Laser ablation in liquid was utilized to prepare a TiO₂ NP suspension in in deionized distilled water using Q-switch Nd: YAG laser at various laser energies and ablation times. The samples were characterized using UV–visible absorption spectra obtained with a UV–visible spectrophotometer (UV-Vis,) Fourier transform infrared (FTIR), X-ray diffraction (XRD), and transmission electron microscope (TEM). While, UV-Vis spectra showed the characteristic band-to-band absorption peak of TiO₂ NPs in the UV range. FTIR analysis showed the existence of O-Ti-O bond. XRD patterns indicated the presence of (101) and (112) plane crystalline phases of TiO₂. TEM images showed a spherical-like structure of TiO₂ NPs with various size distributions depending on the ablation period. It was also found that there is a relationship between laser ablation time and TiO₂ NP size distribution, where longer ablation times led to the smaller size distribution. The antibacterial activity of TiO₂ NPs was evaluated with different species of bacteria such as Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris, and Staphylococcus aureus, using the liquid approach. The optimum activity of TiO₂ NPs is found to be against E. coli at 1000 μg mL⁻¹. Furthermore, adding, TiO₂ NPs (1000 μg mL⁻¹) in the presence of amoxicillin has a synergic effect on E. coli and S. aureus growth, as measured by the well diffusion method. However, both E. coli (11.6 ± 0.57mm) and S. aureus (13.3 ± 0.57mm) were inhibited by this process.

Zinc oxide (ZnO) nanostructure (NS) materials with different shapes were synthesis via pulsed laser ablation in water. The characterizations were done using X-ray diffraction XRD, and scanning electron microscopy SEM. The XRD results proved the presence of the (100) and (002) patterns, referring to the ZnO NS. The SEM images show that the structures were changed from flakes with a thickness of about 10-50 nm to spherical like structures with diameter from 24 - 42 nm and high agglomerated. Also, the antibacterial activity of ZnO NS was studied and the results manifested that the inhibition zone inStaphylococcus aureus (S.aureus)is higher than inEscherichia coli (E.coli),which showed an inhibition zone againstS. aureus(21mm), as well as againstE.coliwas (15mm) for ZnO NS prepared at 25 laser pulses, and these activities increased with an increased number of laser pulses for both type of bacteria. Therefore the ZnO NS materials are recommended as a powerful Anti-bacterial material