Green synthesis of TiO2 nanoparticles and carbon nanotubes by pulsed laser ablation of titanium and graphite in deionised water

摘要

The thesis is divided into three sections: Background of the study, experimental, and finally discussion. The first part includes the literature survey which discusses the studies related to pulsed laser ablation that have been reported so far in the state-of-the-art. From the second part, the reader can study the fundamentals of the experimental methods used in order to understand the results. The third part of the thesis consists of the results from this study and a discussion on them followed by the conclusions for this thesis project.In this study, green synthesis of TiO2 nanoparticles and carbon nanotubes was successfully demonstrated through pulsed laser ablation in deionised water. The nanoparticle yield for ablated titanium suspensions was found to increase with laser fluence till 40% laser power and then decrease at 50% laser power due to reduced laser fluence but again increase at 60% laser power due to overlapping of laser spots. The yield of nanoparticles in ablated graphite suspensions was independent of laser fluence but proportional to laser power until the power was so high that evaporation of liquid interfered and decreased the yield. The transmission electron microscopy of suspensions from ablated titanium target revealed round crystalline TiO2 nanoparticles surrounded by amorphous phase nanoparticles. X-ray diffraction and wide angle x-ray scattering of these nanoparticles confirmed presence of anatase, rutile and brookite. For ablated titanium target, x-ray diffraction detected titanium monoxide, titanium dioxide and titanium (III) oxide besides titanium metal. The particle size measurements from TEM and SAXS indicated decrease in the average size of TiO2 nanoparticle with the increase in laser power. The transmission electron microscopy of the suspensions from ablated graphite target indicated the presence of carbon nanotubes. X-ray diffraction of the ablated graphite target detected the presence of diamond on the target surface.