Investigation Of Magnetic Nanoparticles Coupled Type ? Coinitiator

The researches of photochemistry mainly include two aspects which are photopolymerization and photoreduce. On the one hand, UV curing technology attracted considerable interest in several research fields, ranging from coating, adhesive, fiber, etc. And with the fast polymerization rate, free radical polymerization realize a wide range of applications. However, due to the existed oxygen may quench the excited state of the photoinitiator which cause lower surface conversion rate. Therefore, oxygen inhibition in photocuring still a problem to be solved. On the other hand, the photochemical method due to its controllable and space selective is widely used in the preparation of noble metal nanoparticles, applied to medical diagnosis, surface Raman scattering, catalysts, etc., especially the use of the catalyst closely linked to the evolution of human social environment. However, in practical applications, nanoparticals are normally unstable and tend to aggregate, owing to their high surface energies, resulting in losing their advantage of a high surface/volume ratio, and another major obstacle is the time-consuming centrifugation/re-dispersion cycle, which produces inevitable waste. In this work, comprehensive the above problems in two directions, we designed and prepared magnetic nanoparticles co-initiator, based on magnetic responsiveness and properties of Type II co-initiator to solve the above two questions. The main work was as follows:1. Due to amine is a good co-initiator (or H donors) for the Type II photoinitiator. The Type II photoinitiator, such as isopropyl thioxanthone (ITX) abstracts the H from the amine, then, the amine turns into the radical initiating the reaction that is going on. According to this, the Fe3O4@PEI nanoparticles co-initiators were synthesized through a polyethylene imine (PEI) self-assembly. Taking advantage of magnetic responsiveness, Fe3O4@PEI nanoparticles co-initiators were migrated up to the surface of solution by outside magnetic field. The surface concentration of free radicals increased to meet the oxygen consumption, thereby lowering oxygen polymerization phenomenon.2. Magnetically separable catalyst Fe3O4@SiO2@PEI@Au nanoparticles were successfully constructed by a novel regional selective photo-reduction method. In this process, first, the magnetite particles were coated with a thin SiO2 layer through a sol-gel approach to obtain Fe3O4@SiO2 composites. The SiO2 shells not only avoid Fe3O4 NPs agglomeration, which generates from magnetic dipole-dipole interactions, but also improve their stability and offer them further modifications during following reaction. Second, through a simple epoxide ring-opening reaction, slightly cross-linked PEI chains were linked by chemical bonds. Finally, PEI was employed as the coupling agent and a photo co-initiator to reduce Au3+ under ultraviolet (UV) irradiation with the existence of Type ? co-initiator ITX. Magnetic Fe3O4@SiO2@PEI@Au nanoparticles showed high catalytic performance toward the reduction of 4-nitroaniline to 4-aminophenol by NaBH4, In addition, magnetic Fe3O4@SiO2@PEI@Au nanoparticles could easily be recovered and could be reused.