Lassaad El Mir

CO and NO 2 Selective Monitoring by ZnO-Based Sensors

ZnO nanomaterials with different shapes were synthesized, characterized and tested in the selective monitoring of low concentration of CO and NO2 in air. ZnO nanoparticles (NPs) and nanofibers (NFs) were synthesized by a modified sol-gel method in supercritical conditions and electrospinning technique, respectively. CO and NO2 sensing tests have demonstrated that the annealing temperature and shape of zinc oxide nanomaterials are the key factors in modulating the electrical and sensing properties. Specifically, ZnO NPs annealed at high temperature (700 °C) have been found sensitive to CO, while they displayed negligible response to NO2. The opposite behavior has been registered for the one-dimensional ZnO NFs annealed at medium temperature (400 °C). Due to their adaptable sensitivity/selectivity characteristics, the developed sensors show promising applications in dual air quality control systems for closed ambient such as automotive cabin, parking garage and tunnels.

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.

Anemia and genotoxicity induced by sub-chronic intragastric treatment of rats with titanium dioxide nanoparticles.

Titanium dioxide nanoparticles (TiO2 NPs) are widely used for their whiteness and opacity. We investigated the hematological effects and genotoxicity of anatase TiO2 NPs following sub-chronic oral gavage treatment. TiO2-NPs were characterized by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). Wistar rats were treated with anatase TiO2 NPs by intragastric administration for 60 days. Hematological analysis showed a significant decrease in RBC and HCT and a significant increase in MCV, PLT, MPV and WBC at higher doses. Furthermore, abnormally shaped red cells, sometimes containing micronuclei, and hyper-segmented neutrophil nuclei were observed with TiO2 NPs treatment. The micronucleus test revealed damage to chromosomes in rat bone marrow at 100 and 200mg/kg bw; the comet assay showed significant DNA damage at the same doses.

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.