Co3O4/TiO2 hetero-structure for methyl orange dye degradation.

Advanced oxidation processes based on sulphate radical generated by peroxymonosulphate (PMS) activation is a promising area for environmental remediation. One of the biggest drawbacks of heterogeneous PMS activation is catalyst instability and metal ion leaching. In this study, a simple organic binder mediated route was explored to substitute Ti4+ ions into the Co3O4 host lattice structure to create a Co-O-Ti bond to minimise cobalt leaching during methyl orange degradation. The catalyst was characterised by X-ray diffraction, and scanning and transmission electron microscopy. The as-prepared catalysts with Co3O4:TiO2 ratio of 70:30 exhibited minimal leaching (0.9 mg/L) compared to other ratios studied. However, the pristine Co3O4 exhibited highest catalytic activity (rate constant = 0.41 min-1) and leaching (26.7 mg/L) compared to composite material (70:30 Co3O4:TiO2). Interestingly, the morphology of the composite and leaching of Co2+ ions were found to be temperature dependent, as an optimum temperature ensured strong Co-O-Ti bond for prevention of Co2+ leaching. The classical quenching test was utilised to determine the presence and role of radical species on methyl orange degradation. The fabricated catalyst also exhibited good catalytic activity in degrading mixed dyes and good recyclability, making it a potential candidate for commercial application.

An in ovo investigation into the hepatotoxicity of cadmium and chromium evaluated with light- and transmission electron microscopy and electron energy-loss spectroscopy.

Excessive agriculture, transport and mining often lead to the contamination of valuable water resources. Communities using this water for drinking, washing, bathing and the irrigation of crops are continuously being exposed to these heavy metals. The most vulnerable is the developing fetus. Cadmium (Cd) and chrome (Cr) were identified as two of the most prevalent heavy metal water contaminants in South Africa. In this study, chicken embryos at the stage of early organogenesis were exposed to a single dosage of 0.430 µM physiological dosage (PD) and 430 µM (×1000 PD) CdCl2, as well as 0.476 µM (PD) and 746 µM (×1000 PD) K2Cr2O7. At day 14, when all organ systems were completely developed, the embryos were terminated and the effect of these metals on liver tissue and cellular morphology was determined with light- and transmission electron microscopy (TEM). The intracellular localization of these metals was determined using electron energy-loss spectroscopy (EELS). With light microscopy, the PD of both Cd and Cr had no effect on liver tissue or cellular morphology. At ×1000 PD both Cd and Cr caused sinusoid dilation and tissue necrosis. With TEM analysis, Cd exposed hepatocytes presented with irregular chromatin condensation, ruptured cellular membranes and damaged or absent organelles. In contrast Cr caused only slight mitochondrial damage. EELS revealed the bio-accumulation of Cd and Cr along the cristae of the mitochondria and chromatin of the nuclei.

Preparation of biological monolayers for producing high-resolution scanning electron micrographs.

Scanning electron microscopy (SEM) provides a technical platform for nanoscopic mapping of biological structures. Correct preparation of SEM samples can provide an unprecedented understanding of the nexus between cellular morphology and topography. This comparative study critically examines two coating methods for preparing biological samples for scanning electron microscopy, while also providing novel advice on how to prepare in vitro epithelial or endothelial samples for high-resolution scanning-electron microscopy (HR-SEM). Two obstacles often confront the biologist when investigating cellular structures grown under tissue culture conditions, namely., how to prepare and present the biological samples to the HR-SEM microscope without affecting topographical membrane and cellular structural alterations. Firstly, our use of the Millicell cellulose inserts on which to grow our cellular samples in preparation for HR-SEM is both novel and advantageous to comparing the permeability function of cells to their morphological function. Secondly, biological material is often non-conducting, thermally sensitive and fragile and, therefore, needs to be fixed correctly and coated with thin conducting metal to ensure high-resolution detail of samples. Immortalized mouse brain endothelial cells (bEnd5) was used as a basis for describing the preferences in the use of the protocol. We compare two biological sample coating modalities for the visualizing and analysis of texturized, topographical, membranous ultrastructures of brain endothelial cell (BEC) confluent monolayers, namely, carbon and gold:palladium (Au:Pd) sputter coating in preparation for HR-SEM. BEC monolayers sputter-coated with these two modalities produced three-dimensional micrographs which have distinctly different topographical detail from which the nanostructural cellular data can be examined. The two coating methods display differences in the amount of nanoscopic detail that could be resolved in the nanosized membrane cytoarchitecture of BEC monolayers. The micrographical data clearly showed that Au:Pd sputter-coated samples generate descript imagery, providing useful information for profiling membrane nanostructures compared to carbon-coated samples. The recommendations regarding the contrast in two modalities would provide the necessary guidance to biological microscopists in preparing tissue culture samples for HR-SEM.

Chemical Vapor Deposited Mixed Metal Halide Perovskite Thin Films.

In this article, we used a two-step chemical vapor deposition (CVD) method to synthesize methylammonium lead-tin triiodide perovskite films, MAPb1-xSnxI3, with x varying from 0 to 1. We successfully controlled the concentration of Sn in the perovskite films and used Rutherford backscattering spectroscopy (RBS) to quantify the composition of the precursor films for conversion into perovskite films. According to the RBS results, increasing the SnCl2 source amount in the reaction chamber translate into an increase in Sn concentration in the films. The crystal structure and the optical properties of perovskite films were examined by X-ray diffraction (XRD) and UV-Vis spectrometry. All the perovskite films depicted similar XRD patterns corresponding to a tetragonal structure with I4cm space group despite the precursor films having different crystal structures. The increasing concentration of Sn in the perovskite films linearly decreased the unit volume from about 988.4 Å3 for MAPbI3 to about 983.3 Å3 for MAPb0.39Sn0.61I3, which consequently influenced the optical properties of the films manifested by the decrease in energy bandgap (Eg) and an increase in the disorder in the band gap. The SEM micrographs depicted improvements in the grain size (0.3-1 µm) and surface coverage of the perovskite films compared with the precursor films.

Dataset of N-doped CuO:NiO mixed oxide thin film sensor for glucose oxidation.

In this data in brief article dataset of plasma-assisted nitrogen doping of a binderless, spin-coated CuO-NiO mixed oxide thin film was presented (Palmer et al., 2020). A comparison of the CuO, N-CuO/Cu2O, CuO:NiO and N-CuO/Cu2O:NiO are presented. The as prepared films were used for the application of a glucose sensor. The nitrogen doped species, generated during plasma ignition, resulted in a beneficial phase transformation of CuO to Cu2O. Characterisation techniques such as XPS, particle size distribution and EIS techniques were utilized to study the morphology, structural features, doping profile and electrical properties of the various developed electrodes. The electrochemical performance of the thin film sensors was tested using cyclic voltammetry and chronoamperometry. The CuO exhibited a sensitivity of 830 µA/mM cm2 up to 1.65 mM of glucose, N-CuO/Cu2O had a linear range up to 1.91 mM with a sensitivity of 873 µA/mM cm2 and the CuO:NiO electrode had a linear range up to 1.65 mM with a sensitivity of 1103 µA/mM.cm2 respectively. A detailed description of the methodology used is provided below.

Effects of metals cadmium and chromium alone and in combination on the liver and kidney tissue of male Spraque-Dawley rats: An ultrastructural and electron-energy-loss spectroscopy investigation.

Heavy metal pollution has increased in the last decades. Water sources are contaminated and human exposure is often long term exposure to variable amounts of different metals. In this study, male Sprague-Dawley rats were exposed via oral gavage for 28 days to cadmium (Cd) and chromium (Cr), alone and in combination at concentrations 1000 times the human World Health Organization's acceptable water limits. Rat equivalent dosages were used. Blood markers of liver and kidney function were measured, changes to cellular morphology was determined with transmission electron microscopy and the intracellular metal localisation was determined with the electron energy-loss spectroscopy and energy filtered transmission electron microscopy analysis. Both Cd and Cr caused changes to the nuclear and mitochondrial membranes and irregular chromatin condensation of hepatocytes. Cr exposure caused dilation of the rough endoplasmic reticulum (rER). The combination caused nuclear and mitochondrial membrane damage as well as irregular chromatin condensation. In the kidney tissue, Cd caused irregular chromatin condensation in the cells of the proximal convoluted tubule (PCT). Cr caused changes to the outer nuclear and mitochondrial membrane and chromatin structure. The combination group caused membrane damage, irregular chromatin condensation and rER changes in the PCT. All the metal groups showed damage to the endothelial cells and pedicles, but not to the mesangial cells. Cd and Cr bio-accumulation was observed in the nucleus, mitochondria and rER of the liver and kidney and therefore are responsible for the cellular observed damage that can cause functional changes to the tissues and organs.

Insight on the silver catalyst distribution during silicon nanowire array formation: an X-ray reflectivity study.

Although metal-catalysts are commonly used to create nanoscale materials at surfaces, little is quantitatively known or understood about the depth distribution profile of the catalyst during the growth process. Using X-ray reflectivity, we report the first quantitative investigation, with nanoscale resolution, of the Ag metal-catalyst depth distribution profile during metal-assisted chemical etch (MACE) growth of Si nanowire (SiNW) arrays on Si(100). Given the very low optical reflectivity of these nanowire arrays, specular reflection from these materials in the X-ray region is extremely challenging to measure because it probes interfaces on the nanoscale. Nevertheless, we demonstrate that with suitable investigation, X-ray specular reflection can be measured and utilized to obtain unique structural information about the composition profile of both Ag and Si. The measurements, which also include X-ray diffraction and complementary electron microscopy, reveal that the Ag nanoparticles distribute along the length of the nanowires upon etching with a Ag density that increases towards the etch front. The Ag nanoparticles coarsen with etch time, indicating a high mobility of Ag ions even though we also find that the Ag does not migrate from the SiNW region into the etch bath during etching. The Ag density gradient and the Ag mobility suggest the existence of a strong chemical force that attracts Ag towards the etch front. These results provide unique and important new insight into the growth process for creating SiNWs from wet chemical etching using metal-catalysts.

Ultra-sensitive and selective NH3 room temperature gas sensing induced by manganese-doped titanium dioxide nanoparticles.

The study of the fabrication of ultra-high sensitive and selective room temperature ammonia (NH3) and nitrogen dioxide (NO2) gas sensors remains an important scientific challenge in the gas sensing field. This is motivated by their harmful impact on the human health and environment. Therefore, herein, we report for the first time on the gas sensing properties of TiO2 nanoparticles doped with various concentrations of manganese (Mn) (1.0, 1.5, 2.0, 2.5 and 3.0mol.% presented as S1, S2, S3, S4 and S5, respectively), synthesized using hydrothermal method. Structural analyses showed that both undoped and Mn-doped TiO2 crystallized in tetragonal phases. Optical studies revealed that the Mn doped TiO2 nanoparticles have enhanced UV→Vis emission with a broad shoulder at 540nm, signifying induced defects by substituting Ti4+ ions with Mn2+. The X-ray photoelectron spectroscopy and the electron paramagnetic resonance studies revealed the presence of Ti3+ and singly ionized oxygen vacancies in both pure and Mn doped TiO2 nanoparticles. Additionally, a hyperfine split due to Mn2+ ferromagnetic ordering was observed, confirming incorporation of Mn ions into the lattice sites. The sensitivity, selectivity, operating temperature, and response-recovery times were thoroughly evaluated according to the alteration in the materials electrical resistance in the presence of the target gases. Gas sensing studies showed that Mn2+ doped on the TiO2 surface improved the NH3 sensing performance in terms of response, sensitivity and selectivity. The S1 sensing material revealed higher sensitivity of 127.39 at 20 ppm NH3 gas. The sensing mechanism towards NH3 gas is also proposed.

Synthetic Hemozoin (ß-Hematin) Crystals Nucleate at the Surface of Neutral Lipid Droplets that Control Their Sizes.

Emulsions of monopalmitoylglycerol (MPG) and of a neutral lipid blend (NLB), consisting of MPG, monostearoylglycerol, dipalmitoylglycerol, dioleoylglycerol and dilineoylglycerol (4:2:1:1:1), the composition associated with hemozoin from the malaria parasite Plasmodium falciparum, have been used to mediate the formation of ß-hematin microcrystals. Transmission electron microscopy (TEM), electron diffraction and electron spectroscopic imaging/electron energy loss spectroscopy (ESI/EELS) have been used to characterize both the lipid emulsion and ß-hematin crystals. The latter have been compared with ß-hematin formed at a pentanol/aqueous interface and with hemozoin both within P. falciparum parasites and extracted from the parasites. When lipid and ferriprotoporphyrin IX solutions in 1:9 v/v acetone/methanol were thoroughly pre-mixed either using an extruder or ultrasound, ß-hematin crystals were found formed in intimate association with the lipid droplets. These crystals resembled hemozoin crystals, with prominent {100} faces. Lattice fringes in TEM indicated that these faces made contact with the lipid surface. The average length of these crystals was 0.62 times the average diameter of NLB droplets and their size distributions were statistically equivalent after 10 min incubation, suggesting that the lipid droplets also controlled the sizes of the crystals. This most closely resembles hemozoin formation in the helminth worm Schistosoma mansoni, while in P. falciparum, crystal formation appears to be associated with the much more gently curved digestive vacuole membrane which apparently leads to formation of much larger hemozoin crystals, similar to those formed at the flat pentanol-water interface.