Photocatalytic Studies of Doped and Capped ZnO and CeO2 Nanoparticles

Abstract

The present work deals with the synthesis, characterization and photocatalytic studies of undoped and doped ZnO and CeO2 nanoparticles (NPs). The entire work is divided into six chapters. Chapter 1 includes the background of nanomaterials and their unique properties. It describes the need of waste water treatment and different types of techniques involved in this treatment process. Role of semiconductor photocatalyst and mechanism behind the degradation of organic pollutants are discussed in detail. Various parameters like techniques used for modulation of valance band and conduction band, effect of adsorption and pH, source of radiations, charge carrier trapping, photocatalyst size and quantum confinement effect, which affect the efficiency of photocatalyst, are described in this section. Further, the synthesis of nanoparticles, methods to prevent their agglomeration and to stabilize them by various methods has been discussed in detail. In Chapter 2 details of literature pertaining to ZnO and CeO2 nanoparticles and their unique properties has been described. Various synthesis routes for fabrication of undoped and doped ZnO and CeO2 nanomaterials have been given. The photocatalytic properties of these nanomaterials have been described. Various parameters which affect the photocatalytic efficiency of these nanomaterials like types of irradiations, irradiation time, dopant, effect of doping concentrations, capping, morphology, pH nature of dye solution, photocatalyst dosage, variation in dye concentrations, have been discussed in this chapter. Also, the effect of photodegradation efficiency of these nanomaterials with alteration in photoluminescence intensity with capping and doping has been illustrated. Chapter 3 describes the details of the chemicals used and synthesis procedure adopted to prepare undoped and doped ZnO and CeO2 nanoparticles. Procedure followed to synthesize NPs at different pH is also discussed. Various characterization techniques used to characterize NPs has been described. The set-up of photochemical reactor and the procedure for photocatalysis of organic dyes has been discussed. At the end of the chapter brief introduction about the pollutants selected for photocatalytic study is provided. Chapter 4explains the study of doped ZnO nanoparticles (NPs) synthesized by co- precipitation method. Various techniques viz. X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), UV-Visible spectroscopy, photoluminescence (PL) emission and excitation spectroscopy has been employed to characterize as synthesized doped and capped NPs. Photocatalytic efficiency of synthesized NPs has been studied by evaluating the degradation of crystal violet (CV) dye under UV-Visible irradiations. Further the effect of pH has also been studied in detail. Here it is important to mention that the pH of NPs has been adjusted during synthesis only. Chapter 5 describes the study of doped CeO2 (ceria) nanoparticles (NPs) synthesized by co-precipitation method. Various techniques has been employed to characterize as synthesized doped and capped NPs. Photocatalytic efficiency of synthesized NPs has been studied by evaluating the degradation of rhodamine B (RhB) dye under UV-Visible irradiations. Further the effect of pH has also been studied in detail. Chapter 6 summarizes the results obtained from various experiments discussed in previous chapters. Effect of morphology, capping agent, dopant and doping concentration, irradiation time and pH of the synthesized NPs (pH adjusted during synthesis) has been summarized. Results obtained from doped and capped ZnO NPs has been concluded. The results obtained from the doped CeO2 NPs have been also summarized. Based on the results obtained from the present work, some suggestions have been provided at the end of the chapter to carry out more work in this field.