Controllable Synthesis Of Hydrophobic Dye Doped Silica Particles And Their Application

Dye-doped fluorescent silica particles emerge with great potential for developing fluorescence imaging techniques as a novel and ideal platform for medical diagnostics,visual drug analysis,environmental monitoring and so on.Organic dye-containing fluorescent silica particles exhibit many advantages,such as good chemical stability,excellent biocompatibility,optically transparent,size-tunable and easily modified with various ligands.The outer silica shell matrix protects fluorophores from outside chemical reaction factors and provides a hydrophilic shell for the insoluble nanoparticles,which enhances the photo-stability,brightness and biocompatibility of the organic fluorescent dyes.Evenly several types of organic dyes were doped in one silica particle to achieve muti-channel and sensitive detection of analytes.Plenty of approaches have been developed to incorporate dyes in silica particles,however,several limitations hinder their further advancement.(1)Few types of hydrophobic dye can be doped in silica matrix by electric attraction method and covalent coupling method.In the non-covalent approach,hydrophobic dyes are doped into the silica particles with assistance of surfactants,however,their incorporation efficiency is less than 10%.(2)The structure of the packing of the aliphatic chains of surfactant in the silica matrixes and optimal microenvironment for regulating the performance of the doped dyes were limited studied.(3)Some hydrophobic dyes with high quantum yield of triplet excited state are easily forming aggregation when doped in silica nanoparticles,which limited their applications in imaging,photocatalysis and photodynamic therapy.In this thesis,we fabricated the hydrophobic dyes doped silica particles by using of surfactant such as CTAB and TWEEN 80,and studied the effect of microenvironment in silica particles to the properties of dyes.The resulted dye doped silica particles have the potential in the applications of ethanol detection and singlet oxygen production.Firstly,it is significant to improve doping efficiency of hydrophobic dyes in silica particles.Silica particles doped with pyrene,a hydrophobic dye,were prepared by a modified St?ber method with the assistance of cetyltrimethylammonium bromide(CTAB)micelles.Incorporation efficiency of the dye into the silica particles could be maintained as high as 90% in a wide range of pyrene concentration(20-200 ?M).The average size of the resulting silica particles increased from 150 to 550 nm as the concentration of ammonia increased from 0.06 to and 1.20 M.Emission color of the as-prepared pyrene-doped silica particles was tunable by simply changing the dye concentration.At low pyrene concentration,emission of the particles was dominated by the violet color of pyrene monomer.While emission of the silica particles was dominated by green color of pyrene excimer at high pyrene concentration.Secondly,the microenvironment in mesoporous silica matrixes for regulating the aggregation/disaggregation of the doped dyes was studied.The CTAB created microenvironment in mesoporous silica particles can be readily adjusted by the volume fraction of ethanol(VFE)in ethanol/water mixtures used in the preparations.In the silica particles prepared at low VFE,packing of the aliphatic chains of CTAB is amorphous in character,providing a liquid-like microenvironment for doped BPEA.In the silica particles prepared at high VFE,the aliphatic chains of CTAB were arranged in quasi-crystalline state,providing a pretty rigid microenvironment for the doped dye.When the preparations were carried out at optimized VFE,the aliphatic chains of CTAB are arranged in a less ordered manner,providing a quasi-glassy microenvironment for the doped BPEA.After redispersing the dried powders of the BPEA doped silica particles into ethanol/water mixtures,dispersions of the particles prepared at the optimized VFE re-evolved a gradual color change from green to orange in a wide range of ethanol contents in the mixtures,demonstrating their better sensitivity toward the surrounding media than these prepared at either low or high VFE.The BPEA molecules in CTAB filled-pores showed the similar emission and aggregation behavior in hexadecane.Such a work represents a new strategy to control the microenvironment in mesoporous silica matrixes for regulating the aggregation/disaggregation of the doped dyes and their improved performance in technical applications such as detection and anti-counterfeit.Moreover,the orderly microenvironment has benefit for improving the photostability,and the loosely microenvironment can absorb organic dye dissolved in aqueous solution.Finally,Pd OEP,a hydrophobic dye,was doped in silica particles,which created singlet oxygen for chromogenic reaction of tetramethylbenzidine(TMB).The optimal microenvironment for doping Pd OEP in silica matrix without aggregation was prepared by using surfactant TWEEN-80.The microenvironment created by TWEEN-80 was less orderly than microenvironment of CTAB micelles,which fitted the monomer of Pd OEP.The microenvironment created by TWEEN-80 was in favour of oxygen diffusion.The energy transfer between Pd OEP and oxygen excited the triplet oxygen to singlet oxygen,which has oxidant activity ability for chromogenic reaction of TMB.The role of Pd OEP-doped silica particles can be considered as an nanoenzyme,which has better stability in immunoassay applications.