NaI concentration effect on physical characteristic of poly vinyl alcohol: Sodium iodide nano films for gas sensors

Abstract

The sodium Iodide nanoparticles are added to polyvinyl alcohol with different concentrations at (10, 20,30 and 40) wt.% . The preparation and performance of the blends are prepared by the casting method. The structural morphology is characterized using X-ray diffraction (XRD), furriertransform infrared spectroscope (FTIR) and atomic force microscopy (AFM). The result   showed a uniform blend of  PVA with NaI matrix. The prepared nanocomposites are characterized using UV–VIS spectrophotometer and the optical properties showed that as NaI contents increased to 40% weight, the films' direct allowed optical energy are investigated in the wavelength range 300-1100 nm.  The collected results gap decreased from 4.27 to 4.22.   The electrical conductivity and activation energy are calculated.   Effect of temperature on electrical conductivity are also investigated. Furthermore, in order to understand the
behavior of electrical conductivity in these composites, the alternating electrical conductivity and dielectric permittivity have been investigated for different concentration of NaI at room temperature over the frequency ranging from to 1Hz -10 kHz. The electrical conductivity of the composite increased with increasing temperature and it obeys power law in which s is in the range of 0.99- 0.084 s the sensing properties are evaluated to ascertain the effects of NaI on the sensitivity, selectivity, and response/recovery time of PVA/NaI nanocomposite films. The maximum sensitivity (S) of 127.3 % towards NO2 gas detection at a 50 ppm concentration at temperature 473K with response/recovery times of ~ 25/25 s is observed for nanocomposites with 20 wt% NaI loading in a PVA matrix.