SIZE DEPENDENT SOLVATOCHROMISM OF CADMIUM SULPHIDE NANOPARTICLE

Abstract

Cadmium Sulphide is a group II–VI semiconductor nanoparticle and it has unique sizedependent properties. In this study, size dependent Cadmium sulphide nanoparticle was prepared by chemical precipitation with different molar ratios ((16:1), (8:1), (1:1) and (1:8)) of cadmium acetate and sodium sulphide. The synthesized nanoparticle was characterized with UVvisible spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy and Scanning electron microscope. The structure of nanoparticle was crystal with a particular size of 3.35 nm. Owing to quantum confinement effect the nanocrystals show a unique blend of molecular and solid properties: discrete energy levels with large polarizability that could respond to solvent environments. Furthermore, we have presented the size dependent solvatochromism of Cadmium Sulfide nanoparticles using steady state fluorescence and absorption spectroscopy. The absorption and fluorescence emission spectrum of Cadmium Sulfide shows bathochromic shifts with increasing crystal size and solvent polarity, indicating that the electronic transition involved

Dipole moment of the ground and first excited state of the nanoparticle was investigated. It was revealed that the solvatochromic responses were rather size dependent and fine-tuning of the nanoparticles band gap is possible by appropriate choice of solvent environment. The radius determined from both X-ray diffraction and effective mass approximation calculation was used in the determination of excited and ground state dipole moments. It is observed that the excited state dipole moment is larger than its ground state and the responses increased with the particle size up to a certain size beyond which the response started to decrease again. The molar ratio 1:1 has largest dipole moment change value (21 D) with Lippert-Mataga solvatochromic equation compared with other nanoparticle.