Synthesis, Self-assembly And Applications Of Functional Nanoparticles

In recent years, inorganic nanomaterials are becoming the hotspot in academic research because of their excellent properties. Nanoparticles are intermediate materials between bulk materials and molecules. For the nanoparticles with size less than 100 nm, the proportion of atoms on the surface of particle is extremely high. As a result, volume effect, quantum effect, surface effect and quantum tunneling effect are the basic properties of nanomaterials. Moreover, some other functional properties, such as electric property, luminescence property and magnetic property have extended the application of nanomaterials.In this paper, rattle-type TiO2@SiO2 nanoparticles and monolayer films of upconversion rare earth nanoparticles NaYF4:Yb,Er were prepared. Also the properties of the nanomaterials were investigated. All the research contents and results are shown as follows:(1) Rattle-type TiO2@SiO2 particles, with commercial TiO2 particles encapsulated into hollow SiO2 shell, were fabricated by successive coating of multilayer polyelectrolytes and SiO2 shell onto TiO2 particles and then treatment by UV irradiation to remove the polyelectrolyte layers. TEM observation showed that the composite particles had a unique rattle-type structure in which there was void space between the TiO2 core and SiO2 shell. The photocatalytic degradation of Rhodamine B indicated that these composite particles with larger void space tended to have higher photoactivity. The polyurethane films doped with rattle-type TiO2@void@SiO2 composite particles had very good UV-shielding property.(2) Upconversion rare earth nanoparticles NaYF4:Yb,Er with uniform morphology and excellent luminescence property were prepared by solvothermal method. And then, the nanoparticles were dispersed into chloroform by magnetic stirring. Water was added to the vessel to produce a chloroform/water interface. And then some ethanol was added to the interface at a low rate. At the same time, the rare earth nanoparticles were trapped at the interface gradually to form a monolayer film. Repeating the same strategy, the nanoparticles were also successfully self-assembled into multilayer films. The luminescence intensity was in direct proportion to the number of the layers. The procedure is very simple and effective. These films hold immense promise for a number of technical applications in areas such as display and sensing materials.