Green synthesis of pH-responsive Al2O3 nanoparticles: Application to rapid removal of nitrate ions with enhanced antibacterial activity

Abstract

In this study, the green treated aluminium oxide nanoparticles (Al2O3 NPs) were synthesized through simple biological reduction method and studied the effect of pH disparity on particle size variation. Green synthesis of Al2O3 NPs from Prunus × yedoensis leaf extract (PYLE) used for removal of nitrate and antibacterial activities for the first time. The synthesized Al2O3 NPs were characterized by different standard analytical and microscopy techniques. The Al2O3 NPs formation occurred through reduction of metal ions followed by nucleation. The size of the pH = 7 Al2O3 NPs are spherical and hexagonal shape and the size ranges between 50–100 nm, although some nanoparticles are agglomerated. The band gap energy values of the pH = 7 Al2O3 NPs were 3.1 eV, which corresponds to the reflectance edge of 420 nm. The surface area of pH = 7 Al2O3 NPs determined from BET measurement was found to be 54.5014 m2/g. The green synthesized Al2O3 NPs were found to be highly efficient in removing nitrates upto 94% from aqueous solutions at pH = 7 under the influence of sunlight irradiation. This removal efficiency of the synthesized NPS is appreciable when compared with previously reported materials of same kind and hence proves its potential for its use in various ion removal from contaminant systems. The detailed in vitro antibacterial activities of the green treated Al2O3 NPs also investigated. The synthesized Al2O3 NPs at pH = 7 was found to have effective antibacterial activity against gram-positive Staphylococcus aureus (S. aureus) and gram-negative Escherichia coli (E. coli). The experimental results of the study reveals that on tuning the size of synthesized Al2O3 NPs and optimizing its pH exhibited higher catalytic activity and antibacterial activity. Hence, these green synthesized Al2O3 NPs is found to have promising applications in pollutant ion removal in aquatic systems.