Study On Preparation Of CdSe Quantum Dots And Its Chemical Stabilizer Impact On Determination Of Metal Ions

Quantum dots in physics, which is known to be semiconductor nanocrystals in chemistry field. Because it is a new material level between macroscopic material and microscopic particles, quantum dots have many different properties. Currently, quantum dots have drawn great attention. Because CdSe quantum dots have more excellent properties, it is favored by many investigators. The research with preparation and applications of quantum dots are very popular.Synthesis of quantum dots can be divided into organic phase preparation and water phase preparation. Organic phase preparation has a perfect development. Quantum dots which synthesize by organic phase preparation has excellent dispersion.But the method has many disadvantages.At present, water phase preparation is applied widely.Quantum dots which is synthesized by water phase preparation can affect solution directly.And the mothed has many advantages,such as low cost, simple reaction conditions and small contamination for environment.When we synthesize quantum dots,the selection about stabilizer is important.On the one hand, stabilizer can modify the surface defect to enhance the fluorescence intensity.On the other hand, stabilizer can protect quantum dots to prevent polymerization.It is most important that groups in quantum dots surface can distinguish ions in solution directly.To enhance the intensity and stability of fluorescence,many researchers use two stabilizers to synthesize quantum dots.The different stabilizers can decrease surface defects.Finally we can synthesize the more excellent quantum dots by the method.Heavy metal ions in soil and water are higher than the standard level. Scholars have given great attention to this phenomenon.It is most diffcult that we can use some methods to detect the ions timely.Currently, the methods which can be used to defect ions have many disadvantages. Due to fluorescence of quantum dots has many perfect properties, such as wide and continuous excitation spectrum,narrow emission peaks and strong stability and anti-bleaching of fluorescent, quantum dots are a potential fluorescent probe. The fluorometry with quantum dots as the label, which can be used to detect ions, is a new analysis method. The method is cheap, simple, of high sen-sitivity and so on.In the thesis, the research is based on synthesis of quantum dots, we mainly discuss in the following three aspects:(1)Due to the defect of organic-phase preparation method, we select the water-phase preparation method to synthesize CdSe quantum dots. In the experiment,we use N₂ to exhaust O₂.The source of Cd is CdCl₂·2.5H₂O and stabilizer,the reaction of Se and KBH₄ is to be the source of Se.Through reflux, the source of Cd and Se is used to be CdSe quantum dots.We select the reaction conditions to synthesize CdSe which has the strongest intensity. The CdSe quantum dots were characterized by fluorescene UV-visible absorption and TEM.We find that the size of CdSe quantum dots is 3.8nm.And the stability of fluorescence is strong.It is suitable to apply for further application.(2)We use two stabilizers to synthesize quantum dots.The quantum dots has smal small defects.So the intensity and stability of fluorescence has enhanced greatly. In addition, different stabilizers bring different groups for the surface of quantum dots. The quantum dots can react with different ions.Finally, the application of quantum dots is wildly expanded.(3)The effect of stabilizers on quantum dots is significant.In experiment,we use quantum dots which is modified by different stabilizers to detect metal ions.We find that the suited stabilizers synthesize quantum dots to detect Cu²⁺,Hg²⁺.The reaction of quantum and metal ions lead to fluorescence quenching.We have investigated the possible principle.When quantum dots is used to detect to ions ,we can provide a basis for the selection of stabilizer through this experiment.