Synthesis of CdE (E = S,Se,Te) Nanocrystals From Cadmium Amido Alkoxide and Alkoxide Precursors

摘要

The physical and chemical properties of a material are determined by the type of motion allowed for its electrons,and the space within which the electrons are confined.In a bulk semiconductor,excitation involves the formation of an electron and hole (the charge carriers),which are separated by distances that encompass a number of molecules or ions making the material.At and below the nanometer length scale,the motion of the electrons and thus the properties of the material become sensitive not only to the size but also to the shape and composition of the particles.Colloidal semiconductor nanoparticles (NPs) have attracted a great deal of interest during the past decade.The remarkable size-dependent optical properties of semiconductor nanocrystals or quantum dots were discovered in the early 1980s by the research groups of Brus,Henglein,and Gratzel.In those pioneering works,liquid-phase methods for synthesizing suspensions of nanocrystals in solvents such as water and acetonitrile were developed.The discovery in 1990 of the growth by molecular beam epitaxy (MBE) of germanium islands on silicon,and indium gallium arsenide islands on gallium arsenide,constituted a breakthrough with respect to the assimilation of quantum dots into technology.A more recent development in this field is the electrochemical/chemical method which possesses all of the attributes of the liquid-phase synthetic methods and the technological utility of quantum dots prepared by molecular beam epitaxy.the schematic presentation of this method is given in scheme 1.