Researcher Database

Ewa Kowalska
Institute for Catalysis Photocatalysis Research Division
Associate Professor

Researcher Profile and Settings


  • Institute for Catalysis Photocatalysis Research Division

Job Title

  • Associate Professor


  • PhD(Gdansk University of Technology)

J-Global ID

Academic & Professional Experience

  • 2012/11 - Today Hokkaido University Catalysis Research Center associate professor
  • 2009/09 - 2012/10 FAU & Ulm University, Germany Institute of Inorganic Chemistry Marie Curie fellow
  • 2005/04 - 2009/08 Hokkaido University Catalysis Research Center JSPS & GCOE fellow
  • 2004/05 - 2007/09 Gdansk University of Technology, Poland Faculty of Chemistry, Department of Chemical Technology researcher


  • 1998/10 - 2004/06  Gdansk University of Technology, Poland  Faculty of Chemistry  Ph.D. thesis “Investigations of photochemical degradation of organic compounds”, 28.06.2004
  • 2001/11 - 2002/08  University of Paris Sud, France  Department of Physical Chemistry  Marie Curie fellowship
  • 1993/09 - 1998/06  Gdansk University of Technology, Poland  Faculty of Chemistry  MSc in Environmental Protection, MSc thesis "Photochemical destruction of methoxychlor"

Research Activities

Published Papers

  • Zhishun Wei, Marcin Janczarek, Maya Endo, Kunlei Wang, Armandas Balčytis, Akio Nitta, Maria G. Méndez-Medrano, Christophe Colbeau-Justin, Saulius Juodkazis, Bunsho Ohtani, Ewa Kowalska
    Applied Catalysis B: Environmental 237 574 - 587 0926-3373 2018/12/05 [Refereed][Not invited]
    Octahedral anatase particles (OAP, with eight equivalent {101} facets) and decahedral anatase particles (DAP, with two additional {001} facets) were modified with nanoparticles of noble metals (Au, Ag, Cu). The titania morphology, expressed by the presence of different arrangements of exposed crystal facets, played a key role in the photocatalytic properties of metal-modified faceted titania. In the UV/vis systems, two-faceted configuration of DAP was more favorable for the reaction efficiency than single-faceted OAP because of an efficient charge separation described by the transfer of electrons to {101} facets and holes to {001} facets. Time-resolved microwave conductivity (TRMC) and reversed double-beam photoacoustic spectroscopy (RDB-PAS) confirmed that distribution of electron traps (ET) and mobility of electrons were key-factors of photocatalytic activity. In contrast, metal-modified OAP samples had higher photocatalytic activity than metal-modified DAP and metal-modified commercial titania samples under visible light irradiation. This indicates that the presence of single type of facets ({101}) is favorable for efficient electron transfer via shallow ET, whereas intrinsic properties of DAP result in fast charge carriers’ recombination when gold is deposited on {101} facets (migration of “hot” electrons: Au→{101}→Au).
  • Bajorowicz B, Kowalska E, Nadolna J, Wei Z, Endo M, Niedziółka J, Ohtani B, Zaleska-Medynska A
    Dalton Transactions in press 2018/10 [Refereed][Not invited]
  • Markowska-Szczupak A, Rokicka P, Wang K, Endo M, Morawski A.W, Kowalska E
    Catalysts 8 (8) 316  2018/08 [Refereed][Not invited]
  • Marcin Janczarek, Kunlei Wang, Ewa Kowalska
    Catalysts 8 240  2018/08 [Refereed][Not invited]
  • Z. Wei, M. Janczarek, M. Endo, C. Colbeau-Justin, B. Ohtani, E. Kowalska
    Catalysis Today 310 19 - 25 0920-5861 2018/07/15 [Refereed][Not invited]
    Octahedral anatase particles (OAPs) were modified with silver nanoparticles (NPs) by photodeposition method. The properties of OAPs influenced the properties of silver deposits, and thus the photocatalytic activity of the obtained silver-modified OAPs. Photocatalytic activities were tested under UV and vis irradiation for oxidative decomposition of acetic acid and oxidation of 2-propanol, respectively. The properties of silver-modified OAPs were investigated by XRD, STEM, DRS, XPS and time-resolved microwave conductivity (TRMC) method. It was found that electron traps (ETs) worked as nucleation sites for silver, resulting in formation of smaller silver NPs on smaller OAPs with larger content of ETs. The modification with silver resulted in enhanced photocatalytic activity under both UV and vis irradiation. It was found that larger crystallite size of silver NPs, and thus larger polydispersity of silver deposits resulted in broad and intense plasmon resonance peak causing enhanced visible activity. The correlation between photocatalytic activity and TRMC data, e.g., slower decay of TRMC signal for more active samples, allowed discussion on property-governed photocatalytic activities of silver-modified titania.
  • Endo M, Janczarek M, Wei Z, Markowska-Szczupak A, Ohtani B, Kowalska E
    J. Nanosci. Nanotechnol. 9 829 - 849 2018/03 [Refereed][Invited]
  • Patrycja Parnicka, Pawel Mazierski, Tomasz Grzyb, Wojciech Lisowski, Ewa Kowalska, Bunsho Ohtani, Adriana Zaleska-Medynska, Joanna Nadolna
    Beilstein Journal of Nanotechnology 9 (1) 447 - 459 2190-4286 2018/02/06 [Refereed][Not invited]
    Nd-modified TiO2 photocatalysts have been obtained via hydrothermal (HT) and sol-hydrothermal (SHT) methods. The as-prepared samples were characterized by X-ray diffraction (XRD), BET surface area measurements, scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), luminescence spectroscopy and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of the synthesized samples was evaluated by the degradation of phenol in aqueous solution under irradiation with UV-vis (λ > 350 nm) and vis (λ > 420 nm) light, as well as by the degradation of gaseous toluene under irradiation with vis (λmax = 415 nm) light. It was found that Nd-modified TiO2 is an efficient photocatalyst for the degradation of phenol and toluene under visible light. XPS analysis revealed that the photocatalyst prepared via HT method contains a three-times higher amount of hydroxy groups at the surface layer and a two-times higher amount of surface defects than that obtained by the SHT method. The photocatalytic efficiency of phenol and toluene degradation under vis irradiation in the presence of 0.25% Nd-TiO2(HT) reached 0.62 and 3.36 μmol·dm-1·min-1, respectively. Photocatalytic activity tests in the presence of Nd-TiO2 and scavenger confirm that superoxide radicals were responsible for the visible light-induced degradation of the model pollutant in aqueous solution.
  • Wysocka I, Kowalska E, Trzciński K, Łapiński M, Klimczuk T, Nowaczyk G, Zielińska-Jureka A
    Nanomaterials 8 (28) 2018/01 [Refereed][Not invited]
  • Wang K, Wei Z, Ohtani B, Kowalska E
    Catalysis Today in press 2017/12 [Refereed][Not invited]
  • Marcin Janczarek, Ewa Kowalska
    CATALYSTS 7 (11) 317  2073-4344 2017/11 [Refereed][Not invited]
    Modification of titania with copper is a promising way to enhance the photocatalytic performance of TiO2. The enhancement means the significant retardation of charge carriers' recombination ratio and the introduction of visible light activity. This review focuses on two main ways of performance enhancement by copper species-i.e., originated from plasmonic properties of zero-valent copper (plasmonic photocatalysis) and heterojunctions between semiconductors (titania and copper oxides). The photocatalytic performance of copper-modified titania is discussed for oxidative reaction systems due to their importance for prospective applications in environmental purification. The review consists of the correlation between copper species and corresponding variants of photocatalytic mechanisms including novel systems of cascade heterojunctions. The problem of stability of copper species on titania, and the methods of its improvement are also discussed as important factors for future applications. As a new trend in the preparation of copper-modified titania photocatalyst, the role of particle morphology (faceted particles, core-shell structures) is also described. Finally, in the conclusion section, perspectives, challenges and recommendations for future research on copper-modified titania are formulated.
  • Patrycja Parnicka, Pawel Mazierski, Tomasz Grzyb, Zhishun Wei, Ewa Kowalska, Bunsho Ohtani, Wojciech Lisowski, Tomasz Klimczuk, Joanna Nadolna
    JOURNAL OF CATALYSIS 353 211 - 222 0021-9517 2017/09 [Refereed][Not invited]
    Titanium dioxide (TiO2) nanoparticles (NPs) modified with neodymium (Nd) in the range between 0.1 and 1.0 mol% were prepared via the hydrothermal method. The samples obtained were characterized by diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), X-ray fluorescence (EDX), Brunauer-Emmett-Teller (BET) method, X-ray powder diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL). The photocatalytic activity of the obtained samples was evaluated by photodegradation of phenol in aqueous solution under ultraviolet-visible (UV-Vis, lambda > 350 nm) and visible (Vis, lambda > 420 nm) irradiation. Experimental results showed that the photocatalysts exhibited high photocatalytic activity under Vis light. The sample showing the highest photoactivity under Vis irradiation was in the form of anatase; its surface area equalled 124 m(2)/g (1.16 times larger than that of pristine TiO2). The average crystal size was 10.9 nm, and it was modified with 0.1 mol% of Nd3+ (28% of phenol was degraded after 60 min of irradiation). The photocatalytic tests of phenol degradation in the presence of scavengers confirm that e(-) and O-2(center dot-) were responsible for the visible light degradation of organic compounds in the aqueous phase. Action spectra analysis revealed that although Nd-modified TiO2 could be excited under visible light in the range of 400-480 nm, the up-conversion process is not responsible for the degradation of phenol under Vis irradiation. (C) 2017 Elsevier Inc. All rights reserved.
  • Ana L. Luna, Diana Dragoe, Kunlei Wang, Patricia Beaunier, Ewa Kowalska, Bunsho Ohtani, Daniel Bahena Uribe, Miguel A. Valenzuela, Hynd Remita, Christophe Colbeau-Justin
    JOURNAL OF PHYSICAL CHEMISTRY C 121 (26) 14302 - 14311 1932-7447 2017/07 [Refereed][Not invited]
    TiO2 surface modification with bimetallic nano particles (NPs) has demonstrated to be a strategy to enhance the hydrogen generation via photocatalysis and to minimize the use of expensive noble metals. A better understanding of the role of bimetallic NPs is of crucial importance to design efficient photocatalysts. Here, we show a systematic study of surface modification of commercial TiO2 (P25) with mono and bimetallic (Ni, Pd, and Ni-Pd) NPs synthesized by radiolysis. The photocatalysts were characterized by High Resolution Transmission Microscopy (HRTEM), Scanning Transmission Electron Microscope (STEM), X-ray Diffraction (XRD), Energy-Dispersive X-ray Spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS), and UV-vis Diffuse Reflectance Spectroscopy (DRS). The charge-carrier dynamics was studied by Time Resolved Microwave Conductivity (TRMC). The photocatalytic activity was evaluated for hydrogen generation under UV-vis irradiation using polychromatic and monochromatic lights (action spectra analysis of apparent quantum efficiency). TiO2 modified with Pd-Ni bimetallic NPs exhibits a high activity for H-2 generation, and a synergetic effect of the two metals was obtained. The study of light absorption, charge-carrier dynamics, and photocatalytic activity revealed that the main role of the metal NPs is to act as catalytic sites for recombination of atomic hydrogen.
  • Z. Wei, M. Endo, K. Wang, E. Charbit, A. Markowska-Szczupak, B. Ohtani, E. Kowalska
    CHEMICAL ENGINEERING JOURNAL 318 121 - 134 1385-8947 2017/06 [Refereed][Not invited]
    Octahedral anatase particles (OAPs) were prepared by hydrothermal (HT) reaction of titanate nanowires (TNWs). OAPs were modified with noble metals (Au, Ag, Cu and Pt) by two photodeposition methods: in the absence and in the initial presence of oxygen in the system. Photocatalytic activities for oxidative decomposition of acetic acid and anaerobic dehydrogenation of methanol under UV/vis irradiation and for oxidation of 2-propanol under visible light irradiation were investigated. Antibacterial activities for bacteria (Escherichia coli) and fungi (Candida albicans) were investigated in the dark and under UV irradiation and/or visible light irradiation. It was found that the kind of metal deposition significantly influenced the properties of photocatalysts obtained and thus their photocatalytic and antimicrobial activities. Modification of OAPs with metallic deposits resulted in enhanced photocatalytic activities for all tested systems. Pt-modified OAPs showed the highest activity for dehydrogenation of methanol due to their highest work function and lowest activation overpotential of hydrogen evolution. Cu-modified OAPs exhibited the highest activity for oxidative decomposition of acetic acid under UV/vis irradiation, probably due to the heterojunction between Cu oxides and TiO2. On the other hand, Au-modified OAPs showed the highest photocatalytic activity under visible light irradiation due to their plasmonic properties. Bare OAPs, prepared with various durations of the HT reaction, did not have any antibacterial properties in the dark, while their activity under UV/vis irradiation was correlated with their photocatalytic activities for dehydrogenation of methanol and decomposition of acetic acid. Antimicrobial activity of modified OAPs in the dark and under visible light irradiation was the highest for Ag-modified OAPs. Under UV irradiation, Cu-modified OAPs showed the highest activity for inactivation of both bacteria and fungi. (C) 2016 The Authors. Published by Elsevier B.V.
  • Zhishun Wei, Lorenzo Rosa, Kunlei Wang, Maya Endo, Saulius Juodkazis, Bunsho Ohtani, Ewa Kowalska
    APPLIED CATALYSIS B-ENVIRONMENTAL 206 393 - 405 0926-3373 2017/06 [Refereed][Not invited]
    Octahedral anatase particles (OAPs), prepared by ultrasonication-hydtothermal reaction (US-HT), were modified with 2 wt% of gold by photodeposition. COnditions of US-HT process such as durations of US and durations of HT were varied to obtain OAPs products different by physicochemical and morphological properties. Au/OAPs samples were characterized by X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance spectroscopy (DRS). The photocatalytic activity was tested under UV irradiation for decomposition of acetic acid (CO2 system) and dehydrogenation of methanol (H-2 system) under aerobic and anaerobic conditions, respectively, and for oxidation of 2-propanol under visible light irradiation. Photodeposition of gold was very fast for all OAPs samples (0.5-10 min) under Ar atmosphere, and the clear correlation between the content of electron traps (ETs) and the induction period, during which nanopartiCles (NPs) of gold are formed, indicates that ETs in titania samples are a key-factor for rapidity of gold photodeposition on titania surface. It was found that better morphology of titania (larger content of faceted particles) resulted in formation of larger gold NPs, while small gold NPs were deposited on structural defects. Modification of OAPs with gold NPs resulted in significant enhancement of photocatalytic activity, being e.g., 1.5 (CO2 system), 7.7 (H2 system), and even more than 40 under vis irradiation. It was found that both the properties of titania and gold are crucial for resultant photocatalytic activity, but a direct correlation between one structural/physical property and photocatalytic activity could not be obtained since all structural properties changed simultaneously when conditions of photo catalyst preparation (US-HT) were changed. Therefore, gold NPs of controlled sizes were deposited on OAPs product with the best morphology by modified photodeposition method. Clear correlation between photocatalytic activity under visible light and the size of gold NPs indicates that gold properties are decisive for visible light activity rather than titania properties. 3D-FDTD simulations confirm that an increase in the size of gold NPs results in extended surface areas with field enhancement. (C) 2017 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license.
  • Wei Z, Kowalska E, Wang K, Colbeau-Justin C, Ohtani B
    Catalysis Today 280 29 - 36 2017/02 [Refereed][Not invited]
  • Janczarek M, Wei Z, Endo M, Ohtani B, Kowalska E
    J. Photon. Energy 7 (012008) 1 - 16 2017/01 [Refereed][Invited]
  • Méndez-Medrano M.G, Kowalska E, Lehoux A, Herissan A, Ohtani B, Rau S, Colbeau-Justin C, Rodríguez-López J.L, Remita H
    J. Phys. Chem. C 120 (43) 25010 - 25022 2016/12 [Refereed][Not invited]
  • Paulina Rokicka, Agata Markowska-Szczupak, Lukasz Kowalczyk, Ewa Kowalska, Antoni W. Morawski
    POLISH JOURNAL OF CHEMICAL TECHNOLOGY 18 (4) 56 - 64 1509-8117 2016/12 [Refereed][Not invited]
    Antibacterial properties of 15 titania photocatalysts, mono- and dual-modified with nitrogen and carbon were examined. Amorphous TiO2, supplied by Azoty Group Chemical Factory Police S.A., was used as titania source (Ar-TiO2, C-TiO2, N-TiO2 and N, C-TiO2 calcined at 300 degrees C, 400 degrees C, 500 degrees C, 600 degrees C, 700 degrees C). The disinfection ability was examined against Escherichia coli K12 under irradiation with UV and artifi cial sunlight and in dark conditions. It has been found the development of new photocatalysts with enhanced interaction ability with microorganisms might be a useful strategy to improve disinfection method conducted under artifi cial sunlight irradiation. The effi ciency of disinfection process conducted under artifi cial sunlight irradiation with carbon (C-TiO2) and carbon/nitrogen (N, C-TiO2) photocatalysts was similar as obtained under UV irradiation. Furthermore, during dark incubation, any toxicity of the photocatalyst was noted.
  • Michal Nischk, Pawel Mazierski, Zhishun Wei, Katarzyna Siuzdak, Natalie Amoin Kouame, Ewa Kowalska, Hynd Remita, Adriana Zaleska-Medynska
    APPLIED SURFACE SCIENCE 387 89 - 102 0169-4332 2016/11 [Refereed][Not invited]
    TiO2 nanotubes arrays (NTs), obtained via electrochemical anodization of Ti foil, were modified with monometallic (Cu, Bi) and bimetallic (AgCu) nanoparticles. Different amounts of metals' precursors were deposited on the surface of NTs by the spin-coating technique, and the reduction of metals was performed via gamma radiolysis. Surface modification of titania was studied by EDS and XPS analysis. The results show that AgCu nanoparticles exist in a Ag-core-Cu-shell form. Photocatalytic activity was examined under UV irradiation and phenol was used as a model pollutant of water. Over 95% of phenol degradation was achieved after 60 min of irradiation for almost all examined samples, but only slight difference in degradation efficiency (about 3%) between modified and bare NTs was observed. However, the initial phenol degradation rate and TOC removal efficiency was significantly enhanced for the samples modified with 0.31 and 0.63 mol% of Bi as well as for all the samples modified with Cu and AgCu nanoparticles in comparison with bare titania nanotubes. The saturated photocurrent, under the influence of simulated solar light irradiation, for the most active Bi- and AgCu-modified samples, was over two times higher than for pristine NTs. All the examined materials were resistant towards photocorrosion processes that enables their application for long term processes induced by light. (C) 2016 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license.
  • Ana L. Luna, Ekaterina Novoseltceva, Essyllt Louarn, Patricia Beaunier, Ewa Kowalska, Bunsho Ohtani, Miguel A. Valenzuela, Hynd Remita, Christophe Colbeau-Justin
    APPLIED CATALYSIS B-ENVIRONMENTAL 191 18 - 28 0926-3373 2016/08 [Refereed][Not invited]
    Au and/or Ni nanoparticles were synthesized by radiolysis on TiO2 (commercial P25) at various composition (metal content). The modified photocatalysts were characterized by High Resolution Transmission Microscopy (HRTEM), Energy-Dispersive X-ray Spectroscopy (EDS), UV-vis Diffuse Reflectance Spectroscopy (DRS) and X-ray Photoelectron Spectroscopy (XPS). The charge-carrier mobility was studied by Time Resolved Microwave Conductivity (TRMC). The photocatalytic activities were tested under UV-vis irradiation using polychromatic and monochromatic light (action spectrum analysis of apparent quantum efficiency). Surface modified TiO2 with Au and Ni nanoparticles showed high photocatalytic activity for hydrogen evolution from aqueous methanol solution. The enhanced hydrogen evolution rate was obtained for TiO2 co-modified with Au and Ni, where synergetic effect of the two metals was revealed. A very small amount of gold associated to nickel (atomic ratio Ni:Au 5:1 with a total optimized metal loading of 0.5 at%) can induce a significant increase in H-2 formation. (C) 2016 Elsevier B.V. All rights reserved.
  • Shuaizhi Zheng, Kunlei Wang, Zhishun Wei, Kenta Yoshiiri, Markus Braumueller, Sven Rau, Bunsho Ohtani, Ewa Kowalska
    JOURNAL OF ADVANCED OXIDATION TECHNOLOGIES 19 (2) 208 - 217 1203-8407 2016/07 [Refereed][Invited]
    Ruthenium(II) complex with the phosphonate anchoring groups of [Ru(tbbpy) 2(4,4'-(CH2PO3H2)(2)bpy)](2+) (Ru(II)CP2, tbbpy= 4,4'-di-tert-butyl-2,2'-bipyridine) and silver nanoparticles (Ag NPs) were used as single or co-modifiers on titania surface. For the dual modified titania, two deposition sequences were applied to obtain Ag/Ru(II)CP2 and Ru(II)CP2/Ag, in which at first ruthenium(II) or silver was deposited on titania, respectively. Diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) confirmed the existence of modifiers, and the effect of ruthenium(II) on the properties of Ag NPs regarding their crystallite sizes and oxidation states distributions. Photocatalytic activities of the modified titania were investigated for oxidative decomposition of acetic acid and 2-propanol, and anaerobic dehydrogenation of methanol. Under UV/Vis irradiation for the methanol dehydrogenation, co-modified titania of Ag/Ru(II)CP2 showed the best activity, while for acetic acid degradation, singly modified titania with silver showed the highest activity. In contrary, under visible light irradiation, singly fabricated titania with ruthenium(II) complex possessed the highest photocatalytic performance for 2-propanol oxidation. For all the three tested photocatalytic degradation reactions, Ag/Ru(II)CP2 exhibited better photocatalytic activities than Ru(II)CP2/Ag, indicating the different properties caused by opposite deposition sequences, e.g., DRS indicated the smaller sizes of metal NPs and XPS suggested the binding of ruthenium(II) to Ag NPs for Ru(II)CP2/Ag, which in consequence influenced the overall photocatalytic outcome.
  • Méndez-Medrano M.G, Kowalska E, Lehoux A, Herissan A, Ohtani B, Bahena D, Briois V, Colbeau-Justin C, Rodríguez-López J.L, Remita H
    J. Phys. Chem. C 120 5143 - 5154 2016/02 [Refereed][Not invited]
  • Joanna Reszczynska, Tomasz Grzyb, Zhishun Wei, Marek Klein, Ewa Kowalska, Bunsho Ohtani, Adriana Zaleska-Medynska
    APPLIED CATALYSIS B-ENVIRONMENTAL 181 825 - 837 0926-3373 2016/02 [Refereed][Not invited]
    A series of Y3+, Pr3+, Er3+ and Eu3+ modified TiO2 photocatalysts were obtained via sol-gel (SG) and hydrothermal (HT) methods. Samples prepared this way were characterized by X-ray powder diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), scanning transmission microscopy (STEM), BET surface area method and luminescence spectroscopy. The photocatalytic activity of the synthesized samples was evaluated by the degradation of phenol in aqueous solution under visible and ultraviolet light irradiations. Phenol in aqueous solutions was successfully decomposed under visible light (lambda > 420 nm) using TiO2 modified with RE ions. Luminescence properties of the samples as well as XRD and XPS analyses, indicate that RE are rather in the form of their oxides than in the form of cations in the crystal structure of TiO2. Photocatalysts prepared by SG method possessed higher amount of RE2O3, fewer of OH- groups and Ti3+ species on the surface layer than powders obtained by HT method. Action spectra analysis showed that Pr3+-modified TiO2 could be excited under visible light in the 420-250 nm range. Furthermore, photocatalysts obtained by HT method showed higher photocatalytic activity and lower intensity of luminescence emission than photocatalyst prepared by SG method. (C) 2015 Elsevier B.V. All rights reserved.
  • Marcin Janczarek, Ewa Kowalska, Bunsho Ohtani
    Chem. Eng. J.  - . 2016 [Refereed][Not invited]
  • Shuaizhi Zheng, Zhishun Wei, Kenta Yoshiiri, Markus Braumueller, Bunsho Ohtani, Sven Rau, Ewa Kowalska
    PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES 15 (1) 69 - 79 1474-905X 2016 [Refereed][Not invited]
    Titania of fine anatase nanoparticles (ST01) was modified successively with two components, i.e., a ruthenium(II) complex with phosphonic anchoring groups [Ru(bpy)(2)(4,4'-(CH2PO3H2)(2)bpy)](2+) bpy = 2,2'-bipyridine ((RuCP)-C-II) and gold nanoparticles (Au). Various compositions of two titania modifiers were investigated, i.e., Au, Au + (RuCP)-C-II, Au + 0.5Ru(II)CP, (RuCP)-C-II, 0.5Ru(II)CP and 0.25Ru(II)CP, where Au and (RuCP)-C-II correspond to 0.81 mol% and 0.34 mol% (with respect to titania), respectively. In the case of hybrid photocatalysts, the sequence of modification (ruthenium(II) complex adsorption or gold deposition) was investigated to check its influence on the resultant properties and thus photocatalytic performance. Diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM) were applied to characterize the structural properties of the prepared photocatalysts, which confirmed the successful introduction of modifiers of the ruthenium(II) complex and/or gold NPs. Different distributions of gold particle sizes and chemical compositions were obtained for the hybrid photocatalysts prepared with an opposite sequence. It was found that photocatalytic activities depended on the range of used irradiation (UV/vis or vis) and the kind of modifier in different ways. Gold NPs improved the photocatalytic activities, while (RuCP)-C-II inhibited the reactions under UV/vis irradiation, i.e., methanol dehydrogenation and acetic acid degradation. Oppositely, (RuCP)-C-II greatly enhanced the photocatalytic activities for 2-propanol oxidation under visible light irradiation.
  • Ewa Kowalska, Kenta Yoshiiri, Zhishun Wei, Shuaizhi Zheng, Evelyn Kastl, Hynd Remita, Bunsho Ohtani, Sven Rau
    APPLIED CATALYSIS B-ENVIRONMENTAL 178 133 - 143 0926-3373 2015/11 [Not refereed][Not invited]
    Plasmonic photocatalysts were prepared by deposition of 2 wt% of gold or silver nanoparticles (NPs) on commercial titania particles with different structural properties. Ruthenium(II) complexes with phosphonic and carboxylic acid binding groups were synthesized and adsorbed on bare titania and noble metal-modified titania. The structural properties of the samples were characterized by DRS, XPS, XRD, STEM, TLC, H-1 NMR and 2D-COSY. Large surface area, small crystallite sizes, low pH value, nature of the deprotected phosphonate binding groups, and pre-deposited nanoparticles of noble metals enhanced the adsorption yield. Modification caused titania activation toward visible light (>450 nm) for 2-propanol oxidation and for methanol dehydrogenation under UV/vis irradiation. The modified samples exhibited enhanced activity under UV/vis irradiation for acetic acid oxidation depending on the kind of modifiers and properties of titania, i.e., 2-6, 3-9 and 1-3-fold enhancement was observed after modification with NPs of gold, NPs of silver and Ru(II) complex. The time-resolved microwave conductivity (TRMC) method proved that higher photocatalytic activity of modified titania under UV irradiation was caused by scavenging of mobile electrons by NPs of noble metals, and therefore decreasing the recombination between charge carriers. The photocatalytic activity of hybrid photocatalysts under UV/vis was influenced by the nature of the plasmonic metal and structural properties of the metal and titania, e.g., crystallite size and polymorphic form. Different kinds of action were observed for two plasmonic metals in two reaction systems under UV irradiation, e.g., modification with an Ru(II) complex caused 12-times faster dehydrogenation of methanol for silver-modified large anatase titania (ST41) and hardly changed the activity of gold-modified samples, while during acetic acid oxidation, only hybrid photocatalysts composed of gold NPs and Ru(II) complex exhibited a slight increase of photocatalytic activity (1.1-1.3 times). The difference between gold and silver hybrid photocatalysts might have been caused by differences in surface charges of metallic deposits, i.e., the surface of silver NPs was mainly positively charged, while gold was zero-valent. Therefore, it is thought that the Ru(II) complex bound also to the surface of positively charged silver. Under visible light irradiation, fine titania modified with an Ru(II) complex exhibited the highest level of photocatalytic activity. The presence of an Ru(II) complex highly enhanced photocatalytic activity of titania modified with plasmonic NPs. However, NPs of plasmonic metals hindered the photoactivity of Ru(II)-titania. (C) 2014 Elsevier B.V. All rights reserved.
  • Anna Zielinska-Jureka, Zhishun Wei, Izabela Wysocka, Piotr Szweda, Ewa Kowalska
    APPLIED SURFACE SCIENCE 353 317 - 325 0169-4332 2015/10 [Refereed][Not invited]
    Ag-Pt-modified TiO2 nanocomposites were synthesized using the sol-gel method. Bimetallic modified TiO2 nanoparticles exhibited improved photocatalytic activity under visible-light irradiation, better than monometallic Ag/TiO2 and Pt/TiO2 nanoparticles (NPs). All modified powders showed localized surface plasmon resonance (LSPR) in visible region. The photocatalysts' characteristics by X-ray diffractometry (XRD), scanning transmission electron microscopy (STEM), diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption (BET method for specific surface area) showed that sample with the highest photocatalytic activity had anatase structure, about 93 m(2)/g specific surface area, maximum plasmon absorption at ca. 420 nm and contained small NPs of silver of 6 nm and very fine platinum NPs of 3 nm. The photocatalytic activity was estimated by measuring the decomposition rate of phenol in 0.2 mM aqueous solution under Vis and UV/vis light irradiation. It was found that size of platinum was decisive for the photocatalytic activity under visible light irradiation, i.e., the smaller Pt NPs were, the higher was photocatalytic activity. While, antimicrobial activities, estimated for bacteria Escherichia coli and Staphylococcus aureus, and pathogenic fungi belonging to Candida family, were only observed for photocatalysts containing silver, i.e., Ag/TiO2 and Ag-Pt/TiO2 nanocomposites. (C) 2015 Elsevier B.V. All rights reserved.
  • E. Kowalska, Z. Wei, B. Karabiyik, A. Herissan, M. Janczarek, M. Endo, A. Markowska-Szczupak, H. Remita, B. Ohtani
    CATALYSIS TODAY 252 136 - 142 0920-5861 2015/09 [Refereed][Not invited]
    Commercial titania photocatalysts were modified with 2 wt% of silver by photodeposition. The properties of the samples were characterized by DRS, XPS, XRD, FE-SEM and STEM. The modified samples exhibited activity under visible light and enhanced activity under UV irradiation for 2-propanol and acetic acid oxidation, respectively. The time-resolved microwave conductivity (TRMC) analysis indicated that enhanced activity (2.5-8-fold enhancement depending on titania) under UV irradiation was caused by an electron storage in metallic nanoparticles (NPs), and therefore decreasing the recombination between charge carriers. The action spectrum (AS) analysis proved that localized surface plasmon resonance (LSPR) of silver NPs induced the photocatalytic activity under visible light irradiation. The increase of antimicrobial properties under visible light irradiation indicated that not only intrinsic properties of silver in the dark, but also plasmonic properties of Ag@TiO2 were responsible for overall bacteria killing. The evolution of carbon dioxide under both irradiation ranges indicated mineralization of bacteria cells, and therefore possible application of silver-modified titania for decomposition of chemical and biological pollutants. (C) 2014 Elsevier B.V. All rights reserved.
  • Markowska-Szczupak A, Wang K, Rokicka P, Endo M, Wei Z, Ohtani B, Morawski A.W, Kowalska E
    J. Photochem. Photobiol. B 151 54 - 62 2015 [Refereed][Not invited]
  • Zhishun Wei, Ewa Kowalska, Jonathan Verrett, Christophe Colbeau-Justin, Hynd Remita, Bunsho Ohtani
    NANOSCALE 7 (29) 12392 - 12404 2040-3364 2015 [Refereed][Not invited]
    Octahedral anatase particles (OAPs) were prepared by an ultrasonication (US) hydrothermal (HT) reaction of partially proton-exchanged potassium titanate nanowires (TNWs). The structural/physical properties of OAP-containing samples, including specific surface area, crystallinity, crystallite size, particle aspect ratio, composition and total OAP content, were analyzed. Photocatalytic activities of samples were measured under irradiation (>290 nm) for oxidative decomposition of acetic acid (CO2 system) and dehydrogenation of methanol (H-2 system) under aerobic and deaerated conditions, respectively. Total density of electron traps (ETs) was measured by double-beam photoacoustic spectroscopy (DB-PAS). Mobility and lifetime of charge carriers (electrons) were investigated by the time-resolved microwave conductivity (TRMC) method. The effects of synthesis parameters, i.e., HT duration, HT temperature and US duration, on properties and photocatalytic activities of final products were examined in detail. The sample prepared with 1 h US duration and 6 h HT duration at 433 K using 267 mg of TNWs in 80 mL of Milli-Q water exhibited the highest photocatalytic activity. It was found that change in HT duration or HT temperature while keeping the other conditions the same resulted in changes in all properties and photocatalytic activity. On the other hand, duration of US treatment, before HT reaction, influenced the morphology of both the reagent (by TNWs breaking) and final products (change in total OAP content); samples prepared with various US durations exhibited almost the same structural/physical properties evaluated in this study but were different in morphology and photocatalytic activity. This enabled clarification of the correlation between morphology and photocatalytic activity, i.e., the higher the total OAP content was, the higher was the level of photocatalytic activity, especially in the CO2 system. Although the decay after maximum TRMC signal intensity (I-max) was almost constant for all samples used in this study, photocatalytic activities were roughly proportional to Imax, which tended to be proportional to total OAP content. Assuming that Imax corresponds to the product of density of electrons in mobile shallow ETs and their mobility, the results suggest that OAP particles have beneficial shallow ETs in higher density and thereby the OAP content governs the photocatalytic activities. Thus, morphology-dependent photocatalytic activity of OAP-containing particles was reasonably interpreted by density of ETs presumably located on the exposed {101} facets.
  • The effect of water activity and titania P25 photocatalyst on inactivation of pathogenic fungi
    A. Markowska-Szczupak, K. Janda, K. Wang, A.W. Morawski, E. Kowalska
    Central European Journal of Public Health 23 (3) 267 - 271 2015 [Refereed][Not invited]
  • Zhishun Wei, Ewa Kowalska, Bunsho Ohtani
    MOLECULES 19 (12) 19573 - 19587 1420-3049 2014/12 [Not refereed][Invited]
    The influence of changes in structural and physical properties on the photocatalytic activity of octahedral anatase particles (OAPs), exposing eight equivalent {101} facets, caused by calcination (2 h) in air or grinding (1 h) in an agate mortar was studied with samples prepared by ultrasonication (US; 1 h)-hydrothermal reaction (HT; 24 h, 433 K). Calcination in air at temperatures up to 1173 K induced particle shape changes, evaluated by aspect ratio (AR; d(001)/d(101) = depth vertical to anatase {001} and {101} facets estimated by the Scherrer equation with data obtained from X-ray diffraction (XRD) patterns) and content of OAP and semi-OAP particles, without transformation into rutile. AR and OAP content, as well as specific surface area (SSA), were almost unchanged by calcination at temperatures up to 673 K and were then decreased by elevating the calcination temperature, suggesting that calcination at a higher temperature caused dull-edging and particle sintering, the latter also being supported by the analysis of particle size using XRD patterns and scanning electron microscopic (SEM) images. Time-resolved microwave conductivity (TRMC) showed that the maximum signal intensity (I-max), corresponding to a product of charge-carrier density and mobility, and signal-decay rate, presumably corresponding to reactivity of charge carriers, were increased with increase in AR, suggesting higher photocatalytic activity of OAPs than that of dull-edged particles. Grinding also decreased the AR, indicating the formation of dull-edged particles. The original non-treated samples showed activities in the oxidative decomposition of acetic acid (CO2 system) and dehydrogenation of methanol (H-2 system) comparable to and lower than those of a commercial anatase titania (Showa Denko Ceramics FP-6), respectively. The activities of calcined and ground samples for the CO2 system and H-2 system showed almost linear relations with AR and I-max, respectively, suggesting that those activities may depend on different properties.
  • E. Kowalska, M. Janczarek, L. Rosa, S. Juodkazis, B. Ohtani
    CATALYSIS TODAY 230 131 - 137 0920-5861 2014/07 [Not refereed][Not invited]
    Titania powders were surface modified with gold and/or silver nanoparticles (NPs) by photodeposition method. Gold modified titania exhibited much higher photocatalytic activity during methanol dehydrogenation under UV irradiation than titania modified with monometallic silver and bimetallic Au-Ag NPs. Bimetallic photocatalysts exhibited either enhanced or reduced visible light activity, depending on properties of noble metal NPs, sequence of their deposition on titania, and properties of host titania. Though numerical simulation (3D-FDTD) showed strong plasmonic field enhancement at the interface between titania and bimetallic core(Au)-shell(Ag) NP, it is thought that co-deposition caused an enhancement of charge carriers recombination (by electron sinking in nearby second metal) inhibiting photoactivity under visible light irradiation. The highest level of photoactivity showed large rutile NPs with successively deposited metals, mainly in the form of individual monometallic NPs, due to size/shape polydispersity of deposited NPs, and thus with ability of light absorption in a broad wavelength range. (c) 2013 Elsevier B.V. All rights reserved.
  • Silver modified titania with enhanced photocatalytic and antiseptic properties under UV and visible light irradiation
    E. Kowalska, Z. Wei, B. Karabiyik, B. Ohtani, A. Markowska-Szczupak, H. Remita
    8th European Meeting on Solar Chemistry and Photocatalysis: Environmental Applications (SPEA8), June 25-28, 2014, Thessaloniki, Greece (PC-2-29) 132 - 135 2014/06 [Refereed][Not invited]
  • Hybrid photocatalysts composed of plasmonic titania and ruthenium complexes for oxidation of organic compounds
    E. Kowalska, K. Yoshiiri, Z. Wei, S. Zheng, E. Kastl, S. Rau, B. Ohtani
    8th European Meeting on Solar Chemistry and Photocatalysis: Environmental Applications (SPEA8), June 25-28, 2014, Thessaloniki, Greece (PC-2-31) 110 - 112 2014/06 [Refereed][Not invited]
  • Zhishun Wei, Ewa Kowalska, Bunsho Ohtani
    CHEMISTRY LETTERS 43 (3) 346 - 348 0366-7022 2014/03 [Not refereed][Not invited]
    Titania samples containing octahedral anatase particles (OAPs) were prepared by the ultrasonication-hydrothermal process of partially proton-exchanged potassium titanate nanowires. It was found that increase in the ultrasonication time changed the product morphology, with other structural properties such as specific surface area, crystalline size, and crystallinity remaining almost constant. The results of photocatalytic activity tests for those samples suggested higher activity of a sample with higher OAP content, especially for reactions in the presence of oxygen.
  • Development of plasmonic photocatalysts for environmental application
    E. Kowalska, Z. Wei, B. Karabiyik, M. Janczarek, M. Endo, K. Wang, P. Rokicka, A. Markowska-Szczupak, B. Ohtani
    Adv. Sci. Technol. 93 174 - 183 2014 [Refereed][Not invited]
  • Plasmonic photocatalysts for environmental applications
    E. Kowalska, L. Rosa, A. Markowska-Szczupak, S. Judkazis, B. Ohtani
    CRC International Symposium “New Challenges on the Bio-interfaces: Structures and Dynamics”, 5-6 February, 2013, Sapporo, Japan 51 - 54 2013/02 [Refereed][Not invited]
  • Modification of titanium dioxide with metal nanoparticles induced by radiolysis: application in photocatalysis
    H. Remita, Z. Hai, S. Sorgues, C. Colbeau-Justin, E. Grabowska, A. Zaleska, E. Kowalska
    Second International Conference on Advanced Oxidation Processes. AOP-2012, October 5-8, 2012, Kottyam, India 17 - 18 2012/10 [Refereed][Not invited]
  • Plasmonic photocatalysts for degradation of organic compounds
    E. Kowalska, S. Rau, L. Rosa, S. Juodkazis, B. Ohtani
    Second International Conference on Advanced Oxidation Processes. AOP-2012, October 5-8, 2012, Kottyam, India 10 - 12 2012/10 [Refereed][Not invited]
  • Photocatalysis by gold-loaded titania particles under visible-light irradiation
    B. Ohtani, E. Kowalska
    International Conference on the Nanostructure-Enhanced Photo-Energy Conversion, June 3-6, 2012, Tokyo, Japan P12002 1 - 4 2012/06 [Refereed][Not invited]
  • Mono- and bimetallic plasmonic photocatalysts for degradation of organic compounds under UV and visible light irradiation
    E. Kowalska, S. Rau, B. Ohtani
    6th IWA Specialist Conference Oxidation Technologies for Water and Wastewater Treatment, May 7-9, 2012, Goslar, Germany 11 - 12 2012/05 [Refereed][Not invited]
  • Ewa Kowalska, Sven Rau, Bunsho Ohtani
    Journal of Nanotechnology 1687-9503 2012 [Not refereed][Not invited]
    Plasmonic titania photocatalysts were prepared by titania modification with gold by photodeposition. It was found that for smaller amount of deposited gold (0.1wt%), anatase presence and large surface area were beneficial for efficient hydrogen evolution during methanol dehydrogenation. After testing twelve amounts of deposited gold on large rutile titania, the existence of three optima for 0.5, 2 and 6wt% of gold was found during acetic acid degradation. Under visible light irradiation, in the case of small gold NPs deposited on fine anatase titania, the dependence of photoactivity on gold amount was parabolic, and large gold amount (2wt%), observable as an intensively coloured powder, caused photoactivity decrease. While for large gold NPs deposited on large rutile titania, the dependence represented cascade increase, due to change of size and shape of deposited gold with its amount increase. It has been thought that spherical/hemispherical shape of gold NPs, in comparison with rod-like ones, is beneficial for higher level of photoactivity under visible light irradiation. For all tested systems and regardless of deposited amount of gold, each rutile Au/TiO2 photocatalyst of large gold and titania NPs exhibited much higher photoactivity than anatase Au/TiO2 of small gold and titania NPs. Copyright © 2012 Ewa Kowalska et al.
  • L. Rosa, K. Sun, E. Kowalska, S. Juodkazis
    International Quantum Electronics Conference and Conference on Lasers and Electro-Optics Pacific Rim 2011 (Optical Society of America, 2011), August 28, 2011, Sydney, Australia Article number 6194053 658 - 660 2011/08 [Refereed][Not invited]
  • Searching for new photocatalysts for the decomposition of contaminants in water using the multi N/C 2100 TOC analyzer
    Ewa Kowalska, Sven Rau, Christian Koch
    Labo 06 28 - 31 2011/06 [Refereed][Not invited]
  • Vygantas Mizeikis, Ewa Kowalska, Saulius Juodkazis
    JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 11 (4) 2814 - 2822 1533-4880 2011/04 [Not refereed][Not invited]
    We report results of theoretical simulations of optical field enhancement in a system consisting of spherical and hemispherical noble metal nanoparticles on a smooth titania surface, which is a model system relevant to applications in photo-catalysis and solar energy harvesting. Simulations conducted using Finite-Difference Time-Domain (FDTD) technique reveal presence of resonant optical extinction bands at visible wavelengths, whose optical scattering is weak, but the associated localization and intensity enhancement of optical near-field are significant. For hemispheres, the field is strongly localized at the metal-substrate interface, where intensity enhancement of up to 10(4) times is reached. Moreover, the field is predominantly polarized along the normal to the substrate. These findings indicate potential of the hemisphere-substrate system for applications relying on optically promoted charge transport through the metal-substrate interface, such as photochemical reactions and light-to-current conversion. The results of theoretical analysis are compared with reported experimental data on photo-catalytic reactions.
  • Anna Zielinska-Jurek, Ewa Kowalska, Janusz W. Sobczak, Wojciech Lisowski, Bunsho Ohtani, Adriana Zaleska
    APPLIED CATALYSIS B-ENVIRONMENTAL 101 (3-4) 504 - 514 0926-3373 2011/01 [Not refereed][Not invited]
    The Au-TiO(2) and Ag/Au-TiO(2) nanoparticles have been prepared using a water-in-oil microemulsion system of water/AOT/cyclohexane and water/Triton X-100/cyclohexane. The obtained photocatalysts were subsequently characterized by a BET method, DRS spectroscopy, X-ray photoelectron emission spectroscopy (XPS), scanning transmission electron microscopy (STEM) and X-ray powder diffraction analysis (XRD). For gold-doped titanium (IV) oxide nanoparticles the effect of reducing agent and stabilizer on gold particles size and photocatalytic activity were observed. The effect of crystalline form of TiO(2) and gold nanoparticles size on photocatalytic activity of Au-TiO(2) and Ag/Au-TiO(2) in visible light were also investigated. The photocatalytic activity of noble metals modified-TiO(2) powders under visible light irradiation was estimated by measuring the decomposition rate of phenol in an aqueous solution. The best photocatalytic activity revealed samples with large gold particles (similar to 90 nm) deposited on small titania nanoparticles. It was also found that the bimetallic samples (Ag/Au-TiO(2)) showed a higher photodegradation rate in visible region than monometallic photocatalysts. (C) 2010 Elsevier B.V. All rights reserved.
  • Ewa Kowalska, Sven Rau
    Recent Patents on Engineering 4 242 - 266 1872-2121 2010/12 [Not refereed][Invited]
    Photochemical oxidation of organic and inorganic pollutants is rapidly becoming an attractive technique for water purification and wastewater treatment. Since artificial sources of light require much energy delivery, this method is recommended for toxic contaminants in a specific concentration range below the recommended levels for recovery and above the levels for conventional biological treatment. Selection of a light source and an oxidation system and determination of key-parameters play an important role in the treatment efficiency. Sufficient UV penetration into the radiated liquid is of crucial importance; especially for an opaque environment the UV radiation is only available very close to the UV lamp surface. High mass transfer rates for efficient interaction between the pollutant and the photocatalyst and for high oxygen uptake at the gas-liquid interface is another requirement for practical applications. In this regard, reactor design for efficient wastewater treatment has been a challenging problem. Many types of photoreactors have already been studied, reported and patented. This paper presents a revision of some conventional and novel photoreactors equipped with UV/vis lamps or working under solar radiation for wastewater treatment in laboratory and industrial scales. © 2010 Bentham Science Publishers Ltd.
  • Vygantas Mizeikis, Ewa Kowalska, Bunsho Ohtani, Saulius Juodkazis
    PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS 4 (10) 268 - 270 1862-6254 2010/10 [Not refereed][Not invited]
    We report theoretical simulations of plasmonic near-field enhancement and polarization in a system consisting of an asymmetric spheroidal Ag nanoparticle on a smooth dielectric surface. Finite-difference time-domain (FDTD) simulations reveal resonant optical extinction bands whose near-field is concentrated at the metal-substrate contact point with intensity enhancement by a factor of 10(3) and predominant polarization along the normal to the surface. These features may help explain enhanced photo-catalytic activity observed for colloidal Au and Ag nanoparticles on titania substrates. [GRAPHICS] Electron microscopy image of Ag-nanoparticles on titania and the used model for numerical FDTD simulations. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  • Anna Zielinska, Ewa Kowalska, Janusz W. Sobczak, Izabela Lacka, Maria Gazda, Bunsho Ohtani, Jan Hupka, Adriana Zaleska
    SEPARATION AND PURIFICATION TECHNOLOGY 72 (3) 309 - 318 1383-5866 2010/05 [Not refereed][Not invited]
    A series of Ag-TiO2 photocatalysts were obtained in microemulsion system (water/AOT/cyclohexane), using several Ag precursor amounts ranging from 1.5 to 8.5 mol.%. The photocatalysts' characteristics by X-ray diffraction, STEM microscopy, UV-vis spectroscopy, X-ray photoelectron spectroscopy, BET methods showed that a sample with the highest photo- and bioactivity had anatase structure, about 90 m(2)/g specific surface area, absorbed light over 400 nm and contained 1.64 at.% of silver (0.30 at.% of Ag and 1.34 at.% of Ag2O) and about 13 at.% of carbon in the surface layer. The photocatalytic activity of the catalysts was estimated by measuring the decomposition rate of phenol in 0.21 mM aqueous solution under visible and ultraviolet light irradiation. The bioactivity of silver-doped titanium dioxide nanocomposites was estimated using bacteria Escherichia coli and Staphylococcus aureus, yeast Saccharomyces cerevisiae and pathogenic fungi belonging to Candida family. All modified powders showed localized surface plasmon resonance (LSPR) in visible region with almost the same position of LSPR peaks indicating that similar sizes of silver, regardless of used amount of Ag, is deposited on titania particles during microemulsion method. STEM microscopy revealed that almost 50% of observed silver nanoparticles deposited at the TiO2 surface are in the range from 5 to 10 nm. (C) 2010 Elsevier B.V. All rights reserved.
  • Ewa Kowalska, Orlando Omar Prieto Mahaney, Ryu Abe, Bunsho Ohtani
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 12 (10) 2344 - 2355 1463-9076 2010 [Not refereed][Not invited]
    Fifteen commercial titania (titanium(IV) oxide; TiO2) powders were modified with gold by photodeposition to prepare photocatalysts that work under irradiation with light in the visible range (vis). The gold-modified titania (Au/TiO2) powders were characterized by diffuse reflectance spectroscopy (DRS), field-emission scanning electron microscopy (FE-SEM), scanning transmission microscopy (STEM) and X-ray powder diffraction (XRD). It was shown that all tested powders could absorb visible light with an absorption maximum at localized surface plasmon resonance (LSPR) wavelengths (530-600 nm) and that the size and shape of gold nanoparticles determined the absorption ranges. The photocatalytic activity of Au/TiO2 powders was examined both under ultraviolet and vis irradiation (mainly > 450 nm) for acetic acid and 2-propanol photooxidation. It was found that the activity depended strongly on gold and titania properties, such as particle size and shape, surface area and crystalline form. Under vis irradiation, large rutile particles loaded with gold particles of a wide range of sizes showed the highest level of photocatalytic activity, possibly due to greater light absorption ability in a wide wavelength range resulting from transverse and longitudinal LSPR of rod-like gold particles. Action spectrum analyses showed that visible-light-induced oxidation of organic compounds by aerated gold-titania suspensions was initiated by excitation of LSPR absorption of gold. Although photocatalytic activity of nanosized gold particles under vis irradiation with a wavelength of ca. 430 nm and catalytic activity of gold-modified titania during dark reactions were also found, it was shown that the activities of Au/TiO2 particles originated from activation of LSPR of gold by light of wavelength of 530-650 nm. Participation of molecular oxygen as an electron acceptor and titania as a conductor of electrons is suggested by comparing with results obtained under deaerated conditions and results obtained using a system containing gold-deposited silica instead of gold-titania, respectively. On the basis of these results, the mechanism of visible-light-induced oxidation of organic compounds on gold-titania is proposed.
  • Modification of titanium dioxide with gold for photocatalysis under UV and visible light irradiation
    E. Kowalska, R. Abe, B. Ohtani
    2nd International Symposium on Advanced Particles (ISAP-2009), April 26-29, 2009, Yokohama, Japan 141 - 142 2009/04 [Refereed][Not invited]
  • Ewa Kowalska, Ryu Abe, Bunsho Ohtani
    CHEMICAL COMMUNICATIONS (2) 241 - 243 1359-7345 2009 [Not refereed][Not invited]
    Action spectrum analyses showed that visible light-induced oxidation of 2-propanol by aerated gold-modified titanium(IV) oxide (titania) suspensions is initiated by excitation of gold surface plasmon, and polychromatic irradiation experiments revealed that the photocatalytic reaction rate depends strongly on properties of titania, such as particle size, surface area and crystalline form (anatase or rutile) and on properties of gold deposits, such as size and shape.
  • Paulina Gorska, Adriana Zaleska, Ewa Kowalska, Tomasz Klimczuk, Janusz W. Sobczak, Ewa Skwarek, Wladyslaw Janusz, Jan Hupka
    APPLIED CATALYSIS B-ENVIRONMENTAL 84 (3-4) 440 - 447 0926-3373 2008/12 [Not refereed][Not invited]
    A series of TiO(2) photocatalysts were obtained using several calcination temperatures ranging from 350 to 750 degrees C. The photocatalysts' characteristics by X-ray diffraction, UV-vis and FTIR diffuse reflectance spectroscopies, X-ray photoelectron spectroscopy, BET and BJH methods showed that sample active in vis region had anatase structure, about 200 m(2)/g specific surface area, absorbed light for lambda > 400 nm and contained 10.1 at.% of C-C species. The photocatalytic activity of the catalysts was estimated by measuring the decomposition rate of phenol in 0.21 mM aqueous solution in visible and ultraviolet light. The experimental data clearly indicate correlation between the absorption intensity of irradiation by obtained powders and their photocatalytic performance in phenol degradation. An increase in absorbance over the entire vis region and the highest photocatalytic activity for phenol degradation in visible light (lambda > 400 nm) occurred for photocatalyst calcinated at 350 degrees C. Photocatalyst processed at 450 degrees C had the best activity in UV light (250 < lambda < 400 nm). (C) 2008 Elsevier B.V. All rights reserved.
  • Model studies on degradation of selected pesticides in samples of process wastewater
    M. Grynkiewicz, G. Dembska, G. Sapota, A. Flasinska, S. Wisniewski, B. Aftanas, E. Kowalska
    Ecology and Technology 3 (94) 106 - 113 2008/03 [Refereed][Not invited]
  • E. Kowalska, H. Remita, C. Colbeau-Justin, J. Hupka, J. Belloni
    JOURNAL OF PHYSICAL CHEMISTRY C 112 (4) 1124 - 1131 1932-7447 2008/01 [Not refereed][Not invited]
    TiO2 (commercial-P25 and synthesized by sol-gel method) was surface modified with platinum ions or [Pt-3(CO)(6)](6)(2-) clusters to improve its photocatalytic activity. The physical properties of the synthesized photocatalysts were examined by transmission electron microscopy (TEM), X-ray diffraction (XRD), and Brunauer, Emmett and Teller adsorption (BET) methods. To characterize the absorption ability of visible light, the diffusion reflectance spectra (DRS) were recorded. The charge-carrier lifetimes in TiO2 after UV illumination were determined by microwave absorption experiments using the time-resolved microwave conductivity (TRMC) method. The photocatalyst activity was examined by degradation of exemplary aqueous phase pollutants, such as Rhodamine B and phenol. The impact of the adsorbates on the photocatalytic activity depends strongly on the titania precursor (commercial or synthesized), the irradiation wavelength (UV or visible), and the model compound (dye or phenol). The results show that it is possible to enhance the P25 photocatalytic activity under UV-visible light by doping it with Pt clusters. Also, P25 doping with Pt(II) or Pt clusters results in enhancement of the activity under visible light. Pt(IV)/TiO2 synthesized by sol-gel method exhibits better photoactivity under UV-visible and visible light compared to the unmodified titania. In all mentioned systems, a positive effect of modification with platinum clusters and, in particular, an important enhancement in photocatalytic activity under visible light were obtained. These results are explained by enhancement in visible light absorption and inhibition of charge-carrier recombination.
  • A. Zaleska, P. Gorska, E. Kowalska, J. Hupka
    Polish Journal of Chemical Technology 8 (2) 102 - 105 2006/08 [Refereed][Not invited]
  • Treatment of wastewater from production of wood panels
    J. Hupka, M. Janczarek, R. Aranowski, A. Zaleska, M. Chrzanowska, E. Kowalska
    Selected Aspects of Production of Wood Derivatives Materials, Tleń, November 17-18, 2005, Tlen, Po-land 1 - 7 2005/11 [Refereed][Not invited]
  • Investigation of biological and photochemical treatment of municipal landfill leachates
    M. Chrzanowska, E. Kowalska, J. Hupka
    IWA Specialized Conference: Nutrient Management in Wastewater Treatment Processes and Recycle Streams, 19-21 September, 2005, Cracow, Poland 1107 - 1111 2005/09 [Refereed][Not invited]
  • Visible light activity of TiO2 modified with thioacetamide
    P. Gorska, E. Kowalska, A. Zaleska, J. Hupka
    Second European Conference on Oxidation and Reduction Technologies for Ex-situ and In-situ Treatment of Water, Air and Soil (ECOR-2), June 12-15, 2005, Güttingen, Germany 191 - 192 2005/06 [Refereed][Not invited]
  • The TiO2–assisted photodegradation in gas phase
    Ewa Kowalska, Adriana Zaleska
    Przegląd Komunalny 6 (29) 76 - 77 2005/06 [Refereed][Not invited]
  • Characterization and treatment of industrial pesticide wastewater
    E. Kowalska, M. Chrzanowska, M. Janczarek, A. Blaszke, J. Hupka
    Global Symposium on Recycling, Waste Treatment and Clean Technology (REWAS 2004), September 26-29, 2004, Madrid, Spain 2883 - 2884 2004/09 [Refereed][Not invited]
  • E Kowalska, M Janczarek, J Hupka, M Grynkiewicz
    WATER SCIENCE AND TECHNOLOGY 49 (4) 261 - 266 0273-1223 2004 [Not refereed][Not invited]
    Photodegradation of organic pesticides in industrial wastewater was examined in a UV/H2O2/air system. An experimentally determined optimal amount of hydrogen peroxide (0.008% v/v) indicates that hydrogen peroxide concentration controlled the efficiency of photodegradation. Pre-treatment operations such as sedimentation, filtration and coagulation were used to obtain better efficiency of pesticide removal and to cut down on irradiation time. Finally, scale-up experiments in the air-sparged hydrocyclone (ASH) reactor were carried out. After 5 min irradiation of 100 dm(3) industrial wastewater almost all pesticides were destroyed. Thus the ASH reactor proved to be an effective contactor for carrying out photochemical reactions.
  • Titania modification for photocatalytic wastewater treatment
    E. Kowalska, H. Remita, J. Hupka, J. Belloni
    8th International Conference on TiO2 Photocatalysis: Fundamentals and Applications (TiO2-8), October 26-29, 2003, Montreal, Quebec, Canada 107 - 108 2003/10 [Refereed][Not invited]
  • H2O2/UV enhanced degradation of pesticides in wastewaters
    E. Kowalska, M. Janczarek, J. Hupka, M. Grynkiewicz
    3rd International Conference on Oxidation Technologies for Water and Wastewater Treatment (AOP’3), May 18-22, 2003, Goslar, Germany 374 - 379 2003/05 [Refereed][Not invited]
  • Titania doping for catalytic wastewater treatment
    E. Kowalska, H. Remita, J. Hupka, J. Belloni
    3rd International Conference on Oxidation Technologies for Water and Wastewater Treatment (AOP’3), May, 18-22, 2003, Goslar, Germany 885 - 890 2003/05 [Refereed][Not invited]
  • Photochemical degradation of xylene
    M. Budzisz, E. Kowalska, M. Pertkiewicz-Piszcz
    3rd International Conference on Oil Pollution „Prevention, Characterization, Clean Technology, Septem-ber 8-11, 2002, Gdansk, Poland II 134 - 138 2002/11 [Refereed][Not invited]
  • H. Tyszkiewicz, M. Biziuk, J. Hupka, A. Zaleska, E. Kowalska, A
    Ecological Chemistry and Engineering. S 8 (8-9) 941 - 946 2001/08 [Refereed][Not invited]
  • Photodegradation of Phenol in Gas-sparged Reactor
    Ewa Kowalska (Artuna, Jan Hupka
    7th Meeting of the Central and East European Section of SECOTOX, October 24-28, 2000, Bratislava, Slovakia 199 - 201 2000/10 [Refereed][Not invited]
  • Determination of organochlorines pesticides during degradation in a gas-sparged reactor
    E. Kowalska (Artuna, A. Zaleska, J. Hupka
    Fifth International Symposium on Exhibition on Environmental Contamination in Central and Eastern Europe, September 12-14, 2000, Prague, Czech Republic 83 - 88 2000/09 [Refereed][Not invited]
  • Ewa Kowalska (Artuna, Jan Hupka
    Central European Journal of Public Health 8 (44) 88 - 89 2000/08 [Refereed][Not invited]
  • Photochemical degradation of organic contaminants in aqueous phase
    Ewa Kowalska (Artuna, Jan Hupka
    2nd Conference on Ecological Achievement in Chemical Industry, October 14-15, 1999, Torun, Poland 174 - 182 1999/10 [Refereed][Not invited]
  • H2O2/UV/air oxidation of organic contaminants in the gas-sparged cyclone reactor
    Ewa Kowalska (Artuna, Jan Hupka
    6th Meeting of the Central and Eastern European Regional Section, September, 19-23, 1999, Balatonfőldvár, Hungary 103 - 105 1999/09 [Refereed][Not invited]
  • Photocatalytic Degradation of Almost Non-soluble Organics in Gas-sparged Reactor
    J. Hupka, A. Zaleska, E. Kowalska, R. Bokotko, H. Tyszkiewicz, M. Biziuk
    EF Conference Environmental Technology for Oil Pollution, August 29- September 3, 1999, Jurata, Poland II 37 - 42 1999/08 [Refereed][Not invited]

Books etc

  • Noble metal nanoparticles
    Kowalska E, Endo M, Wei Z, Wang K, Janczarek M (ContributorNANOSCALE MATERIALS IN WATER PURIFICATION)
    Elsevier 2018/10 (ISBN: 9780128139264)
  • Band-gap engineering of photocatalysts: surface modification versus doping
    Kowalska E, Wei Z, Janczarek M (ContributorVisible-Light-Active Photocatalysis: Nanostructured Catalyst Design, Mechanisms and Applications. ed. S. Ghosh)
    Wiley 2018/05 (ISBN: 9783527342938)
  • Plasmonic photocatalysis
    Ewa Kowalska (ContributorGold nanoparticles for physics, chemistry and biology. eds.: C. Louis & O. Pluchery. 2nd edition)
    World Scientific 2017/03 (ISBN: 9781786341242) 46
  • Influence of post-treatment operations on structural properties and photocatalytic activity of octahedral anatase particles prepared by hydrothermal method
    Wei Z, Kowalska E, Ohtani B (ContributorPhotocatalysis: Fundamentals, Materials and Potential. ed.: P. Pichat.)
    MDPI, Basel 2016/07 (ISBN: 9783038421832) 14
  • Silver-gold nano-composites for photo-catalytic and sensing applications, In: Silver Nanoparticles: Synthesis, Uses and Health Concerns
    E. Kowalska, Y. Nishijima, L. Rosa, S.Juodkazis (Contributor)
    Nova Science Publishers 2013 (ISBN: 9781628084023)
  • Development of application of photocatalysts, In: Latest Trends in Plasmonic Nanomaterials
    B. Ohtani, E. Kowalska (Contributor)
    CMC Publishing 2009 (ISBN: 9784781301327) 9
  • Application of spectroscopic method for characterization of Ag-TiO2 nanocomposites. In: Science and In-dustry - Spectroscopic Methods in Practice (Nauka i przemysł - metody spektroskopowe w praktyce)
    A. Zielisnka, A. Zaleska, I. Lacka, M. Gazda, E. Kowalska, J. Hupka (Contributor)
    UMCS Lublin 2008 4
  • UV/VIS light-enhanced photocatalysis for water treatment and protection. In: Soil and Water Pollution Monitoring, Protection and Remediation
    J. Hupka, A. Zaleska, M. Janczarek, E. Kowalska, P. Górska, R. Aranowski (Contributor)
    Springer 2005 (ISBN: 1402047274) 11
  • Determination and pathways of nitrogen during wastewater treatment. In: Pathways of pollutants and miti-gation strategies of their impact on the ecosystems.
    M. Chrzanowska, E. Kowalska, J. Hupka (Contributor)
    Komit. Inż. Środow. PAN, Lublin 2004 9
  • Pathways and degradation of chloroorganic pesticides. In: Pathways of pollutants and mitigation strategies of their impact on the ecosystems
    A. Zaleska, E. Kowalska, J. Hupka (Contributor)
    Komit. Inż. Środow. PAN, Lublin 2004 15

Conference Activities & Talks

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