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Zhong Lin Wang - One of the best experts on this subject based on the ideXlab platform.
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deriving the three dimensional structure of zno nanowires Nanobelts by scanning transmission electron microscope tomography
Nano Research, 2013Co-Authors: Yong Ding, Zhong Lin Wang, Fang ZhangAbstract:Characterizing the three-dimensional (3D) shape of a nanostructure by conventional imaging techniques in scanning electron microscopy and transmission electron microscopy can be limited or complicated by various factors, such as two-dimensional (2D) projection, diffraction contrast and unsure orientation of the nanostructure with respect to the electron beam direction. In this paper, in conjunction with electron diffraction and imaging, the 3D morphologies of ZnO nanowires and Nanobelts synthesized via vapor deposition were reconstructed by electron tomography in a scanning transmission electron microscope (STEM). The cross-sections of these one-dimensional (1D) nanostructures include triangle, hexagonal, and rectangle shapes. By combining the reconstructed shape with the crystalline information supplied by electron diffraction patterns recorded from the same nanowire/nanobelt, the growth direction and its exposed surfaces were uniquely identified. In total, three different growth directions were confirmed. These directions are 〈0001〉, 〈2 $$ \bar 1 $$ $$ \bar 1 $$ 0〉 and 〈2 $$ \bar 1 $$ $$ \bar 1 $$ 3〉 corresponding to 〈001〉, 〈100〉 and 〈101〉 orientations in three-index notation. The 〈0001〉 growth nanowires show triangle or hexagonal cross-sections, with exposed {01 $$ \bar 1 $$ 0} side surfaces. The dominant surfaces of the 〈2 $$ \bar 1 $$ $$ \bar 1 $$ 0〉 growth nanobelt are ±(0001) planes. Both hexagonal and rectangle cross-sections were observed in the 〈2 $$ \bar 1 $$ $$ \bar 1 $$ 3〉 growth ZnO nanostructures. Their surfaces include the {01 $$ \bar 1 $$ 0}, { $$ \bar 1 $$ 101} and { $$ \bar 2 $$ 112} planes. The Nanobelts with a large aspect ratio of ∼10 normally grow along the 〈2 $$ \bar 1 $$ $$ \bar 1 $$ 0〉 direction, while Nanobelts with small aspect ratio grow along 〈2 $$ \bar 1 $$ $$ \bar 1 $$ 3〉 growth direction. The approach and methodology demonstrated here can be extended to any nanostructures that can be crystalline, polycrystalline or even amorphous.
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Deriving the three-dimensional structure of ZnO nanowires/Nanobelts by scanning transmission electron microscope tomography
Nano Research, 2013Co-Authors: Yong Ding, Fang Zhang, Zhong Lin WangAbstract:Characterizing the three-dimensional (3D) shape of a nanostructure by conventional imaging techniques in scanning electron microscopy and transmission electron microscopy can be limited or complicated by various factors, such as two-dimensional (2D) projection, diffraction contrast and unsure orientation of the nanostructure with respect to the electron beam direction. In this paper, in conjunction with electron diffraction and imaging, the 3D morphologies of ZnO nanowires and Nanobelts synthesized via vapor deposition were reconstructed by electron tomography in a scanning transmission electron microscope (STEM). The cross-sections of these one-dimensional (1D) nanostructures include triangle, hexagonal, and rectangle shapes. By combining the reconstructed shape with the crystalline information supplied by electron diffraction patterns recorded from the same nanowire/nanobelt, the growth direction and its exposed surfaces were uniquely identified. In total, three different growth directions were confirmed. These directions are 〈0001〉, 〈2 $$ \bar 1 $$ $$ \bar 1 $$ 0〉 and 〈2 $$ \bar 1 $$ $$ \bar 1 $$ 3〉 corresponding to 〈001〉, 〈100〉 and 〈101〉 orientations in three-index notation. The 〈0001〉 growth nanowires show triangle or hexagonal cross-sections, with exposed {01 $$ \bar 1 $$ 0} side surfaces. The dominant surfaces of the 〈2 $$ \bar 1 $$ $$ \bar 1 $$ 0〉 growth nanobelt are ±(0001) planes. Both hexagonal and rectangle cross-sections were observed in the 〈2 $$ \bar 1 $$ $$ \bar 1 $$ 3〉 growth ZnO nanostructures. Their surfaces include the {01 $$ \bar 1 $$ 0}, { $$ \bar 1 $$ 101} and { $$ \bar 2 $$ 112} planes. The Nanobelts with a large aspect ratio of ∼10 normally grow along the 〈2 $$ \bar 1 $$ $$ \bar 1 $$ 0〉 direction, while Nanobelts with small aspect ratio grow along 〈2 $$ \bar 1 $$ $$ \bar 1 $$ 3〉 growth direction. The approach and methodology demonstrated here can be extended to any nanostructures that can be crystalline, polycrystalline or even amorphous.
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aspect ratio dependence of the elastic properties of zno Nanobelts
Nano Letters, 2007Co-Authors: Marcel Lucas, Zhong Lin Wang, Wenjie Mai, Rusen Yang, Elisa RiedoAbstract:The Young's modulus of ZnO Nanobelts was measured with an atomic force microscope by means of the modulated nanoindentation method. The elastic modulus was found to depend strongly on the width-to-thickness ratio of the nanobelt, decreasing from about 100 to 10 GPa, as the width-to-thickness ratio increases from 1.2 to 10.3. This surprising behavior is explained by a growth-direction-dependent aspect ratio and the presence of stacking faults in Nanobelts growing along particular directions.
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Visible light response of tin oxide Nanobelts
2007 IEEE 20th International Conference on Micro Electro Mechanical Systems (MEMS), 2007Co-Authors: Surajit Kumar, Zhong Lin Wang, Xiangyang Kong, Heungjoo Shin, Yu-bin Chen, Zhuomin M. Zhang, Peter J. HeskethAbstract:In the present work we report the effect of visible (VIS) light on the conductivity of SnO2 Nanobelts. The existence of visible light effect is unusual, since bulk SnO2 is a wide band gap semiconductor. Two types of nanobelt alignment/trapping methods were used in fabricating devices for study of the visible light effect. Fluid flow alignment was used for making individual nanobelt devices, while AC dielectrophoresis was used to trap multiple Nanobelts. DC current passing through the SnO2 nanobelt devices was monitored under VIS and UV light illumination. Visible photoluminescence was also observed in the nanobelt samples.
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Dielectrophoretic Characterization of SnO2 Nanobelts
TRANSDUCERS 2007 - 2007 International Solid-State Sensors Actuators and Microsystems Conference, 2007Co-Authors: Surajit Kumar, Zhong Lin Wang, Heungjoo Shin, Zhengchun Peng, Cantwell G. Carson, Rosario A. Gerhardt, Peter J. HeskethAbstract:In the present work we report the results of AC dielectrophoresis experiments on ethanol suspended SnO2 Nanobelts. AC field (frequency ~ 5 Hz - 10 MHz) was applied between microelectrodes, and detailed and direct observations of the nanobelt motion were performed. It revealed a wide variety of nanobelt motions induced by the dielectrophoretic forces, which include attraction and repulsion depending on the signal frequency range. These forces caused rigid body motion and deformation in long Nanobelts, and pearl chain formation in short Nanobelts and particles. The presence of negative (repulsion) dielectrophoresis is unusual in SnO2, since bulk material properties dictate positive dielectrophoresis in the frequency range studied.
Xiaosheng Fang - One of the best experts on this subject based on the ideXlab platform.
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an optimized ultraviolet a light photodetector with wide range photoresponse based on zns zno biaxial nanobelt
Advanced Materials, 2012Co-Authors: Linfeng Hu, Meiyong Liao, Hongjun Xiang, Xingao Gong, Lide Zhang, Xiaosheng FangAbstract:: A novel 1D/1D nanocomposite-based photodetector is successfully fabricated from high-crystalline ZnS/ZnO biaxial Nanobelts for the first time. Optimized performance of the ZnS/ZnO nanobelt photodetector is much better than that of pure ZnS or ZnO nanostructures, with a wide-range UV-A light photoresponse, high sensitivity, and very fast response speed.
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New ultraviolet photodetector based on individual Nb2O 5 Nanobelts
Advanced Functional Materials, 2011Co-Authors: Xiaosheng Fang, Biao Gao, Linfeng Hu, Lijuan Zhao, Meiyong Liao, Kaifu Huo, Paul K. Chu, Yoshio BandoAbstract:Although human eyes are quite insensitive to ultraviolet (UV) light, most of the longer wavelength UV light (the UV-A band between 320 and 400 nm) does reach the earth surface and after prolonged exposure, the radiation can cause health concerns especially skin cancer. Therefore, it is extremely important to explore ways to effectively monitor the radiation. Herein we report for the first time a new high-performance UV photodetector made of an individual Nb2O5 nanobelt. Quasi-aligned Nb2O5 Nanobelts 100-500 nm wide and 2-10 mu m long were synthesized using a hydrothermal treatment of a niobium foil in a KOH solution followed by proton exchange and calcination treatment. A nanostructured photodetector was constructed from an individual Nb2O5 nanobelt and its optoelectronic properties were evaluated. The detector exhibited linear photocurrent characteristics, excellent light selectivity, and high external quantum-efficiency (EQE) of 6070%. Long-term stability of the photocurrent over a period of 2500 s at an applied voltage of 1.0 V was achieved. The photodetector performance was further enhanced by improving the crystallinity and eliminating the defects in the Nb2O5 nanobelt crystals. These excellent optoelectronic properties demonstrate that Nb2O5 Nanobelts are suitable for visible-blind UV-light sensors and optoelectronic circuits, especially those operating in the UV-A range.
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deep ultraviolet solar blind photoconductivity of individual gallium oxide Nanobelts
Science & Engineering Faculty, 2011Co-Authors: Erwin Auer, Xiaosheng Fang, Meiyong Liao, Yoshio Bando, Ujjal K. Gautam, Tianyou Zhai, Alois Lugstein, Yasuo Koide, Dmitri GolbergAbstract:We designed solar-blind deep-ultraviolet semiconductor photodetectors using individual Ga2O3 Nanobelts. The photoconductive behavior was systematically studied. The photodetectors demonstrate high selectivity towards 250 nm light, fast response times of less than 0.3 s, and a large photocurrent to dark current ratio of up to 4 orders of magnitude. The photoresponse parameters such as photocurrent, response time, and quantum efficiency depend strongly on the intensity of light, the detector environment, and the nanobelt size. The photoresponse mechanism was discussed, which was mainly attributed to the band bending, surface traps, and distribution of traps in the bandgap. Present Ga2O3 Nanobelts can be exploited for future applications in photo sensing, light-emitting diodes, and optical switches.
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Single-crystalline ZnS Nanobelts with sharp ultraviolet (UV) emission at room temperature as UV-light sensors
2010 3rd International Nanoelectronics Conference (INEC), 2010Co-Authors: Xiaosheng Fang, Meiyong Liao, Yoshio Bando, Ujjal K. Gautam, Tianyou Zhai, Dmitri GolbergAbstract:We have demonstrated an effective approach for the synthesis of single-crystalline ZnS Nanobelts possessing sharp UV emission at RT via right selection of source materials and controlling their evaporation and agglomeration rates. Individual ZnS nanobelt-based UV-light sensors were fabricated, these showed a high potential as visible-blind UV photodetectors and ultra-fast optoelectronic switches. The sensor characteristics, including a spectral response, I–V curves under various light illuminations, and a time response were studied. The photoresponsivity of an individual ZnS nanobelt-based UV sensor exhibited over three orders of magnitude gain under the UV light illumination as compared to a visible light. The high spectral selectivity combined with high photosensitivity and fast time response (≪ 0.3 s) make the present single-crystalline ZnS Nanobelts particularly valuable for new “visible-blind” UV photodetectors, especially in the UV-A region.
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Ultrafine ZnS Nanobelts as Field Emitters
Advanced Materials, 2007Co-Authors: Xiaosheng Fang, Yoshio Bando, Ujjal K. Gautam, Guozhen Shen, Pedro M. F. J. Costa, Chunyi Zhi, Chengchun Tang, Dmitri GolbergAbstract:1D nanostructures, such as nanotubes, nanowires, and Nanobelts, have become of interest because of their potential value for leading to an understanding of fundamental physical concepts and constructing nanoscale electric and optoelectronic devices. ZnS, an important semiconductor compound of the II–VI group, has a wide band gap energy of 3.7 eV (1 eV = 1.602 × 10 J) at 300 K. ZnS is one of the first semiconductors discovered and probably one of the most important materials in the electronics industry. Recently, various ZnS 1D nanostructures have successfully been synthesized. Among them, ZnS Nanobelts are one of the most interesting objects. Nanobelts of different widths, ranging from tens of nanometer to several micrometers, have been prepared and studied in detail. Ultrafine ZnO Nanobelts proved to be of particular interest for the general study of size-induced electrical and optical properties of functional oxides. Thus the synthesis and novel property exploration of ultrafine ZnS Nanobelts are indispensable. However, largescale ZnS nanobelt synthesis, especially for small (width < 20 nm) belts, is still a challenge. In this communication, we describe the synthesis of ultrafine ZnS Nanobelts by controlling evaporation and agglomeration rates. The range of the belt widths was 5–30 nm, and peaked at 10–20 nm. The belt thickness varied with width and was typically of only several nanometers. The regarded ultrafine ZnS Nanobelts not only showed a pronounced quantumconfinement effect (a blue-shift of ca. 0.45 eV compared to bulk ZnS materials), but also possessed good field-emitting characteristics: a low turn-on field of 3.47 V lm and a high field-enhancement factor (over 2000). Although the work function of ZnS (7.0 eV) is larger than that of Si (3.6 eV), AlN (3.7 eV), SiC (4.0 eV), C nanotubes (5 eV) or ZnO (5.3 eV), the field-emission (FE) properties of the present tiny ZnS Nanobelts are comparable or even better than those of many other 1D nanostructures because of a characteristically high aspect ratio. Therefore, ultrafine ZnS Nanobelts may be attractive as field emitters and highly useful in novel nanoscale electric and optoelectronic devices. Figure 1 shows FE scanning electron microscopy (SEM) images of the as-grown Nanobelts. A low-magnification SEM image in Figure 1a reveals that the Nanobelts are several to tens of micrometers in length. The corresponding high-magnification SEM image in Figure 1b shows that each nanobelt has a uniform width over its entire length. The typical belt width is in the range of 10–20 nm. A high-magnification SEM image in Figure 1c clearly indicates that a product exhibits numerous beltlike structures. Figure 1d and e shows typical high-magnification SEM images of individual Nanobelts. An X-ray diffraction (XRD) pattern from the product is shown in Figure 1f, where all the diffraction peaks can be indexed to wurtzite-type ZnS with lattice constants of a = 0.382 nm and c = 0.626 nm (Joint Committee for Powder Diffraction Studies (JCPDS) Card: 36-1450). By using electron-beam irradiation in SEM, we found that the Nanobelts were very sensitive to an electron beam. Figure 1S, Supporting Information, depicts nanobelt SEM images after electron-beam irradiation. Clearly, the nanobelt width increased with an increase in irradiation time. High-resolution transmission electron microscopy (HRTEM; using a JEM-3000F high-resolution transmission electron microscope) was used to further characterize the beltlike product. By measuring over 100 Nanobelts, we confirmed that the typical width of the belts is in the range of 5–30 nm and peaked at 10–20 nm. Figure 2a and b show typical belt TEM images. Very narrow nanostructures were observed, less than 20 nm in width. It can also be seen that a thin amorphous carbon layer coats the side belt surfaces, as marked in Figure 2d and e. Figure 2c is an enlarged image from the area c marked in Figure 2b. All Nanobelts are singlecrystalline. The smallest width of ZnS Nanobelts was measured as 7.5 nm (Fig. 2c). This particular nanobelt is likely to be very thin (ca. 1–2 nm). In fact, we could easily see the lattice fringes for the nanobelt laid behind, as shown in Figure 2c. The nanobelt thickness (Fig. 2d) is likely to be only four atomic layers, as indicated by the arrows in Figure 2c. The Nanobelts are easily curled. Figure 2d and e are lattice-resolved HRTEM images taken from individual Nanobelts of 9 and 10 nm width, respectively. The marked interplanar d-spacings of 0.31 and 0.33 nm correspond to the (002) and (010) lattice planes of wurtzite ZnS. From Figure 2c–e, it is C O M M U N IC A IO N
Hong Liu - One of the best experts on this subject based on the ideXlab platform.
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PdO/TiO2 nanobelt heterostructures with high photocatalytic activities based on an exposed highly active facet on ultrathin TiO2 Nanobelts
Solar Energy Materials and Solar Cells, 2017Co-Authors: Yana Wang, Yuanhua Sang, Chen Guohui, Wang Zhou, Hong LiuAbstract:Abstract Combining the high photocatalytic activity of P25 (anatase/rutile bi-phase nanoparticle) and the good recycling property of TiO2 Nanobelts is a promising approach for the preparation of high performance photocatalysts. In this work, through controlling the volume ratio of the component of organic solvent, bi-phase ultrathin TiO2 Nanobelts consisting of both anatase and rutile phases have been successfully synthesized via a one-step solvothermal process by using tetrabutyl titanate as the Ti source and acetic acid/N,N-dimethylformamide (DMF) as the blended organic solvent. Compared with single phase TiO2, the bi-phase TiO2 Nanobelts display a superior photocatalytic activity under ultraviolet light irradiation. Based on the refinement result of the X-ray diffraction (XRD) patterns of TiO2 Nanobelts, the ratio of anatase and rutile phases in the as-synthesized TiO2 Nanobelts were calculated to be 90.8 wt% and 9.2 wt%, respectively. Scanning electron microscope and high resolution transmission electron microscope images demonstrated that the thickness of the Nanobelts is only 3–5 nm, and the main exposed facet is (010), a photocatalytically active facet of anatase. The bi-phase and active facet exposure characteristics endow the ultrathin TiO2 nanobelt with high photocatalytic activity, which is superior to P25. The PdO/TiO2 ultrathin nanobelt heterostructures were synthesized at ambient temperature by using ultrathin Nanobelts as substrates, which exhibited outstanding photodegradation activity with methyl orange, excellent hydrogen generation, and observably enhanced photoelectrochemical activity under simulated solar irradiation. The efficient suppression of the recombination of photo-induced carriers was caused by the bi-phase characteristics of the ultrathin TiO2 Nanobelts. These Nanobelts will have great potential in applications for photocatalytic water treatment and hydrogen generation because of the facile synthesis process and superior photocatalytic activity.
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enhanced photocatalytic property of reduced graphene oxide tio2 nanobelt surface heterostructures constructed by an in situ photochemical reduction method
Small, 2014Co-Authors: Yuanhua Sang, Jian Tian, Huaidong Jiang, Zhenhuan Zhao, Pin Hao, Hong Liu, Jerome P ClaverieAbstract:A facile method is proposed to assemble graphene oxide (GO) on the surface of a TiO2 nanobelt followed by an in situ photocatalytic reduction to form reduced graphene oxide (rGO)/TiO2 nanobelt surface heterostructures. The special colloidal properties of GO and TiO2 nanobelt are exploited as well as the photocatalytic properties of TiO2 . Using water-ethanol solvent mixtures, GO nanosheets are tightly wrapped around the surface of the TiO2 Nanobelts through an aggregation process and are then reduced in situ under UV-light irradiation to form rGO/TiO2 nanobelt surface heterostructures. The heterostructures enhance the separation of the photoinduced carriers, which results in a higher photocurrent due to the special electronic characteristics of rGO. Compared to TiO2 Nanobelts, the rGO/TiO2 nanobelt surface heterostructures possess higher photocatalytic activity for the degradation of methyl orange and for the production of hydrogen from water, as well as excellent recyclability, with no loss of activity over five cycles.
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synthesis of few layer mos2 nanosheet coated tio2 nanobelt heterostructures for enhanced photocatalytic activities
Small, 2013Co-Authors: Weijia Zhou, Jiyang Wang, Hong Liu, Xiao Huang, Zhanxi Fan, Zongyou Yin, Zhiyuan Zeng, Hua ZhangAbstract:MoS(2) nanosheet-coated TiO(2) nanobelt heterostructures--referred to as TiO(2)@MoS(2)--with a 3D hierarchical configuration are prepared via a hydrothermal reaction. The TiO(2) Nanobelts used as a synthetic template inhibit the growth of MoS(2) crystals along the c-axis, resulting in a few-layer MoS(2) nanosheet coating on the TiO(2) Nanobelts. The as-prepared TiO(2)@MoS(2) heterostructure shows a high photocatalytic hydrogen production even without the Pt co-catalyst. Importantly, the TiO(2)@MoS(2) heterostructure with 50 wt% of MoS(2) exhibits the highest hydrogen production rate of 1.6 mmol h(-1) g(-1). Moreover, such a heterostructure possesses a strong adsorption ability towards organic dyes and shows high performance in photocatalytic degradation of the dye molecules.
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Nanopaper based on Ag/TiO2 Nanobelts heterostructure for continuous-flow photocatalytic treatment of liquid and gas phase pollutants
Journal of hazardous materials, 2011Co-Authors: Weijia Zhou, Hong Liu, Yongquan Yin, Guancong Wang, Jinxia Wang, Jiyang WangAbstract:The Ag/TiO(2) nanobelt heterostructures were prepared by the acid-assisted hydrothermal method followed by an in situ photo-reduction process. The photocatalytic activity of TiO(2) Nanobelts was evidently enhanced by the heterostructures between Ag nanoparticles and TiO(2) Nanobelts. The nanopapers based on Ag/TiO(2) nanobelt heterostructures were fabricated via a modified paper-making process. A novel continuous photocatalytic reactor was designed, and MO removal rate of Ag/C-TiO(2) nanopaper was achieved to 100% in 40 min for single layer and only in 6 min for three layers. The self-supported TiO(2) nanopapers with porous structures also showed an excellent continuous photocatalytic performance for toluene gas under UV light irradiation, and the corresponding degradation rate was 69.5% in 184 min. Moreover, the Ag/TiO(2) Nanobelts nanopaper showed a good antibacterial effect. The multifunctional TiO(2) nanopapers modified by the heterostuctures could have potential applications in the environmental and biomaterial fields.
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enhancement of ethanol vapor sensing of tio2 Nanobelts by surface engineering
ACS Applied Materials & Interfaces, 2010Co-Authors: Weijia Zhou, Jiyang Wang, Hong Liu, Jingjie Cui, Duo Liu, Shaowei CheAbstract:TiO2 Nanobelts were prepared by a hydrothermal process, and the structures were manipulated by surface engineering, including surface coarsening by an acid-corrosion procedure and formation of Ag-TiO2 heterostuctures on TiO2 Nanobelts surface by photoreduction. Their performance in the detection of ethanol vapor was then examined and compared by electrical conductivity measurements at varied temperatures. Of the sensors based on the four nanobelt samples (TiO2 Nanobelts, Ag-TiO2 Nanobelts, surface- coarsened TiO2 Nanobelts, and surface-coarsened Ag-TiO2 Nanobelts), they all displayed improved sensitivity, selectivity, and short response times for ethanol vapor detection, in comparison with sensors based on other oxide nanostructures. Importantly, the formation of Ag-TiO2 heterostuctures on TiO2 Nanobelts surface and surface coarsening of TiO2 Nanobelts were found to lead to apparent further enhancement of the sensors sensitivity, as well as a decrease of the optimal working temperature. That is, within the present experimental context, the vapor sensor based on surface-coarsened Ag-TiO2 composite Nanobelts exhibited the best performance. The sensing mechanism was interpreted on the basis of the surface depletion model, and the improvement by oxide surface engineering was accounted for by the chemical sensitization mechanism. This work provided a practical approach to the enhancement of gas sensing performance by one-dimensional oxide nanomaterials.
Yong Ding - One of the best experts on this subject based on the ideXlab platform.
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Deriving the three-dimensional structure of ZnO nanowires/Nanobelts by scanning transmission electron microscope tomography
Nano Research, 2013Co-Authors: Yong Ding, Fang Zhang, Zhong Lin WangAbstract:Characterizing the three-dimensional (3D) shape of a nanostructure by conventional imaging techniques in scanning electron microscopy and transmission electron microscopy can be limited or complicated by various factors, such as two-dimensional (2D) projection, diffraction contrast and unsure orientation of the nanostructure with respect to the electron beam direction. In this paper, in conjunction with electron diffraction and imaging, the 3D morphologies of ZnO nanowires and Nanobelts synthesized via vapor deposition were reconstructed by electron tomography in a scanning transmission electron microscope (STEM). The cross-sections of these one-dimensional (1D) nanostructures include triangle, hexagonal, and rectangle shapes. By combining the reconstructed shape with the crystalline information supplied by electron diffraction patterns recorded from the same nanowire/nanobelt, the growth direction and its exposed surfaces were uniquely identified. In total, three different growth directions were confirmed. These directions are 〈0001〉, 〈2 $$ \bar 1 $$ $$ \bar 1 $$ 0〉 and 〈2 $$ \bar 1 $$ $$ \bar 1 $$ 3〉 corresponding to 〈001〉, 〈100〉 and 〈101〉 orientations in three-index notation. The 〈0001〉 growth nanowires show triangle or hexagonal cross-sections, with exposed {01 $$ \bar 1 $$ 0} side surfaces. The dominant surfaces of the 〈2 $$ \bar 1 $$ $$ \bar 1 $$ 0〉 growth nanobelt are ±(0001) planes. Both hexagonal and rectangle cross-sections were observed in the 〈2 $$ \bar 1 $$ $$ \bar 1 $$ 3〉 growth ZnO nanostructures. Their surfaces include the {01 $$ \bar 1 $$ 0}, { $$ \bar 1 $$ 101} and { $$ \bar 2 $$ 112} planes. The Nanobelts with a large aspect ratio of ∼10 normally grow along the 〈2 $$ \bar 1 $$ $$ \bar 1 $$ 0〉 direction, while Nanobelts with small aspect ratio grow along 〈2 $$ \bar 1 $$ $$ \bar 1 $$ 3〉 growth direction. The approach and methodology demonstrated here can be extended to any nanostructures that can be crystalline, polycrystalline or even amorphous.
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deriving the three dimensional structure of zno nanowires Nanobelts by scanning transmission electron microscope tomography
Nano Research, 2013Co-Authors: Yong Ding, Zhong Lin Wang, Fang ZhangAbstract:Characterizing the three-dimensional (3D) shape of a nanostructure by conventional imaging techniques in scanning electron microscopy and transmission electron microscopy can be limited or complicated by various factors, such as two-dimensional (2D) projection, diffraction contrast and unsure orientation of the nanostructure with respect to the electron beam direction. In this paper, in conjunction with electron diffraction and imaging, the 3D morphologies of ZnO nanowires and Nanobelts synthesized via vapor deposition were reconstructed by electron tomography in a scanning transmission electron microscope (STEM). The cross-sections of these one-dimensional (1D) nanostructures include triangle, hexagonal, and rectangle shapes. By combining the reconstructed shape with the crystalline information supplied by electron diffraction patterns recorded from the same nanowire/nanobelt, the growth direction and its exposed surfaces were uniquely identified. In total, three different growth directions were confirmed. These directions are 〈0001〉, 〈2 $$ \bar 1 $$ $$ \bar 1 $$ 0〉 and 〈2 $$ \bar 1 $$ $$ \bar 1 $$ 3〉 corresponding to 〈001〉, 〈100〉 and 〈101〉 orientations in three-index notation. The 〈0001〉 growth nanowires show triangle or hexagonal cross-sections, with exposed {01 $$ \bar 1 $$ 0} side surfaces. The dominant surfaces of the 〈2 $$ \bar 1 $$ $$ \bar 1 $$ 0〉 growth nanobelt are ±(0001) planes. Both hexagonal and rectangle cross-sections were observed in the 〈2 $$ \bar 1 $$ $$ \bar 1 $$ 3〉 growth ZnO nanostructures. Their surfaces include the {01 $$ \bar 1 $$ 0}, { $$ \bar 1 $$ 101} and { $$ \bar 2 $$ 112} planes. The Nanobelts with a large aspect ratio of ∼10 normally grow along the 〈2 $$ \bar 1 $$ $$ \bar 1 $$ 0〉 direction, while Nanobelts with small aspect ratio grow along 〈2 $$ \bar 1 $$ $$ \bar 1 $$ 3〉 growth direction. The approach and methodology demonstrated here can be extended to any nanostructures that can be crystalline, polycrystalline or even amorphous.
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controlled growth of large area uniform vertically aligned arrays of α fe2o3 Nanobelts and nanowires
Journal of Physical Chemistry B, 2005Co-Authors: Xiaogang Wen, Zhong Lin Wang, Yong Ding, Suhua Wang, Shihe YangAbstract:Vertically aligned iron oxide nanobelt and nanowire arrays have been synthesized on a large-area surface by direct thermal oxidation of iron substrates under the flow of O2. The effects of reactive gas pressure, composition, and temperature have been systematically studied. It was found that Nanobelts (width, tens of nanometers; thickness, a few nanometers) are produced in the low-temperature region (∼700 °C) whereas cylindrical nanowires tens of nanometers thick are formed at relatively higher temperatures (∼800 °C). Both Nanobelts and nanowires are mostly bicrystallites with a length of tens of micrometers which grow uniquely along the [110] direction. The growth habits of the Nanobelts and nanowires in the two temperature regions indicate the role of growth rate anisotropy and surface energy in dictating the ultimate nanomorphologies.
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Doping and planar defects in the formation of single-crystal ZnO nanorings
Physical Review B, 2004Co-Authors: Yong Ding, Xiangyang Kong, Zhong Lin WangAbstract:We have recently reported the growth of freestanding, single-crystal, seamless nanorings of zinc oxide via a spontaneous self-coiling process during the growth of polar-Nanobelts [X.Y. Kong et al., Science 303, 1348 (2004)]. The nanoring is made by coaxial and uniradius loop-by-loop winding of a fine ZnO nanobelt. An important fact is that each and every nanoring is made of a nanobelt that contains basal-plane planar defects, which are suggested to be important for leading the fastest growth of the nanobelt as well as lowering its elastic deformation energy. In this paper, high-resolution transmission electron microscopy is applied to investigate the nature of the planar defects in the Nanobelts and in nanorings. The planar defects were initiated and formed by single-layer segregation of the doping element, such as indium, which was introduced in the growth process. The accumulation of impurity ions forms two vicinal Inu O octahedral layers parallel to the basal plane. They form “head-to-head” and “tail-to-tail” polar-inversion domain boundaries. For a nanobelt that self-coils into a nanoring, we found that the head-to-head and tail-to-tail polar-inversion domain boundaries are paired, thus, the polarity of the nanobelt is unchanged. Therefore, our data support the proposed model [X.Y. Kong et al., Science 303, 1348 (2004)] that the nanoring is initiated by circularly folding a nanobelt due to long-range electrostatic interaction between the surface polar charges on the two sides, and a loop-by-loop winding of the nanobelt forms a complete ring.
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metal semiconductor zn zno core shell Nanobelts and nanotubes
Journal of Physical Chemistry B, 2004Co-Authors: Xiangyang Kong, Yong Ding, Zhong Lin WangAbstract:Heterostructured metal-semiconductor Zn-ZnO core-shell Nanobelts and nanotubes have been synthesized. The core is a belt-shaped Zn single crystal, and the shell is an epitaxially grown ZnO layer of 5n m in thickness. The composite nanobelt grows along [21 h1 h0], its top/bottom being ((0001), and side surfaces ((011 h0). The Zn core is a single crystal, and the ZnO shell has an epitaxial orientation relationship with the core. The metal-based Nanobelts have a distinct morphology from the nanowires reported in the literature. A growth mechanism is proposed on the basis of growth kinetics and thermodynamics. Sublimation of the Zn core results in the formation ZnO nanotubes. Since the discovery of oxide semiconducting Nanobelts, 1 onedimensional (1-D) facet controlled nanomaterials have attracted much attention due to their potential applications in electronic and optoelectronic devices in nanoscale. 2 The terminology of “nanowires” is fairly popular in the literature, but nanowires represent quasi-one-dimensional nanomaterials that grow along a specific axial direction, whereas their side surfaces may not be well-defined. For Nanobelts, it should be emphasized that they represent the 1-D nanomaterials that have specific growth direction and well-defined side facets. Analogous to carbon nanotubes, whose properties depend strongly on the helical angle at which the graphitic layer is rolled up, the properties of the nanowires and Nanobelts should also depend on the anisotropic structure of their facet surfaces. Therefore, it is a critical step in materials synthesis to control the anisotropic growth of the side surfaces, which may lead to unique properties and selectivity.
Meiyong Liao - One of the best experts on this subject based on the ideXlab platform.
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high detectivity solar blind high temperature deep ultraviolet photodetector based on multi layered l00 facet oriented β ga2o3 Nanobelts
Small, 2014Co-Authors: Zhenyu Zhang, Meiyong Liao, Junqing Hu, Liwen Sang, Wenjun ZhangAbstract:: Fabrication of a high-temperature deep-ultraviolet photodetector working in the solar-blind spectrum range (190-280 nm) is a challenge due to the degradation in the dark current and photoresponse properties. Herein, β-Ga2O3 multi-layered Nanobelts with (l00) facet-oriented were synthesized, and were demonstrated for the first time to possess excellent mechanical, electrical properties and stability at a high temperature inside a TEM studies. As-fabricated DUV solar-blind photodetectors using (l00) facet-oriented β-Ga2O3 multi-layered Nanobelts demonstrated enhanced photodetective performances, that is, high sensitivity, high signal-to-noise ratio, high spectral selectivity, high speed, and high stability, importantly, at a temperature as high as 433 K, which are comparable to other reported semiconducting nanomaterial photodetectors. In particular, the characteristics of the photoresponsivity of the β-Ga2O3 nanobelt devices include a high photoexcited current (>21 nA), an ultralow dark current (below the detection limit of 10(-14) A), a fast time response (<0.3 s), a high R(λ) (≈851 A/W), and a high EQE (~4.2 × 10(3)). The present fabricated facet-oriented β-Ga2O3 multi-layered nanobelt based devices will find practical applications in photodetectors or optical switches for high-temperature environment.
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an optimized ultraviolet a light photodetector with wide range photoresponse based on zns zno biaxial nanobelt
Advanced Materials, 2012Co-Authors: Linfeng Hu, Meiyong Liao, Hongjun Xiang, Xingao Gong, Lide Zhang, Xiaosheng FangAbstract:: A novel 1D/1D nanocomposite-based photodetector is successfully fabricated from high-crystalline ZnS/ZnO biaxial Nanobelts for the first time. Optimized performance of the ZnS/ZnO nanobelt photodetector is much better than that of pure ZnS or ZnO nanostructures, with a wide-range UV-A light photoresponse, high sensitivity, and very fast response speed.
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New ultraviolet photodetector based on individual Nb2O 5 Nanobelts
Advanced Functional Materials, 2011Co-Authors: Xiaosheng Fang, Biao Gao, Linfeng Hu, Lijuan Zhao, Meiyong Liao, Kaifu Huo, Paul K. Chu, Yoshio BandoAbstract:Although human eyes are quite insensitive to ultraviolet (UV) light, most of the longer wavelength UV light (the UV-A band between 320 and 400 nm) does reach the earth surface and after prolonged exposure, the radiation can cause health concerns especially skin cancer. Therefore, it is extremely important to explore ways to effectively monitor the radiation. Herein we report for the first time a new high-performance UV photodetector made of an individual Nb2O5 nanobelt. Quasi-aligned Nb2O5 Nanobelts 100-500 nm wide and 2-10 mu m long were synthesized using a hydrothermal treatment of a niobium foil in a KOH solution followed by proton exchange and calcination treatment. A nanostructured photodetector was constructed from an individual Nb2O5 nanobelt and its optoelectronic properties were evaluated. The detector exhibited linear photocurrent characteristics, excellent light selectivity, and high external quantum-efficiency (EQE) of 6070%. Long-term stability of the photocurrent over a period of 2500 s at an applied voltage of 1.0 V was achieved. The photodetector performance was further enhanced by improving the crystallinity and eliminating the defects in the Nb2O5 nanobelt crystals. These excellent optoelectronic properties demonstrate that Nb2O5 Nanobelts are suitable for visible-blind UV-light sensors and optoelectronic circuits, especially those operating in the UV-A range.
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deep ultraviolet solar blind photoconductivity of individual gallium oxide Nanobelts
Science & Engineering Faculty, 2011Co-Authors: Erwin Auer, Xiaosheng Fang, Meiyong Liao, Yoshio Bando, Ujjal K. Gautam, Tianyou Zhai, Alois Lugstein, Yasuo Koide, Dmitri GolbergAbstract:We designed solar-blind deep-ultraviolet semiconductor photodetectors using individual Ga2O3 Nanobelts. The photoconductive behavior was systematically studied. The photodetectors demonstrate high selectivity towards 250 nm light, fast response times of less than 0.3 s, and a large photocurrent to dark current ratio of up to 4 orders of magnitude. The photoresponse parameters such as photocurrent, response time, and quantum efficiency depend strongly on the intensity of light, the detector environment, and the nanobelt size. The photoresponse mechanism was discussed, which was mainly attributed to the band bending, surface traps, and distribution of traps in the bandgap. Present Ga2O3 Nanobelts can be exploited for future applications in photo sensing, light-emitting diodes, and optical switches.
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Single-crystalline ZnS Nanobelts with sharp ultraviolet (UV) emission at room temperature as UV-light sensors
2010 3rd International Nanoelectronics Conference (INEC), 2010Co-Authors: Xiaosheng Fang, Meiyong Liao, Yoshio Bando, Ujjal K. Gautam, Tianyou Zhai, Dmitri GolbergAbstract:We have demonstrated an effective approach for the synthesis of single-crystalline ZnS Nanobelts possessing sharp UV emission at RT via right selection of source materials and controlling their evaporation and agglomeration rates. Individual ZnS nanobelt-based UV-light sensors were fabricated, these showed a high potential as visible-blind UV photodetectors and ultra-fast optoelectronic switches. The sensor characteristics, including a spectral response, I–V curves under various light illuminations, and a time response were studied. The photoresponsivity of an individual ZnS nanobelt-based UV sensor exhibited over three orders of magnitude gain under the UV light illumination as compared to a visible light. The high spectral selectivity combined with high photosensitivity and fast time response (≪ 0.3 s) make the present single-crystalline ZnS Nanobelts particularly valuable for new “visible-blind” UV photodetectors, especially in the UV-A region.
