AVS 66th International Symposium & Exhibition
    Biomaterial Interfaces Division Wednesday Sessions
       Session BI+AS-WeM

Paper BI+AS-WeM6
Nano- and Microscale ZnO with Controllable Abundance of Surface Polarity as a Platform to Study Antibacterial Action.

Wednesday, October 23, 2019, 9:40 am, Room A120-121

Session: Microbes and Fouling at Surfaces
Presenter: Yuri Strzhemechny, Texas Christian University
Authors: J.M. Reeks, Texas Christian University
B. Thach, Texas Christian University
W. Moss, Texas State University
R. Maheshwari, Texas Academy of Mathematics and Science
I. Ali, Texas Christian University
S.M. McGillivray, Texas Christian University
Y.M. Strzhemechny, Texas Christian University
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Nano- and microcrystalline ZnO is a low-cost, easy to synthesize material employed in many current and incipient applications owing to its exceptional optoelectronic, structural and chemical characteristics as well as a broad range of production techniques. Antibacterial action of ZnO is one of these applications, with a growing field of interdisciplinary research. Despite numerous and vigorous studies of the antibacterial nature of ZnO, and, in particular, the well- documented antimicrobial action of micro- and nanoscale ZnO particles, the most fundamental physical and chemical mechanisms driving this action are still not well identified. In particular, the influence of the crystal surface polarity on the antibacterial performance is largely unknown. Normally, hexagonal (wurtzite) ZnO crystals can be terminated with either charged polar (Zn or O) or electrically neutral nonpolar surfaces. In this work, we employ a hydrothermal growth protocol to produce ZnO nano- and microcrystals with tunable morphology, in particular to obtain a dependable control of the prevalent polarity of the free surfaces. This, in turn, can serve as a platform to investigate antibacterial action mechanisms in the synthesized specimens. It is reasonable to assume that one of the key phenomena behind such action is rooted in interactions between ZnO surfaces and the extracellular layers. Thus, excess charge or lack thereof, surface electronic charge traps, as well as variations in the stoichiometry at surfaces with different polarities of ZnO particles may affect interfacial phenomena with cell surfaces. It is possible therefore that the relative abundance of ZnO surfaces with different polarities could significantly influence their antibacterial action. In our studies, we produced ZnO crystals comparable in size with the bacteria employed in our assays, such as s. aureus. This was done intentionally in order to avoid cellular internalization of ZnO particles and thereby to address primarily the mechanisms involving ZnO/cell surface interface. These experiments were performed in conjunction with optoelectronic studies of ZnO crystals (photoluminescence, surface photovoltage) to characterize electronic structure and dominant charge transport mechanisms as fundamental phenomena governing antibacterial characteristics of our samples. We report on the results of these comparative studies relating predominant ZnO surface polarity with the antimicrobial action.