7. Photoresponsive Azobenzene Materials Based on Pyridine-Functionalized Benzoxazines as Surface Relief Gratings
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Wei-Hung Su, Tao Chen, Ahmed El-Mahdy, Shiao-Wei Kuo, and Fang-Wen Lin
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chemistry.chemical_compound ,Monomer ,Materials science ,Polymers and Plastics ,chemistry ,Azobenzene ,Surface relief ,Process Chemistry and Technology ,Organic Chemistry ,Pyridine ,Polymer chemistry - Abstract
We describe the one-pot syntheses of an azobenzene- and pyridine-functionalized benzoxazine monomer (PAPBZ) and a main chain-type polybenzoxazine (BAPBZ) through Mannich condensations of a diamino-...
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- 2019
8. Tailoring Carbosilane Side Chains toward Intrinsically Stretchable Semiconducting Polymers
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Chian-Wen Hong, Tomoya Higashihara, Wen-Chang Chen, Hung-Chin Wu, Yun-Chi Chiang, Chih-Chien Hung, Chi-Ching Kuo, and Han-Fang Wen
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chemistry.chemical_classification ,Materials science ,Polymers and Plastics ,Organic Chemistry ,Stretchable electronics ,Nanotechnology ,02 engineering and technology ,Polymer ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,chemistry ,Materials Chemistry ,Side chain ,0210 nano-technology - Abstract
Carbosilane side chain-equipped isoindigo–bithiophene semiconducting polymers (PII2T) have been designed and synthesized for stretchable electronics applications. Systematically tailoring the lengt...
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- 2019
9. Tuning electronic properties of InSe/arsenene heterostructure by external electric field and uniaxial strain
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Yan Zhang, Zhihui Zhang, Lei Ni, Zifeng Xie, Ran Yao, Yahui Zhang, Jibin Fan, Li Duan, and Fang-Wen Sun
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Materials science ,Band gap ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Condensed Matter::Materials Science ,symbols.namesake ,Electric field ,Strain (chemistry) ,Condensed matter physics ,business.industry ,Heterojunction ,Surfaces and Interfaces ,General Chemistry ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,0104 chemical sciences ,Surfaces, Coatings and Films ,Semiconductor ,symbols ,Direct and indirect band gaps ,Density functional theory ,van der Waals force ,0210 nano-technology ,business - Abstract
First-principles based on density functional theory (DFT) are used to calculate the structural and electronic properties of InSe/arsenene heterostructure. The results show that the InSe/arsenene bilayer forms a type-II van der Waals heterostructure with a direct band gap of 0.876 eV, which is favorable for the separation of photogenerated electron-hole pairs. The properties of InSe/arsenene heterojunction can be effectively regulated by applying an external electric field and uniaxial strain. When an external electric field is applied, the heterostructure experiences a transition from semiconductor to metal. In addition, due to the presence of built-in electric field, the positive and negative electric fields have different effects on the electronic properties of heterostructure. When uniaxial strain is applied, the heterostructure can withstand larger tensile strain than compression strain without damaging the structure and the band gap is more easily decreased by X-direction strain. In addition, the heterostructure undergoes a direct-indirect bandgap transition under strain. When compressive strain is applied in the Y direction, especially e
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- 2019
10. Determination of the number of graphene layers on one-dimensional photonic crystal by using polarization-dependent absorption effect
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Fang Wen, Yu Wang, Jing Xu, and Xiaohui Xu
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Materials science ,business.industry ,Graphene ,Absorption effect ,02 engineering and technology ,Substrate (electronics) ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,law.invention ,010309 optics ,law ,0103 physical sciences ,Optoelectronics ,Electrical and Electronic Engineering ,Polarization dependent ,0210 nano-technology ,business ,Absorption (electromagnetic radiation) ,Layer (electronics) ,Photonic crystal - Abstract
In this paper, we study polarization-dependent optical absorption of a graphene on the top of one-dimensional photonic crystal (1DPC), which offer a method to accurately count the number of graphene layers. The 1DPC is composed of 10 pairs of (SiO2/TiO2), and the two kinds of material is transparent, which is different from the commonly substrate with significant contrast to graphene. The absorption difference fitting formula is given by the 0–10 graphene layer. It may be applicable to other two-dimensional materials optically counting layers.
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- 2019
11. A novel binary Cu2I2 and Cu6S6 cluster-based red emission compound and sensing of Cr(VI) in water
- Author
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Hui-Fang Wen, Li-Juan Su, Rui-Sha Zhou, Jiang-Feng Song, Xiao-Yu Zhang, Wen Zhang, and Li-Dong Xin
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chemistry.chemical_classification ,Materials science ,010405 organic chemistry ,Analytical chemistry ,Infrared spectroscopy ,010402 general chemistry ,01 natural sciences ,Fluorescence ,0104 chemical sciences ,Coordination complex ,Inorganic Chemistry ,chemistry ,Elemental analysis ,X-ray crystallography ,Materials Chemistry ,Thermal stability ,Physical and Theoretical Chemistry ,Luminescence ,Thermal analysis - Abstract
A novel Cu(I)-cluster based coordination compound formulated as {(Cu2I2)2[Cu6(dmpymt)6]}n (Hdmpymt = 4,6-dimethylpyrimidine-2-thione) was synthesized under solvo-thermal condition and characterized by single-crystal X ray diffraction, elemental analysis, IR spectroscopy, thermal analysis, and powder X-ray diffraction. Compound 1 is an infinite 3D structure composed of Cu2I2 and Cu6S6 binary Cu(I) clusters with 66 topology, and displays high thermal stability and good solvent stability. Fluorescence experiments illustrate that compound 1 displays apparently red luminescence emission and selectively turn-off fluorescence response for CrO42− and Cr2O72− in water, showing potential luminescent probes for detecting Cr(VI) ions.
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- 2018
12. High resolution imaging with anomalous saturated excitation
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Fang-Wen Sun, Xiang-Dong Chen, Shao-Chun Zhang, Ze-Hao Wang, En-Hui Wang, Guang-Can Guo, and Bo Du
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Materials science ,FOS: Physical sciences ,02 engineering and technology ,engineering.material ,01 natural sciences ,law.invention ,010309 optics ,Optics ,law ,Confocal microscopy ,Vacancy defect ,0103 physical sciences ,Image resolution ,business.industry ,Diamond ,021001 nanoscience & nanotechnology ,Laser ,Fluorescence ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,engineering ,Spatial frequency ,0210 nano-technology ,business ,Excitation ,Physics - Optics ,Optics (physics.optics) - Abstract
The nonlinear fluorescence emission has been widely applied for high spatial resolution optical imaging. Here, we studied the fluorescence anomalous saturating effect of the nitrogen vacancy defect in diamond. The fluorescence reduction was observed with high power laser excitation. It increased the nonlinearity of the fluorescence emission, and changed the spatial frequency distribution of the fluorescence image. We used a differential excitation protocol to extract the high spatial frequency information. By modulating the excitation laser’s power, the spatial resolution of imaging was improved approximately 1.6 times in comparison with the confocal microscopy. Due to the simplicity of the experimental setup and data processing, we expect this method can be used for improving the spatial resolution of sensing and biological labeling with the defects in solids.
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- 2021
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13. Electric field and uniaxial strain tunable electronic properties of the InSb/InSe heterostructure
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Tingting Guo, Ye Tian, Zhu Wang, Zhihui Zhang, Fang-Wen Sun, Xing Wei, Yan Zhang, Lei Ni, Jibin Fan, Li Duan, and Jian Liu
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Work (thermodynamics) ,Electron mobility ,Materials science ,business.industry ,Band gap ,General Physics and Astronomy ,Heterojunction ,02 engineering and technology ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Condensed Matter::Materials Science ,symbols.namesake ,Semiconductor ,Stark effect ,Electric field ,symbols ,Optoelectronics ,Direct and indirect band gaps ,Physical and Theoretical Chemistry ,0210 nano-technology ,business - Abstract
In this study, the InSb/InSe heterostructure is systematically examined in terms of its electronic properties through first-principles calculations. According to our findings, the InSb/InSe heterostructure is a kind of unique direct band gap semiconductor, which has inherent type-II band alignment, resulting in significant photogenerated electron–hole pair separation in space. When the external electric field is applied, the Stark effect is observed in the band gap. Interestingly, in the application of the −0.3 V A−1 electric field, such a heterostructure is transformed into type-I from type-II. Simultaneously, the band gap is also effectively controlled by uniaxial strain. In particular, high carrier mobility is obtained at a compressive strain of 4% on the Y-axis. To sum up, based on the results in the present work, the InSb/InSe heterostructure can be potentially used in nanoelectronic and optoelectronic devices.
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- 2020
14. Effects of Annealing Time on Triple Cation Perovskite Films and Their Solar Cells
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Meng Zhang, Qiyun Wang, Hua Yu, Changtao Peng, Yuepeng Li, Yuelong Huang, Lin Du, Taotao Hu, Liuwen Tian, Fang Wen, Wenfeng Zhang, and Ma Zhu
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Potential well ,Fabrication ,Materials science ,business.industry ,Annealing (metallurgy) ,Ion migration ,Halide ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,chemistry ,Caesium ,Optoelectronics ,General Materials Science ,0210 nano-technology ,business - Abstract
Cesium (Cs) contained triple-cation and mixed halide perovskite (CsFAMA) is broadly employed as light absorption layers for efficient and stable perovskite solar cells (PSCs) fabrication with high reproducibility. On the other hand, thermal annealing is a universal post-treatment method for perovskite films preparation. Moreover, thermal management highly depends on perovskite materials. However, no specialized study has been reported on CsFAMA perovskite to date. Herein, we have systematically investigated the influence of thermal annealing and annealing time on CsFAMA films and their solar cells. We demonstrated that heating time of 45 or 60 min at 100 °C is desirable. More interestingly, we found that the unannealed CsFAMA films exhibit ultrahigh photoluminescence (PL) intensities, much stronger than that of annealed films. Note that PL intensities gradually weaken as a function of annealing time. In particular, the PL intensities of fresh films (after antisolvent dripping) are at least 200 times higher than that of 60 min annealed films. To our knowledge, it is the first time to report this PL behavior. We speculate that it is due to quantum confinement effect of perovskite crystal nuclei and "cage effect" of DMSO intermediates in the fresh films. To this point, the unannealed CsFAMA films may have great potential in PL emission applications.
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- 2020
15. Uniaxial Compression Fractal Damage Constitutive Model of Rock Subjected to Freezing and Thawing
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Xu He, Fang Wen, Luo Xuedong, Jiang Nan, and Shengtao Zhou
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Materials science ,Fractal ,Constitutive equation ,Uniaxial compression ,Composite material ,Geotechnical Engineering and Engineering Geology ,Civil and Structural Engineering - Abstract
Mechanical properties of the rock in the cold regions are often affected by freeze-thaw cycles and loads. It is of great theoretical significance and engineering value to establish a uniaxial compression damage constitutive model of the rock under freeze-thaw cycles that can reflect the relationship between macroscopic and mesoscopic structural damage. In this paper, macroscopic and mesoscopic methods are combined with statistical methods to quantitatively analyze the damage degree of rock under freeze-thaw cycles and loads. Combined with the fractal features of the macroscopic image of the section, a fractal damage constitutive model considering the residual strength of rock is established. In addition, the model is subsequently verified by the experiment. The experiment shows that the mechanical properties of rocks subjected to freeze-thaw cycles and loads are determined by freeze-thaw damage variables, load damage variables, and their coupling effects. As the number of freeze-thaw cycles increases, the uniaxial compressive strength and elastic modulus of rocks decrease, and peak strain increases. By using the fractal dimension of the compression fracture surface as a bridge considering the residual strength of the rock, the constitutive model can better reflect the compaction stage, elastic deformation stage and plastic deformation stage of the uniaxial compression process of the freeze-thaw rocks.
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- 2020
16. A novel -Pb-O-Pb-Cu-Cl- inorganic layer-based pillared-layer framework: Synthesis, crystal structure and fluorescent property
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Xiao-Yu Xu, Rui-Sha Zhou, Rui-Chao Yao, Hui-Fang Wen, Jiang-Feng Song, and Wen Zhang
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Materials science ,Coordination polymer ,Dimer ,chemistry.chemical_element ,02 engineering and technology ,Crystal structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Fluorescence ,Hydrothermal circulation ,0104 chemical sciences ,Ion ,Inorganic Chemistry ,chemistry.chemical_compound ,Crystallography ,chemistry ,Materials Chemistry ,Chlorine ,Physical and Theoretical Chemistry ,0210 nano-technology ,Layer (electronics) - Abstract
A novel pillared-layer coordination polymer containing -Pb-O-Pb-Cu-Cl- inorganic sheets, [PbCuCl(3.5-pydc)]n (1) (3.5-H2pydc = pyridine-3,5-dicarboxylic acid), was obtained through the hydrothermal method. In compound 1, two symmetry-related Pb centers are bridged into a Pb2O2 dimer by two symmetrically carboxyl oxygen atoms from 3,5-pydc2− anions, each Pb2O2 dimer links four equivalent units into a 2D puckered Pb-O-Pb layer. Two symmetry-related Cu ions are bridged into a Cu2Cl2 dimer by two chlorine ions. Thus the -Pb-O-Pb- layer and Cu2Cl2 dimers are joined into a novel 2D puckered -Pb-O-Pb-Cu-Cl- inorganic layer. The 2D -Pb-O-Pb-Cu-Cl- inorganic layers are further pillared to form a 3D network through 3,5-pydc2− anions. To the best of our knowledge, the pillared-layer framework based on -Pb-O-Pb-Cu-Cl- inorganic layers has never been reported previously. Compound 1 exhibits weak blue light emission with the maximum at 383 nm upon excitation at 260 nm.
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- 2018
17. Synthesis of block copolymers comprised of poly(3-hexylthiophene) segment with trisiloxane side chains and their application to organic thin film transistor
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Tomoya Higashihara, Wen-Chang Chen, Satoshi Miyane, and Han-Fang Wen
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Morphology (linguistics) ,Materials science ,Polymers and Plastics ,Organic Chemistry ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Chemical engineering ,Thin-film transistor ,Materials Chemistry ,Copolymer ,Side chain ,0210 nano-technology - Published
- 2018
18. Charge state depletion nanoscopy with a nitrogen-vacancy center in nanodiamonds
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qiyu wang, Ze-Hao Wang, Guang-Can Guo, Bo Du, Xiang-Dong Chen, and Fang-Wen Sun
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Microscopy ,Materials science ,Light ,Nitrogen ,business.industry ,Lasers ,Charge (physics) ,State (functional analysis) ,Atomic and Molecular Physics, and Optics ,Nanodiamonds ,Optics ,Atomic physics ,business ,Nitrogen-vacancy center - Abstract
The development of super-resolution imaging has driven research into biological labeling, new materials’ characterization, and nanoscale sensing. Here, we studied the photoinduced charge state conversion of nitrogen-vacancy (NV) centers in nanodiamonds (NDs), which show the potential for multifunction sensing and labeling at the nanoscale. Charge state depletion (CSD) nanoscopy is subsequently demonstrated for the diffraction-unlimited imaging of NDs in biological cells. A resolution of 77 nm is obtained with 50 nm NDs. The depletion laser power of CSD nanoscopy is approximately 1/16 of stimulated emission depletion (STED) microscopy with the same resolution. The results can be used to improve the spatial resolution of biological labeling and sensing with NDs and other nanoparticles.
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- 2021
19. Controllable perovskite crystallization via platelet-like PbI2 films from water processing for efficient perovskite solar cells
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Puan Lin, Fang Wen, Yutong Jiang, Xinyi Li, Gongtao Duan, Wenfeng Zhang, Liuwen Tian, Tao Chen, Yuelong Huang, Shenghou Zhou, Lang Yu, Lin Du, Xiangqing Zhou, and Ma Zhu
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Materials science ,Mechanical Engineering ,Water processing ,Metals and Alloys ,02 engineering and technology ,Carrier lifetime ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Grain size ,0104 chemical sciences ,law.invention ,Solvent ,Chemical engineering ,Mechanics of Materials ,law ,Materials Chemistry ,Crystallization ,0210 nano-technology ,Perovskite (structure) - Abstract
The performance of organic-inorganic perovskite solar cells depends largely on the quality of perovskite film. Currently, various methods are applied to prepare the perovskite film. Among them, the two-step method is counted as a promising candidate to obtain high-quality perovskite film. In this study, we attain a special platelet-like PbI2 films by applying pure water to cover wet PbI2 film and standing for a period of time. The unique morphology contributes to the entry of organic cations solution into the PbI2 and promoting its reaction with PbI2, which reducing the residual amount of PbI2 in the perovskite film. Compared to the traditional two-step method, water processing method can obtain a high-quality perovskite film with enlarged grain size, improved crystallization, and prolonged carrier lifetime. As a result, the efficiency of the prepared device based on the film has increased from 17.90% without water processing to 20.14% of water processing. Which demonstrates that this solvent engineering for PbI2 film opens up a possibility to prepare high-quality perovskite in a two-step method and obtain highly efficient perovskite solar cells.
- Published
- 2021
20. Enhanced pseudocapacitive behaviors of Sb-based anodes for lithium ion batteries via dual modification approach of Fe doping combined with double carbon coatings
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Junfei Duan, Lingjun Li, Fang Wen, Chao Zhu, Guang Zeng, and Zhaoyong Chen
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Materials science ,Mechanical Engineering ,Metals and Alloys ,chemistry.chemical_element ,Nanoparticle ,Chemical vapor deposition ,Thermal treatment ,engineering.material ,Anode ,chemistry ,Amorphous carbon ,Chemical engineering ,Coating ,Mechanics of Materials ,Materials Chemistry ,engineering ,Lithium ,Carbon - Abstract
Antimony has emerged as a promising candidate for electrode materials attributed to tempting specific capacity and low cost. Nevertheless, the notorious volume fluctuation and unstable solid-electrolyte interphase (SEI) film give rise to structural degradation and rapid capacity decay. Herein, a remarkable dual-modification approach is investigated on Sb-based anode by Fe doping and double carbon coatings via self-assembling of novel Fe/Sb–hexamine bimetal–organic frameworks strategy followed by thermal treatment and chemical vapor deposition simultaneously. In the as-prepared composite, Fe-doped Sb nanoparticles decorated with in-situ formed amorphous carbon coating are dispersed in interconnected carbon matrices with robust contact (Fe-Sb@NSC). Fe-doping would effectively enhance the electric conductivity, regulate the dispersion of Sb particles, and act as buffer layer to hinder the aggregation of Sb during repeated discharge/charge process. Meanwhile, double carbon layers not only reduce electrolytic corrosion and enhance electric conductivity, but also provide robust shelter layer to restrict the volume variation and coarsening of Sb-based materials. Therefore, the dual-modified sample shows enhanced lithium storage performance with high reversible capacity, outstanding long-term stability and stable structure. Moreover, the kinetics analysis of Li+ storage indicates that the increased pseudocapacitive contribution and decreased charge transfer barriers after cycling may account for the promoted performance.
- Published
- 2021
21. Laser Writing of Color Centers
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Hong-Bo Sun, Hong-Hua Fang, Xiao-Jie Wang, and Fang-Wen Sun
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Optics ,Materials science ,business.industry ,law ,Condensed Matter Physics ,business ,Laser ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,law.invention - Published
- 2021
22. Temperature dependence of optical centers in Ib diamond characterized by photoluminescence spectra
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Huihui Luo, Pengfei Wang, Kaiyue Wang, Zongwei Xu, Jiayu Liu, Changkun Shi, Kun Zhang, Fang-Wen Sun, Yexin Fan, E. Wu, Ying Song, and Bing Dong
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Arrhenius equation ,Photoluminescence ,Materials science ,Mechanical Engineering ,Diamond ,02 engineering and technology ,General Chemistry ,Chemical vapor deposition ,Atmospheric temperature range ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,Spectral line ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,symbols.namesake ,Full width at half maximum ,Materials Chemistry ,symbols ,engineering ,Electrical and Electronic Engineering ,0210 nano-technology ,Line (formation) - Abstract
The optical properties of defects in Ib diamond prepared by Chemical Vapor Deposition (CVD) and High Pressure High Temperature (HPHT) methods are studied by photoluminescence in a temperature range of 77– 297 K. The temperature dependence of color centers in diamond of 2.65 eV center, NV0, NV-, SiV-, 3H is studied. The zero-phonon line (ZPL) shift, intensity and full width at half maxima (FWHM) have a strong temperature dependence. The study shows that, due to the expansion of the lattice and the enhancement of the electron-phonon coupling strength, the ZPL shift can be described by the modified Varshni model which shows great potential in temperature sensing. The FWHM of ZPL matches a cubic function of temperature, this model can be employed to well describe the broadening of ZPLs in the defect-rich diamond. And the thermal quenching of absolute PL intensity can be described by the Arrhenius equation. Meanwhile, the difference of variable PL signal between CVD and HPHT samples is analyzed.
- Published
- 2021
23. Soft Poly(butyl acrylate) Side Chains toward Intrinsically Stretchable Polymeric Semiconductors for Field-Effect Transistor Applications
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Chih-Chien Hung, Yun-Chi Chiang, Chi-Ching Kuo, Hung-Chin Wu, Han-Fang Wen, Wen-Chang Chen, and Junko Aimi
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Materials science ,Polymers and Plastics ,Butyl acrylate ,02 engineering and technology ,Conjugated system ,010402 general chemistry ,01 natural sciences ,Inorganic Chemistry ,chemistry.chemical_compound ,Polymer chemistry ,Materials Chemistry ,Side chain ,Thin film ,chemistry.chemical_classification ,business.industry ,Organic Chemistry ,Polymer ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Semiconductor ,chemistry ,Chemical engineering ,Field-effect transistor ,0210 nano-technology ,Glass transition ,business - Abstract
Poly(butyl acrylate) (PBA) side chain equipped isoindigo-bithiophene (II2T) conjugated polymers have been designed and synthesized for stretchable electronic applications. The PBA segment possesses low glass transition temperature and high softness, offering a great opportunity to improve the mechanical property of semiconducting polymer thin films that typically contain lots of rigid conjugated rings. Polymers with 0, 5, 10, 20 and 100% of PBA side chains, named PII2T, PII2T-PBA5, PII2T-PBA10, PII2T-PBA20, and PII2T-PBA100, were explored, and their polymer properties, surface morphology, electrical characteristics, and strain-dependent performance were investigated systematically. The series polymers showed a charge carrier mobility of 0.06–0.8 cm2 V–1 s–1 with an on/off current ratio over 105 dependent on different amounts of PBA chains as probed using a top-contact transistor device. Moreover, we can still achieve a mobility higher than 0.2 cm2 V–1 s–1 even if 10% of PBA side chains were added (i.e., P...
- Published
- 2017
24. Temperature dependent energy gap shifts of single color center in diamond based on modified Varshni equation
- Author
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Guang-Can Guo, Shen Li, Bo-Wen Zhao, Xiang-Dong Chen, Fang-Wen Sun, Yang Dong, Ming Gong, and Cong-Cong Li
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Materials science ,Condensed matter physics ,Band gap ,Phonon ,Mechanical Engineering ,Diamond ,02 engineering and technology ,General Chemistry ,engineering.material ,Zero field splitting ,021001 nanoscience & nanotechnology ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,symbols.namesake ,Vacancy defect ,0103 physical sciences ,Materials Chemistry ,engineering ,symbols ,Diamond cubic ,Electrical and Electronic Engineering ,010306 general physics ,0210 nano-technology ,Nitrogen-vacancy center ,Debye model - Abstract
Although the diamond has the similar structure (diamond cubic) and symmetry (Oh) as many other conventional semiconductor materials, the extraordinary large Debye temperature and small lattice expansion coefficient make the temperature dependence of energy gaps in diamond to be totally different from those in other semiconductors. Here we propose a modified Varshni formula to describe the temperature dependent zero field splitting and zero phonon line of the nitrogen vacancy center in diamond. The shift of energy gaps shows a T4 scaling at low temperature and a T2 scaling at high temperature. The crossover between these two regimes is determined by two positive parameters in the modified formula. This empirical formula can give an excellent prediction of the temperature dependent energy gaps up to 700 K. We experimentally verify this temperature dependent behavior with single negatively charged nitrogen vacancy centers in diamond. These observations demonstrate the leading role of electron-acoustic phonon interaction in the temperature dependent shift of energy gaps in diamond. This empirical equation can benefit the diamond-based applications such as quantum sensing and computing.
- Published
- 2017
25. Superresolution Multifunctional Sensing with the Nitrogen-Vacancy Center in Diamond
- Author
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Guang-Can Guo, Xiang-Dong Chen, Chun-Hua Dong, Fang-Wen Sun, Deng-Feng Li, Shen Li, Bo Du, Yang Dong, and Yu Zheng
- Subjects
Electromagnetic field ,Materials science ,Atomic de Broglie microscope ,business.industry ,General Physics and Astronomy ,Diamond ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,01 natural sciences ,0103 physical sciences ,Microscopy ,engineering ,Optoelectronics ,010306 general physics ,0210 nano-technology ,business ,Nitrogen-vacancy center ,Quantum ,Image resolution ,Nanoscopic scale - Abstract
High spatial resolution and low perturbation are required for mapping the electromagnetic field at the nanoscale, to provide crucial information about local light-matter interaction. Using optical superresolution microscopy for detection via a nitrogen-vacancy center in diamond, this work demonstrates far-field noninvasive sensing of the local electromagnetic field with high accuracy and a spatial resolution of approximately 50 nm. As the nitrogen-vacancy center is sensitive to various physical quantities, a multifunctional far-field quantum nanoscope is anticipated.
- Published
- 2019
26. Boosting Alkaline Hydrogen Evolution Electrocatalysis over Metallic Nickel Sites through Synergistic Coupling with Vanadium Sesquioxide
- Author
-
Xin Yu Zhang, Peng Fei Liu, Haiyang Yuan, Chun Fang Wen, Fangxin Mao, Lirong Zheng, and Hua Gui Yang
- Subjects
Tafel equation ,Materials science ,General Chemical Engineering ,Alkaline water electrolysis ,chemistry.chemical_element ,Vanadium ,02 engineering and technology ,Overpotential ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrocatalyst ,01 natural sciences ,0104 chemical sciences ,Catalysis ,Nickel ,Sesquioxide ,General Energy ,chemistry ,Chemical engineering ,Environmental Chemistry ,General Materials Science ,0210 nano-technology - Abstract
For renewable and sustainable energy, developing cut-price and high-efficiency electrocatalysts for the hydrogen evolution reaction (HER) by alkaline water electrolysis is of paramount importance. In this study, a compound electrocatalyst composed of nickel-vanadium sesquioxide nanoparticles supported on porous nickel foam (Ni-V2 O3 /NF) is found to exhibit electrocatalytic performance towards HER that is superior to that of the commercial Pt/C catalyst, with nearly zero onset overpotential, an extremely low overpotential of 25 mV to obtain a current density of -10 mA cm-2 , a Tafel slope of 58 mV dec-1 , and a good durability for 24 h in 1.0 m KOH. Theoretical calculations reveal that the presence of V2 O3 optimizes the electronic structure of active Ni components and continuously accelerates the dissociation of water molecules, which in turn improves the HER kinetics. The present work will advance the development of highly efficient nanocomposite electrocatalysts for alkaline water electrocatalysis.
- Published
- 2019
27. Temperature Rise Analysis of the Insulating Blanket in the Live Working of 10 kV Distribution Line
- Author
-
Huang Yin, Li Peng, Tian Wu, Liu Wei, Fang Wen, and Ziheng Pu
- Subjects
Materials science ,Natural convection ,High voltage ,Blanket ,Composite material ,Temperature measurement ,Electrical conductor ,Intensity (heat transfer) ,Line (electrical engineering) ,Conductor - Abstract
Live working is an important method to improve the reliability of the power distribution network. In order to protect the safety of worker, the insulating protective tool, such as insulating blanket, is used to wrap the high voltage conductor. The temperature rise characteristics of the insulating blanket have been researched in this paper. The thermal-fluid coupled calculation is used to simulate the temperature rise and heat dissipation process of the insulating blanket in the live working of 10 kV distribution line (type is JL/G1A-70/10). The simplify method of the steel core aluminum stranded conductor is put forward. The effect of length and thinness of the insulating blanket, wind speed, and sunshine intensity on the temperature distribution of the insulating blanket is analyzed. Results show that the temperature distribution is basically the same when the stranded conductor is simplified to a single conductor. The maximum temperature difference between inside and outside of the insulating blanket is about 22 K under the natural convection environment. The effect of thickness on temperature rise is greater than that of length for this insulating blanket. The wind speed and sunshine have a large influence on the temperature distribution of the insulating blanket.
- Published
- 2019
28. Detecting Axial Ratio of Microwave Field with High Resolution Using NV Centers in Diamond
- Author
-
Fang-Wen Sun, Yu Zheng, Aimin Du, Cuihong Li, Deng-Feng Li, and Ya-Song Ge
- Subjects
Materials science ,Microscope ,MW magnetic field ,02 engineering and technology ,Chemical vapor deposition ,engineering.material ,lcsh:Chemical technology ,01 natural sciences ,Biochemistry ,Article ,Analytical Chemistry ,law.invention ,law ,0103 physical sciences ,Microscopy ,lcsh:TP1-1185 ,Electrical and Electronic Engineering ,010306 general physics ,Instrumentation ,axial ratio ,polarization ,business.industry ,Axial ratio ,Diamond ,NV center ,021001 nanoscience & nanotechnology ,Polarization (waves) ,Atomic and Molecular Physics, and Optics ,Magnetic field ,engineering ,Optoelectronics ,Computer Science::Programming Languages ,0210 nano-technology ,business ,Microwave - Abstract
Polarization property characterization of the microwave (MW) field with high speed and resolution is vitally beneficial as the circularly-polarized MW field plays an important role in the development of quantum technologies and satellite communication technologies. In this work, we propose a scheme to detect the axial ratio of the MW field with optical diffraction limit resolution with a nitrogen vacancy (NV) center in diamond. Firstly, the idea of polarization selective detection of the MW magnetic field is carried out using a single NV center implanted in a type-IIa CVD diamond with a confocal microscope system achieving a sensitivity of 1.7 &mu, T/ Hz . Then, high speed wide-field characterization of the MW magnetic field at the submillimeter scale is realized by combining wide-field microscopy and ensemble NV centers inherent in a general CVD diamond. The precision axial ratio can be detected by measuring the magnitudes of two counter-rotating circularly-polarized MW magnetic fields. The wide-field detection of the axial ratio and strength parameters of microwave fields enables high speed testing of small-scale microwave devices.
- Published
- 2019
29. Thickness dependent surface plasmon of silver film detected by nitrogen vacancy centers in diamond
- Author
-
Shen Li, Lei-Ming Zhou, Deng-Feng Li, Fang-Wen Sun, Nan Zhao, Xiang-Dong Chen, Yu Zheng, Bo-Wen Zhao, Guang-Can Guo, and Li Cuihong
- Subjects
Quantum optics ,Materials science ,business.industry ,Surface plasmon ,Nanophotonics ,Physics::Optics ,Diamond ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,symbols.namesake ,Optics ,Vacancy defect ,0103 physical sciences ,engineering ,symbols ,Optoelectronics ,Spontaneous emission ,010306 general physics ,0210 nano-technology ,business ,Nitrogen-vacancy center ,Raman scattering - Abstract
Precise detection of surface plasmons is crucial for the research of nanophotonics and quantum optics. In this Letter, we used a single nitrogen vacancy center in diamond as a probe to detect the surface plasmon that was tuned by the thickness of a metallic film. The fluorescence intensity and lifetime of the nitrogen vacancy (NV) center were measured to obtain the information of local light–matter interaction. A nonlinear thickness dependent change of the surface plasmon was observed, with the maximum at the thickness of approximately 30 nm. With optimized thickness of silver film, the fluorescence intensity of a single NV center was enhanced 2.6 times, and the lifetime was reduced by a factor of 3, without affecting the coherence time of the NV spin state. The results proved that this system can quantitatively detect the light–matter interaction at nanoscale, and it provides an approach to enhance the fluorescence intensity of a quantum emitter.
- Published
- 2018
30. A robust fiber-based quantum thermometer coupled with nitrogen-vacancy centers
- Author
-
Yang Dong, Fang-Wen Sun, Guanzhong Wang, Xiang-Dong Chen, Wei Zhu, Guang-Can Guo, Bo Du, Hao-Bin Lin, Shen Li, and Shao-Chun Zhang
- Subjects
010302 applied physics ,Quantum Physics ,Materials science ,business.industry ,Quantum sensor ,FOS: Physical sciences ,Diamond ,Physics - Applied Physics ,Applied Physics (physics.app-ph) ,engineering.material ,01 natural sciences ,Temperature measurement ,010305 fluids & plasmas ,Magnetic field ,Robustness (computer science) ,Thermometer ,0103 physical sciences ,engineering ,Optoelectronics ,Sensitivity (control systems) ,Quantum Physics (quant-ph) ,business ,Instrumentation ,Quantum - Abstract
The nitrogen-vacancy center in diamond has been broadly applied in quantum sensing since it is sensitive to different physical quantities. Meanwhile, it is difficult to isolate disturbances from unwanted physical quantities in practical applications. Here, we present a robust fiber-based quantum thermometer which can significantly isolate the magnetic field noise and microwave power shift. With a frequency modulation scheme, we realize the temperature measurement by detecting the variation of the sharp-dip in the zero-field optically detected magnetic resonance spectrum in a high-density nitrogen-vacancy ensemble. Thanks to its simplicity and compatibility in implementation and robustness in the isolation of magnetic and microwave noise, this quantum thermometer is then applied to the surface temperature imaging of an electronic chip with a sensitivity of $18$ $\rm{mK}/\sqrt{\rm{Hz}}$. It paves the way to high sensitive temperature measurement in ambiguous environments., Comment: 10 pages, 6 figures
- Published
- 2021
31. Effective carrier separation in zinc oxide and boron phosphide van der Waals heterostructure
- Author
-
Xing Wei, Ru Zhang, Jibin Fan, Jian Liu, Li Duan, Lei Ni, Zhihui Zhang, Yan Zhang, Ye Tian, Fang-Wen Sun, and Tingting Guo
- Subjects
Materials science ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,Zinc ,010402 general chemistry ,01 natural sciences ,symbols.namesake ,chemistry.chemical_compound ,Electric field ,Monolayer ,business.industry ,Heterojunction ,Surfaces and Interfaces ,General Chemistry ,Photoelectric effect ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,0104 chemical sciences ,Surfaces, Coatings and Films ,chemistry ,symbols ,Optoelectronics ,Direct and indirect band gaps ,van der Waals force ,Boron phosphide ,0210 nano-technology ,business - Abstract
To construct a preeminent photoelectric appliance, effective carrier separation is the critical question. In this study, a novel inherent staggered type-II van der Waals (vdW) heterostructure composed of zinc oxide (ZnO) and boron phosphide (BP) is designed with being simulated by a first-principle calculation. In the heterostructure, electrons and holes are localized in the monolayer of BP and ZnO respectively. That leads to the separation of photoinduced electron-hole pairs. Furthermore, it shows a prominent absorption coefficient of 104 cm−1 from the ultraviolet to infrared region. Interestingly, the band edges can be regulated and changed to a direct band gap at K point when applying an external electric field donating further separation of carriers. Besides, the heterostructure displays a robust type-II band alignment under −2% ~ +2% strain. These results suggest that two-dimensional (2D) ZnO/BP heterostructure will exhibit widespread application prospects in future photovoltaic and optoelectronic nanodevices.
- Published
- 2021
32. Mesoporous LiMnPO4/C nanoparticles as high performance cathode material for lithium ion batteries
- Author
-
Fang Wen, Xianyou Wang, Xiukang Yang, Li Liu, Ruizhi Yu, Jiajia Wan, Weihua Huang, Yuanyuan Zhang, and Hongbo Shu
- Subjects
Nanostructure ,Materials science ,General Chemical Engineering ,Inorganic chemistry ,Nanoparticle ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Cathode ,0104 chemical sciences ,Electrochemical cell ,law.invention ,chemistry ,Chemical engineering ,law ,Specific surface area ,Lithium ,0210 nano-technology ,Mesoporous material - Abstract
LiMnPO 4 has been considered as one of the most promising high voltage cathode materials for next-generation lithium ion batteries. However, LiMnPO 4 suffers from intrinsic drawbacks of extremely low electronic conductivity and ionic diffusivity between LiMnPO 4 /MnPO 4 . In this paper, mesoporous LiMnPO 4 nanoparticles are synthesized successfully via a facile glycine-assisted solvothermal rout. The as-prepared mesoporous LiMnPO 4 /C nanoparticles present well-defined abundant mesoporous structure (diameter of 3 ∼ 10 nm), uniform carbon layer (thickness of 3 ∼ 4 nm), high specific surface area (90.1 m 2 /g). As a result, the mesoporous LiMnPO 4 /C nanoparticles achieve excellent electrochemical performance as cathode materials for lithium ion batteries. It demonstrates a high discharge capacity of 167.7, 161.6, 156.4, 148.4 and 128.7 mAh/g at 0.1, 0.5, 1, 2 and 5C, and maintains a discharge capacity of 130.0 mAh/g after 100 cycles at 1C. The good electrochemical performance is attributed to its special interpenetrating mesoporous structure in LiMnPO 4 nanoparticles, which significantly enhances the ionic and electronic transport and additional capacitive behavior to compensate the sluggish kinetics.
- Published
- 2016
33. Finite Element Simulation on the Distribution of Discharge Gas in Hollow Cathode Plasma
- Author
-
Yan Nian Rui, Yi Fang Wen, and Hong Wei Wang
- Subjects
Materials science ,Computer simulation ,Mechanical Engineering ,Analytical chemistry ,Plasma ,Mechanics ,Cathode ,Finite element method ,law.invention ,Pipe flow ,Mechanics of Materials ,law ,Homogeneity (physics) ,Surface modification ,General Materials Science ,Thin film - Abstract
The graft polymerization in radio frequency hollow cathode plasma (RFHCP) is suitable for the surface modification of large-area thin film materials. The homogeneity of plasma surface modification of large-area thin film materials has always been paid close attention, and it is also the key factor affecting the industrialized applications of the technique. However, the homogeneity of plasma surface modification is thought to depend greatly on the distribution of discharge gas. In this paper, a finite element model is proposed to discuss the flow of discharge gas in hollow cathode plasma. The concentration distribution of the discharge gas has been discussed by the combination of numerical simulation of fluid distribution and pipe flow theory based on the investigation of the transport property of gas under vacuum. Comparisons between available experiments have also been performed to validate the applicability and practicability of the proposed model.
- Published
- 2016
34. Stimulated emission assisted time-gated detection of a solid-state spin
- Author
-
Guang-Can Guo, En-Hui Wang, Bo-Wen Zhao, Shen Li, Bo Du, Yang Dong, Yu Zheng, Xiang-Dong Chen, and Fang-Wen Sun
- Subjects
Fluorescence-lifetime imaging microscopy ,Materials science ,Spin states ,business.industry ,Diamond ,engineering.material ,01 natural sciences ,Fluorescence ,Atomic and Molecular Physics, and Optics ,010309 optics ,Optics ,Excited state ,0103 physical sciences ,engineering ,Spontaneous emission ,Stimulated emission ,Electrical and Electronic Engineering ,business ,Spin (physics) ,Engineering (miscellaneous) - Abstract
The nitrogen vacancy (NV) center in diamond is studied widely for magnetic field and temperature sensing at the nanoscale. Usually, the fluorescence is recorded to estimate the spin state of the NV center. Here we applied a time-gating technique to improve the contrast of the spin-dependent fluorescence. A NIR pulsed laser pumped the stimulated emission of the NV center and depleted the spontaneous emission that was excited by a green laser. We changed the relative delay between the NIR laser and the green laser. Then the spontaneous emission of the NV center in varied time windows was extracted by comparing the fluorescence intensities with and without the NIR laser. The results showed that the spin-dependent fluorescence contrast could be improved by approximately 1.8 times by applying the time gating. The background of the environment was eliminated due to temporal filtering. This work demonstrates that the stimulated emission assisted time-gating technique can be used to improve the performance of an NV center sensor in a noisy environment.
- Published
- 2020
35. Carboxyl functionalized graphite carbon nitride for remarkably enhanced photocatalytic hydrogen evolution
- Author
-
Chun Fang Wen, Hua Gui Yang, Jing Yang Bai, Li Jie Wang, Xue Lu Wang, and Yi Jun Zhang
- Subjects
Materials science ,Process Chemistry and Technology ,Rational design ,Graphitic carbon nitride ,Quantum yield ,02 engineering and technology ,Nitride ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Grafting ,01 natural sciences ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,Photocatalysis ,Charge carrier ,0210 nano-technology ,Recombination ,General Environmental Science - Abstract
Graphitic carbon nitride (g-C3N4) has recently emerged as a promising candidate for photocatalytic hydrogen evolution, but only showed limited activity owing to its sluggish photogenerated carriers separation and migration. Herein, the carboxyl-functionalized g-C3N4 (O CN) was synthesized by a grafting post-treatment method to alleviate the negative influences from this intrinsic drawback. As a result, the surface carboxyl groups greatly improve charge carrier dynamics to suppress carriers recombination via the driving force originated from its electron-withdrawing effects. The resultant O CN exhibits 52 times higher hydrogen evolution rate than the pristine, and possesses a high apparent quantum yield (AQY) of 15.7 % at 420 ± 15 nm. This work deepens the understanding of the surface group related modifications for photocatalytic materials, further providing a promising approach for rational design of photocatalysts with highly efficient solar energy conversion.
- Published
- 2020
36. Fluorescence modulation of the nitrogen-vacancy center with competition between charge-state conversion and stimulated emission
- Author
-
Bo Du, Xiang-Dong Chen, Yang Dong, Shao-Chun Zhang, Guang-Can Guo, Cuihong Li, and Fang-Wen Sun
- Subjects
Materials science ,business.industry ,Nanophotonics ,Diamond ,Statistical and Nonlinear Physics ,engineering.material ,Laser ,01 natural sciences ,Fluorescence ,Atomic and Molecular Physics, and Optics ,law.invention ,010309 optics ,law ,0103 physical sciences ,Microscopy ,engineering ,Optoelectronics ,Stimulated emission ,business ,Biological imaging ,Nitrogen-vacancy center - Abstract
The nitrogen-vacancy (NV) center in diamond has been widely used for quantum information processing, nanophotonics, and biological imaging. In this work, we experimentally studied the charge-state conversion and stimulated emission of the NV center with a near-infrared (NIR) pumping laser. The competition between these two processes resulted in a nonmonotonic dependence of the NV center’s fluorescence intensity on the NIR laser power. Fluorescence enhancement was observed with a weak NIR laser, while fluorescence depletion was observed with a high-power NIR laser. It led to the nonmonotonic change of the spatial resolution with stimulated emission depletion microscopy, which has been used for subdiffraction imaging of the NV center. Our work can help to further understand the optical mechanism and extend the applications of the NV center.
- Published
- 2020
37. Octahedral crystal-field splitting in non-conventional coordinate system
- Author
-
Fang Wen
- Subjects
Work (thermodynamics) ,Materials science ,Condensed matter physics ,Peak shift ,Coordinate system ,Substitution (logic) ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,010309 optics ,Octahedron ,Crystal field theory ,0103 physical sciences ,Electrical and Electronic Engineering ,0210 nano-technology ,Characteristic polynomial - Abstract
This work quantitatively analyzes the octahedral crystal-field effect in non-conventional coordinate setting, which is widely used in explaining the emission peak shift of phosphors. The detailed calculation process involves expansion of the crystal-field potential, the ϕ, θ integration, substitution of the radial part and solution of the secular determinant. It provides a deeper understanding of crystal-field effect.
- Published
- 2020
38. Low power charge state depletion nanoscopy of the defect in diamonds with a pulsed laser excitation
- Author
-
Xiang-Dong Chen, Deng-Feng Li, Bo Du, Fang-Wen Sun, and Guang-Can Guo
- Subjects
Materials science ,business.industry ,Resolution (electron density) ,Physics::Optics ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Laser ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,law.invention ,010309 optics ,Optics ,law ,Vacancy defect ,0103 physical sciences ,Microscopy ,Optoelectronics ,Laser power scaling ,0210 nano-technology ,Spin (physics) ,business ,Image resolution ,Excitation - Abstract
Two-photon charge state conversion has been utilized to improve the spatial resolution of the sensing and imaging with the nitrogen vacancy (NV) center in diamonds. Here, we studied the charge state conversion of the NV center under picosecond pulsed laser excitation. With the same average power, the charge state conversion rate can be improved approximately 24 times by reducing the repetition rate of the laser pulse from 80 to 1 MHz. Subsequently, a pulsed laser with a low repetition rate was applied for the super-resolution charge state depletion microscopy of the NV center. The average power of the depletion laser was reduced approximately 5 times. It can decrease the optical heating, which affects the accuracy and sensitivity of sensing. With the assistance of an additional near-infrared laser, a resolution of 12 nm was obtained with 1 mW depletion laser power. Combined with spin manipulation, we expect our results can be used for the development of a diffraction-unlimited NV center sensing.
- Published
- 2020
39. Electronic structure and photocatalytic properties of H, F modified two-dimensional GeTe
- Author
-
Zhang Peng-Cheng, Kang Wen-Bin, Zhao Jun, and Fang Wen-Yu
- Subjects
Materials science ,Band gap ,General Physics and Astronomy ,Electronic structure ,01 natural sciences ,Molecular physics ,Bond length ,Electronegativity ,Effective mass (solid-state physics) ,0103 physical sciences ,Density of states ,Density functional theory ,Direct and indirect band gaps ,010306 general physics - Abstract
Using the first principle calculation based on the density functional theory, we have systematically investigated the structure stability, electronic structure and photocatalytic properties of two-dimensional single-layered GeTe crystal structure modified by H and F. The results show that the lattice constant, bond angle and bond length of GeTe increase after being modified. The stability analysis shows that all the materials have excellent dynamical, mechanical, and thermal stabilities. The electronic structure analysis shows that the two-dimensional GeTe is an indirect bandgap semiconductor with an energy gap of 1.797 eV, and its energy band is mainly composed of Ge-4p and Te-5p, while it is converted into a direct bandgap semiconductor by H or F modification and H-F co-modification (F and Ge on one side, H and Te on the other), and their corresponding energy gaps are reduced to 1.847 eV (fH-GeTe), 0.113 eV (fF-GeTe) and 1.613 eV (hF-GeTe-hH). However, hH-GeTe-hF is still an indirect band gap semiconductor, and its energy gap is reduced to 0.706 eV. The results of the density of states show that part of the Ge-4p and Te-5p electrons are transferred to a deeper level due to the adsorption of H or F atoms, resulting in a strong orbital hybridization between them and the adsorbed atoms. The effective mass shows that the effective mass of H or F modified and H-F co-modified GeTe (F and Ge on one side, H and Te on the other) decrease, and their carrier mobilities increase. The carrier recombination rates of all modified GeTe materials are lower than that of the intrinsic GeTe, so the semiconductor will be more durable. The electron density difference shows that due to the electronegativities of atoms being different from each other, when H or F is used to modify GeTe, some electrons transfer to H and F atoms, resulting in the weakening of covalent bond between Ge and Te atoms and the enhancement of ion bond. The results of band-edge potential analysis show that GeTe can produce hydrogen and oxygen by photolysis of water. However, the valence band edge potential of the modified GeTe decreases significantly, and its oxidation ability increases considerably, the photocatalytic water can produce O2, H2, O3, OH·, etc. Optical properties show that the modified GeTe can enhance the absorption of visible and ultraviolet spectrum, which indicates that they have great application prospects in the field of photocatalysis.
- Published
- 2020
40. Improving the NV generation efficiency by electron irradiation
- Author
-
Yang Dong, Wei Zhu, Bo-Wen Zhao, Xiang-Dong Chen, Fang-Wen Sun, and Shao-Chun Zhang
- Subjects
Electromagnetic field ,Materials science ,business.industry ,Quantum sensor ,Diamond ,Electron ,engineering.material ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Magnetic field ,Optics ,Vacancy defect ,engineering ,Electron beam processing ,Optoelectronics ,Electrical and Electronic Engineering ,business ,Quantum well - Abstract
The nitrogen vacancy (NV) center in diamond has been well applied in quantum sensing of electromagnetic field and temperature, where the sensitivity can be enhanced by the number of NV centers. Here, we used electron beam irradiation to increase the generation rate of NV centers by nearly 22 times. We systematically studied the optical and electronic properties of the NV center as a function of an electron irradiation dose, where the detection sensitivity of magnetic fields was improved. With such samples with dense NV centers, a sub-pico-Tesla sensitivity in magnetic fields detection can be achieved with optimal controls and detections.
- Published
- 2020
41. Simulation Study of 4H-SiC Trench Insulated Gate Bipolar Transistor with Low Turn-Off Loss
- Author
-
Hong-kai Mao, Fang-wen Su, Xue Wu, and Ying Wang
- Subjects
010302 applied physics ,4H-SiC ,Materials science ,business.industry ,Mechanical Engineering ,turn-off loss ,Doping ,Heterojunction ,02 engineering and technology ,Insulated-gate bipolar transistor ,021001 nanoscience & nanotechnology ,IGBT ,01 natural sciences ,Article ,breakdown voltage (BV) ,Turn off ,Control and Systems Engineering ,0103 physical sciences ,Trench ,Optoelectronics ,Breakdown voltage ,ON-state voltage ,Electrical and Electronic Engineering ,0210 nano-technology ,business - Abstract
In this work, an insulated gate bipolar transistor (IGBT) is proposed that introduces a portion of the p-polySi/p-SiC heterojunction on the collector side to reduce the tail current during device turn-offs. By adjusting the doping concentration on both sides of the heterojunction, the turn-off loss is further reduced without sacrificing other characteristics of the device. The electrical characteristics of the device were simulated through the Silvaco ATLAS 2D simulation tool and compared with the traditional structure to verify the design idea. The simulation results show that, compared with the traditional structure, the turn-off loss of the proposed structure was reduced by 58.4%, the breakdown voltage increased by 13.3%, and the forward characteristics sacrificed 8.3%.
- Published
- 2019
42. Thermal-demagnetization-enhanced hybrid fiber-based thermometer coupled with nitrogen-vacancy centers
- Author
-
Hao-Bin Lin, Xiang-Dong Chen, Wei Zhu, Guanzhong Wang, Shao-Chun Zhang, Bo-Wen Zhao, Guang-Can Guo, Bo Du, Yang Dong, Fang-Wen Sun, Yu Zheng, and Shen Li
- Subjects
Physics - Instrumentation and Detectors ,Materials science ,FOS: Physical sciences ,Applied Physics (physics.app-ph) ,02 engineering and technology ,engineering.material ,01 natural sciences ,010309 optics ,0103 physical sciences ,Fiber ,business.industry ,Quantum sensor ,Demagnetizing field ,Diamond ,Instrumentation and Detectors (physics.ins-det) ,Physics - Applied Physics ,021001 nanoscience & nanotechnology ,Electronic, Optical and Magnetic Materials ,Working range ,Magnetic field ,Thermometer ,Magnet ,engineering ,Optoelectronics ,0210 nano-technology ,business ,Optics (physics.optics) ,Physics - Optics - Abstract
Nitrogen-vacancy centers in diamond are attractive as quantum sensors owing to their remarkable optical and spin properties under ambient conditions. Here we experimentally demonstrated a hybrid fiber-based thermometer coupled with nitrogen-vacancy center ensemble and a permanent magnet, where the temperature sensitivity was improved by converting the temperature variation to the magnetic field change based on the thermal-demagnetization of the permanent magnet. We have achieved both large temperature working range (room temperature to 373 K) and millikelvin sensitivity (1.6 mK/sqrt(Hz)), nearly 6-fold improvement compared with conventional technique. This stable and compact hybrid thermometer will enable a wide range of applications for large-area detection and imaging with high temperature sensitivity., 5 pages, 5 figures
- Published
- 2019
43. High-resolution multiphoton microscopy with a low-power continuous wave laser pump
- Author
-
Ze-Hao Wang, Yang Dong, Guang-Can Guo, Fang-Wen Sun, Xiang-Dong Chen, Bo Du, and Shen Li
- Subjects
Materials science ,Nitrogen ,02 engineering and technology ,engineering.material ,Signal-To-Noise Ratio ,01 natural sciences ,law.invention ,Optics ,Confocal microscopy ,law ,Vacancy defect ,0103 physical sciences ,010306 general physics ,business.industry ,Lasers ,Quantum sensor ,Diamond ,021001 nanoscience & nanotechnology ,Laser ,Atomic and Molecular Physics, and Optics ,Multiphoton fluorescence microscope ,Microscopy, Fluorescence, Multiphoton ,engineering ,Continuous wave ,0210 nano-technology ,business ,Biological imaging - Abstract
Multiphoton microscopy (MPM) has been widely used for three-dimensional biological imaging. Here, based on the photon-induced charge state conversion process, we demonstrated a low-power high-resolution MPM with a nitrogen vacancy (NV) center in diamond. Continuous wave green and orange lasers were used to pump and detect the two-photon charge state conversion, respectively. The power of the laser for multiphoton excitation was 40 μW. Both the axial and lateral resolutions were improved approximately 1.5 times compared with confocal microscopy. The results can be used to improve the resolution of the NV center-based quantum sensing and biological imaging.
- Published
- 2018
44. Improvement of refractive index profiling of a small-core single-mode fiber under partially coherent light excitation
- Author
-
Fang-Wen Sheu, Wan-Shao Tsai, and Bo-Ji Huang
- Subjects
Mode volume ,Materials science ,business.industry ,Physics::Optics ,Guided ray ,Refractive index profile ,Graded-index fiber ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Normalized frequency (fiber optics) ,Optics ,Optoelectronics ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,Radiation mode ,Step-index profile ,business ,Photonic-crystal fiber - Abstract
The refractive index profile of a non-bending small-core single-mode fiber was first reconstructed from the measured guided mode intensity profile and its spatial derivatives. By combining a rotating diffuser with a coherent laser source, the resulting partially coherent light source overcomes the speckles on the guided mode image of a straight fiber, and the corresponding refractive index profile was successfully reconstructed. Furthermore, guided mode images of a bent fiber with a fiber coil at midway were also measured under different coherency light excitations for comparison. The slight asymmetry of the reconstructed index profile of a bent fiber measured under coherent light excitation was greatly improved when measured under partially coherent light excitation. The generated additional leaky modes propagating partly in both core and cladding induced by the effects of the fundamental core mode deformation at the intermediate fiber bending structure and the mode transition at the bent-to-straight fiber section were averaged out with a low coherence transformed light source.
- Published
- 2015
45. Li fast ion conductive La0.56Li0.33TiO3 inlaid LiFePO4/C microspheres with enhanced high-rate performance as cathode materials
- Author
-
Yanqing Fu, Xiukang Yang, Li Liu, Hongbo Shu, Yongqiang Shen, Fang Wen, Xianyou Wang, Qianqian Liang, and Manfang Chen
- Subjects
Materials science ,Scanning electron microscope ,General Chemical Engineering ,Analytical chemistry ,chemistry.chemical_element ,Electrochemistry ,Cathode ,Electrochemical cell ,law.invention ,Dielectric spectroscopy ,chemistry ,law ,Transmission electron microscopy ,Lithium ,Inductively coupled plasma - Abstract
Monodisperse spherical La 0.56 Li 0.33 TiO 3 inlaid LiFePO 4 /C composites with various La 0.56 Li 0.33 TiO 3 content (from 0 wt . % to 3 wt. %) are firstly prepared by an ammonia assisted hydrothermal route. The compositions, morphology and structure of samples are characterized by means of inductively coupled plasma (ICP), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), respectively. The results reveal that nano La 0.56 Li 0.33 TiO 3 particles inlay on the surface of spherical LiFePO 4 , which is coated by a continuous and uniform carbon layer with the thickness of 1∼2 nm. The charge/discharge tests and electrochemical impedance spectroscopy (EIS) measurements indicate that the kinetics of La 0.56 Li 0.33 TiO 3 inlaid LiFePO 4 /C is better than that of LiFePO 4 /C. With the change of La 0.56 Li 0.33 TiO 3 content, 2 wt. % La 0.56 Li 0.33 TiO 3 inlaid LiFePO 4 /C composites reveal a excellent high-rate capability and cycling stability. The initial discharge capacity of the sample is 126.3 and 108.9 mAh/g, and the capacity retention achieves as high as 98.3% and 88.8% till 100 cycles at 5 C and 200 cycles at 10 C, respectively. Furthermore, it still exhibits a high discharge capacity of 62.3 mAh/g even at high rate of 30 C. The improved electrochemical performance of La 0.56 Li 0.33 TiO 3 inlaid LiFePO 4 /C composites can be attributed to reduce the charge transfer resistance and enhance the transfer kinetics of both the lithium ions and electrons.
- Published
- 2015
46. Highly Efficient Rectangular Pulse Emission in a Mode-Locked Fiber Laser
- Author
-
Shumin Zhang, Huaxing Zhang, Xingliang Li, Mengmeng Han, Fang Wen, and Zhenjun Yang
- Subjects
Femtosecond pulse shaping ,Materials science ,business.industry ,Physics::Optics ,Pulse duration ,Laser ,Q-switching ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,law.invention ,Dissipative soliton ,Optics ,law ,Fiber laser ,Laser power scaling ,Electrical and Electronic Engineering ,business ,Bandwidth-limited pulse - Abstract
Dissipative soliton resonance (DSR) has been experimentally investigated in a nonlinear polarization rotation (NPR) mode-locked Yb-doped fiber laser with a long cavity. The adjustable nonlinear transmission function of the NPR and the relatively large nonlinearity of the long cavity play key roles in the formation of high energy rectangular pulses in the DSR region. The intracavity optical-to-optical efficiency can be as high as 46%, and the maximum pulse energy can reach 54.6 nJ with the relatively low pump power of 299 mW. This is so far the highest efficiency in a DSR laser operated at 1-µm wavelength yet achieved to our knowledge. Furthermore, while maintaining the pulse amplitude almost constant and without the appearance of wave-breaking phenomena, the pulse duration could be tuned from 54 to 91 ns by increasing only the pump power.
- Published
- 2014
47. High-energy, tunable-wavelengths, Q-switched pulse laser
- Author
-
Shumin Zhang, Xingliang Li, Zhenjun Yang, Mengmeng Han, Huaxing Zhang, and Fang Wen
- Subjects
Distributed feedback laser ,Materials science ,business.industry ,Physics::Optics ,Pulse duration ,Saturable absorption ,Laser ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,law.invention ,Pulsed laser deposition ,Wavelength ,Interferometry ,Optics ,law ,Fiber laser ,Optoelectronics ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,business - Abstract
An all fiber, wavelength tunable, Q-switched erbium-doped fiber laser (EDFL) based on a graphene saturable absorber (SA) and an unbalanced Mach–Zehnder interferometer (UMZI) has been demonstrated. The wavelengths of the Q-switched laser can be accurately tuned over a range of ~35 nm by inserting into the cavity an UMZI with a variable optical delay line (OVDL) in one arm, which acts as an optical beam filter into the cavity. The Q-switched pulse duration and the pulse energy have all been characterized. The maximum pulse energy of 36.9 nJ was obtained.
- Published
- 2014
48. Refractive index profiling of a few-mode fiber from fundamental mode excitation
- Author
-
Wan-Shao Tsai, Sy-Hann Chen, Yao-Hsuan Wang, Che-Kai Chang, and Fang-Wen Sheu
- Subjects
Mode volume ,Materials science ,business.industry ,Physics::Optics ,Polarization-maintaining optical fiber ,Refractive index profile ,Graded-index fiber ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Optics ,Normalized frequency (fiber optics) ,Optoelectronics ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,Radiation mode ,business ,Step-index profile ,Photonic-crystal fiber - Abstract
The fundamental mode of a small-core step-index few-mode fiber, originally designed for single-mode operation at 1310/1550 nm, was selectively excited at visible wavelengths from a single-mode fiber by adiabatically tapering the fusion splice. A two-dimensional refractive index profile of the few-mode fiber was reconstructed directly from measured guided mode intensity distribution and its spatial partial derivatives with a modified end-fire coupling method using a differential inverse calculation algorithm, which applies only for single-mode guiding.
- Published
- 2014
49. Preparation of Antimicrobial PHEMA-g-PCBMAE Hydrogels with Improved Mechanical Properties
- Author
-
Pi Hui Pi, Shou Ping Xu, Jiang Cheng, Xiu Fang Wen, Qin Liu, and Ren Chang Zeng
- Subjects
chemistry.chemical_compound ,Differential scanning calorimetry ,Materials science ,chemistry ,Polymerization ,Chemical engineering ,Self-healing hydrogels ,Biomaterial ,Chain transfer ,General Medicine ,(Hydroxyethyl)methacrylate ,Raft ,Methacrylate - Abstract
A series of poly (hydroxyethyl methacrylate)-g-polycarboxybetaine methacrylate ester (PHEMA-g-PCBMAE) hydrogels were synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization in the presence of crosslinker. Then differential scanning calorimetry (DSC) was used to characterize PHEMA-g-PCBMAE hydrogels. The compression stresses of these hydrogels were investigated to evaluate the mechanical properties. The mechanical study suggested that PHEMA-g-PCBMAE hydrogels presented improved mechanical strengths comparing with polycarboxybetaine methacrylate ester (PCBMAE) hydrogel. Besides, the antimicrobial properties of PHEMA-g-PCBMAE hydrogels also estimated by usingStaphylococcus aureusas a model bacterial.
- Published
- 2014
50. Cholesterol Effects on the Vesicular Membrane Rigidity and Drug Encapsulation Efficiency of Ethosome-Like Catanionic Vesicles
- Author
-
Chih Fang Wen, Yu Min Yang, and Yu San Liu
- Subjects
chemistry.chemical_compound ,Phase transition temperature ,Materials science ,Chromatography ,chemistry ,Cholesterol ,Vesicle ,Biophysics ,Drug encapsulation ,General Materials Science ,Membrane rigidity - Published
- 2014
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