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In this study, our aim was to synthesize nanocrystalline zirconia by using the simple sol-gel method with organic additive and to study its antibacterial property. The formation of the tetragonal crystalline phase of ZrO2 was confirmed by powder XRD analysis at relatively low temperature using microwave furnace. The morphology, particle size, and nanostructure were analyzed using FESEM. TEM data also confirmed the formation of the nanostructure. TEM micrograph and SAED pattern confirmed the crystalline perfection in the prepared zirconia nanoparticles. Nanocrystalline zirconia does not inhibit cell growth of normal 3T3 mouse fibroblast cells which indicated its nontoxic nature. The zirconia nanoparticles showed the significant antibacterial activity against E. coli and S. aureus bacterial pathogen and also it is stable at the physiological condition. Hence, it can be used for various biomedical applications.

Journal of Nanoscience and Nanotechnology
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The FTIR results confirmed that the synthesis of zirconia under hydrothermal conditions produced nanopowders coated with a surface layer of –OH groups. Annealing the powders at temperatures up to 500 °C did not cause an increase in the crystallite size. Annealing at a temperature of 200 °C converted the amorphous material to crystalline, which was attributed to the evaporation of water adhered to the nanoparticles surface. The presence of clearly distinguishable peaks above that temperature indicates that the remaining hydroxy groups are for well-defined chemical bonds in the deeper layers of the zirconia NPs. An increase in the annealing temperature caused the crystallite diameter to increase to 72 nm (according to the Scherrer equation). The much larger apparent particle size indicated by the specific surface area measurements is the result of particle sintering. That is, the width of the XRD peaks depends on the size of the crystallites, while the specific surface area depends on the exposed surface of the sintered aggregates. During the sintering process, the –OH groups are most likely removed by evaporation of water, and the thus created dangling bonds are presumably saturated by creating chemical bonds between zirconium and oxygen atoms across the grain boundaries.

Regional Centre of Advanced Technologies and Materials

Researche institute in Czech Republic focuses on nanotechnology
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One of the most powerful techniques for the synthesis of a wide range of materials such as zirconia is a solid-state process named mechanochemical treatment. This technique is a non-equilibrium solid-state process in which the final product retains a very fine amorphous or nanocrystalline structure. This process is versatile, simple and cost effective and can be used to synthesize a wide variety of materials with a high yield rate on a commercial scale. This process can also be designed in such a way to synthesize nanocrystalline particles dispersed within a soluble matrix. In other words, chemical precursors react, either during milling or at the subsequent heat treatment stage, to form a nanocrystalline powder embedded within a soluble salt matrix phase. The ultrafine powder is subsequently recovered by selective removal of the matrix phase through washing with an appropriate solvent. The ability to decrease time and temperature of the chemical reaction at low energy consumption is another advantage of this technique, and .