Colorimetric strategy for ascorbic acid detection based on the oxidase‐like activity of silver nanoparticle single‐walled carbon nanotube composites

Abstract A colorimetric assay for the determination and quantification of ascorbic acid (AA) is presented using silver nanoparticle (AgNP) single‐walled carbon nanotube (AgNP/SWCNT) nanocomposites prepared using a microwave‐assisted method. The AgNP/SWCNT nanocomposites possessed oxidase‐like properties toward 3,3′,5,5′‐tetramethylbenzidine (TMB) and could catalyze the oxidation of TMB to form a blue oxidation product (λ max = 652 nm) in the absence of H 2 O 2 . AA can specifically inhibit the oxidation of TMB, resulting in a decline of the absorbance value and blue colour fading. As such, amounts of AA can be assessed easily by the unaided eye and quantitatively using an ultraviolet–visible light spectrophotometer. Under the optimal reaction conditions, this strategy showed a good linearity ranging from 0.4 μM to 5.0 μM for AA detection, and the limit of detection was 130 nM. This assay was also applied for AA measurement in vitamin C tablets and juice samples that yielded satisfactory results.