Tailoring plastic bag derived carbon dots by sulfur-nitrogen passivation for highly selective Fe (III) ion sensing

Plastic bags were used to produce carbon dots (CDs), which can contribute to solving environmental problems. The enhanced quantum yield (QY) was achieved in this study through the passivation of CDs with sulfur (S) and nitrogen (N). Pyrolysis and hydrothermal methods were used to produce S-N co-doped CDs (S-N-CDs) from plastic bags. Notably, S-N-CDs significantly enhanced the QY to 16.20 %. The resulting S-N-CDs retained remarkable fluorescence performance over high ionic strengths and UV light irradiation. The incorporation of functional groups containing oxygen, sulfur, and nitrogen in S-N-CDs created recognition sites that enable specific and highly selective sensing of Fe³⁺ ions, with a quenching ability of up to 62 %. Moreover, these S-N-CDs displayed a wide linearity in the range of 110.64–600 µM for Fe³⁺ ion detection. The sensing system exhibited exceptional performance in detecting Fe³⁺ in actual water samples with %Recovery of 90–100 % and %RSD below 0.39 %, The findings highlight the prospect of S-N-CDs from plastic bags as promising sensors for future environmental analysis, addressing the urgent need for effective and sustainable solutions.