A.  Arlina^1,a,*, NOR Hakimin Abdullah^1,b , HIDAYANI Jaafar^1,c, TEO Pao Ter^1,d ,  AMERAM Nadiah^1,e   and Nik alnur Auli^1,f

¹Advanced Material Research Cluster, Faculty of Bioengineering and Technology, Universiti Malaysia Kelantan, 17600 Jeli, Kelantan, Malaysia.

^aarlina@umk.edu.my, ^bnorhakimin@umk.edu.my, ^chidayani@umk.edu.my, ^dteopaoter@umk.edu.my, ^enadiah@umk.edu.my, ^falnurauli@umk.edu.my 

Abstract. This study investigated the antimicrobial activity using zinc oxide (ZnO) material prepared via hydrothermal method. These investigations have extensive antibacterial capabilities of ZnO nanostructures, effectively targeting a diverse array of microorganisms prevalent in environmental settings, including soil, water, and food. The synthesis of ZnO nanostructures was conducted through a hydrothermal method, varying the pH from 8 to 12, using zinc chloride (ZnCl) and sodium hydroxide (NaOH) as precursors, and subjected to the 24 hours heating process at 180°C. The characterization of the samples involved X-ray diffraction (XRD), Ultraviolet-Visible (UV-Vis) spectroscopy and inhibition zones in E. coli agar plates. The XRD pattern illustrated the hexagonal wurtzite structure of the ZnO nanostructure, with the average crystallite size calculated. UV-Vis spectroscopy indicated absorption peaks of ZnO around 300 to 400 nm, signifying a blue shift. Furthermore, optical band gaps, derived from UV spectroscopy, demonstrated an increment from 2.88 to 3.25 eV across all samples. The size of the inhibitions zone increased as the pH values of ZnO increased. ZnO shows increased inhibition zones with higher pH, hexagonal wurtzite structure and increasing optical band gaps. 

Keywords: Zinc Oxide, Hydrothermal method and antimicrobial activity