Synthesis of CdSe/ZnS Nanoparticles with Multiple Photoluminescence

T K Sliusariak,S A Vojtovych,Y B Khalavka,M A Zhukovskyi,Y M Andriichuk

doi:10.15330/pcss.21.1.105-112

Abstract

The CdSе/ZnS nanostructures of Core-Shell type, that have multi-wave emission, are described and a scheme of possible energy transitions in the studied system is presented. CdSe nuclei were synthesized by mixing cadmium and selenium precursors without creating an inert atmosphere. The cadmium complex with sulphanilamide was used as a cadmium precursor and simultaneously as a stabilizing ligand. To grow the shell, zinc stearate and thiourea were gradually added to the solution of cadmium selenide nuclei in octadecene at 200°C. TEM studies show that the obtained CdSe/ZnS nanoparticles have the shape close to tetrahedral with an effective diameter up to 10 nm. The thickness of the ZnS shell is about 3-4 nm. From the absorption spectra of the CdSe/ZnS nanoparticles, it is clear that the shell growth leads to a sharp increase in the absorption in the short wavelentgh area, which means the formation of a wide gap ZnS material. The obtained CdSe/ZnS nanostructures emit three fluorescence peaks in the visible range. They are attributed to exciton transitions in the nucleus, recombination at defects of the boundary between the core and the shell, and recombination at defects of the shell. Such property provides CdSe/ZnS nanocrystals with a wide range of functionalities.

Highlights

Among semiconductor nanocrystals, cadmium selenide nanocrystals are of special interest
To increase the brightness of PL and its stability, CdSe nanoparticles are covered with the shells of a widegap semiconductor, such as ZnS
To avoid defects at the boundary of two crystal lattices of CdSe and ZnS, between them was placed a layer of cadmium sulfide, which has intermediate crystal lattice parameters and bandgap energy [2]

Summary

Introduction

Cadmium selenide nanocrystals are of special interest. Such structures demonstrate high photoluminescence (PL) quantum yield in a wide range of the spectrum [1]. To increase the brightness of PL and its stability, CdSe nanoparticles are covered with the shells of a widegap semiconductor, such as ZnS. The shell spatially separates the nucleus from the environment, as a result, we can reduce the sensitivity of optical properties to the influence of external factors. To grow such shells, the addition of metal and chalcogenide to the core solution at high temperatures it is often used. To avoid defects at the boundary of two crystal lattices of CdSe and ZnS, between them was placed a layer of cadmium sulfide, which has intermediate crystal lattice parameters and bandgap energy [2]

Methods

Results

Conclusion