Study On The Preparation Of Nanomaterials Via Ultrasound In Room Temperature Ionic Liquid

Nanomaterials’s excellent characteristic is largely relative to their preparing method, recently, which have been studied massively, and among which, ultrasonic irradiation process has become a useful technique due to its unique performances. The technique of applying ultrasound in preparing nanomaterials is called sonochemistry, which depends on not only the ultrasonic device but also the solvents chosen. In this work, a mechanism of ultrasonic irradiation called ultrasonic cavitation, which was applied to preparing nanomaterials, in room temperature ionic liquid (RTIL) has been studied. Besides, nanomaterials zinc oxide (ZnO) and titanium oxide (TiO2) and that doped lanthanide with good dispersibility and stability have been prepared via ultrasonic irradiation. The morphology, properties, optical properties and mechanism of samples have been characterized and studied using X-ray Diffraction (XRD) and Transmission Electron Microscope (TEM) as well as photoluminescence (PL) and photoacoustic spectrum (PAS) techniques. Moreover, a possible mechanism and reaction model are discussed to explain the formation of nanostructures with ultrasound.The thesis is mainly contained by five parts:In the first chapter, a series of especial physical and chemical properties of nanomaterials are summarized briefly as well as some normal preparing method. According to the basic theories of sonochemistry, the preparation methods and application of ultrasonic irradiation are illustrated due to ultrasonic cavitation. Besides, the unique physical and chemical of room temperature ionic liquid which chose as the reaction solution has been introduced. What’s more, the primary coverage and meaning of this thesis are interpreted.In the second chapter, the primary analysis methods are introduced, for instance, XRD, TEM, PL, PAS, among these, not only the backgrounds and basic principle of the PA technique are mainly reviewed, but also the developments and applied fields are introduced. After that, we illuminated the main characteristics and advantage of the PA theories and techniques.In the third chapter, the mechanism of cavitation in solution are analyzed, and ultrasound cavitation effect are simulated and studied in room temperature ionic liquids (RTILs) using Flynn formulation about cavitation. Beyond studying the internal parameters of ultrasonic device, some influence elements, for instance, viscosity and in which atmosphere the solution are put, of the chemical solution are analyzed.In the fourth chapter, the application of room temperature ionic liquids (RTILs) as green solution combined with ultrasonic irradiation are introduced. Sonochemical solution have been used to preparing zinc oxide in RTIL by contrast in triethylene glycol (TEG) under the same condition. Both samples are characterized by XRD and TEM, it is found that the different appearance of zinc oxide nanorods between that obtained in ionic liquid and that obtained in triethylene glycol, which shows that zinc oxide nanostructures of different morphology are associated with different reaction solvents, and RTIL is a key to formulate better crystallization. Based with the RTIL as reaction solution, we have used sonochemical method to successfully prepare lanthanide (La3+, Eu3+, Nd3+) doped zinc oxide nanoparticles synthesized, among these samples, Eu3+ doped zinc oxide has been characterized by transmission electron microscopy and X-ray diffraction so as to study the morphology of samples. Besides, photoacoustic and luminescence techniques are also used to study the samples with different doping. Photoacoustic and luminescence spectral studies indicate that lanthanide doping has changed the relaxation processes of zinc oxide. Emissions of Eu3+ have been observed upon excitation of ZnO host. Moreover, a formation mechanism of lanthanide doped zinc oxide nanoparticles has been established and discussed. In addition, At this work, Eu3+-doped rutile TiO2 nanocrystals have been eventually prepared at room temperature by a sonochemical method. The nanocrystalline sample has been characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. At the same time, the characteristic emissions of Eu3+ could be observed upon excitation in the region of TiO2 absorption, which indicates that an energy transfer from TiO2 to Eu3+ occurs for the doped sample. Additionally, a possible mechanism is proposed to discuss and explain the formation of Eu3+-doped TiO2 nanomaterials.In the last chapter, the work of this thesis is summarized and being outlooked.