Ultraviolet (UV) irradiated induced changes in optical properties of PVA/Ag nanocomposite films

Abstract

PVA/Ag nanocomposite with different concentrations of silver nanoparticles (Ag NPs) was successfully synthesized by the solution casting method. The effect of concentration of Ag NPs and ultraviolet (UV) irradiation on optical and structural properties of PVA/Ag nanocomposites were investigated by UV-Vis spectrophotometer and Fourier transform infrared spectroscopy. The presence of an absorption peak at around 410 nm recorded by UV-Vis spectrophotometer shows silver nanoparticles are formed. The absorption spectra for prepared nanocomposites recorded over the wavelength range of 200-700 nm shows the intensity of absorption band increases with an increase in the concentration of Ag NPs and with the increase in time of ultraviolet (UV) irradiation. Decreases in the broadness of transmission band with an increment in enfeeblement transmission intensity by UV exposure make its use suitable as a bandpass filter. Decrease in the value of the optical band gap from 4.91 eV for pure PVA to 4.32 eV for PVA doped 0.04M Ag was observed which continuously reduces further with an increase in the concentration of Ag NPs (3.67 eV for PVA doped 0.08M Ag). Additionally, as the time for UV exposure increases the value of the optical band gap decreases from 4.32 eV without UV exposure to 3.81 eV and 3.43 eV for UV exposure of 120 min and 240 minutes respectively for PVA doped 0.04M Ag. This reduction in values of the optical band gap corresponds to the formation of charge formation complexes inside the PVA matrix. Various optical parameters such as refractive index, single oscillator energy, lattice dielectric constant, the strength of interband optical transition, average oscillator strength, etc are calculated for nanocomposite with different concentrations of Ag NPs before and after UV exposure for different times. The refractive index values were observed to increase from 1.69 for pure PVA to 1.85 without UV exposure, which further increases to 2.30 for UV exposure of 240 minutes for PVA doped 0.08M Ag. FTIR spectra show the interaction between PVA and Ag NPs and show changes caused in the structure of nanocomposite as the time of UV exposure increases.

Synergic Effect of CdS Nano Additives and UV Exposure on Properties of PVA/CdS Nanocomposite

“…30,31 Figure 5 shows (αℎν) 2 as a function of photon energy for virgin PVA and nanocomposite films with varying filler amount prior to and afterwards UV irradiation for different duration. 32 Table III and Fig. 5 illustrates the band gap of films that is found by extrapolation of fitted straight lines at axis representing photon energy and it can be clearly seen from Fig.…”

“…UV irradiation results in cross-linking of PVA chains making density, molecular weight to alter, which cause increment in the refractive index. 32 Fourier transform infrared spectroscopic analysis.-FTIR is an effective method for the explicating the molecular structure of PVA and PVA embedded with CdS NPs nanocomposite films. Figure 8 displays FTIR analysis of pure PVA and PVA encapsulated with various amounts of CdS NPs in range 500-4000 cm −1 .…”

“…8b-8d it can be clearly seen that with increment in duration of UV irradiation intensity of absorbance bands at 3296 cm −1 , 3310 cm −1 , 1718 cm −1 , 1644 cm −1 , 1430 cm −1 and 633 cm −1 decreases as compared with fresh band. 32 This can be explained on the fact that photo induced reactions cause crosslinking, intermolecular bonding, chain scissoring which leads Cadmium ions to reduce into Cadmium atoms and this results in changing the structure of nanocomposite and hence alters the intensities of absorbance bands. 40 increases.…”

Tailoring of Optical, Dielectric, and Structural Parameters of PVA by CdS-Ag Core-Shell Nanoparticles and UV Irradiation

“…24 Further, UV exposure makes CdS@Ag CSNs to experience Fermi level equilibrium that induces an increment in charge transfer causing band gap to reduce with increasing time of exposure. 25 Refractive index (n) is fundamental factor in determining the productiveness of a substance in optical instruments like filters, switches etc "n" can be calculated using transmission and reflection coefficient as illustrated by Eq. 2.…”

Effect of Ag/CuS nanoparticles loading to enhance linear/nonlinear spectroscopic and electrical characteristics of PVP/PVA blends for flexible optoelectronics

“…In recent years, polymeric blend nanocomposites have been given exceptional concerns owing to their contributions to various applications including optoelectronics, photonics, medicine, photovoltaics and entertainment sectors. [1][2][3][4][5][6][7][8] Polymeric blends (PBs) could be attained by mixing two polymers or more with specific ratios to produce new polymeric materials with certain characteristics. [9][10][11][12] Polymeric nanocomposites (PNCs) are prepared by incorporating polymers or polymeric blends with nano fillers to match desired features.…”