A paper-based lanthanide smart device for acid-base vapour detection, anti-counterfeiting and logic operations

Paper-based devices have attracted extensive attention due to their portability, low-cost, ubiquity, low environmental footprint and ease of operation. In the present study, two lanthanide complexes, namely [Eu(PBA)(3)(H2O)(2)] (Eu-PBA) and [Tb(HPBA)(2)(NO3)(3)] (Tb-HPBA) were synthesized using an amide-type beta-di-ketone building block, N-(2-pyridinyl) benzoylacetamide (HPBA), which is capable of changing its energy-level to match that of Tb3+ and Eu3+ ions in an acid-base environment. This feature was used for the design and assembly of a simple and cost-effective paper-based lanthanide smart device (abbreviated as Paper-Eu/Tb), which was obtained by impregnating the filter paper with both the Eu-PBA and Tb-HPBA complexes; related homometallic Paper-Eu and Paper-Tb materials were also generated and characterized for comparative purposes. The obtained Paper-Eu/Tb device shows excellent luminescence properties, thus allowing its efficient use as a smart sensor for the naked-eye detection of various acid-base vapours with quick response, good reversibility and selectivity. A similar concept and the resulting paper-based device was also successfully expanded for other applications that include anti-counterfeiting and logic gate systems. Full characterization of the paper-based materials and examples of their use are described.