This work demonstrates how formation of strongly chemiluminescent 3-hydroxyphthalic hydrazide by hydroxylation of non-chemiluminescent phthalic hydrazide can be applied as a selective reaction probe to obtain information on authentic hydroxyl radical, i.e., ？OH aq, formation, in black light illuminated Degussa P25 TiO 2 aerated suspensions in the pH range from 3 to 11. The ？OH aq formation was found to be strongly pH dependent. At alkaline pH, the apparent quantum efficiency of ？OH aq formation was estimated to be at the ~10 ？2 level whereas at acidic pH it was near zero. Addition of phosphate and fluoride ions substantially enhanced the ？OH aq production in the acidic pH range. It is suggested that ？OH aq-radical formation in TiO 2 photocatalysis can occur by oxidation of hydroxyl ions in the water layer adsorbed on TiO 2 surfaces.
References
[1]
Ohtani, B. Photocatalysis A to Z - What we know and what we do not know in a scientific sense. J. Photochem. Photobiol. C 2010, 11, 157–178, doi:10.1016/j.jphotochemrev.2011.02.001.
[2]
Keshmiri, M.; Mohseni, M.; Troczynski, T. Development of a novel TiO2 sol-gel derived composite and its photocatalytic activities for trichloroethylene oxidation. Appl. Catal. B 2004, 53, 209–219.
[3]
Agustina, T.E.; Ang, H.M.; Vareek, V.K. A review of synergistic effect of photocatalysis and ozonation of wastewater treatment. J. Photochem. Photobiol. C 2005, 6, 264–273, doi:10.1016/j.jphotochemrev.2005.12.003.
[4]
Malato, S.; Blanco, J.; Alarcon, D.C. Photocatalytic decontamination and disinfection of water with solar collectors. Catal. Today 2007, 122, 137–149, doi:10.1016/j.cattod.2007.01.034.
[5]
Mukherjee, P.S.; Ray, A.K. Major challenges in the design of a large-scale photocatalytic reactor for water treatment. Chem. Eng. Technol. 1999, 22, 253–260, doi:10.1002/(SICI)1521-4125(199903)22:3<253::AID-CEAT253>3.0.CO;2-X.
[6]
Choo, K.H.; Tao, R.; Kim, M.J. Use of a photocatalytic membrane reactor for the removal of natural organic matter in water. Effect of photoinduced desorption and ferrihydrite adsorption. J. Membr. Sci. 2008, 322, 368–374, doi:10.1016/j.memsci.2008.05.069.
[7]
Hurum, D.C.; Agrios, A.G.; Gray, K.A.; Rajh, T.; Thurnauer, M.C. Explaning the enhanced photocatalytic activity of Degussa P25 mixed-phase TiO2 using EPR. J. Phys. Chem. B 2003, 107, 4545–4549, doi:10.1021/jp0273934.
[8]
Turchi, C.S.; Ollis, D.F. Photocatalytic degradation of organic water contaminants; mechanisms involving hydroxyl radical attack. J. Catal. 1990, 122, 178–192, doi:10.1016/0021-9517(90)90269-P.
[9]
Fujishima, A.; Zhang, X.T.; Tryk, D.A. TiO2 photocatalysis and related surface phenomena. Surf. Sci. Rep. 2008, 63, 515–582, doi:10.1016/j.surfrep.2008.10.001.
[10]
Howe, R.F.; Gr？tzel, M. EPR observation of trapped electrons in colloidal titanium dioxide. J. Phys. Chem. 1985, 89, 4495–4499, doi:10.1021/j100267a018.
[11]
Dung, D.; Ramsden, J.; Graetzel, M. Dynamics of interfacial electron-transfer processes in colloidal semiconductor systems. J. Am. Chem. Soc. 1982, 104, 2977–2985.
[12]
Spinks, J.W.T.; Woods, R.J. An Introduction to Radiation Chemistry, 3rd ed.; John Wiley and Sons Inc: New York, NY, USA, 1990.
[13]
Lee, J.; Park, H.; Choi, W. Selective photocatalytic oxidation of NH3 to N2 on platinized TiO2 in water. Environ. Sci. Technol. 2002, 36, 5462–5468, doi:10.1021/es025930s.
[14]
Nakamura, R.; Imanishi, A.; Murakoshi, K.; Nakato, Y. In situ FTIR studies of primary intermediates of photocatalytic reactions on nanocrystalline TiO2 films in contact with aqueous solutions. J. Am. Chem. Soc. 2003, 125, 7443–7450.
[15]
Micic, O.I.; Zhang, Y.; Cromack, K.R.; Trifunac, A.D.; Thurnauer, M.C. Trapped holes on titania colloids studied by electron paramagnetic resonans. J. Phys. Chem. 1993, 97, 7277–7283.
[16]
Murakami, Y.; Endo, K.; Ohta, I.; Nosaka, A.Y.; Nosaka, Y. Can OH radicals diffuse from the UV-irradiated photocatalytic TiO2 surfaces? Laser-induced fluorescence study. J. Phys. Chem. C 2007, 111, 11339–11346.
[17]
Mills, A.; Hunte, S.L. An overview of semiconductor photocatalysis. J. Photochem. Photobiol. A 1997, 108, 1–35.
[18]
Ishibashi, K.; Fujishima, A.; Watanabe, T.; Hashimoto, K. Quantum yields of active oxidative species formed on TiO2 photocatalyst. J. Photochem. Photobiol. A 2000, 134, 139–142, doi:10.1016/S1010-6030(00)00264-1.
[19]
Goldstein, S.; Czapski, G.; Rabani, J. Oxidation of phenol by radiolytically generated ？OH and Chemically Generated SO4？？. A Distinction between ？OH transfer and hole oxidation in in the photolysis of TiO2 colloid solution. J. Phys. Chem. 1994, 98, 6586–6591.
[20]
Salvador, P. On the nature of photogenerated radical species active in the oxidative degradation of dissolved pollutants with TiO2 aqueous suspensions: A revision in the light of the electronic structure of adsorbed water. J. Phys. Chem. C 2007, 111, 17038–17043, doi:10.1021/jp074451i.
[21]
Lawless, D.; Serpone, N.; Meisel, D. Role of hydroxyl radicals and trapped holes in photocatalysis. A pulse radiolysis study. J. Phys. Chem. 1991, 95, 5166–5170, doi:10.1021/j100166a047.
[22]
Oppenl？nder, T. Photochemical Purification of Water and Air; WILEY-VCH Verlag GmbH & Co.: Weinheim, Germany, 2003.
[23]
Sun, L.; Bolton, J.R. Determination of the quantum yield for the photochemical generation of hydroxyl radicals. J. Phys. Chem. 1996, 100, 4127–4134, doi:10.1021/jp9505800.
[24]
Diesen, V.; Jonsson, M.J. Tris(hydroxymetyl) aminomethane as a probe in heterogeneous TiO2 photocatalysis. Adv. Oxid. Technol. 2012, 15, 392–398.
[25]
Ishibashi, K.; Fujishima, A.; Watanabe, T.; Hashimoto, K. Detection of active oxidative species in TiO2 photocatalysis using the fluorescence technique. Electrochem. Commun. 2000, 2, 207–210.
[26]
Hirakawa, T.; Nosaka, Y. Properties of O2？？ and OH？ formed in TiO2 aqueous suspensions by photocatalytic reaction and the influence of H2O2 and Some Ions. Langmuir 2002, 18, 3247–3254, doi:10.1021/la015685a.
[27]
Nosaka, Y.; Komori, S.; Yawata, K.; Hirakawa, T.; Nosaka, A.Y. Photocatalytic OH Radical Formation in TiO2 aqueous suspension studied by several detection methods. Phys. Chem. Chem. Phys. 2003, 5, 4731–4735.
[28]
Reitberger, T.; Gierer, J. Chemiluminescence as a means to study the role of hydroxyl radicals in oxidative processes. Holzforschung 1988, 42, 351–356, doi:10.1515/hfsg.1988.42.6.351.
[29]
Backa, S.; Jansbo, K.; Reitberger, T. Detection of hydroxyl radicals by a chemiluminescence method—A critical review. Holzforschung 1997, 51, 557–564, doi:10.1515/hfsg.1997.51.6.557.
[30]
Gierer, J.; Jansbo, K.; Reitberger, T. Formation of hydroxyl radicals from hydrogen peroxide and their effect on bleaching of mechanical pulps. J. Wood Chem. Tech. 1993, 13, 561–581, doi:10.1080/02773819308020534.
[31]
Backa, S.; Brolin, A. Determination of pulp characteristics by diffuse reflectance FTIR. Tappi J. 1991, 74, 218–226.
[32]
Backa, S.; Gierer, J.; Reitberger, T.; Nilsson, T. Hydroxyl radical activity associated with the growth of white-rot fungi. Holzforschung 1993, 47, 181–187, doi:10.1515/hfsg.1993.47.3.181.
[33]
Miller, C.J.; Rose, A.L.; Waite, T.D. Phthalhydrazide chemiluminescence method for determination of hydroxyl radical production: Modifications and adaptations for use in natural systems. Anal. Chem. 2011, 83, 261–268, doi:10.1021/ac1022748.
[34]
Fang, X.; Pan, X.; Rahmann, A.; Schuchmann, H.-P.; von Sonntag, A.C. Reversibility in the reaction of cyclohexadienyl radicals with oxygen in aqueous solution. Chem. Eur. J. 1995, 1, 423–429, doi:10.1002/chem.19950010706.
[35]
Bielski, B.H.J.; Cabelli, D.E.; Arudi, R.L.; Ross, A.B. Reactivity of HO2/O2？ radicals in aqueous solution. J. Phys. Chem. Ref. Data 1985, 14, 1041–1100, doi:10.1063/1.555739.
[36]
Jonsson, M.; Lind, J.; Reitberger, T.; Eriksen, T.E.; Merényi, G. Free radical combination reactions involving phenoxyl radicals. J. Phys. Chem. 1993, 97, 8229–8233, doi:10.1021/j100133a018.
[37]
Drew, C.H.D.K.; Pearman, F.H. Chemiluminescent organic compounds. Part II the effect of substituents on the closure of phthalhydrizides to 5- and 6-membered rings. J. Chem. Soc. 1937, 64, 26–33.
Lide, D.R.; Frederiksen, H.P.R. CRC Handbook of Chemistry and Physics, 76th ed.; CRC Press Inc.: Boca Raton, FL, USA, 1995.
[40]
Wardman, P. Reduction potentials of one-electron couples involving free radicals in aqueous solution. J. Phys. Chem. Ref. Data 1989, 18, 1637–1755, doi:10.1063/1.555843.
[41]
Matheson, M.S.; Mulac, W.A.; Weeks, J.L.; Rabani, J. The pulse radiolysis of deaerated aqueous bromide solutions. J. Phys. Chem. 1966, 70, 2092–2099, doi:10.1021/j100879a004.
[42]
Schiller, J.; Arnhold, J.; Schwinn, J.; Sprinz, H.; Brede, O.; Arnold, K. Differences in the reactivity of phthalic hydrazide and luminol with hydroxyl radicals. Free Radic. Res. 1999, 30, 45–57, doi:10.1080/10715769900300061.
[43]
Shultz, A.N.; Hetherington, W.M., III; Baer, D.R.; Wang, L.Q.; Engelhard, M.H. Comparative SHG and XPS studies of interactions between defects and N2O on rutile (110) surfaces. Surf. Sci. 1997, 392, 1–7.
[44]
Connor, P.A.; Dobson, K.D.; McQuillan, A.J. Infrared spectroscopy of the TiO2/aqueous solution interface. Langmuir 1999, 15, 2402–2408, doi:10.1021/la980855d.
[45]
Zhao, D.; Chen, C.; Wang, Y.; Ji, H.; Ma, W.; Zang, L.; Zhao, J. Surface modification of TiO2 by phosphate: Effect on photocatalytic activity and mechanism implication. J. Phys. Chem. C 2008, 112, 5993–5600.
[46]
Maruthamuthu, P.; Neta, P. Phosphate radicals, spectra, acid-base equilibriums, and reactions with inorganic compounds. J. Phys. Chem. 1978, 82, 710–713, doi:10.1021/j100495a019.
[47]
Brusa, M.A.; Grela, M.A. Experimental upper bound on phosphate radical production in TiO2 photocatalytic transformations in the presence of phosphate ions. Phys. Chem. Chem. Phys. 2003, 5, 3294–3298, doi:10.1039/b302296j.
[48]
Xu, Y.; Lv, K.; Xiong, Z.; Leng, W.; Du, W.; Liu, D.; Xue, X. Rate enhancement and rate inhibition of phenol degradation over irradiated anatase and rutile TiO2 on the addition of NaF: New insight into the mechanism. J. Phys. Chem. C 2007, 111, 19024–19032, doi:10.1021/jp076364w.
[49]
Petrucci, R.H.; Harwood, W.S.; Herring, F.G. General Chemistry, 8th ed.; Pearson Prentice Hall, Pearson Education Inc.: Upper Saddle River, NJ, USA, 2002; p. 678.
[50]
Du, Y.; Rabani, J. The measure of TiO2 photocatalytic efficiency and the comparison of different photocatalytic titania. J. Phys. Chem. B 2003, 107, 11970–11978, doi:10.1021/jp035491z.
[51]
Wang, C.; Rabani, J.; Bahnemann, D.W.; Dohrmann, J.K. Photonic efficiency and the quantum yield of formaldehyde from methanol in the presence of various TiO2 photocatalysts. J. Photochem. Photobiol. A 2002, 148, 169–176, doi:10.1016/S1010-6030(02)00087-4.
[52]
Cabrera, B.M.I.; Alfano, O.M.; Cassano, A.E. Absorption and scattering coefficients of titanium dioxide particulate suspensions in water. J. Phys. Chem. 1996, 100, 20043–20050, doi:10.1021/jp962095q.
[53]
Buxton, G.V.; Greenstock, C.L.; Helman, W.P.; Ross, A.B. Critical review of rate constants for reactions of hydrated electrons, hydrogen atoms and hydroxyl radicals (？OH/？O？) in Aqueous solution. J. Phys. Chem. Data 1988, 17, 513–886, doi:10.1063/1.555805.
[54]
Fang, X.; Mark, G.; von Sonntag, C. OH radical formation by ultrasound in aqueous solutions part I: The Chemistry underlying the terephthale dosimeter. Ultrason. Sonochem. 1996, 3, 57–63, doi:10.1016/1350-4177(95)00032-1.
[55]
Cheng, H.; Selloni, A. Hydroxide ions at the water/anatase TiO2 (101) interface: Structure and electronic states from first principles molecular dynamics. Langmuir 2010, 26, 11518–11525, doi:10.1021/la100672f.
[56]
Merenyi, G.; Lind, J.; Eriksen, T.E. Nucleophilic addition to diazaquines, formation and breakdown of tetrahedral intermediates in relation to luminol chemiluminescence. J. Am. Chem. Soc. 1986, 108, 7716–7726, doi:10.1021/ja00284a040.
