Synthesis, Characterization And Surface Functionalization Of Cdse And CdTe Quantum Dots

As special properties of the quantum dot nano-materials, making them functional nano-materials in the biomedical R&D occupies a very important position in their application in biomedical research. The important significance and the feasibility are already obvious to all, the theory, preparation and application are increasing. Nevertheless, we can easily find that, there are still many issues to be resolved and a very broad research space. Quantum dots is the key to solve the problem of photochemical stability and water-soluble, the problem of surface modified quantum dots is the premise of its biological applications. Based on this, this article elaborats from the following parts of the quantum dots:Synthesize monodisperse CdSe quantum dots using the organometallic method (Colloid Chemistry), With TOPO / ODA as ligand, high-boiling point of the ODE as the solvent. Study their optical properties by measuring the absorption and emission spectra, and measure the quantum yield of CdSe by contrasting with rhodamineB. Synthesize CdSe / CdS core-shell quantum dots, and improve the stability of quantum dots. Bring the quantum yield from 15% up to 23%.Synthesize the CdTe quantum dots using the water-phase method. Discuss how the reflux time, pH value, concentration and different carboxylic acids impacting on synthesis of quantum dots. The growth of QDs is Ostwald ripening process. Its spectral characterization shows that the fluorescence emission peak shifts to red and the particle size increases. keeping the other conditions all the same, changing the pH value of system, we find that the fluorescence intensity of mercaptoacetic acid coats CdTe nanoparticles strongly depend on the system's pH value. accompany with the diluted solution, the fluorescence intensity first increase and then decrease, having the maximum value, and with the lower concentration, the fluorescence peaks have some certain blue shift; In the same condition, using mercaptoacetic acid as a modifier synthesized CdTe quantum dots has a lower fluorescence intensity than mercaptopropionic acid as a modifier synthesized.Cladding the quantum dots, SiO2 shell coat on the QDs, and surface functionalization is carried out. SiO2 modified CdTe nanoparticles. Using StÇ’ber method, non- premodification, CdTe nanocrystals of mercaptoacetic acid stabling encapsulated inside the SiO2 spheres.We find that Cd / TGA complex layer has important effect on coating effect from the surface of CdTe nanocrystals. SiO2 cladding significantly improves the stability of CdTe nanocrystals.