The Synthesis Of Water-soluble CdTe QDs And The Application Research As Fluorescence Indicators

Quantum dots(QDs), a sort of quasi-zero-dimensional nano-crystals, have many excellent optical properties, such as a wide range of excitation wavelength, a narrow and symmetrical range of emission wavelength, a high quantum fluorescent yield, permanent fluorescence lifetime and stable optical performance etc. As a kind of novel bio-markers, which overcomes the deficiencies of traditional organic fluorescent dyes, QDs are expected to become a new type of fluorescent probes. This research subject takes advantage of quantum dots itself inherent outstanding optical properties, compositing with Calcium Carbonate particles, gelatin, and SF gel in order to get the corresponding fluorescent composites. By means of the characterizations of CdTe QDs, Calcium Carbonate, and their relevant composites to explore and synthesize composite materials, which express a lot of unique properties, such as strong fluorescence intensity, stable fluorescence performance, varied fluorescent colors, and simple preparation process etc. They will exert critical roles and show important application prospects in biological imaging, drug delivery and anti-fake label fields.Methods:1) Different scales of CdTe QDs were prepared through aqueous-phase synthesis method.UV-Vis absorption spectrum and PL spectrum were used to analyze the optical properties of CdTe QDs, in order to establish the stable synthesis method of CdTe QDs. We study the fluorescence intensity of CdTe QDs at the different experiment conditions(such as HCl, NaOH,Cu2+ etc.), and verify the dose-dependent effect and time-dependent effect of the CdTe QDs cell imaging through the cell labeling experiments.2) Calcium Carbonate particles were prepared through chemical precipitation method.Field emision scanning electron microscopy(FE-SEM), X-ray diffraction(XRD), Fourier infrared spectrum(FTIR) were used to character the physical and chemical properties of Calcium Carbonate, in order to establish the stable preparation method of Calcium Carbonate. The imaging performance of the CdTe QDs/Calcium Carbonate complex were studied through cell experiments and animal experiments.3) CdTe QDs/gelatin complex were attained through physical ultrasonic method. We explore the fluorescence quencing of CdTe QDs/gelatin complex induced by differentconcentrations of HCl solution and restored by NaOH solution. The fluorescence quenched by the same concentration of HCl solution and restored by NaOH of CdTe QDs/gelatin complex were also studied.4) Silk fibroin(SF) gel were prepared by the way of CaCl2 and Li Br method. We determine the fluorescence intensity of the supernate and precipitate of CdTe QDs/SF gel complex by fluorescence spectrophotometer, in order to study the composite process of CdTe QDs and SF gel,,respectively.Results:1) By controlling the reflux time of synthesis of CdTe QDs, the products emitting different fluorescent colors can be obtained, such as green, yellow-green, yellow, and red etc. UV-Vis absorption spectrum and PL fluorescence spectrum results demonstrate that the maximum emission wavelength of as-prepared CdTe QDs generates red shift(from 510.0 to 582.2), as the extension of reaction time.TEM results show that the CdTe quantum dots are solid spherical nanoparticles, which have regular shape, similar uniform, excellent dispersion in aqueous solution, whose particle size is about 5 nm. Cell imaging experiment results prove that the CdTe QDs(50 μL, 2 nM) cultured with breast cancer MCF-7 cells for 72 h still show brilliant fluorescent imaging.2) The preparation of spherical calcium carbonate particles, whose crystal form is calcite,their size is about 100 nm. The cell labeling experiments of CdTe QDs/Calcium Carbonate complex shows that the composite can enter cells. Animal in vivo imaging manifests the CdTe QDs/Calcium Carbonate composite can used as bio-markes and show better imaging effect than some biological dyes.3) The fluorescence of CdTe QDs/gelatin composite can be quenched by HCl and be restored by NaOH.4) Based on the exploration of compound process of CdTe QDs and SF gel, we can find that the CdTe QDs can not combined with purified SF gel, however, after inducing some Ca2+,the CdTe QDs/SF gel composite can be formed. The fluorescence intensity of CdTe QDs/SF composite has a positive relationship with Ca2+-dependent dose.