A paper-based ferrous ion sensor fabricated from an ion exchange polymeric membrane coated on a silver nanocluster-impregnated filter paper

- Demonstrate a new type of paper-based colorimetric sensor.
- Use ion exchange polymeric membrane couple with paper-based concept.
- Utilizing of silver nanoclusters as a selective chromogenic material impregnated on the paper substrate.
- Highly selective colorimetric sensor for Fe2+ and can be observed by naked eye.

A paper-based colorimetric sensor was fabricated using polymethylacrylic acid-templated silver nanoclusters (AgNCs) as a sensing probe for the detection of Fe2+ and employing an ion exchange polymeric membrane as a coating layer. AgNCs were impregnated on a cellulose filter paper. The AgNC-impregnated filter paper was then lacquered with a hydrophobic membrane of polyvinyl chloride plasticized with o-NPOE incorporating a hydrophobic cation exchanger. Due to the ion exchange phenomenon at the membrane surface, Fe2+ was extracted into the paper layer, and the bound Ag+ on the AgNCs was reduced by Fe2+. The growth of the cluster could be observed by measuring the increase in the silver nanoparticle (AgNP) plasmon band. The maximum plasmon band on the paper at 447 nm increased as a linear function of the increasing Fe2+ concentration. The proposed sensor was highly selective to Fe2+ over Fe3+ and other cations. The proposed sensor was optimized and could be used to detect Fe2+ solution concentrations as low as 50 μM, with a wide working linear concentration range of 0.2-1.0 mM. The sensor was applied to determine Fe2+ in iron supplement tablet samples with satisfactory results.

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