Low power consumption, fast response and quick recovery times are important parameters for gas sensors performance. Herein, we report the experimental and theoretical studies of ZnO and Cr doped ZnO nanostructures used in low temperature (50 °C) sensors for the detection of CO. The synthesized films were characterized by XRD, UV-Vis, FE-SEM and EDX. The XRD patterns for the ZnO and 0.5 wt% Cr/ZnO films confirm the formation of a single-phase hexagonal wurtzite structure. The reduction of the ZnO optical band gap from 3.12 eV to 2.80 eV upon 0.5 wt% Cr doping is well correlated with the simulation data. The FE-SEM images of the films show spherical morphology with the estimated particle sizes of about ~40 nm and ~ 25 nm were recorded for the ZnO and 0.5 wt% Cr/ZnO films, respectively. Enhanced gas sensing performance is achieved with Cr doping and the sensitivity of ZnO increases from 9.65% to 65.45%, and simultaneously decreasing the response and recovery times from 334.5 s to 172.3 s and from 219 s to 37.2 s, respectively. These improvements in gas sensing performance are due to the reduction in particle size and optical band gap, and an increase in specific surface area.

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A Cerium (IV) oxide nanoparticle (nanoceria) is widely used in different applications such as biomedicine and catalysis due to its unique structural, morphological and catalytic properties. In this report, the dispersion of nanoceria in both aqueous and non-aqueous (methanol and ethanol) media were studied. Adsorption-desorption processes were observed upon addition of different classes of surfactants such as citric acid (CA), cetrimonium bromide (CTAB) and diethanolamine (DEA). Stable dispersions were obtained in both aqueous, non-aqueous and electrolyte assisted media with the overall mechanism being hydrolysis, dissolution and adsorption. XRD, FE-SEM, FTIR and DLS have been used in the present study to characterize the nanoceria and to quantitatively analyze their average particle size distributions in a unique electrolyte mixture of (0.1 M NaOH/ 65% HNO3:H2O, 1:1 v/v) which has not been reported previously. The surface charge study was carried out across a wide pH range between 1.4 – 9.6 and the isoelectric points (IEP) with respect to 15 ml H2O and 50 ml H2O dispersed phases occurred at a pH of about 6.5 and 6.7 respectively. The present study could be useful in a wide range of applications including nanoparticle synthesis, stabilization, and adsorption of toxic materials, biomedical and pharmaceutical.

Aims: The aim of this study is to investigate the heavy metals pollution status and health risks assessment of the vegetables grown at Danbatta irrigation lands. Study Design: The research involved the collection of soil, water and cultivated vegetable from irrigation lands as well as analyzing their heavy metals pollution status. Place and Duration of Study: Samples were collected from Danbatta irrigation lands of Kano state, Nigeria. The research study covered a period of one year. Methodology: This study investigates the prevalence of heavy metals pollution and related health risks associated with the vegetables grown at Danbatta local government of Kano state. This was achieved by collecting irrigation soil, water and vegetables (onion, spinach and lettuce) from the irrigation sites, which were subsequently assayed for several heavy metals such as; Pb, Mn, Cu, Fe, Zn and Co using atomic absorption spectrophotometry (AAS). Results: The results obtained show that the concentrations of Pb, Cu and Zn in water samples to be 0.033, 0.8, and 0.89 mg/ml, respectively, while Mn and Co were not detected. Even though concentrations of these metals in water are within FAO/WHO limits, the soil was found to be contaminated with Cu (12.17 mg/kg), Fe (152.29 mg/kg) and Zn (55.75 mg/kg). Furthermore, both spinach, lettuce and onion were contaminated with Pb, and Mn. However, only lettuce and spinach were contaminated with Cu, Fe and Zn. Health risk assessment of both adults and children show that Pb, Mn, Co and Cu, posed a significant health risk to the population as their health risk index (HRI) is greater than one. The result shows that poor agricultural practices could be responsible for contaminating the soil with heavy metals, which eventually gets accumulated in the edible parts of the plants and posed a great risk to its consumers. Impacts of heavy metals pollution is on the rise across the globe. As such, it becomes necessary to monitor our environment to checkmate the threat of these contaminants and implement a reliable strategy and stable treatment of the pollution to ensure food safety.

ZnO has been widely explored as a remarkable photocatalyst for the degradation of wide ranges of organic pollutants. However, its photocatalytic activity could be enhanced through metal doping. In this study, a rare-earth element, Cerium was doped into the microstructure of ZnO nanoparticles (NPs) using deposition precipitation method to enhance its photocatalytic activity towards methylene blue degradation via UV light irradiation. The resulting degradation efficiencies (DEs) recorded in this study are ∼ 64 %, 85 % and 55 % respectively. Similarly, the recorded rates are also found to be 9 x 10 −3, 21 x10 −3 and 6 x 10 −3 respectively, which are well correlated with the DE values. This superior photocatalytic performance achieved by 1 % Ce doping could be attributed to the reduction in band gap of the pure ZnO NPs from 2.69 eV – 2.60 eV. Therefore, 1 % Ce was the optimum doping of Ce4+ ion into ZnO microstructure, which demonstrates that Ce4+ ion could be used as an effective tool for stabilizing the generation of the reactive oxygen species, slowing down the recombination of the photo-generated charge carriers as well as enhancing their separation. Therefore, the optimum Ce doping into the ZnO NPs could play a remarkable role in facilitating the structural, microstructural, optical and electronic properties of the ZnO semiconductor, and eventually enhanced its photocatalytic activity.