Development of CdS, ZnS Quantum Dots and their Core/Shell Structures by wet chemical method

Abstract

Due to the unique optical properties like size-tunable emission color, narrow emission peak, and high luminescence efficiency semiconductor quantum dots (QDs) are emerging candidates for various applications. Size-controlled zinc sulfide (ZnS) and cadmium sulfide (CdS) quantum dots and their core/shell structures with varying concentration of capping agent were prepared using wet chemical methods. The obtained particles were characterized by XRD, UV/VIS, PL, FTIR and TEM. Corresponding broadening in XRD peaks reveals the reduction in particle size with uniform size distribution in the range particles of 2-10 nm. Optical absorption studies show that the absorption edge shifts due to quantum confinement towards the blue region as the capping agent concentration is increased indicating that effective band gap energy increases with decreasing particle size. Photoluminescence spectroscopy was used to study the luminescence enhancement on the basis of quantum confinement, composition and structure of QDs. The surface characterization of the quantum dots has been performed by FTIR spectroscopy. O-H, N-H and C-O groups were present on the surface of QDs which are functional groups that can easily attach with bio-molecules. Transmission electron microscopy has been performed as the best proof for the particle size and particle size distribution.