Synthesis Of Core-shell ZnS: Cu Nanoparticles And The Effect Of Surface Modification On The Luminescence Of Nanoparticles

With different properties from their bulk materials, semiconductor nanomaterials have drawn considerable interests. As a new type of luminescent materials, there are two key factors determining their optical proerties. Quantum confinement effect may result in the quantum yield raising, but the surface states usually act as radiationless recombination centers. Researching and controlling the effect of surface states on the luminescence of nanoparticles were important for the application of luminescent nanomaterials. So the surface modification of nanoparticles which could passivate the surface becomes an active research field.In this paper, core-shell ZnS: Cu nanoparticles and common ZnS: Cu nanoparticles were prepared in colloid ways, and the effect of the shell which was a layer of ZnS on ZnS: Cu nanoparticles was studied, The purpose of the paper is to study the luminescent progresses of nanocrystals and to provide some theoreticals and experimental bases for establishing modle of energy transfer and its practical application. The important results which were obtained in the paper were list as following:It was studied that the luminescence of ZnS: Cu nanoparticles was good at the condition following: pH = 7~8; [Zn2+]: [Na5P3Oio] 2: 1, [Zn2+] ^5 X l(T4mol/L, [Zn2+]: [Cu2+] = 300: 1. The core-shell ZnS: Cu nanoparticles has best luminescence at the station: [Zn2+]core: [Zn2+]shell = 1 : 1.Studies of the core-shell ZnS: Cu nanoparticles indicated that the maximum luminescence in the region of about 470nm can be obtained by tuning the thickness of ZnS shell. The complete ZnS shell which had an appropriate thickness could enhance the lunminescence of the nanoparticles. If the thickness of ZnS shell further increased, the luminescence at 470nm reduced. These results indicated that ZnS shell made all the Cu2+ ionsoccupy the sites in the nanoparticles, increasing the distance of Cu2+ ions to the surface, blocking a good number of nonradiative relaxation paths, leading to the enhancement of the lunminescence at 470nm. But when the thickness of ZnS shell further increased, the concentration of Cu2+ in the ZnS nanoparticles would discrease, which may result in the reducing of the luminescence.