Structural and photoluminescence properties of a trivalent rare earth Sm ion-doped PVA/PVP blend polymer films

Abstract

Transparent polyvinyl alcohol (PVA)/polyvinylpyrrolidone (PVP) and various concentrations of Sm³⁺ ion-doped PVA/PVP blend-polymer films were prepared using the solution cast method. The structural properties were studied by using XRD and FTIR. Optical UV-Vis, photoluminescence, and decay studies were carried out for prepared PVA/PVP blend polymer films. The XRD confirms the structural change in PVA/PVP blend-polymer with the doping of Sm³⁺ ion. From FTIR, Sm³⁺ ion forms the complex formation within the PVA/PVP polymer structure. The allowed band gap decreased from 5 to 4.6 eV, and the refractive index increased from 2.4 to 2.45, increasing Sm³⁺ ion concentration. From the energy band gap, the bonding parameters ($\overline{\beta \mathrm{ }}$ and δ) were calculated to find the covalent/ionic bond nature of the prepared polymer films. The emission spectra were measured for Sm³⁺: PVA/PVP with the excitation of 402 nm wavelength (⁶H_5/2→⁴F_7/2). ⁴G_5/2→ ⁶H_7/2 shows maximum intensity at 0.4 wt % of Sm³⁺, and beyond concentration, quenching was noticed. It is observed from the decay curve that the lifetime of PVA/PVP samples doped with Sm³⁺ at all concentrations decreases with the increase of Sm³⁺ ion concentration. It was noticed from CIE chromaticity that Sm³⁺: PVA/PVP blend polymer films are more appropriate for enhancing reddish-orange photonic emission. Based on the above results, Sm³⁺: PVA/PVP blend polymer films are suitable for reddish-orange luminescent applications.

Keywords:

• PVA/PVP blend polymer films
• XRD
• FT-IR
• optical absorption
• photoluminescence