Studies On The Synthesis And Properties Of Ru(phen)₃²⁺ Doped Silica Nanoparticles

Nanotechnology and nanomaterials have been widely used in the biomedical research, and that has been deeply developed during the last few decades. A lot of efforts have been done to improve the method of synthesis, especially the application of the luminescent labels, so that they can meet the request in the advanced research. In nowadays, nanoparticles become more and more important for the labeling of biomolecules and physiological process in both animals and human beings. They are playing an important role not only in research but also in the clinic treatment. The dye doped silica nanoparticles is one of the most common kinds of luminescent nanomaterials, the synthesis method of them is the most simplest and the cost is the lowest, especially the positive charged dye molecules doped silica nanoparticles. During the preparation, ones only need inject the dye solution into the normal St?ber reaction system. The silica could provide a perfect protection for the doped dye molecules because of the chemical and physical stability. Further more, the surface of the silica nanoparticles could be modified with many kinds of functional groups, therefore they could be easily coupled with different kinds of biomolecules. In order to get the dye doped nanoparticles with enhanced emission properties, researchers choose better dye molecules which usually have very low polarity. These molecules must be connected with Si-OR so that they could be incorporated into the silica matrix by the formation of Si-O-Si. It will take more cost, and the efficiency of the connection of Si-OR is difficult to control.Due to the difficulties mentioned above, researchers begun to so some efforts to control the doping situation of the dye molecules in the silica nanoparticles. In 1999, A. Imhof et al. investigated the effect of the concentration of the FITC-APS complex. They found that both the absorption peak and the emission peak showed red-shift about 10 nm when the concentration of the FITC-APS was higher (>0.001 M), the average lifetime became short and the pohtostability enhanced. Three classical quenching models could not explain the above data because of the hypothesis that the dye molecules are distributing equably. So the authors made a conclusion that the dye molecules must be aggregated in the silica nanoparticle. In 2007, Montalti et al. used pyrene derivative as dopants to investigate the doping situation. Pyrene molecules are used to be an excellent probe for detecting the structure of nanomaterials. When the concentration of the pyrene is high, they tend to form excimers which the emission properties are different from that of the monomers. The authors used the emission spectra to investigate the doping process, they found the dye molecules distributed in the middle area of the particle when the dye concentration was low; if the dye concentration was higher, they will firstly form excimers and then existed in the center of the particles, the rest of the dye molecules will distribute in the outer layer as monomers. Both of the two works introduced above controlled the distribution of the dye molecules by concentration controlling. However, how to control the distribution at the same dye concentration is still an open problem. Some researchers have tried to control the environment around the dye molecules to improve the emission properties. Lu et al. carried out the dense liquid treatment to close the pore of the silica matrix so that the H+ and solvent molecules can not touch with the dye. The photostability enhanced largely and so did the emission intensity. Sun et al. improve the fixing effect of the silica matrix with the same method because of the condensation happened deep inside the particles. The emission intensity enhanced very much and the average lifetime also been prolonged.In order to explore the highly controllable and repeatable synthesis method, we choose the Ru(phen)32+ as dopant to carry out systematical research to get deep understanding of the St?ber reaction. In chapter 2, we try to control the affect the nucleation of the St?ber reaction. The purpose is to reduce the possibility of the dye aggregation as much as possible during the nucleation process. The strategy we used was to change the units of the nucleation. A high ammonia concentration system was used to get the oligomer-dye complex, and a low ammonia concentration system was used to get a high loading solution of the oligomers. The two systems was incorporated at appropriate time, the oligomer-dye complex could induce the nucleation of the low ammonia system. Therefore, the oligomers without dye would aggregate on the new seeds leading suppression of aggregation between them. Base on the understanding above, if the dye molecules have existed before the nucleation, they must be aggregated by with the oligomers and primary particles when the nucleation happened. This is an unchangeable incident, but it give us inspire to simplify control method. In chapter 3, we choose a changeless St?ber reaction, a series of Ru(phen)32+ doped silica nanoparticles were prepared by introducing the dye at different stages of the St?ber process. The emission properties of the doped silica particles were found to be dependent on the time of the dye introduced into the reaction system. The silica particles prepared by adding the dye before 3 h of the reaction showed increased emission intensity and blue-shift emission maximum with the delayed addition time compared to those of the 0h-doping particles due to the suppressed aggregation of the dye molecules in the silica matrix, whereas the silica particles prepared by adding the dye during the period of 3?8 h of the reaction showed decreased emission intensity and red-shifted emission maximum with the delayed addition time compared to those of the 3h-doping particles due to the increased effect of the solvent and the dissolved oxygen. As far as we know, it is the simplest method to control the emission intensity. In chapter 4, we attempted to further simplify the synthesis method. The dye molecules were adsorbed on the silica particles directly and then protected by silica shell growth. The emission intensity could be as high as 3h-doping particles. We also explored a new method to dope the dyes with long carbon chain into the PS nanoparticles which can be coated by silica layer. The dyes were dissolved by the styrene easily so that excluded the use of other organic solvent. Due to the appetency between the long carbon chain and the polystyrene chain, the dye could be embedded into the polystyrene nanoparticles. We modified the surface of the PS nanoparticles with the MPS during the reaction, then translated the particles into St?ber reaction. The particles could be easily coated by silica layer, red&bule dual-dye-doped nanoparticles could be obtained by the doping method of Ru(phen)32+ mentioned in chapter 3. At last, we take this doping method on the synthesis of the luminescent magnetic nanoparticles. A facile method has been developed by Lu to prepare Fe3O4@SiO2 nanoparticles. They inject the Fe3O4 into the st?ber reaction upon the formation of the nuclei; the oligomers can quickly aggregated with the Fe3O4 nanoparticles leading to suppressing the dipole-dipole interactions between the magnetic particles. We introduced Ru(phen)32+ at later phase of this reaction, so the dye molecules could be absorbed on the Fe3O4@SiO2 nanoparticles directly and be coated by the following growth of the silica layer. This is a simple one pot method to synthesis the luminescent magnetic nanoparticales.