Study On The Synthesis Of Quantum Dot And Its Application In Environmental Pollutants Detection As Label

Semiconductor quantum dot(QD) is a kind of three-dimensional confined cluster with some special physical effects,such as quantum size confinement,quantum tunneling,and coulomb blockade.They can emit the fluorescence like some macromolecules,such as polycyclic aromatics, and it is hopeful to become their substituents.Semiconductor QDs have more virtues than traditional organic fluorescent dyes.They exhibit interesting size-tunable optical properties due to the confinement of the electronic wave functions.They have narrow photoluminescence spectra, high photoluminescence quantum yield,good light stability and biocompatibility.QDs with different sizes can be excited at single wavelength.Recently,the rich light properties and application in biological labels of QDs have attracted great interest in multiplexed biological detection,labeling and imaging,especially the application of quantum dots in biological science and environmental pollutants analyzing.There are also several problems blocking the way of QD's,such as how to develop and perfect the method synthesis,how to improve the stability and bioconjunction and how to conjunct QDs with biomolecules to make stable and special probes and so on.In our research,CdSe QDs was successfully prepared through a simple,convenient, room-temperature biosubstrate-induced new approach employing the Cd(Ac)₂ solution,Na₂SeSO₃ solution as reactants,and the eggshell membrane(ESM),which contains many unique and periodically distributes groups,as the template.The optical property of the product was analyzed by PL and UV-Vis.CdSe QDs was characterized by X-ray powder diffraction(XRD),and Transmission Electron Microscope(TEM).The fabrication mechanism was discussed.The morphology and the size were governed mainly by the configuration and chemical functional residues of the ESM and the synthesis conditions as well as their reciprocities.The functional groups such as amido groups and imido residues of the ESM macromolecules could not only direct the formation of CdSe QDs,but act as a surfactant to well-distributed fine CdSe QDs. The as-prepared CdSe QDs exhibited single-crystalline,small-scaled and well-dispersed performances,which would offer more potential applications in environmental pollutants detection fields.A new approach was developed for the sensitive and selective determination of copper ions with quantum dots as fluorescence probes.Different influencing factors were studied,including the concent ration and pH of buffer,reacting time and quantum dots concent ration.In 0.033 mol/ L KH₂PO₄·Na₂HPO₄with pH 7.40,when the concent ration of quantum dots was 3.8×10^-4mol/ L and the reacting time was 15 minutes,the relative fluorescence intensity decreased linearly with the copper ions'concent ration in the range of 2 to 300μg·L^-1.The detection limit was 2.8μg·L^-1. Based on the charge transfer quenching mechanism,the copper ions bound onto the surface of the quantum dots could absorb electrons from valance band,which resulted in the quenching of quantum dots.We detected Cu²⁺ ions in three kinds of soil samples with CdSe QD as label,and compared it with ASS standard method.the result is satisfying.We also apply CdSe QDs in bio-analysis.The conditions for BSA-CdSe QDs conjugation have been studied.Under the optimal condition,tight linear relationship between fluorescence intensity and the concentration of protein was obtained when:QDs concentration was 1×10^-4 mol/L and the range of BSA concentration was from 0.25-2.8 mg/L.The detection limit of BSA was 0.3mg/L.