Transparent cellulose sheets as synthesis matrices for inorganic functional particles

Transparent cellulose sheets were prepared through tape-casting a solution of cellulose. Flexible, luminescent sheets were produced by adding europium trichloride to the casting solution and treating the sheets with an aqueous solution of ammonium fluoride. Scanning electron micrographs of the resulting sheets showed europium trifluoride particles with diameters from 200 nm to 500 nm. These were found by transmission electron microscopy to be agglomerates of crystallites in the size range of 10-20 nm. The structure of supercritically dried sheets was further assessed by small-angle X-ray scattering and suggests a preferred orientation of slightly elongated pores of roughly 12 nm in diameter. Evaluation of the emission characteristics of the sheets showed the band pattern between 580 nm and 700 nm typical for Eu³⁺ phosphors. Our developed process is a versatile tool for the fabrication of transparent cellulose structures with different shapes and various embedded functional particles.