Synthesis And Characterization Of Cobalt Or Nickel Doped Copper Indium Disulphide Diluted Magnetic Ouantum Dots

Diluted magnetic quantum dots,which can be seen as small amount of magnetic ions doping in zero dimensional nonmagnetic semiconductor quantum dots,are a new optic-magnetic double functional materials.Magnetic ions doped quantum dots with electron charge and spin characteristics,which are expected to be used for information storage and processing devices,and quantum dots as substrate material can affect magnetism due to quantum size effect.More importantly,the fluorescence properties of quantum dots make them very promising as optic-magnetic bi-functional materials.The room temperature ferromagnetism of diluted magnetic quantum dots is the premise of its commercial application.Nowadays,only a few diluted magnetic quantum dots can realize room temperature ferromagnetism.Moreover,most of these works used toxic Cd-contained quantum dots.According to current state of diluted magnetic quantum dots,in this paper,As-prepared nontoxic Co:CuInS2/ZnS quantum dots and CuNiInS quantum dots show both fluorescence and room temperature ferromagnetism.The fluorescent performance of the bi-functional quantum dots provide convenience for the study of magnetic impurity level and the origin of magnetism,more details is as follows:Nontoxic Co:CulInS2 diluted magnetic quantum dots by synthesis of nuclear-doping.According the photo-physical process model,which is built on the fitting result between Co-doping amount and fluorescent intensity of quantum dots,indicates that Co is exactly acting as a quenching center inside CuInS2 quantum dots.As the relation between the degree of fluorescence quenching and Co-doping amount can be expressed by a reciprocal function,proper Co-doping amount is the key to affecting the fluorescence and ferromagnetism of Co:CuInS2/ZnS quantum dots.Excess Co dopant would quench the fluorescence of the quantum dots whereas insufficient Co dopant could not offset the diamagnetism of the CuInS2/ZnS quantum dots.Only under appropriate Co dopant do Co:CuInS2/ZnS quantum dots have both fluorescence and room temperature fer romagnetism.To solve the quenching of the fluorescence caused by Co impurities,CuNiInS dilute magneitc quantum dots with strong fluorescence and room temperature ferromagnetism are prepared by changing the varieties of the magnetic impurities.Fluorescence test result shows that a ferromagnetic Ni cation can preserve the strong luminescence of quantum dots without introducing intermediate energy levels in the center of the forbidden band.The strong luminescence of quantum dots is used as an indicator for monitoring the concentration of vacancy defects inside them,facilitating the investigation of the origin of room temperature ferromagnetism in CuNiInS quantum dots.Our results reveal that the patching of Cu vacancies(Vcu-)with Ni will result in bound magnetic polarons composed of both VCu-and a substitution of Cu by Ni(NiCu+).This results in the transformation from antiferromagnetism to the room temperature ferromagnetism of CuNiInS quantum dots.Due to the concentration of VCu-and Nicu+ changes directly affect the concentration of bound magnetic polarons,the room temperature ferromagnetism of quantum dots can be regulated by controlling the composition of Ni or Cu during the process of its preparation.