Dazzling red emission from TiO2 nanoparticles impregnated co-doped Gd3++Eu3+: PVA polymer nanocomposites for photonic applications

Abstract

Abstract Red emission was obtained from rare earth doped polymer nanocomposites, namely, composites of polyvinyl-alcohol (PVA) co-doped with Gd 3+ and Eu 3+ and embedded with TiO 2 nanoparticles (TiO 2 NP), under ultraviolet (UV) excitation. We successfully synthesized Eu 3+ : PVA, Gd 3+ : PVA, (Gd 3+ + Eu 3+ ): PVA, and (Gd 3+ + Eu 3+ + TiO 2 NP): PVA films by solution casting method. From X-ray diffraction patterns and Fourier-transform infrared spectral profiles, the structural details of the films and the ion–polymer interaction mechanism responsible for their formation were systematically analyzed. The thermal stability and decomposition dynamics of the prepared samples were evaluated by thermogravimetry and differential thermal analysis. Pertinent optical absorption bands related to Eu 3+ and Gd 3+ ions in the polymer composites were observed and assigned to the corresponding electronic transitions. The PVA film containing different concentrations of the Eu 3+ dopant displayed red emission at 618 nm ( 5 D 0 → 7 F 2 ) under UV excitation at 396 nm ( 7 F 0 → 5 L 6 ). Upon co-doping with Gd 3+ to form the (Gd 3+ + Eu 3+ ): PVA film, it exhibited red emission that was stronger than that from the singly doped Eu 3+ : PVA film under 270 nm excitation because of the energy transfer from Gd 3+ to Eu 3+ ions. After the TiO 2 nanoparticles were evenly dispersed in the co-doped (Gd 3+ + Eu 3+ ): PVA films, the photoluminescence properties were remarkably enhanced and prominent red emission was observed under 274 nm excitation. The red emission of Eu 3+ was significantly enhanced through an efficient energy-transfer process from the Gd 3+ ions to Eu 3+ ions and from the TiO 2 nanoparticles to Eu 3+ ions. A possible energy-transfer mechanism was clearly demonstrated by several fluorescent methods and lifetime decay dynamics. Based on the above results, these polymer composite films are promising candidates for red luminescent photonic devices.