半导体金属氧化物(ZnO,ZnSnO_3)纳米材料的合成及其气敏性能研究
详细信息    本馆镜像全文|  推荐本文 |  |   获取CNKI官网全文
摘要
半导体金属氧化物ZnO与ZnSnO3都是良好的气敏材料,ZnO与ZnSnO3纳米材料的合成与制备研究,是研究其特性与应用的基础,对于进一步加深理解晶体的形成过程与机理等物理和化学问题具有重要的意义。在传感领域内,对它们的气敏特性进行研究以及改良,探索其相成分、形貌、结构与敏感性质之间的内在联系,同样也具有重要的理论意义与应用价值。
     在本论文中,以半导体金属氧化物ZnO与ZnSnO3为研究对象,采用湿化学法中的水热合成方法在较低温度制备了各种结构与形貌的ZnO与ZnSnO3微/纳米结构,其中部分结构与形貌特殊的产物是首次合成出来并被报道;同时还对产物的形貌和结构随反应条件的变化、合成机理以及气敏特性进行了详细的研究。结果表明:水热合成法是一种比较理想的制备特殊结构ZnO与ZnSnO3微/纳米材料的方法,所合成出来的ZnO与ZnSnO3微/纳米材料具有结晶性好、尺寸均匀的特点,将它们应用于气敏传感领域,其气敏特性具有灵敏度高和响应快的特点。
     本论文对半导体金属氧化物ZnO和ZnSnO3的水热合成与气敏性质研究做了大量的基础性研究工作,对进一步探索它们的潜在应用具有重要意义。
Up to now, nano- and microcrystalline ZnO with various size and morphologies have been reported, including nanorods, hexagonal plates, nanotubes, nanotube bundles, nanobelts, ring-like, flowerlike, nutlike, and hierarchical structures. The investigation of synthesis of ZnO nanomaterials with various structures and morphologies is the basis of the exploration of characteristics and applications of ZnO. On the other hand, for the ternary semiconducting metal oxide ZnSnO3, there are little reports about its fabrications and applications. How to synthesize ZnO and ZnSnO3 with uniform structure, size and low cost is considered as a hot subject of research. It is of great importance to investigate the gas-sensing properties of ZnO and ZnSnO3 nanostructures and explore the relationship between the component, morphology and gas-sensing properties, which are also the research topic of the modification of the gas-sensing properties of sensitive materials. This dissertation is to study the synthesis, characterization, growth mechanism, and gas-sensing properties of ZnO and ZnSnO3. The main results and significance are as follows.
     Cu-Zn alloy nanoparticles have been prepared by wire electrical explosion method, and Cu-Zn/ZnO core-shell nanocomposites have been prepared by wet-chemical method. The mechanism for the formation of Cu-Zn/ZnO core-shell nanocomposite is also explained. The gas-sensing devices have been fabricated based on the core-shell Cu-Zn/ZnO nanocomposites annealed at different temperatures. The maximal response is obtained for the sensor based on the Cu-Zn/ZnO film annealed at 350°C at the operating temperature of 240°C. The responses of the sensor are about 2.6, 3.3, 6.3, and 9.6 to 20, 50, 100, and 200 ppm CO, respectively. The response and recovery time of the sensor are 20 and 35 s, respectively.
     The aggregated flowerlike ZnO nanostructures have been synthesized by hydrothermal method. The flowerlike ZnO nanostructures have been prepared by Poly (ethylene glycol) (PEG)-assisted hydrothermal process, which are composed of many ZnO nanorods with ZnO nanoparticles as the building blocks. The ZnO nanorods share the same center, which distribute ununiformly. The nanorods gather into bundles from the active sites in several directions. The ZnO nanorods are single-crystal structures composed of many ZnO nanoparticles serving as the building blocks. The diameter and length of the ZnO nanorods are in the range of 50-280 nm and 1-1.5μm, respectively. There are lots of structural faults between the nanoparticles in the surface of the ZnO nanorods, including stacking faults, crystal plane distortions and dislocations. The possible growth mechanism is also discussed, which reveals that PEG plays an important role of template in obtaining the novel flowerlike nanostructures. The gas sensors have been fabricated based on the above sensitive ZnO materials, and the responses of the sensor are about 3.5, 15.6, 87.8, and 154.3 to 1, 10, 50, and 100 ppm ethanol.
     Novel aggregative flowerlike ZnO nanorods have been synthesized through a low temperature hydrothermal route without any surfactants and templates. The effect of the reaction time on the size and morphology of the ZnO products is investigated, and the possible formation mechanism is also discussed. The gas sensors have been fabricated based on the above sensitive ZnO materials, and the responses of the sensor are about 6.4, 10.8, 18.1, and 35.7 to 10, 20, 50, and 100 ppm ethanol. The response and recovery time of the sensor are 4.7 and 15 s, respectively.
     Ti-doped flowerlike ZnO nanorods have been synthesized by a hydrothermal method and the consequent beam evaporation method. The gas sensing properties of the pristine and Ti-doped flowerlike ZnO have also been investigated. It is found that the Ti-doped ZnO sensor exhibits remarkably enhanced selectivity and response to toluene. The Ti-doped ZnO sensor exhibits rapid response and excellent repeatability to toluene. The responses of the sensor are about 1.9, 2.7, 4.3, 5.8, 10.9, and 17.1 to 1, 5, 10, 20, 50, and 100 ppm toluene. The response and recovery time of the sensor are 8 and 20 s, respectively.
     The nutlike ZnO microcrystals with special morphology and structures have been successfully synthesized via a facile triethanolamine(TEA)-assisted hydrothermal process. The average diameter of ZnO microcrystals is 1.8μm, and the average length is about 2.2μm. The structural characterization reveals that the nutlike ZnO microcrystals are composed of two asymmetrical wurtzite single crystal ZnO twinned-cones. The bottom of the relatively large cone is hexagonal and rough, and the surface of the cone is very smooth. The relatively small cone is composed of lots of ZnO nanoparticles with very rough surface. The reaction time plays a crucial role in determining the final size and morphology of the ZnO samples. With increasing the hydrothermal reaction time, the relatively small cone grows rapidly. Extending the reaction time to 12 h causes the formation of symmetric spindlelike ZnO microcrystals. The investigation of the growth mechanism reveals that during the hydrothermal process TEA plays an important dual role. As a surfactant, TEA not only can affect the growth rate of different planes, but also can hydrolyze and release OH- to affect the alkaline of the solution. The nutlike ZnO sensor exhibits rapid response and recovery to ethanol. The response and recovery time of the sensor are 2 and 7 s, respectively. The responses of the nutlike sensor are about 1.8, 2.2, 4.0, 6.9, 14.1, and 27.2 to 1, 5, 10, 20, 50, and 100 ppm ethanol.
     The hollow ZnSnO3 nanocubes with peculiar cage- and skeleton-like architectures have been successfully synthesized for the first time. The side length of the cubic structures is in the range of 200-400 nm. The possible formation process and formation mechanism is proposed. The gas sensors have been fabricated based on the above peculiar ZnSnO3 materials, which exhibits rapid response to ethanol and toluene. The optimal operating temperatures to ethanol and toluene are 270 and 210°C, respectively. The response and recovery time of the sensor are about within 2 and 6 s, respectively. At the optimal operating temperature of 270°C, the responses of the sensor are about 2.8, 4.7, 7.2, 13.1 and 22.5 to 10, 20, 50, 100 and 200 ppm ethanol. At the optimal operating temperature of 210°C, the responses of the sensor are about 1.96, 2.85, 3.14, 3.9 and 4.91 to 10, 20, 30, 40 and 50 ppm toluene.
     Furthermore, the hierarchical ZnSnO3 hollow nanocages have been prepared for the first time. The structural characterizations reveal that the ZnSnO3 nanocages are composed of lots of ZnSnO3 nanoparticles. The reaction time plays a crucial role in determining the final morphology of the ZnSnO3 samples. With the reaction time increasing to 4 h, the hierarchical ZnSnO3 cubes begin to form. With the reaction time prolonged to 8 h, the morphologies and structures of the hierarchical ZnSnO3 cubes are similar to those of the samples with the reaction time of 12 h. When the reaction time is further up to 24 h, the hierarchical ZnSnO3 nanostructures are gradually etched into ZnSnO3 nanoparticles and fragments. There are two key factors in determining the formation of the hierarchical nanostructures: one is the numerous ZnSnO3 nucleus formed in the early stage of the reaction, and the other is the change of the growth rate of {100} and {111} planes by the addition of (CH2)6N4 (HMT). At the corresponding optimal operating temperature, the responses of the sensor are about 3.1, 4.0, 9.2, 13.3 and 30.9 to 10, 20, 50, 100 and 200 ppm ethanol. At the optimal operating temperature of 210°C, the responses of the sensor are about 3.0, 3.7, 4.3 and 5.0 to 10, 20, 30, and 50 ppm toluene.
引文
[1] Kubo R. Electronic properties of metallic fine particles [J]. J. Phys. Soc. Jpn., 1962, 17: 975-986.
    [2] Kawabata A, Kubo R. Electronic properties of fine metallic particles. II. Plasma resonance absorption [J]. J. Phys. Soc. Jpn., 1966, 21:1765-1772.
    [3] Wang Y, Mahler W. Degenerate four-wave mixing of CdS/polymer composite [J]. Opt. Commun., 1987, 61: 233-236.
    [4] Brus L. Electron-electron and electron-hole interactions in small semiconductor crystallites: the size dependence of the lowest excited electronic state [J]. J. Phys. Chem., 1984, 80: 4403-4409.
    [5] Barbara B, Wernsdorfer W. Quantum tunneling effect in magnetic particles [J] Curr. Opin. Solid State. Mater. Sci., 1997, 2: 220-225.
    [6] Averback R S, H?fler H J, Tao R. Processing of nano-grained materials [J]. Mater. Sci. Eng. A 1993, 166: 169-177.
    [7]张立德,牟季美.纳米材料和纳米机构[M].科学出版社,2001.
    [8] Provenzano V, Holtz R L. Nanocomposites for high temperature applications [J]. Mater. Sci. Eng. A 1995, 204: 125-134.
    [9]黄德欢.纳米技术与应用[M].中国纺织大学出版社,2001.
    [10] Liu C H, Zapien J A, Yao Y, Meng X M, Lee C S, Fan S S, Lifshitz Y, Lee S T. High-density, ordered ultraviolet light-emitting ZnO nanowire arrays [J]. Adv. Mater., 2003, 15: 838-841.
    [11] Zheng M J, Zhang L D, Li G H, Shen W Z. Fabrication and properties of large-scale uniform zince oxide nanowire arrays by one-step electrochemical deposition technique [J]. Chem. Phys. Lett., 2002, 363: 123-128.
    [12] Gao P X, Wang Z L. Substrate atomic-termination-induced anisotropic growth of ZnO nanowires/nanorods by the VLS process [J]. J. Phys. Chem. B, 2004, 108: 7534-7537.
    [13] Iijima S. Helical microtubules of graphitic carbon [J]. Nature, 1991, 354: 56-58.
    [14] Huang M H, Mao S, Feick H, Yan H Q, Wu Y Y, Kind H, Weber E, Russo R, Yang P D.Room-temperature ultraviolet nanowire nanolasers [J]. Science, 2001, 292: 1897-1899.
    [15] Li J Y, Chen X L, Li H, He M, Qiao Z Y. Fabrication of zinc oxide nanorods [J]. J. Cryst. Growth, 2001, 233: 5-7.
    [16] Vayssieres L, Keis K, Hagfeldt A, Lindquist S. Three-dimensional array of highly oriented crystalline ZnO microtubes [J]. Chem. Mater., 2001, 13: 4395-4398.
    [17] Wu J J, Liu S C, Wu C T, Chen K H, Chen L C. Heterostructures of ZnO-Zn coaxial nanocables and ZnO nanotubes [J]. Appl. Phys. Lett., 2002, 81: 1312-1314.
    [18] Yao B D, Chan Y F, Wang N. Formation of ZnO nanostructures by a simple way of thermal evaporation [J]. Appl. Phys. Lett., 2002, 81: 757-759.
    [19]新de面具.氧化锌两种晶体结构[EB/OL].[2010-02-08]. http://baike.baidu.com/image/cbc17b38c9fd1e0d97ddd8fe
    [20] Meyer B, Marx D. Density-functional study of the structure and stability of ZnO surfaces [J]. Phys. Rev. B, 2003, 67: 035403.
    [21] Wander A, Schedin F, Steadman P, Norris A, McGrath R, Turner T S, Thornton G, Harrison N M. Stability of polar oxide surfaces [J]. Phys. Rev. Lett., 2001, 86: 3811-3814.
    [22] Staemmler V, Fink K, Meyer B, Marx D, Kunat M, Gil Girol S, Burghaus U, W?ll C. Stabilization of polar ZnO surfaces: validating microscopic models by using CO as a probe molecule [J]. Phys. Rev. Lett., 2003, 90: 106102.
    [23] Wang Z L, Zinc oxide nanostructures: growth, properties and applications [J]. J. Phys.: Condens. Matter, 2004, 16: R829-858.
    [24] Mayer B K, Alves H, Hofmann D M, Kriegseis W, Forster D, Bertram F, Christen J, Hoffmann A, Stra?burg M, Dworzak M, Haboeck U, Rodina A V. Bound exciton and donor-acceptor pair recombinations in ZnO [J]. Phys. Stat. Sol. 2004, 241: 231-260.
    [25] Lu J G, Ye Z Z, Zhang Y Z, Liang Q L, Fujita Sz, Wang Z L. Self-assembled ZnO quantum dots with tunable optical properties [J]. Appl. Phys. Lett., 2006, 89: 023122.
    [26] Heo Y W, Tien L C, Norton D P, Kang B S, Ren F, Gila B P, Pearton S J. Electrical transport properties of single ZnO nanorods [J]. Appl. Phys. Lett., 2004, 85: 2002-2004.
    [27] Li Y B, Bando Y, Golberg D. ZnO nanoneedles with tip surface perturbations: excellent field emitters [J]. Appl. Phys. Lett. 2004, 84: 3603-3605.
    [28] Li Y, Cheng G S, Zhang L D. Fabrication of highly ordered ZnO nanowire arrays in anodicalumina membranes [J]. J. Mater. Res., 2000, 15: 2305-2308.
    [29] Lakshmi B B, Dorhout P K, Martin C R. Sol-gel template synthesis of semiconductor nanostructures [J]. Chem. Mater., 1997, 9: 857-862.
    [30] Liu J P, Huang X T, Sulieman K M, Sun F L, He X. Solution-based growth and optical properties of self-assembled monocrystalline ZnO ellipsoids [J]. J. Phys. Chem. B, 2006, 110: 10612-10618.
    [31] Weintraub B, Deng Y L, Wang Z L. Position-controlled seedless growth of ZnO nanorods arrays on a polymer substrate via wet chemical synthesis [J]. J. Phys. Chem. C, 2007, 111: 10162-10165.
    [32] Zu P, Tang Z K, Wong G K L, Kawasaki M, Ohtomo A, Koinuma H, Segawa Y. Ultraviolet spontaneous and stimulated emissions from Zn0 microcrystallite thin films at room temperature [J]. Solid State Commun., 1997, 103, 459-463.
    [33] Bagnall D M, Chen Y F, Zhu Z, Yao T, Koyama S, Shen M Y, Goto T. Optically pumped lasing of Zn0 at room temperature [J]. Appl. Phys. Lett., 1997, 70: 2230-2232.
    [34] Huang M H, Mao S, Feick H, Yan H, Wu Y, Kind H, Weber E, Russo R, Yang P D. Room-temperature ultraviolet nanowire nanolasers [J]. Science, 2001 292: 1897-1899.
    [35] Pan Z W, Dai Z R, Wang Z L. Nanobelts of semiconducting oxides [J]. Science, 2001, 291: 1947-1949.
    [36]曾毅.硼酸镁纳米线及纳米羟基磷灰石/胶原复合膜的制备与性能研究[D].吉林:吉林大学超硬材料国家重点实验室, 2007.
    [37] Dai Z R, Pan Z W, Wang Z L. Novel nanostructures of functional oxides synthesized by thermal evaporation [J]. Adv. Funct. Mater., 2003, 13: 9-24.
    [38] Kong X Y, Ding Y, Yang R, Wang Z L. Single-crystal nanorings formed by epitaxial self-coiling of polar-nanobelts [J]. Science, 2004, 303, 1348.
    [39] Wang Z L, Nanostructures of zinc oxide [J]. Mater. Today, 2004, 6: 26-33.
    [40] Tian Z R, Voigt J A, Liu J, Mckenzie B, Mcdermott M J. Biomimetic arrays of oriented helical ZnO nanorods and columns [J]. J. Am. Chem. Soc., 2002, 124: 12954-12955.
    [41] Cao B Q, Cai W P, Li Y, Sun F Q, Zhang L D. Ultraviolet-light-emitting ZnO nanosheets prepared by a chemical bath deposition method [J]. Nanotechnology, 2005, 16: 1734-1738.
    [42] Liang J B, Liu J W, Xie Q, Bai S, Yu W C, Qian Y T. Hydrothermal growth and opticalproperties of doughnut-shaped ZnO microparticles [J]. J. Phys. Chem. B, 2005, 109: 9463-9467.
    [43] Qian H S, Yu S H, Gong J Y, Luo L B, Wen L L. Growth of ZnO crystals with branched spindles and prismatic whiskers from Zn3(OH)2V2O7·H2O nanosheets by a hydrothermal route [J]. Cryst. Growth Des., 2005, 5: 935-939.
    [44] Gao X P, Zheng Z F, Zhu H Y, Pan G L, Bao J L, Wu F, Song D Y. Rotor-like ZnO by epitaxial growth under hydrothermal conditions [J]. Chem. Commun., 2004, 12: 1428-1429.
    [45] Mo M S, Yu J C, Zhang L Z, Li S A. Self-assembly of ZnO nanorods and nanosheets into hollow microhemispheres and microspheres [J]. Adv. Mater., 2005, 17: 756-760.
    [46] Wei A, Sun X W, Xu C X, Dong Z L, Yu M B, Huang W. Stable field emission from hydrothermally grown ZnO nanotubes [J]. Appl. Phys. Lett., 2006, 88: 213102.
    [47] Wang J X, Sun X W, Yang Y, Huang H, Lee Y C, Tan O K, Vayssieres L. Hydrothermally grown oriented ZnO nanorod arrays for gas sensing applications [J]. Nanotechnology, 2006, 17: 4995-4998.
    [48] Feng P, Wang Q, Wang T H. Contact-controlled sensing properties of flowerlike ZnO nanostructures [J]. Appl. Phys. Lett., 2005, 87: 213111.
    [49] Yu Q J, Yu C L, Yang H B, Fu W Y, Chang L X, Xu J, Wei R H, Li H D, Zhu H Y, Li M H, Zou G T, Wang G R, Shao C L, Liu Y C. Growth of dumbbell-like ZnO microcrystals under mild conditions and their photoluminescence properties [J]. Inorg. Chem., 2007, 46: 6204-6210.
    [50] Wu G S, Xie T, Yuan X Y, Li Y, Yang L, Xiao Y H, Zhang L D. Controlled synthesis of ZnO nanowires or nanotubes via sol-gel template process [J]. Solid State Commun., 2005, 134: 485-489.
    [51] Li L, Pan S S, Dou X C, Zhu Y G, Huang X H, Yang Y W, Li G H, Zhang L D. Direct electrodeposition of ZnO nanotube arrays in anodic alumina membranes [J]. J. Phys. Chem. C, 2007, 111: 7288-7291.
    [52] Lv Y Z, Li C R, Guo L, Wang F C, Xu Y, Chu X F. Triethylamine gas sensor based on ZnO nanorods prepared by a simple solution route [J]. Sens. Actuators B, 2009, 141: 85-88.
    [53] Ge J P, Wang J, Zhang H X, Wang X, Peng Q, Li Y D. High ethanol sensitive SnO2 microspheres [J]. Sens. Actuators B, 2006, 113: 937-943.
    [54] Bae H Y, Choi G M. Electrical and reducing gas sensing properties of ZnO and ZnO-CuO thin films fabricated by spin coating method [J]. Sens. Actuators B, 1999, 55: 47-54.
    [55] Shen Y, Yamazaki T, Liu Z, Meng D, Kikuta T, Nakatani N, Saito M, Mori M. Microstructure and H2 gas sensing properties of undoped and Pd-doped SnO2 nanowires [J]. Sens. Actuators B, 2009, 135: 524-529.
    [56] Radecka M, Zakrzawska K, Rkas M. SnO2-TiO2 solid solutions for gas sensors [J]. Sens. Actuators B, 1998, 47: 194-204.
    [57] Xu J Q, Han J J, Zhang Y, Sun Y A, Xie B. Studies on alcohol sensing mechanism of ZnO based gas sensors [J]. Sens. Actuators B, 2008, 132: 334-339.
    [58] Bie L J, Yan X N, Yin J, Duan Y Q, Yuan Z H. Yuan, Nanopillar ZnO gas sensor for hydrogen and ethanol [J]. Sens. Actuators B, 2007, 126: 604-608.
    [59] Gong H, Hu J Q, Wang J H, Ong C H, Zhu F R. Nano-crystalline Cu-doped ZnO thin film gas sensor for CO [J]. Sens. Actuators B, 2006, 115: 247-251.
    [60] Liu J Z, Yan P X, Yue G H, Chang J B, Zhuo R F, Qu D M. Controllable synthesis of undoped/Cd-doped ZnO nanostructures [J]. Mater. Lett., 2006, 60: 3122-3125.
    [61] Saxena V, Aswal D K, Kaur M, Koiry S P, Gupta S K, Yakhmi J V, Kshirsagar R J, Deshpande S K. Enhanced NO2 selectivity of hybrid poly(3-hexylthiophene): ZnO-nanowire thin films [J]. Appl. Phys. Lett., 2007, 90: 043516.
    [62] Li L M, Li C C, Zhang J, Du Z F, Zou B S, Yu H C, Yang Y G, Wang T H. Bandgap narrowing and ethanol sensing properties of In-doped ZnO nanowires [J]. Nanotechnology, 2007, 18, 225504(4 pp).
    [63] Geng B Y, Fang C H, Zhan F M, Yu N. Synthesis of Polyhedral ZnSnO3 microcrystals with controlled exposed facets and their selective gas-sensing properties [J]. Small, 2008, 4: 1337-1343.
    [64] Wang Z L. Transmission electron microscopy of shape-controlled nanocrystals and their assemblies [J]. J. Phys. Chem. B, 2000, 104: 1153-1175.
    [65]徐甲强,刘艳丽,牛新书,ZnSnO3纳米粉体的合成及其气敏特性研究[J].硅酸盐学报,2002, 30: 321-324.
    [66] Shen Y S, Zhang T S. Preparation, structure and gas-sensing properties of ultramicro ZnSnO3 powder [J]. Sens. Actuators B, 1993, 12: 5-9.
    [67] Xu J Q, Jia X H, Lou X D, Xi G X, Han J J, Gao Q H. Selective detection of HCHO gas using mixed oxides of ZnO/ZnSnO3 [J]. Sens. Actuators B, 2007, 120: 694-699.
    [68] Xue X Y, Chen Y J, Wang Y G, Wang T H. Synthesis and ethanol sensing properties of ZnSnO3 nanowires [J]. Appl. Phys. Lett.. 2005, 86: 233101.
    [69]徐开先.实用新型传感器及其应用[M].辽宁:科学技术出版社,1995.
    [70]牛德芳.半导体传感器原理及其应用[M].大连:理工大学出版社,1993.
    [71]何丽萍.基于金属氧化物的甲醛气敏元件的研制[M].吉林:吉林大学电子科学与工程学院,2007.
    [72] Gong J W, Chen Q F, Lian M R, Liu N C, Stevenson R G, Adami F. Micromachined nanocrystalline silver doped SnO2 H2S senor [J]. Sens. Actuators B, 2006, 114: 32-39.
    [73] Kanda K, Maekawa T. Development of a WO3 thick-film-based sensor for the detection of VOC [J]. Sens. Actuators B, 2005, 108: 97-101.
    [74] Morrison S R. Selectivity in semiconductor gas sensors [J]. Sens. Actuators B, 1987, 12: 425-440.
    [75] Bielansky A, Haber J. Oxygen in catalysis on transition metal oxides [J]. Catal. Rev. Sci. Eng., 1979, 19: 1-41.
    [76] McAlleer J, Moseley P, Norris O W, Williams D E. Tin Dioxide gas sensors [J]. J. Chem. Soc., Faraday Trans., 1987, 183: 1323-1346.
    [77] Nanis L, Advani G. Effect of sorbed oxygen on tin oxide conductance [J]. Int. J. Electron., 1982, 52: 345-349.
    [78] Morrison S R. Semiconductor gas sensors [J]. Sens. Actuators B, 1982, 2: 329-341.
    [79] Yamazoe N, Sakai G, Shimanoe K. Oxide semiconductor gas sensors [J]. Catal. Surv. Asia, 2003, 7: 63-75.
    [80] Sberveglieri G, Coccoli G, Benussi P, Groppelli S, Nelli P. Electrical studies on oxygen ionosorption at ambient pressure on SnO2 (In) thin films [J]. Appl. Surf. Sci., 1989, 40: 169-174.
    [81]康昌鹤,唐省吾.气、湿敏感器件及其应用[M] .北京:科学出版社,1988.
    [82] Zemel J N. Theoretical description of gas-film interaction on SnOx [J]. Thin Solid Films, 1988, 163: 189-202.
    [83] G?pel W. Solid-state chemical sensors: atomistic models and research trends [J]. Sens. Actuators, 1989, 16: 167-193.
    [84] Coppa B J, Fulton C C, Kiesel S M, Davis R F, Pandarinath C, Burnette J E, Nemanich R J, Smith D J. Structural, microstructural, and electrical properties of gold films and Schottkycontacts on remote plasma-cleaned, n-type ZnO{0001} surfaces [J]. J. Appl. Phys., 2005, 97: 103517.
    [85] Gergintschew Z, Forster H, Kositza J, Schipanski D. Two-dimensional numberical simulation of semiconductor gas sensors [J]. Sens. Actuators B, 1995, 26: 170-173.
    [86] Yamazoe N. New approaches for improving semiconductor gas sensors, Sens. Actuators B [J]. 1991, 5: 7-19.
    [87] Caruso F. Nanoengineering of particle surfaces [J]. Adv. Mater., 2001, 13: 11-22.
    [88] Abe M, Kuroda J. Magneto-optical effects calculated for granular composites with magnetized nano-onions dispersed in matrixes [J]. J. Appl. Phys., 2002, 91: 7305.
    [89] Li J B, Wang L W. First principle study of core/shell structure quantum dots [J]. Appl. Phys. Lett., 2004, 84: 3648-3650.
    [90] Umakoshi M, Yoshitomi T, Kato A. Preparation of alumina and alumina-silica powders by wire explosion resulting from electric discharge [J]. J. Mater. Sci., 1995, 30: 1240-1244.
    [91] Wang Q, Yang H B, Shi J L, Zou G T. Preparation and characterization of nanocrystalline powders of Cu-Zn alloy by wire electrical explosion method [J]. Mater. Sci. Eng. A, 2001, 307: 190-194.
    [92] Zhang J, Sun L D, Yin J L, Su H L, Liao C H, Yan C H. Control of ZnO morphology via a simple solution route [J]. Chem. Mater., 2002, 14: 4172-4177.
    [93] Choi J D, Choi G M. Electrical and CO gas sensing properties of layered ZnO-CuO sensor [J]. Sens. Actuators B, 2000, 69: 120-126.
    [94] Nakamura Y, Yoshioka H, Miyayama M, Yanagida H, Tsurutani T, Nakamura Y. Selective CO gas sensing mechanism with CuO/ZnO heterocontact [J]. Electrochem., 1990, 137: 940-943.
    [95] Patil D R, Patil L A. Room temperature chlorine gas sensing using surface modified ZnO thick film resistors [J]. Sens. Actuators B, 2007, 123: 546-553.
    [96] Morrison S R. Mechanism of semiconductor gas sensor operation [J]. Sens. Actuators, 1987, 11: 283-287.
    [97] Chen H Y, Lau S P, Chen L, Lin J, Huan C A, Tan K L, Pan J S. Synergism between Cu and Zn sites in Cu/Zn catalysts for methanol synthesis [J]. Appl. Surf. Sci., 1999, 152: 193-199.
    [98] Malagu C, Guidi V, Stefancich M, Carotta M C, Martinelli G. Model for Schottky barrier and surface states in nanostructured n-type semiconductors [J]. J. Appl. Phys., 2002, 91: 808-814.
    [99] Hsueh T J, Hsu C L, Chang S J, Chen I C. Laterally grown ZnO nanowires ethanol gas sensors [J]. Sens. Actuators B, 2007, 126: 473-477.
    [100] Yoon D H, Yu J H, Choi G M, CO gas sensing properties of ZnO-CuO composite [J]. Sens. Actuators B, 1998, 46: 15-23.
    [101] Gao X D, Li X M, Yu W D. Flowerlike ZnO nanostructures via hexamethylenetetramine-assisted thermolysis of zinc-ethylenediamine complex [J]. J. Phys. Chem. B, 2005, 109: 1155-1161.
    [102] Fang Z, Tang K B, Shen G Z, Chen D, Kong R, Lei S J. Self-assembled ZnO 3D flowerlike nanostructures [J]. Mater. Lett., 2006, 60: 2530-2533.
    [103] Wang Z, Qian X F, Yin J, Zhu Z K. Large-scale fabrication of tower-like, flower-like, tube-like ZnO arrays by a simple chemical solution route [J]. Langmuir, 2004, 20: 3441-3448.
    [104] Pan A L, Yu R C, Xie S S, Zhang Z B, Jin C Q, Zou B S. ZnO flowers made up of thin nanosheets and their optical properties [J]. J. Cryst. Growth, 2005, 282: 165-172.
    [105] Shao S F, Jia P J, Liu S C, Bai W. Stable field emission from rose-like zinc oxide nanostructures synthesized through a hydrothermal route [J]. Mater. Lett., 2008, 62: 1200-1203.
    [106] Chen S J, Liu Y C, SHao C L, Mu R, Lu Y M, Zhang J Y, Shen D Z, Fan X W. Structural and optical properties of uniform ZnO nanosheets [J]. Adv. Mater., 2005, 17: 586-590.
    [107] Damen T C, Porto S P S, Tell B. Raman effect in zinc oxide [J]. Phys. Rev., 1966, 142: 570-574.
    [108] Porto S P S, Tell B, Damen T C. Near-forward Raman Scattering in zinc oxide [J]. Phys. Rev. Lett., 1966, 16: 450-452.
    [109] Pradhan A K, Zhang K, Loutts G B, Roy U N, Cui Y, Burger A. Structural and spectroscopic characteristics of ZnO and ZnO: Er3+ nanostructures [J]. J. Phys.: Condens. Matter, 2004, 16: 7123-7129.
    [110] Govender K, Boyle D S, Kenway P B, O’Brien P. Understanding the factors that govern the deposition and morphology of thin films of ZnO from aqueous solution [J]. J. Mater. Chem., 2004, 14: 2575-2591.
    [111] Zhang Z P, Sun H P, Shao X W, Li D F, Yu H D, Han M Y. Three-dimensionally oriented aggregation of a few hundred nanoparticles into monocrystalline architectures [J]. Adv. Mater., 2005, 17: 42-47. 109
    [112] Li Z Q, Xiong Y J, Xie Y. Selected-control synthesis of ZnO nanowires and nanorods via a PEG-assisted route [J]. Inorg. Chem., 2003, 42: 8105-8109.
    [113] Pachiolshi C, Kornowski A, Weller H. Self-assembly of ZnO: from nanodots to nanorods [J]. Angew. Chem., Int. Ed., 2002, 41: 1188-1191.
    [114] Zhang J, Sun L D, Liao C S, Yan C H. A simple route towards tubular ZnO [J]. Chem. Commun., 2002, 3: 262-263.
    [115] Yamazoe N, Fuchigami J, Kishikawa M, Seiyama T. Interaction of tin oxide surface with O2, H2O and H2 [J]. Surf. Sci., 1979, 86: 335-344.
    [116] Gerigintschew Z, F?rster H, Kositza J, Schipanski D. Two-dimensional numerical simulation of semiconductor gas sensors [J]. Sens. Actuators B, 1995, 26: 170-173.
    [117] Feng P, Xue X Y, Liu Y G, Wan Q, Wang T H. Achieving fast oxygen response in individualβ–Ga2O3 nanowires by ultraviolet illumination [J]. Appl. Phys. Lett., 2006, 89: 112114.
    [118] Halperin W P. Quantum size effects in metal particles [J]. Rev. Mod. Phys., 1986, 58: 533-606.
    [119] Zhang H, Yang D R, Ji Y J, Ma X Y, Xu J, Que D L. Low temperature synthesis of flowerlike ZnO nanostructures by cetyltrimethylammonium bromide-assisted hydrothermal process [J]. J. Phys. Chem. B, 2004, 108: 3955-3958.
    [120] Zhang H, Yang D R, Li D S, Ma X Y, Li S Z, Que D L, Controllable growth of ZnO microcrystals by a capping-molecule-assisted hydrothermal process [J]. Cryst. Growth Des., 2005, 5: 547-550.
    [121] mm285954.甲苯的球棍模型[EB/OL].[2010-01-28]. http://baike.baidu.com/image/35da1d3b5033ffc815cecb8d
    [122] Shinde V R, Gujar T P, Lokhande C D. LPG sensing properties of ZnO films prepared by spray pyrolysis method: effect of molarity of precursor solution [J]. Sens. Actuators B, 2007, 120: 551-559.
    [123] Jung S Y, Cho W, Lee H J, Oh M. Self-template-directed formation of coordination-polymer hexagonal tubes and rings, and their calcination to ZnO rings [J]. Angew. Chem., Int. Ed., 2008, 47: 1-5.
    [124] Yao K X, Sinclair R, Zeng H C. Symmetric linear assembly of hourglass-like ZnO nanostructures [J]. J. Phys. Chem. C, 2007, 111: 2032-2039.
    [125] Liu B, Zeng H C. Fabrication of ZnO“dandelions”via a modified Kirkendall process [J]. J. Am. Chem. Soc., 2004, 126: 16744-16746.
    [126] Gao P X, Wang Z L. Mesoporous polyhedral cages and shells formed by textured self-assembly of ZnO nanocrystals [J]. J. Am. Chem. Soc., 2003, 125: 11299-11305.
    [127] Peng W Q, Qu S C, Cong G W, Wang Z G. Synthesis and structures of morphology-controlled ZnO nano- and microcrystals [J]. Cryst. Growth Des., 2006, 6: 1518-1522.
    [128] Sounart T L, Liu J, Voigt J A, Huo M, Spoerke E D, McKenzie B. Secondary nucleation and growth of ZnO [J]. J. Am. Chem. Soc., 2007, 129: 15786-15793.
    [129] Jiang P, Zhou J J, Fang H F, Wang C Y, Wang Z L, Xie S S. Hierarchical shelled ZnO structures made of bunched nanowire arrays [J]. Adv. Funct. Mater., 2007, 17: 1303-1310.
    [130] Yu Q J, Fu W Y, Yu C L, Yang H B, Wei R H, Li M H, Liu S K, Sui Y M, Liu Z L, Yuan M X, Zou G T, Wang G R, Shao C L, Liu Y C. Fabrication and optical properties of large-scale ZnO nanotube bundles via a simple solution route [J]. J. Phys. Chem. C, 2007, 111: 17521-17526.
    [131] Li P, Wei Y, Liu H, Wang X K. Growth of well-defined ZnO microparticles with additives from aqueous solution [J]. J. Solid State Chem., 2005, 178: 855-860.
    [132] Sun X F, Qiu X Q, Li L P, Li G S. ZnO Twin-cones: synthesis, photoluminescence, and catalytic decomposition of ammonium perchlorate [J]. Inorg. Chem., 2008, 47: 4146-4152.
    [133] Penn R L, Banfield J F. Imperfect oriented attachment: dislocation generation in defect-free nanocrystals [J]. Science, 1998, 281: 969-971.
    [134] Zhao F H, Lin W J, Wu M M, Xu N S, Yang X F, Tian Z R, Su Q. Hexagonal and prismatic nanowalled ZnO microboxes [J]. Inorg. Chem., 2006, 45: 3256-3260.
    [135] Rosa E D L, Sepúlveda-Guzman S, Reeja-Jayan B, Torres A, Salas P, Elizondo N, Yacaman M J. Controlling the growth and luminescence properties of well-faceted ZnO nanorods [J]. J. Phys. Chem. C, 2007, 111: 8489-8495.
    [136] Lin K F, Cheng H M, Hsu H C, Hsieh W F. Band gap engineering and spatial confinement of optical phonon in ZnO quantum dots [J]. Appl. Phys. Lett., 2006, 88: 263117.
    [137] Yin Y D, Rioux R M, Erdonmez C K, Hughes S, Somorjai G A, Alivisatos A P. Formation of hollow nanocrystals through the nanoscaled Kirkendall Effect [J]. Science, 2004, 304: 711-714.
    [138] Park S, Lim J H, Chung S W, Mirkin C A. Self-assembly of mesoscopic metal-polymer amphiphiles [J]. Science, 2004, 303: 348-351.
    [139] Lu X M, Au L, McLellan J, Li Z Y, Marquez M, Xia Y N. Fabrication of cubic nanocages and nanoframes by dealloying Au/Ag alloy nanoboxes with an aqueous etchant based on Fe(NO3)3 or NH4OH [J]. Nano Lett., 2007, 7: 1764-1769.
    [140] Fowler C E, Khushalani D, Mann S. Interfacial synthesis of hollow microspheres of mesostructured silica [J]. Chem. Commun., 2001, 19: 2028-2029.
    [141] Liu B, Zeng H C. Mesoscale organization of CuO nanoribbons: formation of“dandelions”[J]. J. Am. Chem. Soc., 2004, 126: 8124-8125.
    [142] Kim S W, Kim M, Lee W Y, Hyeon T. Fabrication of hollow palladium spheres and their successful application to the recyclable heterogeneous catalyst for suzuki coupling reactions [J]. J. Am. Chem. Soc., 2002, 124: 7642-7643.
    [143] Sun Y, Mayers B T, Xia Y N, Template-engaged replacement reaction: a one-step approach to the large-scale synthesis of metal nanostructures with hollow interiors [J]. Nano. Lett., 2002, 2: 481-485.
    [144] Yin Y D, Erdonmez C, Aloni S, Alivisatos A P. Feceting of nanocrystals during chemical transformation: from solid silver spheres to hollow gold octahedral [J]. J. Am. Chem. Soc., 2006, 128: 12671-12673.
    [145] Kim D, Park J, An K, Yang N K, Park J G, Hyeon T. Synthesis of hollow iron nanoframes [J]. J. Am. Chem. Soc., 2007, 129: 5812-5813.
    [146] Penn R L, Banfield J F. Morphology development and crystal growth in nanocrystalline aggregates under hydrothermal conditions: insights from titania [J]. Geochim. Cosmochim. Acta, 1999, 63: 1549-1557.
    [147] Banfield J F, Welch S A, Zhang H Z, Ebert T T, Penn R L. Aggregation-based crystal growth and microstructure development in natural iron oxyhydroxide biomineralization products [J]. Science, 2000, 289: 751-754.
    [148] Huang F, Zhang H Z, Banfield J F. Two-stage crystal-growth kinetics observed during hydrothermal coarsening of nanocrystalline ZnS [J]. Nano Lett., 2003: 373-378.
    [149] Kim Y S, Ha S C, Kim K, Yang H, Choi S Y, Kim Y T, Park J T, Lee C H, Choi J, Paek J, Lee K. Room-temperature semiconductor gas sensor based on nonstoichiometric tungsten oxide nanorods film [J]. Appl. Phys. Lett., 2005, 86: 213105.