Background: An increasing amount of populations all over the world are reported to have no access to clean and fresh water. Some traditional chemical disinfectants (free chlorine, chloramines, and ozone) are already widely used in the water industry; alarmingly, many of these are carcinogens. Furthermore, the resistance of microorganisms to these common chemical disinfectants is increasing; superior alternatives are therefore necessary. The development of nanoscience and nanotechnology within the last decades provides opportunities to deal with this problem. Objectives: In this study, the solvothermal method was employed to synthesize SnO 2 nanoparticles with spherical morphology in the absence of templates or structure-directing agents under mild conditions. The nanoparticles used to in the inactivation efficiencies for two microorganisms under UV irradiation and dark conditions. Materials and Methods: In this experimental study, tin dioxide (SnO 2) nanoparticles have been synthesized via a simple solvothermal method in the absence of templates or structure-directing agents under mild conditions. The prepared SnO 2 sample was employed for the inactivation of Gram-negative Escherichia coli (ATCC 25922) and Gram-positive Staphylococcus aureus (ATCC 29213) in MilliQ water under dark and UV illumination. The antibacterial activity of the synthesized SnO2 nanoparticles was evaluated using bacterium as per colony count method. Results: SnO 2 nanoparticles were successfully synthesized via solvothermal method under mild condition. SEM image showed SnO 2 nanoparticles were spherical when a mixture of water and ethanol used as solvent. The prepared SnO 2 nanoparticles were employed for the inactivation of gram-negative Escherichia coli (ATCC 25922) and gram-positive S.aureus (ATCC 29213) in MilliQ water. It was found that SnO 2 nanoparticles show much higher activity against E. coli than S.aureus. Conclusions: According to the result of this study, SnO 2 nanoparticles are an excellent antibacterial agent for bactericidal applications.

A new bidentate O,S donor thiourea ligand (L 1 ), namely N-(2-hydroxyethyl)-N′-2-chlorobenzoylthiourea, and its oxazolidine derivative (L 2 ) were synthesized.Derivative L 2 was used for the preparation of Ni(L 2 ) 2 and Cu(L 2 ) 2 complexes. The compounds were investigated using X-ray crystallography and Fourier transform infrared, 1 H NMR and UV-visible spectroscopies. Single-crystal Xray analysis showed strong hydrogen bonding interactions between carbonyl oxygen and N(10) ─ H in the L 1 ligand. In addition, the antibacterial activities of these compounds were evaluated against Gram-positive and Gram-negative bacteria, measured using the colony count method. The Cu(L 2 ) 2 complex exhibited a significant antibacterial activity while the activity of the other compounds was much lower. Finally, the relationship between the structure and antibacterial properties of these compounds was investigated using highest occupied and lowest unoccupied molecular orbital energies calculated by density functional theory method based on the 6-31G*/LANL2DZ basis set.

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