Synthesis of Cadmium-Free InP/ZnS Quantum Dots by Microwave Irradiation

Abstract

Recently, significant progress has been made in adapting the properties of cadmium-free quantum dots (Cd-free QDs) for sensing applications. Cd-free QDs are fascinating because of their low toxicity and suitability for bio-applications. In this paper, we present a new procedure for the rapid synthesis of luminescent InP/ZnS QDs using microwave irradiation, and surface modification of the QDs with L-cysteine amino acid. The high-resolution transmission electron microscopy images demonstrated that the L-Cys-capped InP/ZnS QDs were 3-5 nm in size. The X-ray diffraction patterns revealed that all the QDs exhibited a zincblende InP structure. Fourier transform infrared spectroscopy was used to characterize the functional groups of the surface-modified L-cysteine-capped InP/ZnS QDs, while UV-vis and photoluminescence (PL) spectroscopy were employed to study their optical properties. The QDs exhibited red shifting of the absorption peak with reaction time because of the increase in particle size, and the full width at half maximum of the PL spectra increased because of broadening of the particle size distribution.