Polyaniline/TiO2 (PANI/TiO2) nanocomposite was synthesized by the oxidative
polymerization of aniline with ammonium peroxydisulfate (APS) in water, in the
presence of colloidal TiO2 nanoparticles of an average diameter ~5 nm. The
resulting PANI/TiO2 composite powder was used for photocatalytic degradation of
methylene blue (MB). Its photocatalytic activity has been compared with activity
of neat colloidal TiO2 nanoparticles

Nedeljković, Jovan

Radoičić, Marija B.

Ćirić-Marjanović, Gordana N.

Čomor, Mirjana

Šaponjić, Zoran

Repository of the Vinča Nuclear Institute (VinaR)

       PHYSICAL CHEMISTRY 2010  10th International Conference on Fundamental and Applied Aspects of Physical Chemistry  Proceedings      The Conference is dedicated to the 100th Anniversary of the academician Pavle Savić birthday and 20th Anniversary of the Society of Physical Chemists of Serbia         21-24 September 2010 B E L G R A D E                            ISBN 978-86-82475-17-0 Title: Physical Chemistry 2010. (Proceedings) Editors: S. Anić and Ž. Čupić Published by: Society of Physical Chemists of Serbia, Studentski trg 12-16 P.O.Box 47, 11158 Beograd, 218, Srbija Publisher: Society of Physical Chemists of Serbia For Publisher: S. Anić, President of Society of Physical Chemists of Serbia Printed by: “Jovan” Printing and Publishing Company; 200 Copies; Number of pages 16 + 388, Format: B5; Printing finished in September 2010.  Text and Layout: “Jovan”  200 - Copy printing    II   The Society of Physical Chemists of Serbia  in co-operation with   Institute of Catalysis, Bulgarian Academy of Sciences  Boreskov Institute of Catalysis, Siberian Branch of  the Russian Academy of Sciences  Faculty of Physical Chemistry, University of Belgrade, Serbia  Institute of Chemistry Technology and Metallurgy, University of Belgrade, Serbia  Vinča Institute, University of Belgrade, Serbia   Institute of General and Physical Chemistry, Serbia                         IV  International Organizing Committee  Chairman:             S. Anić (Serbia) Vice-chairman:     N. Stepanov (Russia)                                B. Adnađević (Serbia)  Members: M. Gabrovska (Bulgaria), N. Cvijetićanin (Serbia), T. Grozdić (Serbia),  D. Jovanović (Serbia), M. Lalić (BiH), D. Marković (Serbia), B. Milosavljević (USA), N. Miljević (Serbia), M. Mojović (Serbia), N. Ostrovski (Serbia), C. Pona (Italy), B. Simonović (Serbia), D. Stanisavljev (Serbia), A. G. Stepanov (Russia), V. Vasić (Serbia), N. Vukelić (Serbia), V. Vukojević (Sweden)   International Scientific Committee  Chairman:              Ž. Čupić (Serbia) Vice-chairmans:     V. N. Parmon (Russia)                                 M. Franko (Slovenia)  V. Vasić (Serbia)  Members: A. Antić-Jovanović (Serbia), G. Bačic (Serbia), R. Cervellati (Italy), R. Compton (United Kingdom), V. Gaspar (Hungary),  M. Jeremić (Serbia), A. L. Kawczyñski (Poland), Lj. Kolar-Anić (Serbia), S. Kuchanov (Russia), R. Leblanc (USA),  S. Mentus (Serbia), S. Milonjić (Serbia), Lj. Morozova-Roche (Sweden),  D. Moscone (Italy), J. Nedeljković (Serbia), Z. Noszticzius (Hungary), M. Perić (Serbia), V. Petruševski (Macedonia), M. Plavšić (Serbia), G. Smulevich (Italy),  G. Schmitz (Belgium), I. Schreiber (Czech), P. Ševčik (Slovakia), N. Stepanov (Russia), M. Trtica (Serbia), D. Veselinović (Serbia)  Local Executive Committee  Chairman:              B. Adnadjević Vice-chairmans:    S. Blagojević                                 A. Ivanović  Members: A. Abu Rabi-Stanković, P. Banković, N. Begović, S. N. Blagojević,  N. Cvjetičanin, M. Daković, A. Đerić, A. Ignjatović, Lj. Ignjatović, A. Jović,  J. Krstić, S. Kuprešak, D. Lončarević, J. Maksimović, V. Marković, M. Milenković, M. Milojević, Z. Mojović, B. Nedić, I. Pašti, N. Pejić, A. Popović-Bjelić, M. Petković, N. Potkonjak, D. Ranković, R. Ranković, M. Stević,  I. Stojković, B. Šljukić, M. Vujković    VPHOTOCATALYTIC PROPERTIES OF POLYANILINE/TiO2 NANOCOMPOSITE   M. Radoičić1, Z. Šaponjić1, G. Ćirić-Marjanović2,  J. M. Nedeljković1 and M. Čomor1  1Vinča Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade, Serbia 2Faculty of Physical Chemistry, University of Belgrade, Studentski Trg 12-16,   11158, Belgrade, Serbia  Abstract Polyaniline/TiO2 (PANI/TiO2) nanocomposite was synthesized by the oxidative polymerization of aniline with ammonium peroxydisulfate (APS) in water, in the presence of colloidal TiO2 nanoparticles of an average diameter ~5 nm. The resulting PANI/TiO2 composite powder was used for photocatalytic degradation of methylene blue (MB). Its photocatalytic activity has been compared with activity of neat colloidal TiO2 nanoparticles.  Introduction TiO2 is one of the most investigated semiconductors in the field of photocatalytic degradation of pollutants. Its high chemical stability, adsorption capability, photocatalytic efficacy for decomposition of organic compounds in air and water, relative low-price and nontoxicity are the reasons for such keen researcher’s interest. However, the wide band gap of TiO2 (3.2 eV) only allows it to absorb the photons of ultraviolet light (< 400 nm) that occupies only small fraction (< 5 %) of solar spectrum, which limits its wider use. One of the possible ways to utilize the broader part of the solar spectrum is sensitization of TiO2 with a suitable sensitizer [1]. High absorption coefficients in the visible part of the spectrum, high mobility of charge carriers (consequence of the presence of extended π-conjugated electron systems) and good environmental stability of conductive polymers make them a good choice for TiO2 sensitization. Moreover, many conductive polymers in their doped or undoped states are efficient electron donors and good hole transporters upon visible light excitation [2]. The subject of this work was in situ synthesis and characterization of PANI/TiO2 nanocomposite. Its potential applicability as a photocatalyst was checked using a typical photodegradation reaction of methylene blue (MB) in a suspension. MB is a stable organic dye occasionally used as a model compound for estimation of activity of TiO2 based photocatalysts, in reactions of photodegradation.  Experimental Colloidal TiO2 solution, containing nanoparticles of an average diameter ~5 nm, was prepared according to the procedure described elsewhere [3]. In a typical procedure for preparing PANI in the presence of TiO2 nanoparticles, the aqueous  146solutions of aniline, oxidant (APS), and colloidal TiO2 were mixed at room temperature [4]. Initial mole ratio of aniline/TiO2 was 1:100. The reaction mixture was stirred for 20 days. In order to remove residual monomer, oxidant and low-molecular weight fractions, PANI/TiO2 composite was dialyzed in Milli-Q deionized water. Finally, the nanocomposite was dried in vacuum oven at 60oC until a constant mass was reached (~3 h). As a reference sample dry colloidal TiO2 powder was used.  400 500 600 700 800 9000.00.51.01.52.02.53.0   PANI/TiO2 TiO2 collAbsorbance Wavelength (nm)Fig.1. UV/vis absorption spectra of pure TiO2 and PANI/TiO2 nanocomposite.  0 100 200 300 400 500 600 700 800-3.0-2.5-2.0-1.5-1.0-0.50.00.5    Time (min) PANI/TiO2 TiO2 collLn (C/C0)Methylene blue Fig.2. Kinetic plots of degradation of MB using neat TiO2 and PANI/TiO2 nanocomposite as photocatalyst.  UV/Vis spectra of the samples were obtained using Evolution 600 spectrophotometer (Thermo Scientific). The photocatalytic activities of the prepared samples were evaluated by the degradation of MB in aqueous solution. MB aqueous solution (50 ml) with concentration of 10 mg·L−1 was mixed with 1 g·L−1 catalyst (PANI/TiO2 or neat colloidal TiO2). Suspensions were placed into quartz vessel which was exposed to light of Xenon lamp (300 W). Samples were saturated with air and stirred during the irradiation. Aliquots of 1 ml were taken out from the suspensions every 15 min during the irradiation. The photocatalyst was separated from the solution by centrifugation and absorbance intensity of the MB in the supernatant was measured at λ=664 nm.   Results and Discussion UV/Vis absorption spectra of the colloidal TiO2 nanoparticles and PANI/TiO2 nanocomposite are shown in Figure 1. It can be seen that both TiO2 nanoparticles and PANI/TiO2 nanocomposite absorb light below 400 nm. Above this wavelength only the nanocomposite absorbs light giving rise to a peak at 440 nm, which corresponds to PANI chains in emeraldine salt form [5]. In addition to the band at about 440 nm, ordinary conducting PANI emeraldine salt usually shows the band at ~780 nm, both bands at ~440 and ~780 nm being connected with creation of polarons (radical cations) [5]. The absence of distinct band at ~780 nm in the UV-Vis spectrum of PANI/TiO2 could be result of partial deprotonation of PANI with water during the dialysis procedure, and reduced extent of delocalization of electrons in PANI. 147Kinetic plots of photodegradation of MB, obtained using neat TiO2 and PANI/TiO2 nanocomposite as a photocatalyst, are presented in Figure 2. Direct photolysis of MB was also followed and it was less than 10% of the initial MB concentration. At the beginning of the photodegradation process, until about 300 min, both photocatalysts had almost the same efficacy. It can be observed that PANI/TiO2 nanoparticles significantly enhance photocatalytic activity compared to bare colloidal TiO2 nanoparticles for longer times of irradiation. This effect could be explained by enhanced absorption and synergistic effect between PANI and TiO2 nanoparticles [2, 6].  Conclusion PANI/TiO2 nanocomposite has been in situ synthesized by the chemical oxidative polymerization of aniline with APS in colloidal TiO2 solution without added acid. Obtained nanocomposite has enhanced absorption in visible part of spectrum, compared to neat colloidal TiO2. PANI/TiO2 nanocomposite was successfully applied for discoloration of methylene blue using whole spectral range of Xenon lamp (simulation of solar spectrum). Nanocomposite catalyst showed higher efficacy toward discoloration of MB compared to bare TiO2, for longer irradiation times (> 300 min).  References [1]  X. Chen, S. Mao, Chem. Rev. 2007, 107, 2891-2959. [2]  X. Li, D. Wang, G. Cheng, Q. Luo, J. An, Y. Wang, App. Catal. B: Environ., 2008, 81, 267–273. [3]  T. Rajh, D. Tiede, M. Thurnauer, J. Non-Cryst. Solids, 1996, 207, 815. [4]  M. Radoičić, Z. Šaponjić, J. Nedeljković, G. Ćirić-Marjanović, J. Stejskal, Synth. Met., 2010, 160, 1325–1334. [5]  J. Laska, J. Mol. Struct. 2004, 701, 13–18. [6]  H. Zhang, R. Zong, J. Zhao, Y. Zhu, Environ. Sci. Technol. 2008, 42, 3803–3807. 148

Photocatalytic properties of polyaniline/TiO2 nanocomposite

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Photocatalytic properties of polyaniline/TiO2 nanocomposite

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