Structural and optical characteristics of polyvinylpyrrolidone doped with nanocrystal NaF films

Abstract

In this study, doped PVP with nanostructure NaF using different preparations such as a wet casting, quartz cell and spin-coating techniques with concentrations (0, 2, 4, 6, 8, 10, 12 and 14 wt%) was achieved. The X–ray diffraction of the samples indicate that the pure PVP are amorphous in structure and the doped are polycrystalline for selective 4, 8, 12 and 14 wt% with nanocrystal grain sizes, 30.10, 26.00, 22.88 and 31.79 nm, respectively. It was observed that the amorphisation decreases with increasing NaF concentration. The Fourier Transform Infrared (FTIR) spectrometer measurements show that the stretching vibration in the oxygen containing chain polymer changes the covalent bond distribution with fluoride ion bonds, which is the greatest. An increment of UV-Vis absorption produced maximum peak absorbance spectra of different techniques at about 0.5 to 0.6 values with a high shifting in casting method. The indirect Eg_opt of pure and doped PVP films were estimated to decrease at about 3.65, 3.57, 3.55, 3.45, 3.33, and 3.25 eV for indirect allowed transitions, whereas the indirect forbidden band gaps were determined as 3.52, 3.50, 3.41, 3.31, 3.18 and 3.13 eV with increase sodium fluoride contents, respectively. The prepared samples appeared near band edge peak absorption at about 300 nm of different deposition, which is close to each other for bulk specimens (solution), shifting at higher frequencies.

Keywords: Polyvinylpyrrolidone, doping, structural, optical properties, optical energy gap, concentration, sodium fluoride.