ABSTRACT
2D transition metal dichalcogenides have performed exceptionally as the active layer for chemiresistive gas sensors. Combining these materials with semiconductor oxides of tunable properties has proved to improve gas sensing and overall device performance due to the synergizing effect of the hybrid nanostructures. In this manuscript, we report the synthesis of a Co3O4/MoS2 nanostructure-based highly sensitive chemiresistive gas sensor selective toward NOx gases. An increase in air pollution has caused an equal increase in the concentrations of toxic NOx gases in the atmosphere. Exposure to these gases leads to grave health hazards such as pulmonary diseases and cardiovascular diseases. Furthermore, recent studies prove that NOx gases are also a contributor to COVID-19 fatality. We investigated the effect of the change in precursor concentration of cobalt nitrate (CoN2O6) and temperature on the gas sensor response. The precursor concentration was varied over an increasing range of molarities (1, 5, 10, and 25 mM), and it was observed that the gas sensor with a precursor concentration of 25 mM and an operating temperature of 200 °C exhibited the highest response of 145.7% toward NO2 gas (4.3 ppm) and then 105.37% toward NO (2.75 ppm). It was also noted that the device responded to NO2 gas of concentration as low as 300 ppb. This device was then subjected to an increasing range of temperatures (50, 100, 150, 200, 250, and 300 °C). A clear increase in the device performance was observed with an increase in temperature. It was found that the gas sensor was the most sensitive toward NO2 gas (4.3 ppm) and exhibited a response of 186.2% at 250 °C followed by NO (2.75 ppm) with a response of 141.6%. A stable and excellent response toward a low concentration of 50 ppb of NO2 was observed. Two activation energies (Ea) were calculated from the Arrhenius plot Ea1 (0.846 eV) between 150 and 200 °C and Ea2 (1.316 eV) between 200 and 250 °C, indicating multiple energy trapping. These results pave a way for a plausible application of Co3O4/MoS2 hybrid nanostructures for the detection and monitoring of NOx gases in the air. ©
ABSTRACT
With the outbreak of the Coronavirus Disease-2019 (COVID-19) pandemic, it is not uncommon to see patients who present with respiratory symptoms secondary to an abdominal pathology, being suspected of having COVID-19. Here, authors report a case of an elderly female who presented with recent-onset dyspnoea, shortness of breath, pain abdomen and non passage of flatus and stools. Examination revealed that the patient had tachycardia, tachypnoea, and dyspnoea with an oxygen saturation (SpO(2)) of 92%. Her abdomen was distended, non tender with no free fluid detected. All the hernial orifices were free. Computed Tomography (CT) scan revealed a left diaphragmatic hernia and a left-sided obturator hernia with obstructed ileal segment. However, intraoperatively a Type IV hiatus hernia was discovered, where the Gastrooesophageal (GE) junction, stomach, colon, and omentum were the contents. This case highlights an unusual clinical presentation of a rare cause of intestinal obstruction and its management during the COVID-19 pandemic. Obstructed obturator hernia is associated with high morbidity and mortality.