Hot injection blended tunable CdS quantum dots for production of blue LED and a selective detection of Cu2+ ions in aqueous medium

Abstract

Cadmium sulphide (CdS) quantum dots (QDs) were synthesized via hot injection colloidal technique, while oleic acid (OA) is used as capping agent to control the particle size and to prevent agglomeration. Further, using ligand exchange technique to transform hydrophobic QDs into hydrophilic. The circular shape and size (2.7–4.0 nm) of QDs were investigate through high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and Brous hypothesis respectively. The HRTEM and XRD of prepared QDs show high crystallinity and wurtzite structure. The CdS QDs showed a strong absorption and photoluminescence (PL) properties in the visible region. The absorption and PL band maxima shifted from 366–450 nm and 425–456 nm respectively with increase in the time (15–105 min). The prepared QDs show that the increased quantum yield (QY) and reduce in PL-lifetime with increasing synthesis time. The CIE-1931 chromaticity diagram of CdS QDs with varying time has lie in blue region which indicate the synthesized QDs has serve as a blue colour producing material for light emitting diode (LED). The fluorescence intensity of MPA-CdS QDs was significantly quenched in the presence of Cu2+ metal ions and limit of detection (LOD) were observed in the range of 0.63×10-3ML-1. On the basic of PL quenching peak position and Stern-Volmer relation the quenching mechanism of QDs appeared as static in nature. These finding would be helpful for determining the suitability of the CdS QDs as LED and Cu2+ optical sensor.