ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Optical efficiency of CdTe QDs for metal ion sensing in the presence of different thiol-based capping agents

Pooja Yadav and Papia Chowdhury

Department of Physics and Materials Science and Engineering, Jaypee Institute of Information Technology, Noida, India

E-mail: papia.chowdhury@jiit.ac.in

Received: 18 June 2021  Accepted: 17 November 2021

Abstract:

In the present work, various capping ligands [thioglycolic acid (TGA), glutathione reduced (L-GSH) and L-cysteine (L-Cyst.)] have been used to modify the surface chemistry of CdTe quantum dots (QDs). Different capped CdTe QDs are prepared by aqueous phase route and characterized by UV–visible, photo-luminescence and FTIR spectrometry. The structural properties of uncapped and capped CdTe QDs were investigated by the scanning electron microscopy and energy-dispersive X-ray spectroscopy. Optical signal of distinct capped CdTe QDs was observed to be pH, time and temperature dependent. In the presence of most of the metals ions (Xⁿ⁺), capped CdTe has shown strong “Turn-Off” fluorescence responses due to 1:1 complexation between metal ions and QDs except for Cr³⁺ and Pb²⁺metal ions. In the presence of Cr³⁺ and Pb²⁺ metal ions “Turn-On” fluorescence response appeared for L-Cyst. + CdTe QDs due to fluorescence resonance energy transfer. The output of Benesi–Hildebrand relation and graphical Job’s plots have established the existence of strong 1:1 complexation (Xⁿ⁺: TGA + CdTe, L-GSH + CdTe, L-Cyst. + CdTe) between distinctly capped CdTe and metal ions. Further, strong appearance of relative fluorescence intensities (F − F₀/F₀) established the better sensing capability of L-Cyst. + CdTe and TGA + CdTe QDs for Cr³⁺, Pb²⁺ ions. The lower value of limit of detection for TGA + CdTe QDs for Pb²⁺ and L-Cyst. + CdTe QD for Cr³⁺ and Pb²⁺ metals have showed better results towards sensing. The performance of capped CdTe QD in the presence of real sample shows good recovery (66–109%), precision and accuracy(0.2–2%) with a sensitivity of 10^–7 M. Our findings have shown a strong possibility of L-Cyst. and TGA capped CdTe QDs to be used as better metal ion sensors for Cr³⁺ and Pb²⁺.

Keywords: CdTe quantum dots; Capping agent; Metal ion; Sensing

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-021-01991-3

Chemical Papers 76 (3) 1833–1850 (2022)