Nd-oxide-based nanoparticle-embedded transparent and photoluminescent composite films

In this study, we fabricated Nd-based PL composites by embedding Nd compounds in a transparent resin and investigated the relationship between the size of Nd-based particles and PL properties. Nd(III)-based photoluminescent composite films were fabricated using neodymium nitrate hexahydrate and transparent urethane resin. The resulting Nd-based composite film was pale blue in color. The composite films exhibited near-infrared PL properties with a peak at 1.06 μm (⁴F_3/2 → ⁴I_11/2) by irradiation with UV-visible-near-infrared light using a halogen lamp. In the case of the composite film, further irradiation with UV light (using a Hg lamp) for 2 h or less resulted in the film showing strong PL at 1.06 μm under halogen lamp irradiation. Upon UV irradiation for more than 2 h, the film turned brown owing to the reaction of urethane with nitric acid derived from the Nd raw material, and the PL intensity became weaker. The Nd₂O₃ nanoparticles in the composite film were measured using transmission electron microscopy, and the particle size ranged from 15.0–35.1 nm. The PL intensity of the composite films was strongest when the size of the Nd-based particles was approximately 20 nm.