Synthesis Of Dye-doped Silica Nanoparticles With StÇ'ber Reaction

Due to the excellent chemistry and colloidal stability, biocompatibility and thedeveloped surface modifying technology, dye-doped silica particles (DDSN) werewidely used to the field bio-analysis and bio-imaging. Specially, the multicolordye-doped silica particles prepared with doping two or more dyes, which couldapplied to the high-flux bio-analysis, also have a wide application prospect. At thepresent time, the synthesis methods of DDSN were mainly based on StÇ’ber reactionand water-in-oil microemulsion. Because of the using of large amount of organicsolvents and surfactant, the water-in-oil microemulsion was polluting for theencironment, and the difficulty to clearly remove the surfactant was unfavorable to thefurther surface modifying and bio-application. To the contrary, the StÇ’ber reaction wasmore eco-friendly. Furthermore, the silica particles prepared with StÇ’ber system havea wilder size range (10nm²um). With the StÇ’ber system, there are two synthesismethods of DDSN, which were covalent coupling and electrostatic adsorptionmethods.Although, those two incorporation methods of dyes was widely used and studied,there are also several shortcomings in the field of DDSN synthesis.(1) The formationmechanism of silica particles with StÇ’ber reaction was not clear, and the problem ofthe large size polydispersity of small silica particles was not resolved.(2) There werefew species of dye could be chose with current methods. For the covalent couplingmethod, dyes must take special group which could react with silane coupling agent.And for the electrostatic adsorption method, it was only suitable to the positivecharged metal-organic dyes. For the most commercial water-soluble dyes, there always have negative charged groups, such as hydroxyl, carboxyl and sulfonic group,on their molecules. Those anionic dyes could not be incorporated into the negativecharged silica matrix, because of the electrostatic repulse interaction.(3) For thecovalent coupling method, the doping efficiency of dyes was too low to only10%.(4)Although many research groups had reported the preparation of the multi-color DDSN,the choosing of dyes was only according to spectrum matching of the donor andacceptor, and the principle of chromaticity was neglected.In this thesis, we will study and resolve those problems in the field of DDSNsynthesis. Firstly,we studied the mechanism of St ber reaction with monitored thedynamics processes of the hydrolysis and condensation of TEOS, in the St ber systemcontain varied concentrations of NH₃(C_NH3). We found that, when the C_NH3was high,the constant of hydrolysis reaction was closer to condensation than the system withlow C_NH3. As a result, the surface of the silica particles in the early stage of St berreaction could accumulate more Si-OH, which could take negative charges withdeprotonation. To the contrary, when C_NH3was low, the amount of negative chargeson the silica particles was little, which will lend to the aggregation of silica particlesin the early stage and broaden the size distribution of the resultant particles. From thisconclusion, we introduced NaOH in the St ber system and allow the stable nucleationas the mode of high C_NH3system, and added NH₃for the slow growth of particles. Asa result, the small silica particles with excellent size distribution were obtained.In the second part of this thesis, we reported a universal incorporation method ofanionic dyes into silica particles with positive charged polyelectrolyte (PDADMAC).The anionic dyes and PDADMAC were firstly allowed to form dye-PE complex, thenthose complexes were introduced into the pre-hydrolyzed St ber system. With therapidly adsorption of soluble silica species, the surface potential of dye-PE complexcould be reversed quickly. Then, those complexes will be stabilized with negativecharge throughout the reaction. The shortest pre-hydrolysis time was the key factorfor the successful incorporation. Shorter than this time or without pre-hydrolysis, thesoluble silica species were not enough to stabilize the complex, and then theflocculation will occur. With this method, anionic dyes could be doped into the silica particles, because of the strong electrostatic interaction between dyes and PDADMAC,the protonation process of the hydroxyl group on the dyes was suppressed, whichcaused t the dye-doped particles insensitive to pH value.In the third part, we report a efficient doping method of amino-reactive dyesbased on the surface coupling. Firstly, we separately prepared the silica particles andmodified those particles with APS. Then, FITC and TRITC were coupling on thisNH2-group modified silica particles. We found that both FITC and TRITC have ahigh coupling efficiency, but when those dye coupled silica particles dispersed intothe solution which contain water or NH₃, the dyes shed seriously. To protect the dyescoupled on the surface, a further silica shell was synthesized with introducing thatdye-SiO2into the pre-hydrolyzed St ber system without which flocculation willhappen. With standing the resultant particles in the PBS buffer for a month, there wereno leaking of dyes happened. Furthermore, the silica shell could improve theluminescence property of both FITC and TRITC. At last we incorporated FITC andTRITC simultaneously with this method and the multi-color silica particles wereobtained with the color could be tuned from green to orange yellow.In the last part, we introduced a multi-color cording system built up withincorporating three dyes, which luminescent blue (HCA), green (5-CFL) and orangered light (Ru(phen)₃²⁺), base on electrostatic interaction. HCA and5-CFL wereco-doping with the doping method with PDADMAC and the (Ru(phen)₃²⁺was dopedas the formation of silica shell. For the co-doping experiments, we found that thereexist a competitive relation between5-CFL and HCA. When the adding amount of5-CFL was increased, the doping amount of HCA decreased. When we change theadding amount of HCA, the doping amount of5-CFL was not affected, which becausethe electrostatic interaction between PDADMAC and5-CFL was stronger than HCAthat take less negative charged group. According as this, we could exactly calculatethe doping amount ratio of5-CFl/HCA. As the doping amount of5-CFL wasincreased, the color of the resultant particles tuned from blue to blue-green. For thecore-shell stepwise-doping experiments, HCA was doped in the core with thePDADMAC, with the completely covering of HCA-PDADMAC complex with silica and the growth of silica shell, the Ru(phen)₃²⁺was added and doped with electrostaticinteraction. With tuning the doping amount of Ru(phen)₃²⁺, the color could beadjusted from blue, pink, purple to orange yellow. With calculation of the coordinatesof the colors on the CIE colorimeter diagram, we found that those colors were all fallon the line between the two point represent HCA and5-CFL (for co-doping particles),and HCA and Ru(phen)₃²⁺(for stepwise-doping particles), which mean this systemwas match the colorimetric principle. At last, we combined the co-doping andstepwise-doping method and simultaneously doped all the three dyes. As a result, thecolors fall in the triangular area made up with HCA,5-CFL and Ru(phen)₃²⁺, with aspecial doping amount ratio, a white light luminescent dye-doped particle wasobtained.