K. Omri

Effects of nanoparticle zinc oxide on emotional behavior and trace elements homeostasis in rat brain

Over recent years, nanotoxicology and the potential effects on human body have grown in significance, the potential influences of nanosized materials on the central nervous system have received more attention. The aim of this study was to determine whether zinc oxide (ZnO) nanoparticles (NPs) exposure cause alterations in emotional behavior and trace elements homeostasis in rat brain. Rats were treated by intraperitoneal injection of ZnO NPs (20–30 nm) at a dose of 25 mg/kg body weight. Sub-acute ZnO NPs treatment induced no significant increase in the zinc content in the homogenate brain. Statistically significant decreases in iron and calcium concentrations were found in rat brain tissue compared to control. However, sodium and potassium contents remained unchanged. Also, there were no significant changes in the body weight and the coefficient of brain. In the present study, the anxiety-related behavior was evaluated using the plus-maze test. ZnO NPs treatment modulates slightly the exploratory behaviors of rats. However, no significant differences were observed in the anxious index between ZnO NP-treated rats and the control group (p > 0.05). Interestingly, our results demonstrated minimal effects of ZnO NPs on emotional behavior of animals, but there was a possible alteration in trace elements homeostasis in rat brain.

Sub-Acute Oral Toxicity of Zinc Oxide Nanoparticles in Male Rats

ZnO-NPs suspended in distilled water were administered to Wistar rats at dose of 10 mg/ kg body weight through oral gavage for 5 consecutive days. The mean body weight gain in rats given ZnO-NPs was similar to this of control group, so no significant differences in the relative organs weight were observed between the ZnO-NPs treated-rats and control. Moreover, ZnO-NPs-exposed rats showed normal values for the complete blood count test. However, biochemical assays showed that sub-acute exposure to ZnO-NPs induced a marked increase of aspartate aminotransferase (AST) and alanine aminotransferase (ALT). Therefore, uric acid, creatinine and glucose levels are not modulated by ZnONPs administration. These biochemical findings were supported by histopathology examination, which showed minor morphological changes in rat tissues. Sub-acute exposure to ZnO-NPs does not affect the exploratory behaviors and the anxious index of rats.

Effect of Ca-doping on microstructure and photocatalytic activity of ZnO nanoparticles synthesized by sol gel method

Abstract We report the synthesis of Zn1−xCaxO nanoparticles prepared by a sol–gel processing technique for x ranging from 0 to 0.05. The structural, morphological and optical properties of the nanoparticles were investigated by X-ray diffraction, transition electron microscopy, UV measurements, and photoluminescence spectroscopy. The photoactivity of the Ca-doping ZnO photocatalysts was evaluated by the photocatalytic degradation of methylene blue dye. The structural properties showed that the obtained nanoparticles are in wurtzite single crystalline phase and no secondary phases were detected which indicated that Ca substituted Zn ions. The absorption edge of the prepared photocatalysts is clearly shifted to the visible region as compared to undoped ZnO. The study of the effect of Ca loading on the photocatalytic activity shows that the Zn0.96Ca0.04O is the most photoactive. The effect of some parameters such as catalyst loading, initial dye concentration and light intensity were investigated.

Negative differential resistance in carbon-silica nanocomposites

In this work, carbon–silica nanocomposites have been elaborated by sol–gel technique. SiO2 nanoparticles were mixed with resorcinol–formaldehyde (RF) carbon precursor solution with RF/SiO2 mass ratio being 1. The samples were dried by increasing temperature from ambient to 150°C by step 10°C/day and then pyrolysis at several temperatures 675°C (RF–SiO2–675), 700°C (RF–SiO2–700) and 725°C (RF–SiO2–725) under controlled argon atmosphere. The XRD investigations carried out on these samples outline that material has amorphous phase. TEM micrograph shows that RF–SiO2–675 sample was made by homogenous nanoparticles with about 14–20 nm in diameter. Current–voltage characteristics exhibit non–linear and symmetric behaviour for all measurement temperatures between 80 and 300 K. Therefore, a Negative Differential Resistance (NDR) phase has been detected at room temperature for RF–SiO2–675 sample. However, this non–linear behaviour appears for lower measurement temperatures when the pyrolysis temperature increases. The current threshold after each the NDR phase appears is found to increase with increasing the sample temperature while the threshold voltage decreases. (Vth)1/2 decreases linearly with measurement temperature and the threshold power (Vth*Ith) follows a Gaussian behaviour. The found results reveal that the NDR in the studied nanocomposites is a consequence of Joule heating effect.

Effect of the different concentrations of ZnO:Mn incorporation on the microstructure and dielectric properties of epoxy nanocomposites

The Mn:ZnO/epoxy nanocomposites (MZO–EP-NCs) resin samples are prepared using the ultrasonication method. This work deals with the systematic investigation of microstructural, optical and electrical properties of MZO fillers incorporating to the epoxy resin. These samples are characterized by scanning electron microscopy (SEM), X-ray diffraction and UV–Vis spectroscopy. SEM micrographs revealed that the as-prepared MZO nanocrystals are presented in the spherical clusters. X-ray diffraction indicates that the MZO–EP-NCs samples exhibit the presence of MZO nanocrystals peaks. Optical analyses showed a decrease in the band gap energy with increasing the MZO concentrations and a high UV-absorption of MZO–EP-NCs due to the light scattering due to the incorporating MZO particles in the epoxy. Such changes can be described by the shift of HOMO and LUMO band’s transition in the studied samples. Our results support the correlation between structure and optical properties of the mentioned nanocomposites. At high electromagnetic waves, the dielectric permittivities are decreased linearly with the addition of MZO clusters compared to neat epoxy. The obtained optical parameters supporting the improvement of the UV shielding properties of MZO–EP-NCs samples.

Optical, electrical and sensing properties of ZnO nanoparticles synthesized by sol-gel technique

Optical, electrical and sensing properties of ZnO nanoparticles, prepared by sol-gel process and subsequent dried in supercritical conditions, are presented. To investigate the morphological and microstructural properties, transmission electron microscopy (TEM), X-ray powder diffraction (XRD), UV-visible spectroscopy and photoluminescence (PL) spectroscopy analysis have been used. From microstructure analysis we showed that pure ZnO nanoparticles were polycrystallines and exhibited the hexagonal wurtzite structure. Chemoresistive sensor consisting of a thick layer of ZnO nanoparticles annealed at 400 °C for 2h in air on interdigitated alumina substrate has been fabricated and its electrical and sensing characteristics were investigated. The sensor performances towards carbon monoxide (CO) with and without UV illumination were reported. An increase of sensitivity, along a reduction of ZnO thick film resistance, was observed when the sensor operates under UV irradiation.