Design of smart optical sensor using polyvinyl alcohol/Fluorescein sodium salt: Laser filters and optical limiting effect

Pure poly (vinyl alcohol) (PVA) and PVA doped Fluorescein-Sodium salt (FSS/PVA composite films) have synthesized on wide scale laser optical filters. The investigated polymeric composite films have been characterized using several methods. The XRD patterns exhibit a decrease of the average crystalline size and an increase of the internal strain, which explained the imperfection and distortion in the prepared films. The optical characterizations showed a decrease in the transmission of the incident light for different samples, which may be explained to the layer formed by intermolecular hydrogen bonding between the PVA matrix and the FSS particles. The FSS/PVA polymeric composite films are being a completely blocking in the UV–Vis light at the range between 190 and 560 nm, agreement with the optical limiting effect, which makes the composite films suitable for CUT-OFF laser filters applications. The decrease in its, directly and indirectly, allowed transition band gaps were controlled by the added FSS dyes molecules. The variation of the exponent frequency (s) of the power law for FSS/PVA polymeric composite films has been characterized to improve the hopping conduction mechanism in the materials. The dielectric permittivity (e′) and dielectric loss (e’’) have been decreased with increasing the applied frequency, and the incorporated FSS molecules due to the DC electric conductivity can cause the decreases of the polarization of the as-prepared films over the studied ranges.