Direct ink written ZnS:Cu photocatalytic luminous monoliths

Abstract

Traditional monolithic contactors have the advantages of good mass transfer and lower pressure drops; however, similar to packed bed and annular (wall-coated) reactors, monoliths are also plagued with low light utilization efficiencies. Multifunctional luminous monoliths for potential photocatalytic applications were printed using a Direct Ink Writing (DIW) approach in order to achieve intrinsic illumination of monoliths even after an external light source was terminated. A ZnS:Cu - based monolith incorporated with SrAlO4:Eu:Dy blue phosphor (Bp), that emitted light in the absorption range of ZnS:Cu was developed. Results demonstrated that the printed monoliths maintained the absorption profile of the base ZnS:Cu catalyst, exhibited whole structure luminescence, and showed a multipeak photoluminescence profile post excitation, that was representative of the peaks of the phosphor and ZnS:Cu. Additionally, the ZnS:Cu:Bp print exhibited steady illumination for up to 30 min. DIW guidelines were developed for the fabrication of afterglow monoliths, and a route to ameliorate the light distribution challenge of monolithic systems was achieved due to the whole luminescence that was displayed by the prints. Although this work was focused on a specific starting semiconductor (ZnS:Cu), the methods are broadly applicable to different materials that form printable inks.