Synthesis and Characterizations of Bare CdS Nanocrystals Using Chemical Precipitation Method for Photoluminescence Application

H L Lee,M Alnot,M B Assouar,H Rinnert,A M Issam,M Belmahi

doi:10.1155/2009/914501

Abstract

Bare cadmium sulfide (CdS) nanocrystals were successfully synthesized by the thermolysis of a single‐source organometallic precursor, cadmium chloride hemipentahydrate (CdCl2 · 2.5H2O) with thiourea in ethanol. The microstructure of the CdS samples was characterized using XRD, TEM, and Raman spectroscopy. The XRD′s results showed that there was a transformation from cubic to hexagonal crystalline phase when higher mass of CdCl2 · 2.5H2O was used. Further experimental with different Cd2+ source showed ion Cl− originated from CdCl2 · 2.5H2O attributed to this crystalline phase transformation. The UV‐Visible analysis indicated that quantum confinement effect took place when compared to the bulk CdS. However, the photoluminescence experiments revealed that the red‐light emission was observed in all samples. This finding could be ascribed to deep trap defects that were due to sulfur vacancies as suggested by XPS and also the fact that the bare CdS nanoparticles are in contact with each other as shown in the TEM images.

Highlights

Semiconductor quantum dots (QDs) have been extensively researched due to their unique size-dependent optical and electrical properties [1, 2]
The reaction of cadmium hydroxide and thiourea produces the side products of diazomethane (CH2N2), water, Cd2+ions and S2− ions. These ions eventually form as Cadmium sulfide (CdS) nanoparticles that precipitate as yellow powders
We have successfully synthesized bare CdS based on thermolysis of a single-source organometallic precursor

Summary

Introduction

Semiconductor quantum dots (QDs) have been extensively researched due to their unique size-dependent optical and electrical properties [1, 2]. Remarkable efforts have been made to develop methods for high-quality CdS nanocrystals such as controlled precipitation reactions, the thermolysis of single precursors at relatively high temperature, and rapid hot-injection-based synthesis. Our task is to study the effect of Cd2+ ions mass concentration and source of Cd2+ ions in determining the crystalline phase of the bare CdS nanoparticles. We employed a facile, low-cost, and environmentally friendly synthetic method which is based on thermolysis of a single-source organometallic precursor. This method is adapted with slight modification from Tong and Zhu [8]. We have performed several instrumentation techniques such as XRD, SEM-EDX, UV-Vis Spectroscopy, TEM, XPS, and PL spectroscopy to characterize the bare CdS nanoparticles

Experimental

Results and Discussion

Conclusions