Dual-signal colorimetric sensor based on Fe,Ce-CDs for ultra-sensitive detection of nitrite in tobacco

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Abstract
Iron-cerium co-doped carbon dots (Fe,Ce-CDs) were synthesized by one-step hydrothermal method using tartaric acid and L-tryptophan as ligands. Fe,Ce-CDs shows excellent peroxidase-like (POD) activity and nitrite (NO2−) can promote the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to its blue oxidation product (oxTMB) due to the formation of ∙NO2 free radical. NO2− further react with oxTMB to form a yellow color via diazotization resulting in the absorbance Change at 450 nm. By Fe,Ce-CDs + NO2− + TMB + H2O2 and oxTMB + NO2− systems, a dual-signal colorimetric nanosensor for NO2− detection is developed with lower detection limits (LODs) of 0.272 μg/L and 0.019 mg/L, respectively. The proposed methods were applied to the detection of NO2− in tobacco samples with good recovery from 91.20 to 110.61%, achieving similar results and indicating their high accuracy and feasibility. Graphical Abstract

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