Photocatalytic Activity of Zinc Oxide Nanoparticles Prepared by Laser Ablation in a Decomposition Reaction of Rhodamine
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PHOTOCATALYTIC ACTIVITY OF ZINC OXIDE NANOPARTICLES PREPARED BY LASER ABLATION IN A DECOMPOSITION REACTION OF RHODAMINE B E. A. Gavrilenko,1 D. A. Goncharova,1 I. N. Lapin,1 M. A. Gerasimova,2 and V. A. Svetlichnyi1
UDC 535.37, 535.33/.34, 544.52, 544.576
The development of the routes for synthesizing photocatalysts and the methods for investigating their properties is very appealing for applications in ecology and renewable energy production. Zinc oxide is one of the promising photocatalytic materials. In this study, ZnO nanopowders are produced by pulsed laser ablation (Nd:YAG laser, 1064 nm, 7 ns) in water and air, followed by their heat treatment. The structure and composition of the resulting powders are examined using transmission electron microscopy, X-ray diffraction, and differential scanning calorimetry. The nature of the defect states of nanoparticles is investigated using fluorescence spectroscopy. Their photocatalytic activity is tested during photodegradation of Rhodamine B under excitation by the broadband visible and UV-visible light. The influence of the composition and morphology of zinc oxide and the nature of defect states on its photocatalytic activity is discussed. Keywords: zinc oxide, pulsed laser ablation, nanoparticles, spectral-luminescent properties, defects, photocatalysis, Rhodamine B.
INTRODUCTION Designing new effective materials for photocatalytic decomposition of organic compounds for the purposes of ecology, chemical technologies, and renewable energy engineering – is one of the most important avenues of today’s scientific research [1, 2]. By now, the absolute leading materials in terms of the wide range of their investigations and practical applications are the photocatalysts based on titanium dioxide [3, 4]. On the other hand, TiO2 has a number of disadvantages, which stimulates a search for new photocatalytic materials and their synthesis routes. An efficient and inexpensive alternative to TiO2 could be zinc oxide, ZnO – a direct-gap semiconductor of the AIIBVI group (Eg ~ 3.3– 3.4 eV, exciton binding energy 60 meV [5]) possessing a number of specific properties due to its energy band structure, which make it applicable in photocatalysis and in devices in optoelectronics, spintronics, solar power engineering, and sensorics. Having the band gap comparable with that of TiO2, ZnO frequently shows an advantage over the latter in its response to visible light excitation [6]. Its high reactivity due to the unsaturated bond of surface atoms of the ZnO powder and its capacity of generating active oxygen forms make it an efficient inhibitor of the pathogenic bacteria growth, which is applied in the biomedical materials and supplies. Being relatively safe for ecology and human health in contrast to other semiconductor oxides, in the water treatment applications ZnO offers solutions to both effective photocatalytic decolorization and disinfection. Among the large number of the methods for manufacturing ZnO nanoparticles (NPs), such as hydrothermal, microwave and sonochemical methods, a
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