Cellulose Biofilms, New Biotemplates in the Synthesis of Cuprate Superconductors

Bacterial cellulose (BC), obtained from fermented food byproducts (Symbiotic Culture of Bacteria and Yeast, and Nata de Coco), was successfully used as a template for the synthesis of a YBa₂Cu₃O_6+δ (YBCO) superconductor. As previous studies have shown, a dry template is needed to ensure the maximum uptake of the precursor solution. BC used is obtained in a wet state; it must be dried before use as a template. A variety of template drying techniques were investigated to assess the efficacy. This included air, oven, freeze, and solvent exchange drying. Among these, freeze-drying proved to be the most effective method as it best preserved the porous internal structure of the template. The addition of ethylenediaminetetraacetic acid (EDTA), a polychelating acid, also had a beneficial effect on the synthesis, improving both phase purity and the contribution of the superconducting phase. Waste-derived BC was shown to be a suitable substrate for the sol-gel synthesis of cuprate superconductors, providing an alternative to the ionic-liquid/nanocellulose-based approach used previously.