Immobilization of anthocyanin extract from red-cabbage into electrospun polyvinyl alcohol nanofibers for colorimetric selective detection of ferric ions

Abstract An effective nanofibrous metallochromic sensor mat was developed. Electrospun nanofibers were generated from a solution of polyvinyl alcohol (PVA) as a host polymer and anthocyanin extract from red-cabbage as an active detection sites. Using PVA as a supramolecular hosting matrix and anthocyanin phenolic dye (AC) as a spectroscopic probe, a novel, simple, rapid, portable and colorimetric sensor was developed for ferric ions (Fe3+) in aqueous environments. Binding these toxic ferric cations causes an appreciable color change from colorless to pink as proved by the CIE Lab color parameters. The visible color variation was found to change proportionally depending on increasing the concentration of ferric ions. The naked-eye recognition of Fe3+ was rationalized on the basis of Fe(III)-phenolic anthocyanin complex formation. High Performance Liquid Chromatography Mass Spectrometry (HPLC-MS) was applied to characterize the anthocyanin extract. The surface morphology and structural characterization of the generated nanofibers were explored by scanning electron microscopy (SEM) and energy-dispersive X-ray analyzer (EDS). The generated electrospun PVA-AC nanofibrous film displayed an average diameter of 150–250 nm. They were firstly cross-linked using the vapors of glutaraldehyde to turn them into water-insoluble nanofibers. Both selectivity and detection limit have been also studied. The anthocyanin-containing nanofibers display an excellent simplicity and reusability with a limit of detection in the range between 1 and 350 mg/L. The detection limit was monitored as low as 1 mg/L. PVA-AC showed excellent selectivity compared to other transition metal ions, including Cu2+, Mg2+, Hg2+, Co2+, Ba2+, Zn2+, Ni2+, Cr3+, Al3+, Ca2+, K+, Na+, Cd2+ and Mn2+. The best optimized conditions for the detection of Fe3+ was achieved in a pH range from 3.75 to 6.0. The proposed assay has the advantage of rapidity, simplicity, facile fabrication, low cost, environmental safety and easy to operate compared to other detection techniques.