Rational Synthesis of Highly Fluorescent N, S Co-Doped Carbon Dots Using Biogenic Creatinine for Cu2+ Analysis in Drinking Water

Abstract

Herein, highly fluorescent sulfur and nitrogen co-doped carbon dots (N, S-CDs) had been employed as a fluorescent probe to analyze Cu²⁺ in drinking water. The biogenic creatinine is known to form a stable complex with Cu²⁺; hence, it was rationally selected as a bioinspired nitrogen substrate for the first time to enhance N, S-CDs selectivity towards Cu²⁺. Moreover, the literature was surveyed to guide the selection of sulfur and carbon sources to optimize N, S-CDs quantum yield (QY), so thiourea and disodium edetate are co-carbonized with biogenic creatinine at 270°C for 40 min and characterized using different techniques. The resulting N, S-CDs have a homogeneous particle size distribution and high QY (60.5% ± 2.09%, n = 5). The produced N, S-CDs fluorescence intensity (FI) had been quantitatively quenched by Cu²⁺, achieving a detection limit reached of 0.07 μM. The developed environmentally friendly and sustainable platform, according to the results of three widely greenness assessment tools and the innovative RGB 12 model, had been successfully employed to detect Cu²⁺ in drinking water with excellent recovery. Finally, as this sensing platform is rapid and selective, it can be successfully employed to determine the Cu²⁺ in real-life applications.

Keywords: copper ions sensing; creatinine as bioinspired substrate; high quantum yield carbon dots; method sustainability assessment.