Silica nanoparticles were synthesized by a sol-gel method and mixed with different amounts of polyvinyl chloride (PVC) to get nanocomposite films. The samples were characterized by XRD, HR-TEM, SEM, and FTIR. High resolution transmission electron microscopy (HR-TEM) proved that the average particle size of the nanosilica is 15 nm. The scanning electron microscopy (SEM) showed that the nanosilica was well dispersed on the surface of the PVC films. Fourier Transform Infrared (FTIR) spectra for nanocomposite films intimate a significant change in the intensity of the characteristic peaks of the functional group with addition of nanosilica. The optical band gap was found to decrease with the addition of nanosilica while the refractive index increased. The dielectric constantε′, the dielectric loss modulusM′′, and AC conductivity(σAC)were also studied. It was found thatε′increases with temperature for all samples, clear dielectricα-relaxation observed from dielectric lossM′′around the glass temperature (Tg), and this could be related to micro-Brownian motion of the main PVC chain. The activation energy was calculated, and the AC conductivity could be a hopping one. The results of this work are discussed and compared with previously obtained data.

Bariumtitanate/polyvinylidene fluoride (BaTiO 3 ) x (PVDF) 100-x composite samples were prepared and characterized using X-ray diffraction (XRD) and differential scanning calorimetry (DSC) techniques. In this work, the ratio of the constituents of this composite was altered, and the structural and thermal changes were studied. Also, the variation of tetragonality of BaTiO 3 (BT) in the composite samples as a function of BT content was studied for the first time. The results show that all the samples are in the a-phase, and the hindrance to the PVDF crystallization increases with the increase of BaTiO 3 (BT) ratio in the composite. Tetragonal distortion of BT nanoparticles in the composite increases with the increase in BT ratio up to 30%, where it gets a saturation value. Also, it seems that stretching the samples enhances the BT tetragonality. Both melting and crystallization behaviors of the composite samples show double-melting endotherms (reorganization) and crystallization exotherms. The inclusion of BT in the composite samples results in a decrease in the melting temperature of the samples.

The complex dielectric permittivity (ε * = ε − jε ) and ac conductivity σ (ω, T) as a function of temperature (90-375 K) and frequency (0.4 kHz to ≈ 100 kHz) were measured in this work for polycrystalline samples of hydroxyl ammonium sulfate, (NH 3 OH) 2 SO 4 . The measured electrical parameters revealed the existence of a structural phase transition at T ≈ 312 K, which was further confirmed by a differential thermal analysis thermogram, where a clear endothermic peak centered at ≈ 312 K is observed. Regarding the charge transport mechanism, it is likely that the behavior of frequency-dependent conductivity follows the universal dynamic response σ (ω,T ) = A(T )ω s(T ) . Moreover, the temperature dependence of the frequency exponent s(0 s 1) suggests the quantum mechanical tunneling model to be the most likely one that describes the electrical transport mechanism. The data correlate with the crystal structure and the hydrogen-bonding system.

Chitosan-stabilized gold nanoparticles (Cs/Au) film was prepared by casting strategy without a need for reducing and/or stabilizing agents. The shape, size, and crystalline phase were studied using UV-visible (UV-vis) spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD). The nature of the interaction between the Cs and Au nanoparticles was studied using the Fourier transformer infrared (FTIR) spectroscopy. The as-prepared Cs/Au nanocomposite film showed high activity in the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP)in the presence of an excess amount of NaBH 4 . Furthermore, the Cs/Au film is easily separable, as well as remains active after reused for 3 times. The Cs/Au nanocomposite film could be a promising candidate for various catalytic reactions. K E Y W O R D S4-Nitrophenol, catalytic reduction, chitosan, gold, nanocomposite

In this work, ZnO NPs were prepared by a simple co-precipitation technique. Cotton fibers loaded with ZnO NPs were prepared also. X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-Vis spectrophotometer have been used to characterize the prepared samples. The photocatalytic properties of the cotton loaded with ZnO (C-ZnO) and ZnO NPs, were studied under sunlight irradiation and lamp illumination as a function on time. The results showed that X-ray diffraction of ZnO NPs has a single-phase wurtzite structure with an average particle size of 29 nm. The morphology on the surface of ZnO NPs has a spherical shape. The optical band gap of ZnO nanoparticles was 3.37 eV. The photocatalytic confirms that C-ZnO exhibited higher photocatalytic activities than ZnO NPs.