27 results on '"Haihua Tao"'
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2. Stabilizing the reversible capacity of SnO2/graphene composites by Cu nanoparticles
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Yong Jiang, Wenrong Li, Bing Zhao, Haihua Tao, Shoushuang Huang, Wei Jiang, Yanyan Wan, and Zhiwen Chen
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Materials science ,Graphene ,General Chemical Engineering ,Composite number ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Industrial and Manufacturing Engineering ,0104 chemical sciences ,law.invention ,Anode ,Adsorption ,chemistry ,Chemical engineering ,law ,Environmental Chemistry ,Lithium ,0210 nano-technology ,Capacity loss ,Tin - Abstract
Low electronic conductivity and the tin coarsening caused irreversible capacity loss are the primary cause of poor cycle performances in SnO2 materials. In this work, a ternary SnO2/Cu/graphene composite is synthesized by a one-pot selective reduction method to improve the cycle life of SnO2-based composite anode. During the liquid-phase synthesis process, the Cu2+ and Sn2+ cations are adsorbed uniformly on the surface of GO sheets under electrostatic attraction, which are then selective reduced by N2H4·H2O because of its moderate reduction falling in between these two components (Eϴ(Cu2+/Cu) 0.34 V > Eϴ(Sn2+/Sn) −0.14 V). The electrochemical active SnO2 and inactive Cu nanoparticles anchor tightly on the flexible conductive graphene sheets and locate in close proximity to each other. Cu nanoparticles can promote the charge transfer kinetics of insulating SnO2 at the interfaces, compress the volume stress as lithium ions insertion/deinsertion, and obstruct the aggregation of metallic Sn and LixSn alloy, thus continuously promoting the reversibility of conversion reaction from Sn/Li2O to SnO2. The as-prepared composite displays an excellent long-term cycling stability, delivering a reversible capacity of 890.6 mAh g−1 at 100 mAg−1 even after 200 cycles without any capacity decay. The excellent cyclic stability and facile liquid-phase synthesis method demonstrate the promising candidate of the Cu nanoparticles in stabilizing the reversible capacity of SnO2/graphene composite and its candidate in scalable application.
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- 2019
3. Composition-dependent lithium storage performances of SnS/SnO2 heterostructures sandwiching between spherical graphene
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Haihua Tao, Zhiwen Chen, Yong Jiang, Yaqing Yang, Shoushuang Huang, Zhixuan Wang, Jinlong Jiang, Yanyan Wang, Hua Zhuang, and Bing Zhao
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Materials science ,Graphene ,General Chemical Engineering ,Composite number ,chemistry.chemical_element ,Nanoparticle ,Heterojunction ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Electron transport chain ,0104 chemical sciences ,law.invention ,Ion ,chemistry ,Chemical engineering ,law ,Lithium ,0210 nano-technology - Abstract
Heterostructures have broad potential application in energy conversion material and optoelectronic device since of novel interface effect and enhanced electron transport dynamics at heterointerfaces. Herein, we report a heterostructured SnS/SnO2/spherical graphene composite, in which ultrafine SnS/SnO2 nanoparticles with heterostructures are sandwiched between multi-layers of graphene sheets, exhibiting a hollow spherical architecture as a whole. Detailed electrochemical studies indicate that the molar ratio of SnS to SnO2 has great influence on the charge transport efficiency. Theoretical calculation reveals that SnS and SnO2 exhibit different work functions and the Fermi level shift is affected by the SnS/SnO2 molar ratio, thus the hybrid with the ratio close to 1.0 owns the most adsorbed lithium ions, which leads to the highest specific charge-transfer kinetics and lowest ion-diffusion resistance than other samples. Electrochemical tests show that the composite with appropriate composition delivers the best lithium storage rate performance (620 and 312.7 mAh g−1 at 1 C and 10 C). A much stable and high reversible specific capacity of 850 mAh g−1 is obtained after 200 cycles at 0.1 C. The appropriate molar ratio of nano-heterostructures and the novel sandwich hollow spherical composite structure are attributed to the excellent electrochemical performances.
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- 2019
4. Hierarchically assembled 3D nanoflowers and 0D nanoparticles of nickel sulfides on reduced graphene oxide with excellent lithium storage performances
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Zheng Jiao, Bing Zhao, Zhiwen Chen, Yong Jiang, Nguyen Tronganh, Yang Gao, Wei Jiang, Haihua Tao, and Shanshan Wang
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Materials science ,Composite number ,Oxide ,General Physics and Astronomy ,Nanoparticle ,chemistry.chemical_element ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,law.invention ,chemistry.chemical_compound ,law ,Nanocomposite ,Graphene ,Heterojunction ,Surfaces and Interfaces ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,0104 chemical sciences ,Surfaces, Coatings and Films ,Tetraethyl orthosilicate ,chemistry ,Lithium ,0210 nano-technology - Abstract
Constructing heterostructure can endow composites with many novel physical and electrochemical properties due to the built-in specific charge transfer dynamics. However, controllable fabrication route to heterostructures is still a great challenge up to now. In this work, a SiO2-assisted hydrothermal method is developed to fabricate heterostructured nickel sulfides/reduced graphene oxide (NiSx/rGO) composite. The SiO2 particles hydrolyzed from tetraethyl orthosilicate could assist the surface controllable co-growth of 3D nanoflowers and 0D nanoparticles of Ni3S2/NiS decorated on reduced graphene oxide, and the possible co-growth mechanism is discussed in detail. In this composite, the heterostructured nanocomposite with different morphologies, chemical compositions and crystal structures, along with varied electronic states and band structure, can promote the interface charge transfer kinetics and lead to excellent lithium storage performances. Electrochemical measurements reveal that the NiSx/rGO composite presents 1187.0 mA h g−1 at 100 mA g−1 and achieves a highly stable capacity of 561.2 mA h g−1 even when the current density is up to 5 A g−1.
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- 2018
5. UV Rewritable Hybrid Graphene/Phosphor p-n Junction Photodiode
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Xiang Ma, Shubin Su, He Tian, Zhenhua Ni, Xianfeng Chen, Haihua Tao, Chenhui Liang, Meizhen Huang, Hao Li, Ting Zhang, and Xuhong An
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Materials science ,Photoisomerization ,business.industry ,Graphene ,Doping ,02 engineering and technology ,Photodetection ,010402 general chemistry ,021001 nanoscience & nanotechnology ,medicine.disease_cause ,01 natural sciences ,0104 chemical sciences ,Photodiode ,law.invention ,law ,medicine ,Optoelectronics ,General Materials Science ,0210 nano-technology ,business ,p–n junction ,Ultraviolet ,Visible spectrum - Abstract
Graphene-based p-n junction photodiodes have a potential application prospect in photodetection due to their broadband spectral response, large operating bandwidth, and mechanical flexibility. Here, we report an ultraviolet (UV) rewritable p-n junction photodiode in a configuration of graphene coated with an amorphous phosphor of 4-bromo-1,8-naphthalic anhydride derivative polymer (poly-BrNpA). Under moderate UV irradiation, occurrence of photoisomerization reaction in the poly-BrNpA film leads to its drastically modified optical characteristics and a concurrent n-type doping in the underneath graphene. Meanwhile, the poly-BrNpA film, highly sensitive to water molecules, has a capability of restoring graphene to its initial p-type doping status by means of water adsorption. Based on these findings, a lateral graphene/poly-BrNpA p-n junction photodiode, responsive to visible light at the junction interface, can be written by UV irradiation and then erased via water adsorption. The p-n junction photodiode is rewritable upon such repetitive loops showing repeatable optoelectronic properties. This study provides a new scheme and perspective of making graphene-based rewritable p-n junction photodiodes in a flexible and controllable way, and it may contribute to expanding new families of optoelectronic devices based on two-dimensional materials.
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- 2019
6. Ultraviolet photodetector based on the hybrid graphene/phosphor field-effect transistor
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Meizhen Huang, Xiang Ma, Guanghui Yu, Shubin Su, Hao Li, Haihua Tao, and Chenhui Liang
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Materials science ,Photodetector ,02 engineering and technology ,Specific detectivity ,010402 general chemistry ,medicine.disease_cause ,01 natural sciences ,law.invention ,Inorganic Chemistry ,Responsivity ,law ,medicine ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,Spectroscopy ,Photocurrent ,business.industry ,Graphene ,Organic Chemistry ,021001 nanoscience & nanotechnology ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Photodiode ,Optoelectronics ,Field-effect transistor ,0210 nano-technology ,business ,Ultraviolet - Abstract
Recently, a hybrid graphene/poly-BrNpA phosphor structure was used to fabricate rewritable p-n junction photodiode responsive to visible light. In this process, photoisomerization occurred under moderate ultraviolet (UV) irradiation (λ = 365 nm, optical intensity IUV = 1.318 μW μm−2), and the subsequent water (H2O) molecule adsorption facilitate charge transfer at the interface. In this study, we explore the feasibility of making UV photodetector based on the hybrid graphene/poly-BrNpA field-effect transistor. The incident UV light (λ = 365 nm, IUV≤1.81 × 10−4 μW μm−2), which is at least four orders weaker than that used to induce observable photoisomerization in the phosphor, is mostly absorbed to create photo-induced electron-hole pairs. The subsequent separation and transfer of the photo-induced electrons to graphene contribute to high photocurrent by the photogating effect. The photodetector has a responsivity and specific detectivity up to 159 A W−1 and 1.55 × 1011 Jones, respectively, when biased at VDS = 1 V. The photodetector has a slow response, especially to UV shut-off with the fall time τF up to 881 s. By virtue of H2O molecule adsorption, τF can be reduced to 6.6 s by accelerating the reversion and recombination of electrons with the photo-induced holes trapped in the poly-BrNpA film through introducing defect states. This work brings a new perspective for developing photodetectors through combining the functional two-dimensional materials and phosphors.
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- 2020
7. Exploring the working mechanism of graphene patterning by magnetic-assisted UV ozonation
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Shubin Su, Haihua Tao, Wu Yixuan, Huan Yue, Xianfeng Chen, Hao Li, and Zhenhua Ni
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Magnetic moment ,Chemistry ,Graphene ,Intermolecular force ,Inorganic chemistry ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,medicine.disease_cause ,01 natural sciences ,Oxygen ,0104 chemical sciences ,law.invention ,Paramagnetism ,Chemical physics ,law ,medicine ,Molecule ,Diamagnetism ,Physical and Theoretical Chemistry ,0210 nano-technology ,Ultraviolet - Abstract
When assisted with an inhomogenous vertical magnetic field, ultraviolet (UV) ozonation turns directional and is testified to be applicable to graphene patterning. Using a more cost-effective low-pressure mercury lamp, we further explore the underlying working mechanism by changing oxygen content, introducing reactive ozone or inert nitrogen molecules, and study the lateral under-oxidation impeded Dirac point shifts for a graphene field-effect transistor under UV irradiation. The paramagnetic oxygen molecule X3Σ−g accelerates toward graphene with the magnetic moment aligned parallel to the magnetic field. The O(3P) atoms, stemming from such a directional oxygen molecule, have a high initial velocity before being further accelerated, and therefore enhance the oxidation capability compared with those from weak diamagnetic ozone molecules. Intermolecular or atomic-molecular collisions between the high-speed oxygen molecules/atoms and the randomly moved weak diamagnetic molecules, including nitrogen and ozone, appear crucial in deteriorating graphene patterning by increasing the lateral under-oxidation. This study may shed light on our understanding of graphene patterning by magnetic-assisted UV ozonation.
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- 2017
8. Patterning Graphene Film by Magnetic-assisted UV Ozonation
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Shubin Su, Ziyu Zhang, Wu Yixuan, Haihua Tao, Hao Li, Zhenhua Ni, Huan Yue, and Xianfeng Chen
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Materials science ,chemistry.chemical_element ,02 engineering and technology ,Chemical vapor deposition ,Substrate (electronics) ,010402 general chemistry ,medicine.disease_cause ,01 natural sciences ,Article ,law.invention ,Paramagnetism ,Xenon ,law ,medicine ,Microscale chemistry ,Multidisciplinary ,business.industry ,Graphene ,021001 nanoscience & nanotechnology ,Excimer lamp ,0104 chemical sciences ,chemistry ,Optoelectronics ,0210 nano-technology ,business ,Ultraviolet - Abstract
Developing an alternative method for fabricating microscale graphene patterns that overcomes the obstacles of organic contamination, linewidth resolution, and substrate damaging is paramount for applications in optoelectronics. Here we propose to pattern chemical vapor deposition grown graphene film through a stencil mask by magnetic-assisted ultraviolet (UV) ozonation under irradiation of a xenon excimer lamp. In this process, the paramagnetic oxygen molecules and photochemically generated oxygen radicals are magnetized and attracted in an inhomogenous external magnetic field. As a consequence, their random motions convert into directional, which can greatly modify or enhance the quality of graphene patterns. Using a ferromagnetic steel mask, an approximately vertical magnetic-field-assisted UV ozonation (BZ = 0.31 T, ∇BZ = 90 T · m−1) has a capability of patterning graphene microstructures with a line width of 29 μm and lateral under-oxidation less than 4 μm. Our approach is applicable to patterning graphene field-effect transistor arrays, and it can be a promising solution toward resist-free, substrate non-damaging, and cost effective microscale patterning of graphene film.
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- 2017
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9. Intergrown SnO2–TiO2@graphene ternary composite as high-performance lithium-ion battery anodes
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Saisai Xia, Shuai Yuan, Zheng Jiao, Laiqiang Xu, Haijiao Zhang, Haihua Tao, and Renmei Gao
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Battery (electricity) ,Nanostructure ,Materials science ,Graphene ,Inorganic chemistry ,Composite number ,Nanoparticle ,Bioengineering ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Lithium-ion battery ,0104 chemical sciences ,Anode ,law.invention ,Chemical engineering ,law ,Modeling and Simulation ,General Materials Science ,0210 nano-technology ,Ternary operation - Abstract
In recent years, a lot of metal oxides with high theoretical capacity have widely investigated as the high-performance anode materials for lithium-ion batteries (LIBs). In this work, a simple, facile and effective one-pot hydrothermal strategy toward ternary SnO2–TiO2@graphene composite has been developed by using SnCl2 and TiOSO4 as the starting materials. The obtained composite demonstrates a unique structure and high surface areas, in which both SnO2 and TiO2 nanoparticles are well grown on the surface of graphene. More interestingly, the SnO2 and TiO2 nanoparticles are intergrowth together, totally different with the traditional ternary hybrids. When used as anode material for LIBs, the introduction of TiO2 plays a crucial role in maintaining the structural stability of the electrode during Li+ insertion/extraction, which can effectively prevent the aggregation of SnO2 nanoparticles. The electrochemical tests indicate that as-prepared SnO2–TiO2@graphene composite exhibits a high capacity of 1276 mA h g−1 after 200 cycles at the current density of 200 mA g−1. Furthermore, the composite also maintains the specific capacity of 611 mA h g−1 at an ultrahigh current density of 2000 mA g−1, which is superior to those of the reported SnO2 and SnO2/graphene hybrids. Accordingly, the remarkable electrochemical performance of ternary SnO2–TiO2@graphene composites is mainly attributed to their unique nanostructure, high surface areas, and the synergistic effect not only between graphene and metal oxides but also between the intergrown SnO2 and TiO2 nanoparticles. Intergrown SnO2 and TiO2 nanoparticles have been successfully anchored onto the graphene nanosheets as high-performance lithium-ion battery anodes.
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- 2016
10. Supercapacitor performances of thermally reduced graphene oxide
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Dengyu Pan, Weiwen Xu, Haihua Tao, Yong Jiang, Bing Zhao, Jinsong Song, Tao Fang, and Peng Liu
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Supercapacitor ,Materials science ,Renewable Energy, Sustainability and the Environment ,Graphene ,Graphene foam ,Inorganic chemistry ,Energy Engineering and Power Technology ,Graphite oxide ,Capacitance ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Pyrolytic carbon ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,Composite material ,Graphene nanoribbons ,Graphene oxide paper - Abstract
In this paper, graphene sheets with different reduction levels have been produced through thermal reduction of graphene oxide in the temperature range of 200–900 °C. The effects of interlayer spacing, oxygen content, BET specific surface area and disorder degree on their specific capacitance were explored systematically. The variation of oxygen-containing groups was shown to be a main factor influencing the EDL capacitor performances of the pyrolytic graphene. The highest capacitance of 260.5 F g −1 at a charge/discharge current density of 0.4 A g −1 was obtained for the sample thermally reduced at about 200 °C.
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- 2012
11. The Morphology of Graphene Sheets Treated in an Ozone Generator
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Joel Moser, Haihua Tao, C. M. Sotomayor-Torres, Qian Wang, Francesc Alzina, Ministerio de Ciencia e Innovación (España), and European Commission
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Materials science ,Ozone ,chemistry.chemical_element ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Oxygen ,law.invention ,chemistry.chemical_compound ,symbols.namesake ,law ,Phase (matter) ,Graphite ,Physical and Theoretical Chemistry ,Graphene ,021001 nanoscience & nanotechnology ,Nanocrystalline material ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,General Energy ,Amorphous carbon ,chemistry ,Chemical engineering ,symbols ,0210 nano-technology ,Raman spectroscopy - Abstract
Using atomic force microscopy and Raman spectroscopy, we characterize the highly disordered morphology of single-layer and multilayer graphene sheets that results from long exposures to ozone molecules and oxygen radicals in an ozone generator. We identify a crossover from a nanocrystalline phase to an amorphous carbon phase in single-layer graphene as the exposure time is increased. We then consider the nanocrystalline phase and compare the morphology of single-layer sheets, multilayer sheets, and graphite flakes. Finally, we find that salient structures, such as steps and folds, act as sinks for disorder. © 2011 American Chemical Society., Support from the Spanish Ministry of Science and Innovation (projects FIS2008-06830 and FIS2009-10150) and the EU project NANOPACK (project no. 216176) is gratefully acknowledged.
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- 2011
12. Low temperature synthesis of mesoporous silicon carbide via magnesiothermic reduction
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Minghong Wu, Zhijin Tan, Zheng Jiao, Haijiao Zhang, Bing Zhao, and Haihua Tao
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Materials science ,Silicon ,Magnesium ,Mechanical Engineering ,Metallurgy ,chemistry.chemical_element ,Mesoporous silica ,Condensed Matter Physics ,Carbide ,chemistry.chemical_compound ,Mesoporous organosilica ,chemistry ,Chemical engineering ,Mechanics of Materials ,Silicon carbide ,General Materials Science ,Mesoporous material ,Carbon - Abstract
Mesoporous silicon carbides (SiC) with high surface areas (above 300 m2/g) have been prepared successfully at a relative low temperature of 650 °C via magnesiothermic reduction of mesoporous silica/carbon (SiO2/C) composites. The physicochemical properties and the structure of the products were characterized by various techniques such as XRD, FT-IR, SEM, TEM and N2 adsorption–desorption isotherm. The experimental results indicate that the obtained SiC materials by this new method have similar structure to corresponding silica matrix templates. It was found that the magnesium (Mg) plays an important role in determining the structure and properties of the final products, which is used as a dual role agent both reducer and catalyst. The formation mechanism of mesoporous SiC has been also discussed.
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- 2011
13. Multichannel filters with shape designing in two-dimensional photonic crystal slabs
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Ya-Zhao Liu, Shuai Feng, Jie Tian, Cheng Ren, Haihua Tao, Zhi-Yuan Li, Bing-Ying Cheng, Dao-Zhong Zhang, and Qiang Luo
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Light filters -- Usage ,Photonics -- Optical properties ,Optics -- Research ,Physics - Abstract
The effect of the irregular shape of air holes on the optical characteristics channel-drop filters built in a two-dimensional photonic crystal (PhC) slab is examined. The results have shown the importance of shape engineering of the atoms of PhC devices as a new freedom to tune the optical characteristics of these devices.
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- 2007
14. Quasi-Talbot effect of the sub-wavelength Ag grating
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Xia Wan, Qingkang Wang, and Haihua Tao
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Materials science ,Holographic grating ,business.industry ,Surface plasmon ,Physics::Optics ,Dielectric ,Grating ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,law.invention ,Ultrasonic grating ,Optics ,law ,Blazed grating ,Talbot effect ,Physics::Atomic Physics ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,business ,Beam (structure) - Abstract
When a TM-polarized beam incidents normally on a thick sub-wavelength Ag grating with small opening ratio, self-images form in the transparent dielectric layer due to contributions not only from waves radiating from the slits, but also from the Surface Plasmons (SPs) created on Ag surface. These two contributions make the self-images connect together along the propagation direction and form continuous stripes with period equal to half of that of the grating. We define this phenomenon as quasi-Talbot effect. For a thin sub-wavelength Ag grating or a grating with large opening ratio, its intensity distribution conforms to the conventional Talbot effect. Investigation on quasi-Talbot effect of sub-wavelength metal grating can develop new applications in nano-scale devices.
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- 2010
15. Ordered CoO/CMK-3 nanocomposites as the anode materials for lithium-ion batteries
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Zheng Jiao, Haihua Tao, Minghong Wu, Haijiao Zhang, Bing Zhao, and Yong Jiang
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Materials science ,Nanocomposite ,Renewable Energy, Sustainability and the Environment ,Inorganic chemistry ,Energy Engineering and Power Technology ,chemistry.chemical_element ,Nanoparticle ,Lithium battery ,Anode ,chemistry ,Lithium ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,Mesoporous material ,Carbon ,Cobalt - Abstract
A novel ordered mesoporous carbon hybrid composite, CoO/CMK-3, is prepared by an infusing method using Co(NO 3 ) 2 ·6H 2 O as the cobalt source. The products are characterized by X-ray diffraction, transmission electron microscopy and N 2 adsorption–desorption analysis techniques. It is observed that the CoO nanoparticles are loaded in the channels of mesoporous carbon. The mesopore structure of CMK-3 is destroyed gradually with increasing of the CoO content. The electrochemical properties of samples as the anode materials for lithium-ion batteries are studied by galvanostatic method. The results show that the CoO/CMK-3 composites have higher reversible capacities (more than 700 mAh g −1 ) and better cycle performance in comparison with the pure mesoporous carbon (CMK-3). Based on the above results, a mechanism is proposed to explain the reason of such a substantial improvement of electrochemical performance in the CoO/CMK-3 composites.
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- 2010
16. Morphology and electrical properties of carbon coated LiFePO4 cathode materials
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Haijiao Zhang, Zheng Jiao, Mingyang Zhong, Haihua Tao, Bing Zhao, and Yong Jiang
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Materials science ,Renewable Energy, Sustainability and the Environment ,Composite number ,Energy Engineering and Power Technology ,chemistry.chemical_element ,Mineralogy ,Chemical vapor deposition ,Polyvinyl alcohol ,Grain size ,symbols.namesake ,chemistry.chemical_compound ,Amorphous carbon ,chemistry ,Chemical engineering ,symbols ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,Raman spectroscopy ,Carbon ,Powder diffraction - Abstract
Core-shell LiFePO 4 @C composites were synthesized successfully from FePO 4 /C precursor using the polyvinyl alcohol (PVA) as the reducing agent, followed by a chemical vapor deposition (CVD) assisted solid-state reaction in the presence of Li 2 CO 3 . Some physical and chemical properties of the products were characterized by X-ray powder diffraction (XRD), Raman, SEM, TEM techniques. The effect of morphology and electrochemical properties of the composites were thoroughly investigated. XRD patterns showed that LiFePO 4 has an order olivine structure with space group of Pnma . TEM micrographs exhibited that the LiFePO 4 particles encapsulated with 3-nm thick carbon shells. The powders were homogeneous with grain size of about 0.8 μm. Compared with those synthesized by traditional organic carbon source mixed method, LiFePO 4 @C composite synthesized by CVD method exhibited better discharge capacity at initial 155.4 and 135.8 mAh g −1 at 0.1C and 1C rate, respectively. It is revealed that the carbon layer coated on the surface of LiFePO 4 and the amorphous carbon wrapping and connecting the particles enhanced the electronic conductivity and rate performances of the cathode materials.
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- 2009
17. Making few-layer graphene photoluminescent by UV ozonation
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Guqiao Ding, Haihua Tao, Hao Li, Xianfeng Chen, Ziyu Zhang, and Zhenhua Ni
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Materials science ,Photoluminescence ,Graphene ,02 engineering and technology ,Substrate (electronics) ,010402 general chemistry ,021001 nanoscience & nanotechnology ,medicine.disease_cause ,01 natural sciences ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,law.invention ,Chemical engineering ,Impurity ,law ,medicine ,Thin film ,0210 nano-technology ,Luminescence ,Silicon oxide ,Ultraviolet - Abstract
Ultraviolet (UV) ozonation is employed for making graphene photoluminescent. We find that photoluminescence (PL) varies with the ozonation temperature. For room-temperature ozonized few-layer graphene (FLG), PL is localized at the edges and in the suspended areas of FLG. At an ozonation temperature of 120 °C, PL localized at the edges of FLG disappears, and the surface of trilayer graphene becomes luminescent. These graphene flakes are topographically and chemically characterized to understand the origin of PL. We propose that sp2 clusters play a key role in making graphene photoluminescent, and that intact carbon layers and charged impurities at the surface of silicon oxide substrate may quench PL.
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- 2016
18. Magnetotransport in disordered graphene exposed to ozone: From weak to strong localization
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Joel Moser, C. M. Sotomayor Torres, Stephan Roche, Adrian Bachtold, Haihua Tao, Francesc Alzina, European Science Foundation, European Commission, and Ministerio de Ciencia e Innovación (España)
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Ozone ,Materials science ,Condensed matter physics ,Orders of magnitude (temperature) ,Graphene ,Conductivity ,Condensed Matter Physics ,Gate voltage ,Electronic, Optical and Magnetic Materials ,law.invention ,Weak localization ,chemistry.chemical_compound ,Mild disorder ,chemistry ,Electrical resistivity and conductivity ,law - Abstract
6 páginas, 7 figuras.-- PACS number(s): 72.80.Vp, 72.15.Rn, We present a magnetotransport study of graphene samples into which a mild disorder was introduced by exposure to ozone. Unlike the conductivity of pristine graphene, the conductivity of graphene samples exposed to ozone becomes very sensitive to temperature: it decreases by more than three orders of magnitude between 100 and 1 K. By varying either an external gate voltage or temperature, we continuously tune the transport properties from the weak to the strong localization regime. We show that the transition occurs as the phase coherence length becomes comparable to the localization length. We also highlight the important role of disorder-enhanced electron-electron interaction on the resistivity., This work was supported by a EURYI grant, the EU under Grant No. FP6-IST-021285-2, and the MICINN under Grants No. FIS2008-06830 and No. FIS2009-10150. S.R. acknowledges the ANR/P3N2009 (NANOSIM-GRAPHENE Project No. ANR-09-NANO-016-01).
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- 2010
19. Damaging graphene with ozone treatment: A chemically tunable metal - Insulator transition
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Jean-Christophe Charlier, Adrian Bachtold, Joel Moser, Francesc Alsina, Aurélien Lherbier, Clivia M. Sotomayor Torres, Nicolas Leconte, Haihua Tao, Stephan Roche, and Pablo Ordejón
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Materials science ,Disordered graphene ,Ab initio ,General Physics and Astronomy ,Epoxide ,Nanotechnology ,Numerical simulation ,02 engineering and technology ,01 natural sciences ,law.invention ,chemistry.chemical_compound ,law ,0103 physical sciences ,General Materials Science ,Metal–insulator transition ,010306 general physics ,Graphene ,Scattering ,General Engineering ,021001 nanoscience & nanotechnology ,Thermal conduction ,Metal−insulator transition ,Quantum transport ,chemistry ,Chemical physics ,Ozone treatment ,Surface modification ,Nanometre ,0210 nano-technology - Abstract
6 paginas., We present a multiscale ab initio study of electronic and transport properties of two-dimensional graphene after epoxide functionalization via ozone treatment. The orbital rehybridization induced by the epoxide groups triggers a strong intervalley scattering and changes dramatically the conduction properties of graphene. By varying the coverage density of epoxide defects from 0.1 to 4%, charge conduction can be tuned from a diffusive to a strongly localized regime, with localization lengths down to a few nanometers long. Experimental results supporting the interpretation as a metal−insulator transition are also provided.
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- 2010
- Full Text
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20. Mapping of complex optical field patterns in multimode photonic crystal waveguides by near-field scanning optical microscopy
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Hai-Qiang Ma, Yazhao Liu, Haihua Tao, Zhi-Yuan Li, Rong-Juan Liu, Ze-Bo Zhang, Daozhong Zhang, Cheng Ren, Shuai Feng, Ling-An Wu, and Bingying Cheng
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Waveguide (electromagnetism) ,Materials science ,Silicon photonics ,Multi-mode optical fiber ,Wave propagation ,business.industry ,Physics::Optics ,Optical field ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Wavelength ,Optics ,Dispersion (optics) ,Optoelectronics ,Near-field scanning optical microscope ,business - Abstract
We use near-field scanning optical microscopy (NSOM) operating in collection mode to map the optical field distribution of continuous wave infrared light propagating along an air-bridged W3 silicon photonic crystal (PC) slab multimode waveguide in a subwavelength resolution. The detected near-field optical intensity distribution patterns show very different longitudinal propagation features and transverse field profiles at different wavelength ranges. We have analyzed the dispersion of the guided modes in the PC waveguide and the corresponding eigenfield profile for each guided mode by means of the three-dimensional plane-wave expansion simulations. It is found that the experimentally observed complex while interesting near-field pattern features can be well explained by the field profiles of the multiple waveguide modes and their superposition at different excitation wavelengths. The detection and analysis of this multimode PC slab waveguide via NSOM could help us to understand complex wave propagation behavior and to further design novel PC devices.
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- 2006
21. Tunable surface plasmons interference patterns with the same mask in nanolithography
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Qingkang Wang, Xia Wan, and Haihua Tao
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Materials science ,business.industry ,Surface plasmon ,General Engineering ,Physics::Optics ,Photoresist ,Grating ,Atomic and Molecular Physics, and Optics ,Wavelength ,Optics ,Nanolithography ,Interference (communication) ,Dispersion (optics) ,Optoelectronics ,Nuclear Experiment ,business ,Refractive index - Abstract
When a transverse magnetic-polarized beam illuminates normally on an Ag grating mask with sub-wavelength slits, the surface plasmon (SP) interference patterns are formed on the Ag surface. According to the dispersion relationship of SPs, the wavelength of SPs (λsp) is tunable by altering the refractive index of the photoresist or the illumination wavelength. Various λsp form interference patterns with different size. The interference patterns are tunable using the same mask with period microns in size, which can save the cost of fabricating a different mask. This method will have potential applications to nanolithography.
- Published
- 2012
22. Near-field observation of anomalous optical propagation in photonic crystal coupled-cavity waveguides
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Daozhong Zhang, Cheng Ren, Yazhao Liu, Qingkang Wang, Zhi-Yuan Li, and Haihua Tao
- Subjects
Physics ,business.industry ,Impedance matching ,Near and far field ,Slow light ,Atomic and Molecular Physics, and Optics ,law.invention ,Wavelength ,Optics ,law ,Group velocity ,Optoelectronics ,Near-field scanning optical microscope ,business ,Waveguide ,Photonic crystal - Abstract
An air-bridged silicon-based photonic crystal coupled-cavity waveguide (PCCCW) connected with an input and output W1 PC waveguide (PCW) was designed and fabricated. We mapped its intensity distributions with a near-field scanning optical microscope (NSOM) at near-infrared wavelengths around 1550 nm. Surprisingly, the intensity distributions demonstrate that the second odd eigenmode dominates in such a PCCCW, even though it possesses a much slower group velocity of light than that of the first even one. Further considering the measured transmission spectrum, we find that the modal profile and impedance matching between the eigenmodes in the PCW and PCCCW plays an important role in the optical propagation efficiency. Mode conversion between the first even and the second odd eigenmode was also detected at the interfaces between the W1 PCW and PCCCW.
- Published
- 2010
23. Nanolithography in the quasi-far field based on the destructive interference effect of surface plasmon polaritons
- Author
-
Xia Wan, Haihua Tao, and Qingkang Wang
- Subjects
Diffraction ,Materials science ,business.industry ,Surface plasmon ,Physics::Optics ,Near and far field ,Grating ,Surface plasmon polariton ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,law.invention ,Nanolithography ,Optics ,law ,Optoelectronics ,Computer Vision and Pattern Recognition ,Plasmonic lens ,Photolithography ,business ,Computer Science::Databases - Abstract
On the principle of phase-shift mask, the metal segment of a sub-wavelength Ag grating on a quartz substrate is used as a phase-shifting layer in this photolithography method. When the radiation modes of the surface plasmon polaritons (SPPs) excited on the Ag surface have optical phase opposite to that of the waves emitting from the slits, destructive interference occurs and the diffraction limit can be broken through. The SPPs excited on the surface between Ag and water can be transformed into propagation modes in the photoresist. Therefore, nanolithography can be achieved in the quasi-far field with this method.
- Published
- 2010
24. Multichannel filters with shape designing in two-dimensional photonic crystal slabs
- Author
-
Cheng Ren, Yazhao Liu, Haihua Tao, Zhi-Yuan Li, Bingying Cheng, Jie Tian, Shuai Feng, Daozhong Zhang, and Qiang Luo
- Subjects
Coupling ,Materials science ,business.industry ,Physics::Optics ,General Physics and Astronomy ,Heterojunction ,Filter (signal processing) ,Focused ion beam ,Waveguide (optics) ,Optics ,Lattice constant ,Slab ,business ,Photonic crystal - Abstract
We investigated the influence of the irregular shape of air holes on the optical characteristics of channel-drop filters built in a two-dimensional photonic crystal slab. Three differently shaped structures are tested by experiments and simulations to demonstrate the shape-tuning capability of the optical devices. A four-channel filter based on this shape design is presented. The photonic crystal consists of a triangular array of air holes fabricated by focused ion beam lithographic technology on a silicon slab with thickness of 260 nm. The filter contains a heterostructure with different lattice constants of 420 and 430 nm. In each channel, the filtering functionality is guaranteed by the indirect resonant coupling between waveguide and cavity. The elliptical air holes that surround the cavity have different parameters, and this leads to a fine tuning of the cavity’s resonant frequencies. The performance of the multichannel filter is found to be very encouraging.
- Published
- 2007
25. Optical improvement of photonic devices fabricated by Ga[sup +] focused ion beam micromachining
- Author
-
Zhi-Yuan Li, Bingying Cheng, Haihua Tao, Yazhao Liu, Aizi Jin, Shuai Feng, Cheng Ren, and Daozhong Zhang
- Subjects
Materials science ,Silicon ,business.industry ,Annealing (metallurgy) ,Laser beam machining ,Physics::Optics ,chemistry.chemical_element ,Condensed Matter Physics ,Waveguide (optics) ,Focused ion beam ,Surface micromachining ,Optics ,chemistry ,Electrical and Electronic Engineering ,Photonics ,business ,Photonic crystal - Abstract
The authors propose a novel post-focused-ion-beam (FIB) treatment method to improve the optical properties of photonic devices fabricated by the Ga+ FIB technique on the silicon substrate with low temperature liquid annealing process. A conventional micrometric ridge waveguide is first fabricated and then annealed to roughly detect the improvement of its optical properties. Then a nanometric 12-fold photonic quasicrystal waveguide is designed to further study its topography variation as well as the subtle influence on its optical properties with different post-FIB treatments. By comparing the experimental results with the theoretical results that are made by means of the three-dimensional finite-difference time-domain method, the authors find that the proposed low temperature liquid annealing method can efficiently improve the optical properties of photonic devices by decreasing Ga+ contamination, removing redeposited Si–SiO2 composites, and restoring damaged silicon lattice structures caused by Ga+ bomba...
- Published
- 2007
26. High resolution three-port filter in two dimensional photonic crystal slabs
- Author
-
Zhi-Yuan Li, Jie Tian, Bingying Cheng, Kun Ren, H. X. Yang, Haihua Tao, Shuai Feng, Daozhong Zhang, Cheng Ren, and Yazhao Liu
- Subjects
Materials science ,business.industry ,Photonic integrated circuit ,Physics::Optics ,Port (circuit theory) ,Integrated circuit ,Atomic and Molecular Physics, and Optics ,law.invention ,Wavelength ,Resonator ,Optics ,Filter (video) ,law ,Q factor ,Optoelectronics ,business ,Photonic crystal - Abstract
An in-plane, three-port filter consisting of input/output waveguides and two point-defect cavities in a 2D PC slab is designed and fabricated, where a new feedback method is introduced, and its transmission properties are measured. The measured minimum output wavelength spacing between two channels is 1.5 nm, which is realized by slightly adjusting the size of the resonant cavities. The measured resonant wavelengths of two cavities agree well with the calculated ones and the quality factors of the cavities are almost the same. It is believed that this kind of filter may be useful in optical integrated circuits with high density.
- Published
- 2006
27. Tunable surface plasmons interference patterns with the same mask in nanolithography.
- Author
-
Xia Wan, Qingkang Wang, and Haihua Tao
- Subjects
PHONON-plasmon interactions ,PLASMONIC Raman sensors ,IMAGE processing ,IMAGE quality analysis ,IMAGE stabilization - Abstract
When a transverse magnetic-polarized beam illuminates normally on an Ag grating mask with sub-wavelength slits, the surface plasmon (SP) interference patterns are formed on the Ag surface. According to the dispersion relationship of SPs, the wavelength of SPs (λ
sp ) is tunable by altering the refractive index of the photoresist or the illumination wavelength. Various λsp form interference patterns with different size. The interference patterns are tunable using the same mask with period microns in size, which can save the cost of fabricating a different mask. This method will have potential applications to nanolithography. [ABSTRACT FROM AUTHOR]- Published
- 2012
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