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

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.