Synthesis of Zn x Mg 1-x O Nanocrystals and the Assessment of their Antimicrobial Activity against Escherichia Coli
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Synthesis of ZnxMg1-xO Nanocrystals and the Assessment of their Antimicrobial Activity against Escherichia Coli Yarilyn Cedeño-Mattei1,2, Rosa Concepción-Abreu3, and Oscar Perales-Pérez1,2 1
Department of Engineering Science and Materials, University of Puerto Rico, Mayaguez, PR 00681-9000, U.S.A. 2 Department of Chemistry, University of Puerto Rico, Mayaguez, PR 00681-9000, U.S.A. 3 Department of Biology, Chemistry, and Environmental Sciences, Interamerican University of Puerto Rico, San Germán, PR 00683, U.S.A. ABSTRACT The present work focuses on the synthesis and evaluation of the antimicrobial activity of ZnxMg1-xO solid solutions. ZnxMg1-xO solid solutions were synthesized through the thermal decomposition of ZnMg-precursor synthesized in aqueous and ethanol solutions via a two-steps process. The antimicrobial activity of ZnxMg1-xO solid solution against E. coli was evaluated using the spread plate method in presence of ZnxMg1-xO powder of different contents of Zn species, ‘x’. The powder concentrations evaluated were 500, 1000, and 1500 ppm. Zn0.10Mg0.90O powders exhibited a bacterial growth inhibition between 38% and 100% when the powder concentration increased from 500 up to 1500 ppm, respectively. A decreasing trend was observed for x = 0.30 and above; the corresponding bacterial growth inhibition was 12%, 6%, and 5% when the particles concentration was, respectively, 500, 1000, and 1500 ppm. X-Ray diffraction analyses suggested the incorporation of Zn ions into the MgO lattice for ‘x’ values below 0.10, enhancing the antimicrobial activity; the formation of two isolated oxide phases observed at larger ‘x’ values (e.g. x = 0.30 and x = 0.50 Zn), could explain the detected inhibition of the corresponding antimicrobial activity. INTRODUCTION Food packaging is indispensable to preserve the quality and safety of the food from the time of manufacturing to the final use by the consumer. It is indispensable to evaluate new materials with enhanced antimicrobial capacity that could be then dispersed in biodegradable polymers for food packaging applications. ZnO and MgO have been suggested as antimicrobial agents among others [1–3]. It would be expected that synthesizing a unique nanostructure containing Mg and Zn species as ZnxMg1-xO solid solutions, should be conducive to a synergistic effect and enable the tailoring in the corresponding antimicrobial activity to a broader kind of microorganisms. Taking into account the above considerations, the present work addresses the development of a novel protocol to synthesize ZnxMg1-xO nanocrystals, their structural and morphological characterization, and the composition-based assessment of the corresponding antimicrobial activity in presence of E. coli.
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EXPERIMENTAL Materials Suitable amounts of Mg(NO3)2 (ACS, 98-102%, Alfa Aesar), Zn(OOCCH3)2.2H2O (ACS, 98101%, Alfa Aesar), Na2CO3 (≥ 99%, Sigma-Aldrich), and NaOH (pellets, 98%, Alfa Aesar) were used for the synthesis of the Mg-Zn carbonate hydroxide precursor. All regents were used without any further purification
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