Growth kinetics of MPS-capped CdS quantum dots in self-assembled thin films

Kenan Koç,Galip G Tepehan,Fatma Z Tepehan

doi:10.1186/1556-276x-7-610

Abstract

For this study, we prepared colloidal CdS quantum dots using 3-mercaptopropyltrimethoxysilane as capping agent. Colloidal CdS quantum dots were directly deposited on glass substrates by a spin-coating process. Coated substrates were heat-treated between 225°C and 325°C for various heat treatment time intervals to investigate the growth kinetics of the quantum dots. Results showed that sizes of the CdS quantum dots grew approximately from 2.9 to 4.6 nm, and the E1s1s energy values shifted approximately from 3.3 to 2.7 eV. Results showed that the average size of quantum dots increase by thermal treatment due to Ostwald ripening. The thermal process used to grow the size of quantum dots was examined according to the Lifshitz-Slyozov-Wagner theory. The activation energy of CdS quantum dots in thin films was calculated at approximately 44 kJ/mol.

Highlights

Unlike bulk materials, optical and electronic properties of nanoparticles depend on their crystal dimension due to quantum confinement effect
High-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectroscopy (EDS) The HRTEM picture and the EDS pattern of MPScapped CdS quantum dots are given in Figure 1a,b, respectively
Cadmium acetate and thioacetamide were used as a Cd source and as an S source, respectively, in a molar ratio of 1 as explained in the ‘Methods’ section

Summary

Introduction

Optical and electronic properties of nanoparticles depend on their crystal dimension due to quantum confinement effect. Several techniques have been used to control the growth process of nanoparticles. One of the most important technique is the growth of nanoparticles in glasses. High heat treatment temperatures over 550°C were needed to control the growth process of nanoparticles for this technique [1,2,3]. Nanoparticles can grow by chemical reactions in liquid or thin film media. Low heat treatment temperature and very narrow size distributions of nanoparticles in liquid or in thin film media are the obvious advantages compared with the growth of nanoparticles in glasses [4,5,6,7,8,9,10,11]

Methods

Results

Conclusion