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Szeged, Hungary

Veres A.,University of Szeged | Menesi J.,University of Szeged | Juhasz A.,Nanocolltech Ltd. | Berkesi O.,University of Szeged | And 7 more authors.
Colloid and Polymer Science

The plasmonic Ag-TiO2 (with 0.5 wt% Ag) photocatalyst was prepared on P25 TiO2 surface. The presence of AgNPs on the titania was indicated by the UV-vis spectrum, which showed a plasmonic absorbance band in the visible range (λmax = 455 nm). XPS measurements suggested that Ag was in metallic (Ag) and in oxide forms on TiO2. Ag-TiO2 photocatalyst and TiO2 were embedded in [poly(ethyl acrylate-co-methyl methacrylate; p(EA-co-MMA)] copolymer to attain mechanically stable, photocatalytically active nanocomposite films. The photooxidation of ethanol was slower on the photocatalyst/polymer nanocomposites, but it could be significantly improved by irradiating them with UV light. The photoaging was applied as a post-preparation treatment to improve the photocatalytic activity of the nanocomposite films. Changed surface morphology and the partial destruction of the polymer were supported by AFM and FTIR results. Contact angle measurements were used to determine the surface free energies of the prepared and the photoaged nanocomposite films. © 2013 Springer-Verlag Berlin Heidelberg. Source

Tallosy S.P.,University of Szeged | Janovak L.,University of Szeged | Menesi J.,University of Szeged | Nagy E.,University of Szeged | And 5 more authors.
Environmental Science and Pollution Research

Nanosilver-modified TiO2 and ZnO photocatalysts were studied against methicillin-resistant Staphylococcus aureus on the surface and against naturally occurring airborne microorganisms. The photocatalysts/polymer nanohybrid films were prepared by spray coating technique on the surface of glass plates and on the inner surface of the reactive light source. The photoreactive surfaces were activated with visible light emitting LED light at λ = 405 nm. The optical properties of the prepared photocatalyst/polymer nanohybrid films were characterized by diffuse reflectance measurements. The photocatalytic properties were verified with the degradation of ethanol by gas chromatography measurements. The destruction of the bacterial cell wall component was examined with transmission electron microscope. The antibacterial effect of the photocatalyst/polymer nanohybrid films was tested with different methods and with the associated standard ISO 27447:2009. With the photoreactive coatings, an extensive disinfectant film was developed and successfully prepared. The cell wall component of S. aureus was degraded after 1 h of illumination. The antibacterial effect of the nanohybrid films has been proven by measuring the decrease of the number of methicillin-resistant S. aureus on the surface and in the air as the function of illumination time. The photocatalyst/polymer nanohybrid films could inactivate 99.9 % of the investigated bacteria on different thin films after 2 h of illumination with visible light source. The reactive light source with the inner-coated photocatalyst could kill 96 % of naturally occurring airborne microorganisms after 48 h of visible light illumination in indoor air sample. The TEM results and the microbiological measurements were completed with toxicity tests carried out with Vibrio fischeri bioluminescence bacterium. © 2014, Springer-Verlag Berlin Heidelberg. Source

Veres A.,University of Szeged | Janovak L.,Nanocolltech Ltd. | Bujdoso T.,University of Szeged | Rica T.,University of Szeged | And 5 more authors.
Journal of Advanced Oxidation Technologies

Phosphate and silver co-functionalized TiO 2 catalysts were prepared by varying amount of silver (0-1 wt.%) with constant phosphate content (0.25 wt.%). Two methods, the well-know photodeposition and a new simple method, i.e. heterocoagulation, are presented for preparing Ag-TiO 2 and the optical, photochemical and photobiological properties of the different samples have been compared. Due to the silver modification, the photocatalysts showed a new Plasmon resonance peak at λ max=455 nm. The photocatalytic efficiencies of the new photocatalysts were studied under UV-A/visible (λ≥ 360 nm) irradiation. Mechanically stable hydrophilic poly(EA-co-MMA) and hydrophobic poly(Bi.A-co-Ech.) based composite films were prepared by spray coating technique. The photocatalytic efficiencies decreased only by ∼ 15% on the hydrophilic and ∼ 63% on the hydrophobic polymer compared to the reference pure photocatalyst films. The antibacterial activity of the films was also studied under visible light (λ≥ 400 nm) irradiation. Methicillin resistant Staphylococcus aureus (MRSA) was used as test bacterium. The best antibacterial activity (90% of bacteria destruction in 15 minutes) could be observed on the Ag-TiO 2/p(EA-co-MMA) film. © 2012 Science & Technology Network, Inc. Source

Csapo E.,Hungarian Academy of Sciences | Oszko A.,University of Szeged | Varga E.,University of Szeged | Juhasz A.,Nanocolltech Ltd. | And 5 more authors.
Colloids and Surfaces A: Physicochemical and Engineering Aspects

Bimetallic silver-gold nanoparticles (NPs) with different structures were prepared. Namely, silver-gold alloy and core(Ag)-shell(Au) type nanoparticles were synthesized at various Ag/Au ratios using only sodium citrate as reductant without any stabilizers. The synthesized NPs were characterized by different structure analysis methods. The unique optical properties of these NPs were studied by UV-vis spectroscopy. For Ag/Au alloy NPs the λmax values are linearly tunable from ∼408nm to 525nm depending on the composition. The plasmon band of core-shell NPs can be shifted to higher wavelengths by depositing a gold shell with increasing thickness. The HRTEM images clearly confirm the two different structures of the NPs. We found that the size of alloy nanoparticles decrease from d ∼15nm to d ∼8nm with the increase in gold content. In contrast, core(Ag)-shell(Au) type NPs with progressively increasing size (d=13-16nm) along with separately formed smaller gold NPs were formed. © 2012 Elsevier B.V. Source

Veres A.,University of Szeged | Rica T.,University of Szeged | Janovak L.,Nanocolltech Ltd. | Domok M.,University of Szeged | And 7 more authors.
Catalysis Today

Plasmonic noble metal nanoparticles (NPs) (silver and gold) are able to sensitise photocatalysts in visible light by modifying the TiO 2 surface with 0.5 wt% loading. These plasmonic catalysts were supported by optically transparent zirconium dioxide and layer silicate. The hybrid catalyst films (with ∼10 μm thickness) were prepared by sputtering the aquatic suspension of the catalyst/support suspension on glass slides and irradiated the films by visible light (λ ≥ 435 nm). The photocatalytic efficiency was studied on decomposition of ethanol vapour, and the residual concentration of ethanol was monitored. The intermediates during illumination were analysed by GC-MS. Modifications with silver and gold lead to a change in the optical properties due to the plasmonic light absorption on TiO 2. The supporting binding materials are almost transparent in UV-vis wavelength range, thus Ag- and Au-modified TiO 2 can be excited by the incoming light without much loss of the photon energy. Furthermore, the layered silicate promoted the photocatalytic process by its high adsorption capacity. Due to these two phenomena, a synergistic effect was found on the photocatalytic activity of the nanocomposite hybrid films. © 2011 Elsevier B.V. All rights reserved. Source

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