Luminescent PVDF nanocomposite films and fibers encapsulated with La2Hf2O7:Eu3+ nanoparticles

Abstract

Luminescent films and fibers are in high demand in display devices and optoelectronics owing to their higher flexibility and mechanical strength compared to powder samples. Keeping that in mind, we have encapsulated La2Hf2O7:Eu3+ (LHOE) nanoparticles (NPs) synthesized by a molten salt method into polyvinylidene fluoride (PVDF) films and fibers. The LHOE-PVDF nanocomposite fibers were manufactured using a Forcespinning® technology while the counterpart films were fabricated by a drop-casting technique. Their photophysical properties were analyzed and compared. Specifically, the red emission with optimum lifetime, color coordinates, and branching ratio of the LHOE NPs can be reproduced even when incorporated inside the PVDF films and fibers. Our studies demonstrate that the LHOE-PVDF films have better emission output, excited-state lifetime, quantum yield, and color purity than the fibers. This is attributed to lower defect density and better surface texture of the LHOE-PVDF films compared to the fibers. Based on the Judd–Ofelt analysis, we have also elucidated that the Eu–O bond is more polarizable and has a higher degree of covalency in the LHOE-PVDF films compared to that in the fibers. The trend of the Judd–Ofelt parameters suggested that Eu3+ has a more asymmetric environment in the films compared to the fibers which impart higher red color purity to the former.