Rapid Microwave Assisted Synthesis of N-Doped CQDs for Highly Selective 'Turn-Off' Sensing of Bismuth(III) Ions in Wastewater

Abstract

The growing utilization of bismuth across diverse industries and pharmaceuticals has raised concerns about its environmental accumulation and the potential for neurotoxic and nephrotoxic effects in humans. Currently available techniques for its detection are often complex and costly, making CQDs an appealing alternative due to their low toxicity, cost-effectiveness, and ease of synthesis. Herein, a novel, environmentally sustainable one-pot microwave-assisted method for the synthesis of nitrogen-doped carbon quantum dots (N-CQDs) has been reported for the selective and sensitive detection of bismuth ions (Bi³⁺). The synthesized N-CQDs, with an impressive quantum yield of 47.5%, exhibited remarkable stability and were applied as fluorescent sensors for detecting Bi³⁺ ions, achieving highly selective detection through fluorescence quenching. The detection limit was calculated to be 0.365 μM within a linear concentration range of 0.95–61.5 μM, with the quenching mechanism identified as dynamic quenching via a photoinduced electron transfer (PET) process. The practical applicability of this sensing platform was demonstrated through the analysis of various real-world samples, including tap water, industrial wastewater and agricultural runoff, with recovery rates ranging from 98.7% to 101.6%. The applications of these N-CQDs as fluorescent ink and in anti-counterfeiting were demonstrated. Further, the N-CQDs were combined with an RGB analysis tool to detect Bi³⁺. This method- notable for its simplicity, cost-efficiency, and scalability- offers a sustainable and effective approach for detecting Bi³⁺ ions in various environmental contexts, presenting a significant advancement in the field of metal ion sensing.