Surface passivation by l-arginine and enhanced optical properties of CdS quantum dots co-doped with Nd3+–Li+

Abstract

l-Arginine-passivated Nd3+ and Li+ co-doped CdS quantum dots (QDs) were synthesized by chemical precipitation method. Ultraviolet–visible absorption spectra of prepared QDs show absorption in the range of 477–450 nm indicating huge blue shift in energy band gap as compared to the bulk CdS due to quantum confinement effect. The optical band gap is found increasing from 2.44 to 2.97 eV as the doping concentration increased from 1 to 5 wt%. Photoluminescence spectra showed that co-doped CdS QDs are highly luminescent and emit multiple intense violet (362, 371, 385, 395 nm) and blue (422, 445, 456 and 465 nm) coloured peaks with increasing intensity with co-dopant concentration. Fourier transform infrared study confirmed the interaction between CdS nanoparticles and l-arginine ligands. The structural and morphological study revealed the formation of orthorhombic crystal structure. The size of CdS QDs, as analysed by X-ray diffraction and high-resolution transmission electron microscopy, is found reducing with co-dopant concentration. The energy dispersive X-ray analysis shows no impurities present except dopants indicating high purity of the prepared samples. Based on the results, we proposed that this material is a new class of luminescent material suitable for optoelectronics devices’ application, especially in light emitting devices, electroluminescent devices and display devices.