Synthesis, Characterization and Applications of Antimicrobial Materials

Three distinct materials were synthesised, characterized, and tested as antibacterial agents in this thesis. The ability of the synthesised materials to decontaminate polluted water was also studied. Firstly (in chapter 1), a novel compound ({[1,3-bis(2,4,5-trichlorophenoxy) propan-2- yl] oxy}-3-(2,4,5-trichlorophenoxy) hexan-2-ol) (TPTH) was synthesized and characterized. Biological evaluation of the compound was investigated by performing an antimicrobial activity and cytotoxic assays. The compound displayed good antimicrobial activity with minimum inhibition concentration detected as 0.02μg/mL, 0.08μg/mL and 0.15μg/mL against Methicillin Sensitive Staphylococcus Aureus (MSSA), Methicillin Resistant Staphylococcus Aureus (MRSA) and Escherichia coli (E. coli) respectively. Additionally, a well diffusion assay demonstrated that the zone of inhibition of S. aureus, MRSA and E. coli was 24 mm, 22 mm and 18 mm respectively. MTT assay results revealed that, at a range of effective anti-microbial concentrations, TPTH is non-toxic against stem cells. Secondly (in chapter 2), ethylenediamine-epichlorohydrin-trichlorophenol (EET) crosslinked polymer was synthesized and characterized. EET exhibited substantial antibacterial activity with inhibition zones of 38 and 64 mm against E. coli and S. Aureus bacteria. Therefore, it was applied to treat methyl orange (MO) and rhodamine B (RB) dyes containing synthetic aqueous solutions under varying operation parameters. Notably, 10 and 15 mg of EET removed 98.72 % of MO at pH 8 and 92.45% of RB at pH 3. The EET demonstrated a fast adsorption rate and the adsorption data fit well with the pseudo-second-order for both dyes, suggesting chemisorption. Also, considering the correlation coefficient values, the experimental dataset fit suitably with the Temkin equation for RB and Langmuir equation for MO. Lastly (in chapter 3), novel Li doped Zn0.5Ni0.5Fe2O4 (Li/ZNF) photosensitive catalyst was prepared to degrade toxic antiseptic 2,4,5-trichlorophenol (TCP) and inhibit bacteria. Characterization of Li/ZNF nanoparticles revealed it possesses a bandgap of 2.89 eV, exhibited a total pore volume of 0.298 cm3 /g with a crystallite size and percent crystallinity of 16.9 nm and 76.8% respectively. Degradation of TCP (50 ppm) with 10 mg Li/ZNF under optimized conditions (pH 3, 4 mM H2O2 and 353 nm UV- light) reached 80% after 6 h with a degradation rate constant of 0.0019 min-1 . The efficiency of reusable Li/ZNF composite to degrade 50 ppm TCP decreased by 14% after the fifth cycle. According to the antibacterial tests; 15 and 25 mg of Li/ZNF were sufficient to completely inhibit both S. aureus and E. coli bacteria under UV and dark (without UV light) conditions, respectively. The photocatalytic mechanism was established based on the active radical quenching tests which revealed the contribution of •OH and •O2 - radicals.