Constitution of a visual detection system for lead(ii) on polydiacetylene–glycine embedded nanofibrous membranes

Abstract

With the aim to develop pH-paper-like lead ion (Pb²⁺) sensing materials, we demonstrate a colorimetric strip, which relies on a SiO₂ nanoparticle (NP) decorated polydiacetylene embedded polyacrylonitrile nanofibrous membrane (PAN NFM), that undergoes a brilliant blue-to-red color transition as well as ‘Turn-On’ fluorescence upon incubation with Pb²⁺. The introduction of an amino acid (glycine) headgroup into a supramolecularly assembled 10,12-pentacosadiynoic acid results in a Pb²⁺-induced chromic conjugated polymer that is quickly photopolymerizable, rapidly responsive to Pb²⁺ and specifically identifiable. Moreover, the SiO₂ NPs are certified as an efficient sensitivity promoter when their content reaches 0.5 wt% in the strip. With this understanding, the color change that is caused by 0.24 μM Pb²⁺ at ambient temperature can be easily perceived by the naked eye, which indicates the superiority of our strip compared with previous approaches, and it is also noteworthy that a fluorescent signal could also be produced in 2 min. Furthermore, RGB (red-green-blue) digital parameters obtained from images of the strips and automatic read outs via a smartphone were processed statistically through principal component analysis and then used to elaborate the standard curve and quantify Pb²⁺ concentration. This methodology for assaying and quantifying Pb²⁺ avoids time-consuming sample preparation, expensive laboratory techniques, and specialized personnel required to carry out conventional analytical methods.