The Ag-nanoparticles (Ag-NP)/TiO 2 composite thin films with various amounts of Ag (10 mol% ≤ n ≤ 80 mol%) were examined as a potential photocatalyst by decoloration reaction of methylene blue (MB) in an aqueous solution. These composite thin films of ca. 100 nm thickness were fabricated by the MPM at 600 °C in air. The decoloration rates monitored by the absorption intensity of the MB solution indicated that the composite thin films of Ag with an amount less than 40 mol% are not effective under vis-irradiation, though they can work as a photocatalyst under UV-irradiation. Further, the UV-sensitivity of the composite thin films gradually decreased to almost half the level of that of the TiO 2 thin film fabricated under the identical conditions when the Ag amount increased from 10 to 40 mol%. Contrarily, the composite thin films of Ag content larger than 50 mol% showed the vis-responsive activity, whose level was slightly lower than the decreased UV-sensitivity. Diffuse reflectance spectra suggested that the vis-responsive activity of the composite thin films is due to the conductivity, localized surface plasmon resonance and surface plasmon resonance of Ag-NP. It was also elucidated that the vis-responsive level of the composite thin films corresponds to their electrical conductivity that depends on the Ag content.
References
[1]
Fujishima, A.; Rao, T.N.; Truk, D.A. Titanium dioxide photocatalysis. J. Photochem. Photobiol. C 2000, 1, 1–21, doi:10.1016/S1389-5567(00)00002-2.
[2]
Fujishima, A.; Honda, K. Electrochemical photolysis of water at a semiconductor electrode. Nature 1972, 238, 37–38, doi:10.1038/238037a0.
[3]
Rehman, S.; Ullah, R.; Butt, A.M.; Gohar, N.D. Strategies of making TiO2 and ZnO visible light active. J. Hazard. Mater. 2009, 170, 560–569, doi:10.1016/j.jhazmat.2009.05.064.
[4]
Hamal, D.B.; Klabunde, K.J. Synthesis, characterization, and visible light activity of new nanoparticle photocatalysts based on silver, carbon, and sulfur-doped TiO2. J. Colloid Interface Sci. 2007, 311, 514–522, doi:10.1016/j.jcis.2007.03.001.
[5]
K？r？si, L.; Bertóti, S.P.I.; Dékány, I. Surface and bulk composition, structure and photocatalytic activity of phosphate modified TiO2. Chem. Mater. 2007, 19, 4811–4819, doi:10.1021/cm070692r.
[6]
K？r？si, L.; Oszkó, A.; Galbács, G.; Richardt, A.; Z？llmer, V.; Dékány, I. Structural properties and photocatalytic behaviour of phosphate-modified nanocrystalline titania films. J. Appl. Catal. B 2007, 77, 175–183, doi:10.1016/j.apcatb.2007.07.019.
[7]
Janovák, L.; Veres, á.; Bujdosó, T.; Rica, T.; Fodor, E.; Tallósy, S.; Buzás, N.; Nagy, E.; Dékány, I. Silver and phosphate functionalized reactive TiO2/polymer nanocomposite films for destructions resistant bacteria using visible light. J. Adv. Oxid. Technol. 2011, 15, 205–216.
[8]
Loganathan, K.; Bommusamy, P.; Muthaiahpillai, P.; Velayutham, M. The syntheses, characterizations, and photocatalytic activities of silver, platinum, and gold doped TiO2 nanoparticles. Environ. Eng. Res. 2012, 16, 81–90.
[9]
Liu, S.X.; Qu, Z.P.; Han, X.W.; Sun, C.L. A mechanism for enhanced photocatalytic activity of silver-loaded titanium dioxide. Catal. Today 2004, 93–95, 877–884.
[10]
Jakob, M.; Levanon, H.; Dame, N. Charge distribution between UV-irradiated TiO2 and gold nanoparticles: Determination of shift in the fermi level. Nano Lett. 2003, 3, 353–358, doi:10.1021/nl0340071.
[11]
Hirakawa, T.; Kamat, P.V. Charge Separation and Catalytic Activity of Ag@TiO2 Core-Shell Composite Clusters under UV-Irradiation. J. Am. Chem. Soc. 2005, 127, 3928–3934, doi:10.1021/ja042925a.
[12]
Yu, J.; Dai, G.; Huang, B. Fabrication and characterization of visible-light-driven plasmonic photocatalyst Ag/AgCl/TiO2 nanotube arrays. J. Phys. Chem. C 2009, 113, 16394–16401, doi:10.1021/jp905247j.
[13]
Dahmen, C.; Sprafke, A.N.; Dieker, H.; Wuttig, M.; von Plessen, G. Opticaland structural changes of silver nanoparticles during photochromic transformation. Appl. Phys. Lett. 2006, 88, 11923, doi:10.1063/1.2163268.
[14]
Standridge, S.D.; Schatz, G.C.; Hupp, J.T. Toward Plasmonic Solar Cells: Protection of Silver Nanoparticles via Atomic Layer Deposition of TiO2. Langmuir 2009, 25, 2596–600, doi:10.1021/la900113e.
[15]
Wodka, D.; Bielańska, E.; Socha, R.P.; Elzbieciak-Wodka, M.; Gurgul, J.; Nowak, P.; Warszyński, P. Photocatalytic activity of titanium dioxide modified by silver nanoparticles. ACS Appl. Mater. Interfaces 2010, 2, 1945–1953, doi:10.1021/am1002684.
[16]
Rad, B. Enhancement of photocatalytic activity of TiO2 nanoparticles by silver doping: photodeposition versus liquid impregnation methods. Global NEST J. 2008, 10, 1–7.
[17]
Turkevich, J.; Stevenson, P.C.; Hillier, J. A study of the nucleation and growth processes in the synthesis of colloidal gold. Discuss. Faraday Soc. 1951, 11, 55, doi:10.1039/df9511100055.
[18]
Enustun, B.V.; Turkevich, J. Coagulation of colloidal gold. J. Am. Chem. Soc. 1963, 85, 3317, doi:10.1021/ja00904a001.
[19]
Frens, G. Controlled nucleation for the regulation of the particle size in monodisperse gold suspensions. Nat. Phys. Sci. 1973, 20, 241.
[20]
Kumar, K.P.; Paul, W.; Sharma, C.P. Green synthesis of silver nanoparticles with zingiber officinale extract and study of its blood compatibility. BioNanoScience 2012, 2, 144–152, doi:10.1007/s12668-012-0044-7.
[21]
Kuntyi, O.; Okhremchuk, Y.; Bilan’, O.; Hapke, J.; Saldan, I. Silver particles growth by pulse electrolysis in acetonitrile solutions. Central Eur. J. Chem. 2013, 11, 514–518, doi:10.2478/s11532-012-0189-9.
[22]
Patakfalvi, R.; Papp, S.; Dékány, I. The kinetics of homogeneous nucleation of silver nanoparticles stabilized by polymers. J. Nanopart. Res. 2007, 9, 353–364, doi:10.1007/s11051-006-9139-9.
Grabowska, E.; Zaleska, A.; Sorgues, S.; Kunst, M.; Etcheberry, A.; Colbeau-Justin, C.; Remita, H. Modification of titanium(IV) dioxide with small silver nanoparticles: application in photocatalysis. J. Phys. Chem. C 2013, 117, 2013.
[25]
Li, H.; Zhao, G.; Song, B.; Han, G. Effect of incorporation of silver on the electrical properties of sol-gel-derived titania film. J. Cluster Sci. 2008, 19, 667–673, doi:10.1007/s10876-008-0207-4.
[26]
Takahashi, Y.; Tatsuma, T. Electrodeposition of thermally stable gold and silver nanoparticle ensembles through a thin alumina nanomask. Nanoscale 2010, 2, 1494–1499, doi:10.1039/c0nr00230e.
[27]
Awazu, K.; Fujimaki, M.; Rockstuhl, C.; Tominaga, J.; Murakami, H.; Ohki, Y.; Yoshida, N.; Watanabe, T. A plasmonic photocatalyst consisting of silver nanoparticles embedded in titanium dioxide. J. Am. Chem. Soc. 2008, 130, 1676–1680, doi:10.1021/ja076503n.
[28]
Ménesi, J.; Kékesi, R.; Oszkó, A.; Z？llmer, V.; Seemann, T.; Richardt, A.; Dékány, I. Photocatalysis on silver-layer silicate/titanium dioxide composite thin films at solid/vapour interface. Catal. Today 2009, 144, 160–165, doi:10.1016/j.cattod.2009.02.030.
[29]
Ménesi, J.; Kékesi, R.; Z？llmer, V.; Seemann, T.; Richardt, A.; Dékány, I. Photooxidation of ethanol on Cu-layer silicate/TiO2 composite thin films. React. Kinet. Calal. Lett. 2009, 96, 367–377, doi:10.1007/s11144-009-5532-6.
[30]
Sato, M.; Hara, H.; Niside, T.; Sawada, Y. A Water-resistant precursor in a wet process for TiO2 thin film formation. J. Mater. Chem. 2006, 6, 1767–1770.
[31]
Nagai, H.; Aoyama, S.; Hara, H.; Mochizuki, C.; Takano, I.; Honda, T.; Sato, M. Photoluminescence and photoreactivity affected by oxygen defects in crystal-oriented rutile thin film fabricated by molecular precursor method. J. Mater. Sci. 2010, 45, 5704–5710, doi:10.1007/s10853-010-4640-z.
[32]
Likius, D.S.; Nagai, H.; Aoyama, S.; Mochizuki, C.; Hara, H.; Baba, N.; Sato, M. Percolation threshold for electrical resistivity of Ag-nanoparticle/titania composite thin films fabricated using molecular precursor method. J. Mater. Sci. 2012, 47, 3890–3899, doi:10.1007/s10853-011-6245-6.
[33]
Daniel, L.S.; Nagai, H.; Sato, M. Photoelectrochemical property and the mechanism of plasmonic Ag-NP/TiO2 composite thin films with high silver content fabricated using molecular precursor method. J. Mater. Sci. 2013, doi:10.1007/s10853–013–7533–0.
[34]
Kang, J.-G.; Sohn, Y. Interfacial nature of Ag nanoparticles supported on TiO2 photocatalysts. J. Mater. Sci. 2012, 47, 824–832, doi:10.1007/s10853-011-5860-6.
[35]
Wan, L.; Li, J.F.; Feng, J.Y.; Sun, W.; Mao, Z.Q. Improved optical response and photocatalysis for N-doped titanium oxide (TiO2) films prepared by oxidation of TiN. Appl. Surface Sci. 2007, 253, 4764–4767, doi:10.1016/j.apsusc.2006.10.047.
[36]
He, W.F.Z.Y.L.; Zhang, M.S.; Yin, Z.; Chen, Q. Raman scattering study on anatase TiO2 nanocrystals. J. Phys. D 2000, 33, 912, doi:10.1088/0022-3727/33/8/305.
[37]
Li, J.; Xu, J.; Dai, W.; Fan, K. Dependence of Ag Deposition Methods on the Photocatalytic Activity and Surface State of TiO2 with Twistlike Helix Structure. J. Phys. Chem. C 2009, 113, 8343–8349.
[38]
Kortum, G. Reflectance Spectroscopy; Springer-Verlag: Berlin, Germany, 1969; p. 180.
[39]
K？r？si, L.; Papp, S.; Ménesi, J.; Illés, E.; Z？llmer, V.; Richardt, A.; Dékány, I. Photocatalytic activity of silver-modified titanium dioxide at solid-liquid and solid-gas interfaces. Colloids Surfaces A 2008, 319, 136–142, doi:10.1016/j.colsurfa.2007.11.030.
[40]
Nagai, H.; Mochizuki, C.; Hara, H.; Takano, I.; Sato, M. Enhanced UV-sensitivity of Vis-responsive Anatase Thin Films Fabricated by Using Precursor Solutions Involving Ti Complexes. Solar Energy Mater. Solar Cell. 2008, 92, 1136–1144, doi:10.1016/j.solmat.2008.04.005.
[41]
Christopher, P.; Xin, H.; Linic, S. Visible-light-enhanced catalytic oxidation reactions on plasmonic silver nanostructures. Nat. Chem. 2011, 3, 467–472.
[42]
Li, H.; Bian, Z.; Zhu, J.; Huo, Y.; Li, H.; Lu, Y. Mesoporous Au/TiO2 nano-composites with enhanced photocatalytic activity. J. Am. Chem. Soc. 2007, 129, 4538, doi:10.1021/ja069113u.
[43]
Kosanic, M.M. Photocatalytic degradation of oxalic acid over TiO2 power. J. Photochem. Photobiol. A 1998, 119, 119–122, doi:10.1016/S1010-6030(98)00407-9.
[44]
Kiyonaga, T.; Mitsui, T.; Torikoshi, T.M.; Takekawa, M.; Soejima, T.; Tada, H. Ultrafast photosynthetic reduction of elemental sulfur by Au nanoparticle-loaded TiO2. J. Phys. Chem. B 2006, 110, 10771, doi:10.1021/jp061528e.
[45]
Yang, X.; Wang, Y.; Xu, L.; Yu, X.; Guo, Y. Silver and indium oxide codoped TiO2 nanocomposites with enhanced photocatalytic activity. J. Phys. Chem. C 2008, 112, 11481–11489, doi:10.1021/jp803559g.
[46]
Lee, P.C.; Meisel, D.J. Adsorption and surface-enhanced Raman of dyes on silver and gold sols. Phys. Chem. 1982, 86, 3391–3395, doi:10.1021/j100214a025.
[47]
Nagai, H.; Hasegawa, M.; Hara, H.; Mochizuki, C.; Takano, I.; Sato, M. An important factor controlling the photoreactivity of titania: O-deficiency of anatase thin film. J. Mater. Sci. 2008, 43, 6902–6911, doi:10.1007/s10853-008-2993-3.
[48]
Nagai, H.; Aoyama, S.; Hara, H.; Mochizuki, C.; Takano, I.; Baba, N.; Sato, M. Rutile thin film responsive to visible light and with high UV light sensitivity. J. Mater. Sci. 2009, 44, 861–868, doi:10.1007/s10853-008-3185-x.
