Studying The Interactions Between CdTe Quantum Dots,DNA And Glycopeptide Antibiotic By Resonance Rayleigh Scattering And Fluorescence Spectra,and Its Application

Quantum dots (QDs). as a new kind of luminescent semiconductor, due to their unique optical and electronic properties, has grown tremendously in both fundamental research and technical applications by many researchers.In this paper, glutathione (GSH) capped CdTe QDs, thioglycollic acid (TGA) capped CdTe QDs and glyphosate (Glyp) capped CdTe/CdS QDs were synthesized in aqueous solution. The morphology characteristics and particle size of the prepared QDs were characterized by transmission electron microscope (TEM) and atomic force microscope (AFM), fluorescence microscope (FM), fluorescence lifetime instrument and Fourier infrared spectrum.the interaction between QDs, ct-DNA, antibiotics and vancomycin has been studied by ultraviolet-visible absorption spectra (UV vis) and fluorescence spectrum and resonance Rayleigh scattering (RRS), and fourier transform infrared spectroscopy (FTIR). The fluorescence quenching mechanism about the interaction between CdTe QDs and ct DNA under certain conditions was discussed and the CdTe QDs was used as fluorescent probes in the high sensitive detection of ct-DNA.Based on photoinduced electron transfer mechanism, the fluorescence reversible regulation between CdTe QDs and sparfloxacin was explored and a new method for sparfloxacin detection was established using CdTe QDs as a fluorescent probe. In addition, the interaction process of CdTe QDs and vancomycin was also discussed based on the electron transfer process of dynamic quenching, and a new method of vancomycin sensor was established using CdTe QDs as probe. The main results are as follows:1 Study on the interaction between new functional water-soluble CdTe quantum dots and its application in ct-DNA detection used as fluorescence probeCdTe/CdS QDs was novelly modified by glyphosate (Glyp) and used as fluorescence probe in detection of ct-DNA. Firstly, thioglycolic acid (TGA) modified CdTe/CdS QDs was synthesized. Then, we used Glyp to replace the TGA on the surface of the CdTe/CdS QDs to get the Glyp modified CdTe/CdS QDs. The morphology characteristics and particle size of the prepared QDs were characterized by transmission electron microscope (TEM),fluorescence microscope (FM), fluorescence lifetime instrument and Fourier infrared spectrum. The interaction between Glyp modified CdTe/CdS QDs and ct-DNA was studied by fourier transform infrared spectroscopy (FTIR), fluorescence lifetime, fluorescence spectrum and resonance Rayleigh scattering (RRS). Fourier infrared spectroscopy (FTIR) shows that Glyp in of the Glyp- CdTe/CdS QDs combined with ct-DNA by static binding effect which prompting Glyp CdTe/CdS QDs static quenching. Beside, both of the fluorescence life and ultraviolet absorption show that Glyp combined with ct-DNA role by chemical combination which accompanied with dynamic rather than static electron transfer. When it interacted with calf thymus DNA (ct-DNA), the fluorescence intensity of the system was obviously quenched and the RRS was enhanced, both in good linear relations. The linear ranges of the functionalized QDs fluorescence intensity and RRS intensity versus the concentration of ct-DNA were 0.109～70μg mL-1 and 0.482-90 μg mL-1, respectively. The corresponding detection limits by fluorescence quenching and by RRS enhancing methods were 0.0327 ug mL-1 and 0.146 ug mL-1, respectively. Based on that, a novel fluorescence biosensor for sensitive and selective detection of ct-DNA was developed. The proposed method was applied to detect ct-DNA in synthetic sample with satisfactory results.2 The interaction mechanism about electron transfer between GSH-CdTe QDs and Sparfloxacin and Its analytical applicationGlutathione (GSH) modified CdTe quantum dots (GSH-CdTe QDs) were synthesized in aqueous solution. The stabilizing agents (Glutathione) self-assembled on the surface of CdTe QDs to form larger complex anion. It is well known that certain excitation to the GSH-CdTe QDs would cause the promotion of electron from its valence band to the conduction band and result in the formation of a positively charged hole in its valence band and a free electron in the conduction band. In the absence of sparfloxacin, the recombination of the electron and hole would result in the fluorescence. While introducing sparfloxacin, which serves as efficient electron acceptor for the conduction band electron from the GSH-CdTe QDs, to the solution of QDs, it would prevent the electron-hole recombination at the interfaces of GSH-CdTe QDs and cause the fluorescence quenching. The biosensor could be used for the determination of sparfloxacin with a high sensitivity. Under optimum conditions, the linear range was from 0.2789 to 40.0 μg ml-1 with a correlation coefficient of 0.9983, and the detection limit was 83.7 ng ml-1. Furthermore, this method has been applied to the determination of sparfloxacin in the synthetic environmental water samples and the spiked human serum samples with satisfactory results.3 Study on the interaction between CdTe quantum dots and caffeic acid based on fluorescence reversible tuneA simple and sensitive fluorescence "turn-off’ biosensor for detection of vancomycin at nanogram level was proposed based on the electron transfer mechanism and the fluorescence quenching of the CdTe quantum dots (QDs). The mechanism of the interaction between vancomycin and CdTe QDs was investigated by ultraviolet/visible (UV/vis) absorption, fluorescence spectroscopy and fluorescence lifetime. The degree of the electron transfer and as resulted fluorescence quenching was proportional to the increasing of vancomycin concentrations in of range 1.534 ng mL-1-20 μg mL-1, with a corresponding detection limit of 0.4605 ng mL-1. This proposed a biosensor that could be applied to determine vancomycin in environmental water samples, pharmaceutical formulation and spiked human serum with all of the recoveries over 95.8%. The mechanism about the detection was dynamic quenching with an electron transfer (ET) process. The experimental conditions, key affecting factors and the influence of the coexisting substances have also been optimized and studied.