Preparation Of CdS/ZnS Quantum Dots And It Used To Determine Trace Cu²⁺

Quantum dots are three-dimensional clusters composed of a small number of semiconductor nanoparticles.The limited three-dimensional structure leads to quantum dots having many different physical & chemical properties with macro- and micro-systems and unique lightening properties.Especially for that cadmium-based quantum dots have more excellent fluorescence properties and more applicable to the fluorescent markers analysis than other nuclear structure quantum dots,cadmium-based quantum dots are the favor of many researchers,and the study of its preparation and uses in analytical research is also very popular。This entire research is based on cadmium-based quantum dots as the core and mainly works in the following three aspects:1.Synthesis CdS quantum dots in the water phase.Since the reaction of synthesis CdS quantum dots with thioacetamide as sulfur source is slow and takes a long time,a new synthesis way is raised in this paper.We use Na₂S as material,first reacting with CdCl₂ and getting sol,then protected by stabilizer,finally reflux makes sol particles grow to quantum dots.The results show that by this way the fluorescence properties of CdS quantum dots are very good.At the same time we also synthesize CdSe quantum dots and compare them with CdS quantum dots.We find that in the synthesis process the fluorescence of CdS quantum dots affected by oxygen in the air is much smaller than that of CdSe.This method is of low experimental demands,easily prepared and conducive to the promotion.2.Synthesis new CdS/ZnS quantum dots based on CdS quantum dots.The quantum yield of the new nuclear - shell quantum dots are higher than the shell of the CdS quantum dots,and such nuclear-shell quantum dots fluorescence are more stable than shell quantum dots.In the preparation of CdS the S source are easily available, without using NaBH₄ or H₂Se or other toxic chemicals to get Se source.The CdS/ZnS quantum dots were characterized by fluorescence,UV-visible absorption and SEM. The results show that CdS/ZnS quantum dots are of small size,evenly distributed and with excellente fluorescent properties. 3.We expand the application area of quantum dots and apply new CdS/ZnS quantum dots which are prepared in water phase to detection of metal ions.According to the coordination of -SH group and Cu²⁺ion,a new fluorescence quenching method determining Cu²⁺ion with quantum dots as fluorescent probe is established.The reasons of fluorescence quenching are also explained on the mechanism.This method of determining Cu²⁺overcomes the defects of organic fluorescent dyes which are of low intensity and poor light stability in traditional fluorescence analysis.Thus the detection sensitivity and testing range are improved to a certain degree,and simultaneously the method becomes simple,rapid,of high sensitivity and moderate conditions.The water samples of Yan lake Chengdu University of Technology are determined in this way,and the results are good.The ion concentration and the relative intensity of fluorescence I_F⁰/I_F has good linear relationship between the range of 10^-7～10^-8mol·L^-1.regression coefficient is 0.9939 and detection limit is 0.2μg·L^-1. The experimental methods for the quantitative detection of metal ions provide a new train of thought and further expand the application of quantum dots.