Synthesis, Optical Properties Of Core/Shell ZnSe@CdS(e) Nanocrystals And CNTs/ZnSe@CdSe Heterostructures

The studies of unique properties of nano-materials and nano-structures have great importance in both basic theory studies and practical applications. One particularly intriguing case is the study of the structures and properties of nanoscale assembled systems, One-dimensional nanostructured materials is the base to get and develop nanodevice, low dimensional nanostructured materials have special physical and chemical properties. So, this aspect was highly strengthened in recent years. All kinds of one-dimensional nanotructured materials were gradually prepared and their physical and chemical properties were widely investigated. Specially, with the recent advance in the design of nanotube architecture, the obvious challenge is to use carbon nanotube as support to anchor light-harvesting semiconductor nanocrystals. Based on upper background, we had done some special work on core@shell nanocrystals and nanocrystals-carbon nanotubes heterostructures in this paper, the main contents are as follows:The synthesis nanocrystals were conducted in noncoordinating solvents. We choose High injection, low growth temperatures. In the reverse type-I and type-II core/shell nanocrystals, because of their special structure of the"band gap", emission spectra can be continuously tunable (from violet to NIR) compared to the so-called type-I nanocrystals. We synthesized inverse type-I ZnSe@CdSe and type-II ZnSe@CdS core@shell nanocrystals (NCs) in noncoordinating solvents. The results showed that in the inversed type-I nanocrystals the photoluminescence (PL) is continuously tunable between 400 and 650 nm with the different thickness of shell, the size of the core/shell nanocrystals ranged from 3.5nm to 8nm; in the type-II nanocrystals system, photoluminescence (PL) is continuously tunable between 400 and 580 nm with the different thickness of shell。We choose carbon nanotubes as Scaffolds. We report on carbon nanotubes nanocrystals (CNs/NCs) heterostructures. Colloidal semiconductor nanocrystals were covalently attached to CNTs, which were pre-functionalized by a polymer wrapping technique that is not invasive and does not introduce defects to the structure of CNTs, via the self-assembly approach developed very recently. The pre-functionalized CNTs have high stability in a range of organic solvents. The results showed that the number of bound quantum dots per nanotube can relatively be controlled by varying the quantum dot/nanotube mole ratio, Upon light excitation at 350 nm, the emission of ZnSe@CdSe nanocrystals is totally quenched when it is bound to the CNTs, A possible pathway for the deactivation of excited ZnSe@CdSe nanocrystals is electron transfer to the CNTs. this quenching effect improved charge separation which is very prone to photo-current occurrence。It enhanced the electrical properties of CNTs.