International Journal of Science and Research (IJSR) ISSN (Online): 2319-7064 Impact Factor (2012): 3.358 Volume 3 Issue 12, December 2014 www.ijsr.net Licensed Under Creative Commons Attribution CC BY Structural, Photocatalytic and Antibacterial Activity of ZnO and ZrO 2 Doped ZnO Nanoparticles Sohair Abd El Hakam 1 , Shady Mohamed El-Dafrawy 2* , Salah Fawzy 3 , Shawky Mohamed Hassan 4 Chemistry Department, Faculty of Science, Mansoura University, Egypt Abstract: A series of ZnO and ZrO 2 doped ZnO catalysts were prepared by sol-gel method. X-ray diffraction analysis of these catalysts showed the formation of phase pure nanoparticles with wurtzite ZnO structure. Scanning electron microscope (SEM) images emphasized the formation of spherical shaped ZnO and ZrO 2 doped ZnO nanoparticles. Transmission electron microscope (TEM) images emphasized that all prepared catalysts are in nanoscale and are spherically shaped. The Methylene Blue (MB) decomposition rate of the synthesized pure ZnO and ZrO 2 doped ZnO nanoparticles were studied under the UV–Vis region. In the UV–Vis region, synthesized pure ZnO and ZrO 2 doped ZnO decomposed Methylene Blue (MB). However, the MB decomposition rate obtained using pure ZnO was much higher than that by doped ZnO. The antibacterial property test was carried out via disk diffusion method, and the result indicated antibacterial activity of the prepared catalysts. Keywords: ZnO, Sol-gel, photocatalysis, antimicrobial, ZnO /ZrO 2 1. Introduction Dyes and organic compounds are widely used in industry and daily life. Large amounts of these compounds were released in waste water resulting in considerable problems to microorganisms, aquatic environments and human beings [1-3] . Unfortunately, most of these dyes are chemically stable and cannot be removed by chemical oxidation via traditional biochemical and physicochemical methods used widely [4-6] . Additionally, traditional methods used widely like chlorination, generates carcinogenic and mutagenic by products [7] . Recently, heterogeneous photocatalysis is investigated widely to replace traditional methods because of its ability to completely decompose targeted pollutants including dyes and organic compounds besides inactivating microorganisms such as bacteria and viruses [1, 6-9] . ZnO is a semiconductor material with a wide band gap (3.2eV) [10] , low cost, abundant in nature and environmental friendly so it worth to be studied as one of the most promising materials capable of achieving green chemistry [11-13] . As a heterogeneous photocatalyst, ZnO has comparable band gap with TiO 2 (3.2eV) [14-15] , lower productivity cost [16-18] , larger quantum efficiency than TiO 2 [19-20] so it absorbs over larger fraction of the solar spectrum than TiO 2 [21-28] . Although ZnO and TiO 2 have similar band gaps, ZnO has higher photoactivity (by a factor of 2 – 3) in both UV and sunlight irradiation for the decontamination of water [29-35] . This is due to the higher efficiency of ZnO in the production of OH ¯ and reduced recombination of photo induced electron–hole pairs [16-18, 36-41] . Point defects mainly from oxygen vacancies are the main reason for the higher efficiency of ZnO in the production of OH ¯ and reduced recombination of photo induced electron–hole pairs [42-46] . The heterogeneous photocatalytic process is initiated when a semiconductor material such as ZnO or TiO 2 is illuminated with photons possess energy equal or greater than the bending energy of electrons in the valence band, resulting in the generation of mobile electrons in the higher energy conduction band (E cb ) and positive holes in the lower energy valence band (E vb ) of the catalyst [47] . The photocatalytic reaction depends on holes formed in the valence band which catalyze formation of hydroxyl radicals at the semiconductor surface and mobile electrons in the conduction band which reduce molecular O 2 . These reactions represent steps to both mineralization of organic species and removal of inorganic cations [48-51] . In this work, we aimed to synthesize nontoxic, environmental friendly and affordable photocatalyst to investigate in the removal of MB as a well-known water pollutant. MB is a heterocyclic organic dye, frequently used in textile, cosmetic and pharmaceutical industries. MB can cause permanent injury to humans and animals on inhalation and ingestion and the risk of the presence of this dye in water may be arisen from the burning effect of eye, nausea, vomiting and diarrhea [52] . Moreover, we studied the antimicrobial activity of ZnO and ZrO 2 doped ZnO against gram positive and gram negative bacteria. 2. Experimental 2.1. Preparation of Catalysts: 2.1.1. Zinc Oxide nanoparticles synthesis: Zinc Oxide nanoparticles were prepared by sol-gel method from zinc acetate dihydrate and oxalic acid using ethanol as solvent [53-54] . ZnO gel was obtained by dissolving 10.99g zinc acetate dihydrate in 300ml ethanol (C 2 H 6 O) and refluxing for 30 minutes. 17.71g oxalic acid (H 2 C 2 O 4 ) was mixed with 200ml of ethanol; stirred for 1 hr at 50 ° C and added to the previous solution slowly .The final mixture was refluxed at 50 ° C for 60 minutes before left cool down to room temperature. Finally, the prepared ZnO gel was dried at 80 ° C for 20 hrs (xerogel), and the powder calcined under flowing air (0.1mmolS -1 ) for 3 hrs at (400,500 and 600 ° C). Paper ID: SUB14238 779