Synthesis Of Quantum Dots And SIO₂Encoding Fluorescent Nanoparticles Based On Quantum Dots And Fluorescent Dyes

In the recent years, method of single target detection can not ensure to cover all quality inspection requirements as the increasing of analysis objects.There is an urgent requirement of an analysis technology which can adapt to the fast development in the biological science, especially for the multivariate analysis technology that simultaneously detect a variety of components for the same samples, in order to shorten the analysis time, to reduce the test cost simplify the operation steps and to reduce the dosage of samples.Most important is that it can help to make the measuring results have better comparative, reproducibility and reliability.Therefore, researchers reference to the traditional bar code technology developed a optical encoding technology to provide a more wide and superior fluorescent markers for multivariate analysis.Fluorescent encoding nanoparticles mainly includes two parts:(1) the fluorescent coding elements;(2) the code carrier.through certain effect, fluorescent coding technique integrate fluorescence coding elements with different colors with micro or nano materials.By controlling the kinds, proportion and concentration of fluorescent materials, we can successfully achieve the target of coding.The combination of fluorescent material with different species, different ratios and different concentration will have different fluorescence characteristics, and can be used to identify a particular substance or life events. It attractes a lot of researchers’ attention as its broad application prospects in the biology, medicine, pharmacy and chemistry.Organic fluorescent dyes is one kind of fluorescent elements which is common and early used.Generally, they are some fluorogens with fluorophore or fluorescent auxochrome. Fluorescent metal complexes is also a kind of typical fluorescent code elements. Quantum dots are quasi-zero-dimensiona lparticles and are1～100nm in size. It launchs fluorescence as its continuous band was split by the quantum confinement of electrons and holes.Being comparied with organic fluorescent dyes and fluorescent metal complexes, quantum dots have a lot of advantages, such as narrow emission spectrum, stronger emission intensity, continuous and adjustable excitation spectrum, better photochemical stability, can be used for multicolor maker and can avoid the emission spectrum overlap.For this reason it attracts attentions form various fields, becomes a new kind of ideal fluorescent code elements.Silica nanoparticles and organic microspheres for example polystyrene are the main code carrier. Silica is a kind of excellent carrier material since it is simple to prepare, easy to disperse in water and ethanol, and easily surface modification and compatibility to biological.Based on the above theory, this essay aqueous synthesis CdTe quantum dots (QDs) with emission wavelength from green to near infrared in one pot. Then use CdTe QDs and organic dye as the coding elements, preparing fluorescent encoding nanoparticles with different fluorescent properties. The paper mainly includes following parts:(1) CdTe quantum dots (QDs) is synthesized in aqueous phase when mercaptopropionic acid (MPA) acts as capping reagent. The effects of temperature of pH of reaction solution and molarratios of Cd/Te on the emission peak of CdTe QDs are investigated, respectively.(2) espectively synthesis the surface aminated silicon dioxide (SiO2) nanoparticles (NPs) which wraps fluorescein isothiocyanate (FITC), and CdTe quantum dots (QDs) protected by glutathione (GSH). Then by the dehydration condensation of EDC·HCl, CdTe QDs was bond on the surface of the SiO2NPs.Finally, capping the achieved (FITC/SiO2-CdTe QDs) nanoparticles with a SiO2shell, obtained the composite structure (FITC/SiO2-CdTe QDs)-SiO2fluorescence coding nanoparticles. Fluorescence spectrum, scanning tunneling microscope (SEM) and transmission electron microscopy (TEM) was used to characterize the SiO2NPs and composite structure fluorescent coding nanoparticles. The test results show that the SiO2NPs and fluorescent coding nanoparticles we got are uniformly distributed and spherical in shape. The partical size of the former is about200nm, the later is about300nm. What’s more,(FITC/SiO2-CdTe QDs)-SiO2fluorescent coding nanoparticles have distinguished dual fluorescence signal. Post-coding the (FITC/SiO2-CdTe QDs)-SiO2fluorescent coding nanoparticles as the fluorescent quenching effection that Cu2+make on CdTe QDs. By changing the concentration of Cu2+, a series of multiple emission characteristics fluorescent post-coding nanoparticles were acquired.(3) Using Isothiocyanate Rhodamine B (RBITC)and CdTe quantum dots (QDS) as the fluorescent coding elements, while SiO2as fluorescence encoding carrier. By chemical bonding, fixed the organic fluorescent dye is inside the silica nanospheres carrier and assembled the quantum dots on the surface of silica nanospheres carrier, and continue coated with silica in order to make the fluorescence encoding more stable. The achieved composite (RBITC/SiO2-CdTe QDs)-SiO2fluorescent encoding nanoparticles have distinguished double fluorescence signal. Fluorescence spectra, scanning tunneling microscopy (SEM) and transmission electron microscopy (TEM) characterized the FITC/SiO2and (FITC/SiO2-CdTe QDs)-SiO2fluorescent encoding nanoparticles.