Ready-to-use strip for L-ascorbic acid visual detection based on polyaniline/polyamide 66 nano-fibers/nets membranes

A ready-to-use L-ascorbic acid (L-AA) colorimetric strip based on polyaniline (PANI)/polyamide 66 (PA 66) nanofiber/net (NFN) membrane with spider-web-like structure was fabricated through a facile bend electrospinning/netting process. Introduction of PANI component into the membrane turns the strip undergoes a brilliant brown-to-green color transition within 30 min upon incubation with L-AA. Moreover, ascribing to the three-dimensional microscopic structural, continuous pore channels, and distinctive nano-nets structure, the color change that is caused by 50 ppb L-AA can be easily perceived by naked eyes. Furthermore, RGB (red-green-blue) digital parameters that obtained from photographs of the strips were automatically read out via an iPhone. Subsequently, the parameters were converted into a color-difference map and processed statistically through principal component analysis, then used to elaborate standard curve. Combining the map and curve, we realized a method for assaying and quantifying L-AA concentration in real food samples, which avoids the time-consuming sample preparation, expensive laboratory techniques, and specialized personnel needed to carry out conventional analytical methods.