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

Sustainable synthesis of highly luminescent carbon dots for ultra-sensitive detection of Pb²⁺ and Fe²⁺ in aquatic ecosystems

Priyal Kaushik, Gurmeet Kaur, and Imran Hasan

Department of Chemistry, Chandigarh University, (Mohali), India

E-mail: kaushikp9184@gmail.com

Received: 17 March 2025  Accepted: 30 June 2025

Abstract:

Carbon dots (CDs) have gained significant attention due to their unique optical properties, biocompatibility, and environmentally friendly synthesis routes. In this study, highly fluorescent CDs were synthesized from Citrus limetta peels using pyrolysis followed by sonication. The CDs were characterized using UV–Vis spectroscopy, fluorescence spectroscopy, FTIR, XRD, TEM, DLS, and Raman spectroscopy, confirming their optical properties, functional groups, crystalline nature, size distribution, and morphology. The CDs exhibited intense blue fluorescence under a 365 nm UV lamp. Through the HR-TEM, CDs were found to be spherical in shape with average particle size of 6 nm. Also, the XRD analysis showed largely disordered carbon structure with diffraction peaks at 2θ = 27.35° and 44.18°. Their sensing capabilities were evaluated for Fe²⁺ and Pb²⁺ detection in aqueous solutions, demonstrating fluorescence quenching upon metal ion interaction due to complex formation. The detection limits were determined to be 2.75 µM for Fe²⁺ and 1.26 µM for Pb²⁺, showcasing high sensitivity and selectivity. This work demonstrates a green and scalable approach to synthesizing highly fluorescent CDs from Citrus limetta peels for heavy metal ion detection. The CDs excellent sensitivity and selectivity highlight their potential as cost-effective, eco-friendly nanoprobes for environmental monitoring. These findings pave the way for sustainable water quality assessment strategies, addressing the urgent need for rapid and efficient heavy metal ion detection systems.

Keywords: Carbon dots; Citrus limetta peels; Sensing; Heavy metals; Fluorescence

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-025-04229-8

Chemical Papers 79 (10) 6865–6877 (2025)