Biofunctionalized CdS Quantum Dots: A Case Study on Nanomaterial Toxicity in the Photocatalytic Wastewater Treatment Process

Kavitha Shivaji, Kishore Sridharan, D. David Kirubakaran, Jayaramakrishnan Velusamy, Seyedeh Sadrieh Emadian, Satheesh Krishnamurthy, Anitha Devadoss, Sanjay Nagarajan, Santanu Das, Sudhagar Pitchaimuthu

Research output: Contribution to journalArticlepeer-review

8 Citations (SciVal)

Abstract

The toxic nature of inorganic nanostructured materials as photocatalysts is often not accounted for in traditional wastewater treatment reactions. Particularly, some inorganic nanomaterials employed as photocatalysts may release secondary pollutants in the form of ionic species that leach out due to photocorrosion. In this context, this work is a proof-of-concept study for exploring the environmental toxicity effect of extremely small-sized nanoparticles (<10 nm) like quantum dots (QDs) that are employed as photocatalysts, and in this study, cadmium sulfide (CdS) QDs are chosen. Typically, CdS is an excellent semiconductor with suitable bandgap and band-edge positions that is attractive for applications in solar cells, photocatalysis, and bioimaging. However, the leaching of toxic cadmium (Cd2+) metal ions due to the poor photocorrosion stability of CdS is a matter of serious concern. Therefore, in this report, a cost-effective strategy is devised for biofunctionalizing the active surface of CdS QDs by employing tea leaf extract, which is expected to hinder photocorrosion and prevent the leaching of toxic Cd2+ ions. The coating of tea leaf moieties (chlorophyll and polyphenol) over the CdS QDs (referred to hereafter as G-CdS QDs) was confirmed through structural, morphological, and chemical analysis. Moreover, the enhanced visible-light absorption and emission intensity of G-CdS QDs in comparison to that of C-CdS QDs synthesized through a conventional chemical synthesis approach confirmed the presence of chlorophyll/polyphenol coating. Interestingly, the polyphenol/chlorophyll molecules formed a heterojunction with CdS QDs and enabled the G-CdS QDs to exhibit enhanced photocatalytic activity in the degradation of methylene blue dye molecules over C-CdS QDs while effectively preventing photocorrosion as confirmed from cyclic photodegradation studies. Furthermore, detailed toxicity studies were conducted by exposing zebrafish embryos to the as-synthesized CdS QDs for 72 h. Surprisingly, the survival rate of the zebrafish embryos exposed to G-CdS QDs was equal to that of the control, indicating a significant reduction in the leaching of Cd2+ ions from G-CdS QDs in comparison to C-CdS QDs. The chemical environment of C-CdS and G-CdS before and after the photocatalysis reaction was examined by X-ray photoelectron spectroscopy. These experimental findings prove that biocompatibility and toxicity could be controlled by simply adding tea leaf extract during the synthesis of nanostructured materials, and revisiting green synthesis techniques can be beneficial. Furthermore, repurposing the discarded tea leaves may not only facilitate the control of toxicity of inorganic nanostructured materials but can also help in enhancing global environmental sustainability.

Original languageEnglish
Pages (from-to)19413-19424
Number of pages12
JournalACS OMEGA
Volume8
Issue number22
Early online date22 May 2023
DOIs
Publication statusPublished - 6 Jun 2023

Bibliographical note

Funding Information:
This research received no external funding, and the APC was funded by Heriot-Watt University. S.D. and S.P. gratefully acknowledge Swansea University, UK, for financial support for this work through the EPSRC Impact Acceleration Account at Swansea University (IAA-RIF-2020, grant no: FP11581 IAA-RIF-2020). This work was partially supported by the Marie Skłodowska-Curie Actions (MSCA) grant within the European Union’s Horizon 2020 program (grant no.: 101025385 to J.V.).

Funding Information:
K.S. thanks and acknowledges the Principal and Head, Department of Biotechnology, K.S. Rangasamy College of Technology, Tiruchengode, Tamil Nadu, India, for the support offered toward this study. Moreover, K.S. thanks the Center for Nano Science and Technology, Satyabhama Institute of Science and Technology, India, for stereo microscope analysis. S.P. thanks the Management of K.S. Rangasamy Group of Institutions, Tiruchengode, Tamil Nadu, India, for supporting this work through UK-India Joint Research initiatives. S.P. acknowledges the Institute of Mechanical, Processing and Energy Engineering (IMPEE), School of Engineering and Physical Sciences, Heriot-Watt University, for seed grant support. S.K. acknowledges the European Commission Smart innovative system for recycling wastewater project id: 958491 and creating closed loops in textile manufacturing industrial processes.

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering

Fingerprint

Dive into the research topics of 'Biofunctionalized CdS Quantum Dots: A Case Study on Nanomaterial Toxicity in the Photocatalytic Wastewater Treatment Process'. Together they form a unique fingerprint.

Cite this