TiO2 及 ZnO具高催化活性、高穩定性、環境友善性而且售價便宜，廣泛運用於光催化，感測設備、光電設備等。含氯揮發性有機物(Cl-VOCs)大多具毒性及致癌性，易累積於環境中，TCE及CHCl3更因其在工業上的高使用率及高毒性而被認為是重點污染物之ㄧ，因此發展具新穎性、穩定性且高效率的處理方法成為本研究之重點，因此，本研究之主要目的包括：(1) 合成氧化鋅奈米柱(ZnO nanorods)薄膜；(2) ZnO nanorods薄膜感測及催化降解Cl-VOCs (TCE及CHCl3)；(3) 合成新穎自組網狀奈米線；及(4) 自組網狀奈米線催化TCE之測試；(5)感測及催化Cl-VOCs之鋅、鈦及鐵之即時精細結構分析。
實驗結果顯示，薄膜表面由直徑約150 nm排列良好之奈米柱所組成，ZnO nanordos薄膜對CHCl3 的感測性隨溫度上升而增加，而且具可接受之靈敏度(Rair/RCHCl3)，在溫度為573 K時，薄膜的靈敏度為13，X射線吸收光譜之延伸區微細結構(extended X-ray absorption fine structural (EXAFS))光譜顯示ZnO薄膜中鋅之Zn-O鍵距為1.962 Å，當通入1000 ppm CHCl3後Zn-O鍵距微幅減少至1.961 Å。進行光催化測試，發現經過300分鐘的UV光照射，約有40% 的污染物TCE被降解，並有中間產物產生。
SEM及VSM分析，發現TiO2磁性奈米催化劑的Fe與Ti分布均勻，並具易於收集及散佈的亞鐵磁性(ferrimagnetic)，在無磁場催化測試中，TiO2/Fe3O4@C (57%)與TiO2/Fe2O3 (55%)的催化效果均優於奈米TiO2 (P25)，除此之外，不論磁場存在與否，TiO2/Fe3O4@C的催化效果均高於TiO2/Fe2O3，並且在250 Gauss的磁場測試中，其降解效率高達70%。 即時X射線吸收近邊緣結構(X-ray absorption near edge structural, XANES)光譜顯示TiO2/Fe3O4@催化劑中鈦之主要物種為奈米TiO2 (77%)及TiO2原子簇(23%)，經過120分鐘的UV光照射後，在鐵的XANES光譜圖中發現，Fe3O4有接受電子往FeO移動變化的趨勢，其中FeO的含量由14%小幅增加至33%，

TiO2 and ZnO being environmental friendly and high chemical and mechanical stability are very effective in photocatalysis degradation processes. Nanosize ZnO and TiO2 have attracted great research interests and applications such as optoelectronics, sensing, field emission and piezoelectrics. Chlorinated volatile organic compounds (Cl-VOCs) are carcinogenic and extremely persistent in the environment. Of which, TCE and CHCl3 is chosen as the probe molecules because their emissions are associated to a wide range of industrial processes and are of great environmental concern. Thus, the main objectives of this work were (1) Synthesis of ZnO nanorods thin films, (2) Determination of sensitivity and photocatalysis of the ZnO thin films with Cl-VOCs (such as TCE and CHCl3), (3) Synthesis of novel reticular TiO2 nanowires, (4) Determination of photocatalysis of the reticular TiO2 nanowires with TCE, (5) Speciation studies of Zn, Ti and Fe in the ZnO nanorods thin films and reticular TiO2 nanowires.
Experimentally, well aligned ZnO nanorod arrays with a diameter of about 150 nm and a length of 2500 nm have been formed on the glass substrate. The sensitivities of the ZnO nanorod thin films in the presence of 1000 ppm CHCl3 are measured at 300-573 K. Note that the sensitivity of the ZnO nanorods is increased as the reaction temperature increases. For instance, at 573 K, the sensitivity of ZnO nanorods thin films is 13 approximately. The EXAFS data also shows that as CHCl3 is introduced onto the ZnO nanorods thin film, the bond distance of Zn-O is decreased slightly from 1.962 to 1.961 Å. During photocatalysis, by in situ FT-IR spectroscopy, splitting of C­H bonding of trichloroethylene (TCE) has been observed. Prolong the UV irradiation to 300 min, about 40% of TCE can be photocatalytically degraded. The intermediate dichloroacetyl chloride yielded during photocatalytic degradation of TCE has also been observed and eventually is oxidized to CO2 and HCl.
Scanning electron microscopy (SEM) and superconducting quantum interference device vibrating sample magnetometer (SQUID VSM) show that Fe and Ti are well dispersed. With typical ferrimagnetic properties, the catalyst well suspended and assembled in solution under an external magnetic field. During photocatalysis, in the presence of TiO2/Fe3O4@C and TiO2/Fe2O3, about 57% and 55% of TCE can be photocatalytically degraded without an external magnetic field. Under 250 Gauss magnetic field, the TiO2/Fe3O4@C has a greater efficiency (about 70%) for photocatalytic degradation of TCE.
The Ti K-edge least-square fitted XANES spectra of the TiO2/Fe3O4@C photocatalyst show that the main titanium species are nanosize TiO2 (9 nm) (77%) and bulky TiO2 (23%). Speciation of titanium in the TiO2/Fe3O4@C during photocatalytic degradation of 100 ppm trichloroethylene (TCE) has also been studied by in situ X-ray absorption near-edge structural (XANES) spectroscopy. TiO2 is not perturbed during the course of photocatalysis. Nevertheless, about 33% of FeO and 67% of Fe3O4 are observed under photocatalytic degradation of TCE for 120 min, suggesting that the carbon layer on the TiO2/Fe3O4@C photocatalysts can reduce the process of photoexcited electron-hole recombination as usually found on the relatively narrow bandgap of ferric oxide during photocatalysis.

REFERENCES
Amama, P. B., Itoh, K., & Murabayashi, M. (2001). Photocatalytic oxidation of trichloroethylene in humidified atmosphere. Journal of Molecular Catalysis a-Chemical, 176(1-2), 165-172.

Ao, Y. H., Xu, J. J., Fu, D. G., Ba, L., & Yuan, C. W. (2008). Deposition of anatase titania onto carbon encapsulated magnetite nanoparticles. Nanotechnology, 19(40), 6.

Ao, Y. H., Xu, J. J., Fu, D. G., Shen, X. W., & Yuan, C. W. (2008). A novel magnetically separable composite photocatalyst: Titania-coated magnetic activated carbon. Separation and Purification Technology, 61(3), 436-441.

Bae, H. Y., & Choi, G. M. (1999). Electrical and reducing gas sensing properties of ZnO and ZnO-CuO thin films fabricated by spin coating method. Sensors and Actuators B-Chemical, 55(1), 47-54.

Bandyopadhyay, S., Paul, G. K., Roy, R., Sen, S. K., & Sen, S. (2002). Study of structural and electrical properties of grain-boundary modified ZnO films prepared by sol-gel technique. Materials Chemistry and Physics, 74(1), 83-91.

Bene, R., Kiss, G., Perczel, I. V., Meyer, F. A., & Reti, F. (1998). Application of quadrupole mass spectrometer for the analysis of near-surface gas composition during DC sensor-tests.Vacuum. 331-337.

Berlier, G., Pourny, M., Bordiga, S., Spoto, G., Zecchina, A., & Lamberti, C. (2005). Coordination and oxidation changes undergone by iron species in Fe-MCM-22 upon template removal, activation and red-ox treatments: an in situ IR, and XANES study. Journal of Catalysis, 229(1), 45-54.

Beydoun, D., Amal, R., Low, G. K. C., & McEvoy, S. (2000). Novel photocatalyst: Titania-coated magnetite. Activity and photodissolution. Journal of Physical Chemistry B, 104(18), 4387-4396.

Beydoun, D., Amal, R., Low, G., & McEvoy, S. (2002). Occurrence and prevention of photodissolution at the phase junction of magnetite and titanium dioxide. Journal of Molecular Catalysis a-Chemical, 180(1-2), 193-200.

Cheng, X. L., Zhao, H., Huo, L. H., Gao, S., & Zhao, J. G. (2004). ZnO nanoparticulate thin film: preparation, characterization and gas-sensing property. Sensors and Actuators B-Chemical, 102(2), 248-252.

Chen, C. L., Dong, C. L., Rao, S. M., Chern, G., Chen, M. C., Wu, M. K., & Chang, C. L. (2008). Investigation of the valence states of Fe and Co in Fe1-xCoxOy (0 < x < 1) thin films by x-ray absorption spectroscopy. Journal of Physics-Condensed Matter, 20(25), 4.

Chien, Y. C., & Wang, H. P. (2005). In situ X-ray absorption spectroscopic studies of CCl4 mineralization with CuO. Journal of Electron Spectroscopy and Related Phenomena, 315-318.

Choopun, S., Hongsith, N., Mangkorntong, P., & Mangkorntong, N. (2007). Zinc oxide nanobelts by RF sputtering for ethanol sensor. Physica E-Low-Dimensional Systems & Nanostructures, 39(1), 53-56.

D'Andrea, P., Lai, K. C. K., Kjeldsen, P., & Lo, I. M. C. (2005). Effect of groundwater inorganics on the reductive dechlorination of TCE by zero-valent iron. Water Air and Soil Pollution, 162(1-4), 401-420.

Decher, G. (1997). Fuzzy nanoassemblies: Toward layered polymeric multicomposites. Science, 277(5330), 1232-1237.

Driessen, M. D., Miller, T. M., & Grassian, V. H. (1998). Photocatalytic oxidation of trichloroethylene on zinc oxide: characterization of surface-bound and gas-phase products and intermediates with FT-IR spectroscopy. Journal of Molecular Catalysis a-Chemical, 131(1-3), 149-156.

Fountain, J. C., (1998) “Technology for Dense Nonaqueous Phase LiquidSource Zone Remediation”, Ground-Water Remediation Technologies Analysis Center, TE-98-02.

Fu, X. Z., Zeltner, W. A., & Anderson, M. A. (1995). The Gas-Phase Photocatalytic Mineralization of Benzene on Porous Titania-Based Catalysts. Applied Catalysis B-Environmental, 6(3), 209-224.

Fujishima, A., Hashoimoto K., Watanabe T. (1999) TiO2 Photocatalysis Fundamentals and Application. BKC Inc.125.

Gonzalez-Velasco, J. R., Aranzabal, A., Gutierrez-Ortiz, J. I., Lopez-Fonseca, R., & Gutierrez-Ortiz, M. A. (1998). Activity and product distribution of alumina supported platinum and palladium catalysts in the gas-phase oxidative decomposition of chlorinated hydrocarbons. Applied Catalysis B-Environmental, 19(3-4), 189-197.

Hartnagel, H. L., Dawar, A. L., Jain, A. K., and Jagadish, C (1995). Semiconducting transparent thin films, Institude of Physics Publishing, London.

Hermanson, K. D., Lumsdon, S. O., Williams, J. P., Kaler, E. W., & Velev, O. D. (2001). Dielectrophoretic assembly of electrically functional microwires from nanoparticle suspensions. Science, 294(5544), 1082-1086.

Hoffmann, M. R., Martin, S. T., Choi, W. Y., & Bahnemann, D. W. (1995). Environmental Applications of Semiconductor Photocatalysis. Chemical Reviews, 95(1), 69-96.

Holger T. Grahn, (1999). Introduction to Semiconductor Physics

Hong, R. Y., Zhang, S. Z., Di, G. Q., Li, H. Z., Zheng, Y., Ding, J., & Wei, D. G. (2008). Preparation, characterization and application of Fe3O4/ZnO core/shell magnetic nanoparticles. Materials Research Bulletin, 43(8-9), 2457-2468.

Huang, Z. P., Wu, J. W., Ren, Z. F., Wang, J. H., Siegal, M. P., & Provencio, P. N. (1998). Growth of highly oriented carbon nanotubes by plasma-enhanced hot filament chemical vapor deposition. Applied Physics Letters, 73(26), 3845-3847.

Huang, Y. J. & Wang, H. P. (1999). Reduction of NO with CH4 effected by copper oxide clusters in the channels of ZSM-5. Journal of Physical Chemistry A, 103(33), 6514-6516.

Huang, C. P., Hsieh, W. P., Pan, J. R. S., & Chang, S. M. (2007). Characteristic of an innovative TiO2/Fe0 composite for treatment of azo dye. Separation and Purification Technology, 58(1), 152-158.

Hsiung, T. L., Wang, H. P., Lu, Y. M., & Hsiao, M. C. (2006). In situ XANES studies of CuO/TiO2 thin films during photocatalytic degradation of CHCl3. Radation Physics and Chemistry, 75(15), 2054-2057.

Jacoby, W. A., Blake, D. M., Fennell, J. A., Boulter, J. E., Vargo, L. M., George, M. C., & Dolberg, S. K. (1996). Heterogeneous photocatalysis for control of volatile organic compounds in indoor air.

Kang, M., Lee, J. H., Lee, S. H., Chung, C. H., Yoon, K. J., Ogino, K., Miyata, S., & Choung, S. J. (2003).
Preparation of TiO2 film by the MOCVD method and analysis for decomposition of trichloroethylene using in situ FT-IR spectroscopy. Journal of Molecular Catalysis a-Chemical, 193(1-2), 273-283.

Kao, C. M., Chen, S. C., & Su, M. C. (2001). Laboratory column studies for evaluating a barrier system for providing oxygen and substrate for TCE biodegradation. Chemosphere, 44(5), 925-934.

Kao, C. M., Chen, Y. L., Chen, S. C., Yeh, T. Y., & Wu, W. S. (2003). Enhanced PCE dechlorination by biobarrier systems under different redox conditions. Water Research, 37(20), 4885-4894.

Kao, C. M., Huang, K. D., Wang, J. Y., Chen, T. Y., & Chien, H. Y. (2008). Application of potassium permanganate as an oxidant for in situ oxidation of trichloroethylene-contaminated groundwater: A laboratory and kinetics study. Journal of Hazardous Materials, 153(3), 919-927.

Kawi, S., & Te, M. (1998). MCM-48 supported chromium catalyst for trichloroethylene oxidation. Catal Today, 44, 101-109.

Khodja, A. A., Sehili, T., Pilichowski, J. F., & Boule, P. (2001). Photocatalytic degradation of 2-phenylphenol on TiO2 and ZnO in aqueous suspensions. Journal of Photochemistry and Photobiology A-Chemistry, 141(2-3), 231-239.

Koshizaki, N., & Oyama, T. (2000). Sensing characteristics of ZnO-based NOx sensor. Sensors and Actuators B-Chemical, 66, 119–121.

Lee, M. H., Clingenpeel, S. C., Leiser, O. P., Wymore, R. A., Sorenson, K. S., & Watwood, M. E. (2008). Activity-dependent labeling of oxygenase enzymes in a trichloroethene-contaminated groundwater site. Environmental Pollution, 153(1), 238-246.

Li, B. S., Liu, Y. C., Zhi, Z. Z., Shen, D. Z., Lu, Y. M., Zhang, J. Y., Kong, X. G., & Fan, X. W. (2002). Effect of the growth temperature on ZnO thin films grown by plasma enhanced chemical vapor deposition. Thin Solid Films, 414(2), 170-174.

Li, Q. C., Kumar, V., Li, Y., Zhang, H. T., Marks, T. J., & Chang, R. P. H. (2005). Fabrication of ZnO nanorods and nanotubes in aqueous solutions. Chemistry of Materials, 17(5), 1001-1006.

Lin, K. S., & Wang, H. P. (1999). Shape selectivity of trace by-products for supercritical water oxidation of 2-chlorophenol effected by CuO/ZSM-48. Applied Catalysis B-Environmental, 22(4), 261-267.

Lin, K. S., & Wang, H. P. (2000). Byproduct shape selectivity in supercritical water oxidation of 2-chlorophenol effected by CuO/ZSM-5. Langmuir, 16(6), 2627-2631.

Linsebigler, A. L., Lu, G. Q., & Yates, J. T. (1995). Photocatalysis on TiO2 Surfaces - Principles, Mechanisms, and Selected Results. Chemical Reviews, 95(3), 735-758.

Lu, L., Lai, M. O., & Zhang, S. (1994). Fabrication of Ni3al Intermetallic Compound Using Mechanical Alloying Technique. Journal of Materials Processing Technology, 48, 683-690.

Mitra, P., Chatterjee, A. P., & Maiti, H. S. (1998). ZnO thin film sensor. Materials Letters, 35(1-2), 33-38.

Namiesnik, J., Gorecki, T., Kozdronzabiegala, B., & Lukasiak, J. (1992). Indoor Air-Quality (Iaq), Pollutants, Their Sources and Concentration Levels. Building and Environment, 27(3), 339-356.

Nilsen, M. H., Nordhei, C., Ramstad, A. L., Nicholson, D. G., Poliakoff, M., & Cabanas, A. (2007). XAS (XANES and EXAFS) investigations of nanoparticulate ferrites synthesized continuously in near critical and supercritical water. Journal of Physical Chemistry C, 111(17), 6252-6262.

Nimios, M. R., Jacoby, W. A., Blake, D. M., & Milne, T. A. (1993). Direct Mass-Spectrometric Studies of the Destruction of Hazardous Wastes .2. Gas-Phase Photocatalytic Oxidation of Trichloroethylene over TiO2 - Products and Mechanisms. Environmental Science & Technology, 27(4), 732-740.

Ohyama, M., Kozuka, H., & Yoko, T. (1997). Sol-gel preparation of ZnO films with extremely preferred orientation along (002) plane from zinc acetate solution. Thin Solid Films, 306(1), 78-85.

Paria, S. (2008). Surfactant-enhanced remediation of organic contaminated soil and water. Advances in Colloid and Interface Science, 138(1), 24-58.

Prins, F. E., Lehr, G., Burkard, M., Nikitin, S. Y., Schweizer, H., & Smith, G. W. (1993). Quantum Dots and Quantum Wires with High Optical-Quality by Implantation-Induced Intermixing. Japan J Applied Physics, 6228-6232.

Ranjit, K. T., & Viswanathan, B. (1997). Synthesis, characterization and photocatalytic properties of iron-doped TiO2 catalysts. Journal of Photochemistry and Photobiology a-Chemistry, 108(1), 79-84.

Roh, Y., Lee, S. Y., Elless, M. P., & Moon, H. S. (2000). Electro-enhanced remediation of trichloroethene-contaminated groundwater using zero-valent iron. Journal of Environmental Science and Health Part a-Toxic/Hazardous Substances & Environmental Engineering, 35(7), 1061-1076.

Roobol, N.R. (1991) Industrial Painting: Principles and Practices. Carol Stream, IL: Hitchcock Publishing Co.
Ryoo, R., Joo, S. H., Kruk, M., & Jaroniec, M. (2001). Ordered mesoporous carbons. Advanced Materials, 13(9), 677-681.

Sakthivel, S., Neppolian, B., Shankar, M. V., Arabindoo, B., Palanichamy, M., & Murugesan, V. (2003). Solar photocatalytic degradation of azo dye: comparison of photocatalytic efficiency of ZnO and TiO2. Solar Energy Materials and Solar Cells, 77(1), 65-82.

Saito, S., Miyayama, M., Koumoto, K., & Yanagida, H. (1985). Gas Sensing Characteristics of Porous ZnO and Pt/ZnO Ceramics. Journal of the American Ceramic Society, 68(1), 40-43.

Samuneva, B., Kozhukharov, V., Trapalis, C., & Kranold, R. (1993). Sol-Gel Processing of Titanium-Containing Thin Coatings.1. Preparation and Structure. Journal of Materials Science, 28(9), 2353-2360.

Schleibinger, H., & Ruden, H. (1999). Air filters from HVAC systems as possible source of volatile organic compounds (VOC) - laboratory and field assays. Atmospheric Environment, 33(28), 4571-4577.

Sharma, A., Rao, P., Mathur, R. P., & Ameta, S. C. (1995). Photocatalytic Reactions of Xylidine Ponceau on Semiconducting Zinc-Oxide Powder. Journal of Photochemistry and Photobiology A-Chemistry, 86(1-3), 197-200.

Stambolova, I., Konstantinov, K., Vassilev, S., Peshev, P., & Tsacheva, T. (2000). Lanthanum doped SnO2 and ZnO thin films sensitive to ethanol and humidity. Materials Chemistry and Physics, 63(2), 104-108.

Song, X. F., & Gao, L. (2007). Fabrication of bifunctional titania/silica-coated magnetic spheres and their photocatalytic activities. Journal of the American Ceramic Society, 90(12), 4015-4019.

Stern, E. A., Newville, M., Ravel, B., Yacoby, Y., & Haskel, D. (1995). The Uwxafs Analysis Package - Philosophy and Details. Physcia B-Condensed Matter 208&209.117-120.

Toshko, G. N., & Stefcho, P. Y. (1996). Ceramic sensors, Technomic Publishing Company Inc. New Holland Avenue.
U. S. EPA. (1993). An Overview of Underground Storage Tank Remediation Options. Office of Solid Waste and Emergency Response. EPA-510-F-93-029.

Vogelpohl, A., & Kim, S. M. (2004). Advanced oxidation processes (AOPs) in wastewater treatment. Journal of Industrial and Engineering Chemistry, 10(1), 33-40.

Wendler, L., & Kandler, E. (1994). Theory of the Photoacoustic Effect of Semiconductor Quantum-Wells. Applied Physics a-Materials Science & Processing, 58(2), 167-175.

Xu, J. X., & Wang, K. Y. (2008). Pulsed electrodeposition of monocrystalline Ni nanowire array and its magnetic properties. Applied Surface Science, 254(20), 6623-6627.

Xu, S., & Shangguan, w. (2007). Preparation and photocatalytic properties of magnetically separable TiO2 supported on nickel ferrite. Applied Catalysis B-Environmental, 71, 177-184

Xuan, S. H., Hao, L. Y., Jiang, W. Q., Gong, X. L., Hu, Y., & Chen, Z. Y. (2007). A facile method to fabricate carbon-encapsulated Fe3O4 core/shell composites. Nanotechnology, 18(3), 6.

Yasunaga, N., & Hirotsuji, J. (2008). Efficient decomposition of trichloroethylene (TCE) in groundwater by ozone-hydrogen peroxide treatment. Ozone-Science & Engineering, 30(2), 127-135.

Yin, Y., & Allen H. E. (1999). In Situ Chemical Treatment. GroundWater Remediation Technologies Analysis Center, TE-99-01.

Yoon, J., Choi, Y., Cho, S., & Lee, D. (2003). Low trihalomethane formation in Korean drinking water. Science of the Total Environment, 302(1-3), 157-166.

Yubuta, K., Sato, T., Nomura, A., Haga, K., & Shishido, T. (2007). Structural characterization of ZnO nano-chains studied by electron microscopy. Journal of Alloys and Compounds, 436(1-2), 396-399.

Zabinsky, S. I., Rehr, J. J., Ankudinov, A., Albers, R. C., & Eller, M. J. (1995). Multiple-Scattering Calculations of X-Ray-Absorption Spectra. Physical Review B, 52(4), 2995-3009.

Zhai, X. H., Hua, I., Rao, P. S. C., & Lee, L. S. (2006). Cosolvent-enhanced chemical oxidation of perchloroethylene by potassium permanganate. Journal of Contaminant Hydrology, 82(1-2), 61-74.

Zhang, M., Zhou, Z. Y., Yang, X., Ye, X. Y., & Wang, Z. L. (2008). Fabrication of ZnO nanowire devices via selective electrodeposition. Electrochemical and Solid State Letters, 11(9), D69-D71.

Zou, L., Luo, Y. G., Hooper, M., & Hu, E. (2006). Removal of VOCs by photocatalysis process using adsorption enhanced TiO2-SiO2catalyst. Chemical Engineering and Processing, 45(11), 959-964.