Titanium-dioxide Nanomaterials Fabrication With Ultrashort Laser Ablation For Pollutant Degradation In Water

The worldwide industrial growth has tremendously increased the generation of waste by-products.Due to these products the environmental pollution has become severe problem with the passage of time.The pollutants such as heavy metals and organic dyes from industrial waste contaminate the waste streams,which ultimately lead to contamination of ground water.In order to address these challenges,researchers are striving to unveil new techniques.Keeping in view the new materials fabrication and their applications for pollutant degradation in water is imperative.Among different nanomaterials,titanium-dioxide?TiO₂?in the form of nanoparticles and nanocomposites has provoked great deal of attention in the field of research.This is because of its numerous interesting applications in photocatalysis for redox reactions,detoxification of polluted waste water,dye degradation,and solar cells fabrication.Much effort has been devoted to TiO₂ nanoparticles fabrication with different techniques,such as hydrothermal chemical method,Sol-Gel method and thermal decomposition method.These techniques are nevertheless time-consuming and require extra detergent in the synthesis processes,and in most cases the generated nanoparticles are chemically impure.Ultrashort Laser ablation provides a substitutive approach for nanomaterials fabrication.It has been employed for variety of nanomaterials processing such as metals,nonmetals and semiconductors.Laser materials processing includes fabrication of thin films,nanocrystals fabrication,cleaning of the surface and fabrication of microelectronics devices as well.The nanomaterials fabrication with laser ablation does not require extra treatments to remove surfactants and other hazardous chemicals.Therefore,the technique of laser ablation for nanomaterials fabrication is green fabrication approach.In this context,our work has been devoted to nanomaterials fabrication with ultrashort laser ablation and their applications for pollutant degradation in water.The work in this thesis has been organized according to the following structure.The first chapter is related with background,the objective of the current work and structure of the thesis.The second chapter describes ultrashort laser ablation,experimental setup protocols,samples preparation and fabrication of fiber system for ultrashort laser.The details about pellet formation with CIP have been included in this chapter as well.The third chapter is dedicated to TiO₂ nanoparticles fabrication with“self-made”fiber laser system in water.The fabrication of nanoparticles with“self-made”fiber laser leads to increase in the ablation yield of TiO₂ nanoparticles.We have observed that the nanoparticles fabricated with pellets pressed under higher pressure exhibited a phase angle shift from rutile to anatase phase of TiO₂.The nanocomposites of anatase TiO₂ mixed with MoO₃ were synthesized,which is described in chapter four.The photosensitivity of the fabricated nanocomposites was tested interms of photovoltaic and photocatalytic dye degradation.The fabricated nanocomposites exhibited efficient photosensitivity as compared with TiO₂nanoparticles for current-voltage and MB dye degradation.The work in chapter five is devoted to photocatalytic dye degradation by mixing rutile TiO₂ with Cu and WO₃.The characterization techniques such as UV-Visible,XRD,XPS and Electron spin resonance?ESR?were employed for the characterization of nanocomposites.The solar and visible light sources were used to carry out MB dye degradation.It was observed that MB dye degradation took more time under visible light illumination in contrast with solar light as dye degradation source.The delay in MB dye removal from the solution under visible light illumination was attributed to less OH^·radicals generation.In chapter six the glow discharge plasma electrolysis?GDPE?fabrication of reduced TiO₂ was carried out.The glow discharge was produced by employing Ti plate as a cathode and two anodes of Ti bar.The varying powers were applied for producing the glow discharge in the electrolytic solution.As a result of glow discharge the Ti³⁺self-doped gray Ti O_2-x-x was fabricated.The fabricated gray TiO_2-x-x nanoparticles were used for RhB dye removal from the solution,which demonstrated efficient dye removal under visible light irradiation.The efficient light harvesting of the fabricated nanoparticles was attributed to presence of oxygen vacancies and bulk/surface crystal defects.Finally,on the basis of research work in this thesis,the conclusion has been drawn in chapter seven.