The Preparation And Properties Of Functional Fluorescent Microspheres Based On CdTe Quantum Dots And Allyl-Rhodamine B Respectively

Biological fluorescent labeling technology has wide applications in life science, medicine and related areas. At present, most biological fluorescent materials being widely used include organic dyes, fluorescent proteins, semiconductor quantum dots and rare earth luminescent nanomaterials and so on. In order to extend the application of these materials, such as the screening of cancer cells, biomarkers and immunofluorescence assay, it is necessary to endow these materials with chemical reactivity and stimuli responsivity. Under this background, two different synthesis methods were presented in this thesis to prepare two kinds of functional fluorescent microspheres respectively:CdTe/poly(NIPAM-co-AA) hybrid microgels with temperature-sensitive fluorescence emission behavior, fluorescent polyvinylsiloxane microspheres grafted with carboxyl groups and allyl-rhodamine B. The research work includes the following four aspects:(1) Oleic-coated CdTe QDs were synthesized through high temperature injection method with oleic acid as ligands and paraffin as solvent. The effects of reaction time, concentration of CdTe QDs and different solvents on the fluorescence properties of the products were investigated. With reaction time increasing, the luminescent color of QDs changed from green to red with narrow emission spectral bandwidths. UV-vis absorption spectrum of oleic-coated CdTe QDs was red shifted, which indicated that their size was gradually increasing. In terms of toluene solution of CdTe QDs, its absorbance changes linearly with the concentration. When CdTe QDs were dissolved in three different solvent, its absorbance in n-hexane is highest among these three solvent; the next is in tobuene and the lowest is in chloroform.In order to prepare water soluble CdTe QDs more effectively, ligand exchange method was used to transfer oleic-coated CdTe QDs to water soluble mercaptopropionic acid -coated CdTe QDs and cysteamine-coated CdTe QDs. These water soluble CdTe QDs also had good fluorescence properties. However, in the next experiment, it was found that these water soluble CdTe QDs have drawbacks of agglomeration and being easily oxidized. Especially when they mix with poly(NIPAM-co-AA) microgels, their fluorescence is prone to be quenched. Thus, it was required to synthesize stable water soluble CdTe QDs using other ways. Here, aqueous reflux method was used.(2) Stable cysteamine-coated CdTe QDs were synthesized by using aqueous reflux method and poly(NIPAM-co-AA) microgels were prepared by using half-pot method. TEM results show that the morphology of CdTe QDs was irregular and close to globularity, and their size had several nanometers. XRD results show that CdTe QDs had a zinc blende structure. As for the poly(NIPAM-co-AA) microgels, optical microscope characterization results showed that their size was about 1 μm; Dynamic light scattering particle size analyzer measured hydration dynamics size of microgels at pH= 5, and the result was 2417 nm. It was confirmed by FT-IR that microgels were copolymer of NIPAM and AA.(3) Poly(NIPAM-co-AA) hybrid microgels containing cysteamine-coated CdTe QDs were prepared based on multiple interactions, including electrostatic interaction, hydrogen-bonding interaction and AA/Cd coordination. Due to these interactions, when poly(NIPAM-co-AA) microgels mixed with CdTe QDs according to a certain proportion, microgel diameter decreased from 2417 nm to 1531 nm. Besides, with relative content of QDs decreasing, UV-vis absorption spectra and fluorescence emission spectra were blue shifted, which means that effective diameter of QDs was decreasing, and the speed of blue shift was slowing, the reason for which is that the etching of the carboxyl group to QDs reached saturation. A series of CdTe/poly(NIPAM-co-AA) hybrid microgels with different fluorescent characteristics were prepared according to different ratios of two different CdTe QDs during preparation. Furthermore, CdTe/poly(NIPAM-co-AA) hybrid microgels have reversible temperature-sensitive fluorescence emission behavior:with the temperature increasing, the fluorescence intensity decreased and fluorescence spectra were red shifted and vice versa.(4) Allyl-rhodamine B was synthesized by using rhodamine B as raw material through nucleophilic substitution method and polyvinyl silicone microspheres were synthesized by using vinyltrimethoxysilane as raw material through sol-gel method. The size distribution of polyvinyl silicone microspheres is narrow and the size is about 1 μm. It was confirmed by FT-IR spectra that microspheres had carbon-carbon double bond, which can be used to polymerization with other monomers. Subsequently, fluorescent polyvinyl silicone microspheres grafted with carboxyl groups and allyl-rhodamine B were synthesized by using surface graft polymerization. The fluorescent intensity of microspheres can be adjusted by changing the added amount of AA, allyl-rhodamine B and AIBN. SEM results showed that smooth surface of polyvinyl silicone microspheres became rough after graft polymerization. It can be clearly seen that fluorescent polyvinyl silicone microspheres emitted bright fluorescence under the fluorescence microscope.