SYNTHESIS OF GREEN Ag-BENTONITE & ZnO-BENTONITE NANOCOMPOSITEFOR ANTIBACTERIAL APPLICATION

Abstract

The World Health Organization (WHO) estimated that, by 2050 bacterial infections, which are caused bytwo or more bacterial species, will cause more deaths than cancer. This implies the need to develop newantibacterial agents. This project work reports the synthesis and characterization of Ag/Bentonite, andZnO/Bentonite nanocomposites (NCs) using Hagenia abyssinica plant extract and their antibacterialstudy. The synthesized NCs were characterized by using many advanced techniques such as; X-raydiffraction (XRD), thermal analysis (TGA/DTA), UV-Vis/DRS, FTIR, SEM/EDX and high resolutiontransmission electron microscopy (HRTEM). The FTIR spectral analysis revealed the presence ofhydroxyl, carbonyl and other functional groups in the synthesized NCs. The TEM analysis revealed theformation of Ag NPs and ZnO NPs with hexagonal, rod-shaped and spherical structures and averageparticle sizes of 52 nm and 17.9 nm respectively. HRTEM also revealed the presence of (101) plane ofZnO and (002) plane of bentonte in ZnO/Bentonite nanocomposite with average composite particle sizeof 15.7 nm. The SAED of Ag/Bentonite displayed five spots; two spots ((100) and (300)) of bentoniteplanes and three spots; (111), (220) and (311) of Ag NPs planes of the composite. The antibacterialactivities of the composites suspension were evaluated against E. coli ATCC 25922 and S. aureus ATCC25923 by the disk diffusion and broth dilution methods. The inhibition zone results of ZnO/Bentonitenanocomposites suspension synthesized with 300 ml (ZB300)and 50 ml of (ZB50) volumes of plantextract at 30 mg/mL are 15.3  0.2 mm and 100.3 mm against E. coli ATCC 25922 and 13.3 0.3 mmand 80.3 against S. aureus ATCC 25923 respectively. All the Ag/Bentonite synthesized for this workinhabited better than ZnO/Bentonite at one third concentration of the suspension (10 mg/mL) against bothbacteria strains. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration(MBC) values of ZnO/Bentonite (Z300) and Ag/Bentonites NCs ( AB01) were found to be 6.25x102μgmL-1, 1.25x103 μgmL-1 and 78.125 μgmL-1, 156.25 μgmL-1 for E. Coli and 78.125 μgmL-1, 156.25μgmL-1 and 39.1 μgmL-1 , 78.125 μgmL-1 S. aureus respectively. This investigation results revealed thatbio-synthesized ZnO/Bentonite nanocomposites is a promising bactericidal composite.