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

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 (lambda(max) = 652 nm) in the absence of H2O2. 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 mu M to 5.0 mu M 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.