Studying The Interaction Between CdTe Quantum Dots, Drugs And Albumin By Resonance Rayleigh Scattering, Absorption And Fluorescence Spectra

In recent years, the unique nature of semiconductor quantum dots has attracted increasing attention in physical, chemistry, materials, biology. Compared with organic dye, quantum dots have their unique physical and chemical properties, such as size-dependent tunable photoluminescence, broad excitation spectra, narrow emission bandwidths, and good photostability.CdTe QDs were synthesized using different stabilizing reagents in aqueous solution and were characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM) and fourier transform infrared spectroscopy (FTIR). The interactions of CdTe QDs with ovalbumin, propafenone, coumaric acid, caffeic acid and BSA have been investigated in depth by ultraviolet-visible (UV-vis) absorption, fluorescence quenching spectrometry, and resonance Rayleigh scattering spectroscopy (RRS). The causes for the enhancement of RRS and the quenching fluorescence of ovalbumin are investigated to shed light on the quenching mechanism. The binding constant, and thermodynamics parameters of CdTe QDs with ovalbumin during the binding process were obtained. The reaction mechanism of CdTe QDs with propafenone was discussed and a simple and high sensitive RRS approach to determinate propafenone is developed. The fluorescence quenching mechanism of GSH/TGA-CdTe QDs by coumaric acid, caffeic acid was discussed. The binding constant and thermodynamics parameters of BSA-coumaric acid and BSA-caffeic acid during the binding process were calculated in the paper.The major results are as follows:1 Study on the interaction between water-soluble CdTe quantum dots and Ovalbumin by optical spectroscopyCdTe QDs modified by 2-mercaptoethylamine hydrochloride (CA) and thioglycolic acid (TGA), respectively, were synthesized in aqueous medium. The interaction of CdTe QDs with ovalbumin has been investigated in depth by FTIR, UV-vis absorption, fluorescence quenching spectrometry, and RRS. Fluorescence data show that the quenching type of ovalbumin by CA-CdTe QDs is static quenching with the binding constant being 10-4 M-1 and the number of binding sites is 1. The calculated thermodynamic parameters demonstrate that the main binding forces are hydrophobic interaction and electrostatic attraction. In contrast, the quenching style of ovalbumin by TGA-CdTe QDs is verified to be dynamic quenching. Under suitable acidity conditions, the interaction of CA-CdTe QDs or TGA-CdTe QDs with ovalbumin leads to the remarkable enhancement of RRS and the increments are found to be in proportional to the concentration of ovalbumin in a certain range. Consequently, a simple and highly sensitive RRS approach for determining ovalbumin is developed. In addition, the causes for the enhancement of RRS and the quenching of fluorescence are investigated to shed light on the quenching mechanism.2 Resonance Rayleigh Scattering and Fluorescence Method for Determination of Propafenone with CdTe QDs as ProbeCdTe QDs were synthesized using thioglycolic acid as stabilizing reagents in aqueous solution. The stabilizing agents self-assembled on the surface of CdTe QDs to form larger complex anion. In a weak acid, propafenone was positively charged and could bind with the ion-association complex to form larger aggregates via electrostatic attraction and hydrogen bond. Moreover, the larger aggregates induced the intensities of RRS, second-order scattering (SOS) and frequency doubling-scattering (FDS) spectroscopy increased and the quenching of CdTe QDs'fluorescence. Under optimum conditions, the increments of RRS, SOS and FDS intensity and the quenched of fluorescence were in direct proportion to the concentration of propafenone in certain ranges. Among them, the RRS method has the highest sensitivity. There is linear relationship between the intensity of RRS and concentration of propafenone in the range from 0.003 to 7.0μg·mL-1, with a detection limit of 0.96 ng·mL-1. The detection limit is lower and the concentration ranges are wider than other methods. There was no interference to coexisting foreign substances including common ions, amino acid and glucide. The proposed method here is simple, rapid, sensitive and shows promising application to the detection of propafenone in human serum. Moreover, the reaction mechanism was discussed.3 Study on the interaction of CdTe quantum dots with coumaric acid and caffeic acid based on fluorescence reversible tune This paper describes the synthesis of CdTe QDs together capped by glutathione and thioglycolic acid (GSH and TGA) in aqueous solution. The narrow photoluminescence (fwhm≤40 nm) CdTe QDs, whose emission spans most of the visible spectrum from green through red, has a quantum yield (QY) of 68% at room temperature. GSH/TGA-CdTe QDs are characterized by various experimental techniques such as optical absorption, photoluminescence and AFM measurements. Coumaric acid and caffeic acid is able to quench the fluorescence of GSH/TGA-CdTe QDs, and the fluorescence intensity is linearly proportional to the concentration of quenchers. The addition of BSA restores the fluorescence intensity of GSH/TGA-CdTe QDs-coumaric acid system and GSH/TGA-CdTe QDs-caffeic acid system. The fluorescence recovery was due to the interaction of BSA with coumaric acid and caffeic acid, leading to the freeing of the GSH/TGA-CdTe QDs. The fluorescence quenching mechanism of GSH/TGA-CdTe QDs was discussed. The binding constant and thermodynamics parameters of BSA-coumaric acid and BSA-caffeic acid during the binding process were calculated in the paper.