Improving Nonenzymatic Biosensing Performance of Electrospun Carbon Nanofibers decorated with Ni/Co Particles via Oxidation.

Nonenzymatic biosensors do not require enzyme immobilization nor face degradation problem. Hence, nonenzymatic biosensors have recently attracted growing attention due to the stability and reproducibility. Here, a comparative study was conducted to quantitatively evaluate the glucose sensing of pure/oxidized Ni, Co, and their bimetal nanostructures grown on electrospun carbon nanofibers (ECNFs) to provide a low-cost free-standing electrode. The prepared nanostructures exhibited sensitivity (from 66.28 to 610.6 µA mM-1 cm-2), linear range of 2-10 mM, limit of detection in the range of 1 mM, and the response time (< 5 s), besides outstanding selectivity and applicability for glucose detection in the human serum. Moreover, the oxidizable interfering species, such as ascorbic acid (AA), uric acid (UA), and dopamine (DA), did not cause interference. Co-C and Ni-C phase diagrams, solid-state diffusion phenomena, and rearrangement of dissolved C atoms after migration from metal particles were discussed. This study undoubtedly provides new prospects on the nonenzymatic biosensing performance of mono-metal, bimetal, and oxide compounds of Ni and Co elements, which could be quite helpful for the fabrication of biomolecules detecting devices.

Rheological Behavior and Filtration of Water-Based Drilling Fluids Containing Graphene Oxide: Experimental Measurement, Mechanistic Understanding, and Modeling.

Any improvement in drilling technology is critical for developing the oil and gas industry. The success of drilling operations largely depends on drilling fluid characteristics. Drilling fluids require enough viscosity to suspend the particles and transport them to the surface and enough capability to control the fluid loss into the formation. Rheology and filtration characteristics of drilling fluids are crucial factors to consider while ensuring the effectiveness of a drilling operation. Graphene oxide (GO), xanthan gum (XG), and low-viscosity carboxymethyl cellulose (CMC LV) are being utilized in this research to produce high-performance, low-solid water-based drilling fluids (WDFs). Rheological and filtration behaviors of GO/XG/CMC LV-WDF were investigated as a function of GO, XG, and CMC LV at low concentrations (0.0-0.3% w/w) and atmospheric conditions. According to the findings, GO improved the rheological and filtration capabilities of the WDF. By adding 0.15 wt % GO, shear stress could be doubled, especially at a high shear rate of 1022 s-1. The plastic viscosity of the fluid could be expanded from 6 to 13 centipoise, and a fluid loss of 8.7 mL over 30 min was observed during the API fluid test, which would be lower than the suggested fluid loss value (15.0 mL) for water-based mud. At the same concentration of XG and CMC LV, XG had a more significant influence on rheological characteristics in the presence of GO. Adding 0.3 wt % XG could increase fluid shear stress from 20.21 to 30.21 Pa at a high shear rate of 1022 s-1. In contrast, CMC LV had more impact on filtration properties, acting as a filtration control agent by decreasing the API fluid loss of fluid from 21.4 to 14.2 mL over 30 min. The addition of XG and CMC LV to the GO solution may influence the microstructure of the filter cake, resulting in a tree-root morphology. Indeed, in the GO/CMC LV solution, the individual platelets may bind together, form a jellyfish shape, and block the micropores. The incorporation of CMC LV helped develop compact filter cakes, resulting in excellent filtration. Five rheological models were employed to match the fluid parameters quantitatively. The Herschel-Bulkley model outperformed the other models in simulating fluid rheological behavior. The findings of this study can be utilize to provide low-cost, stable, and environmentally compatible additives for drilling low-pressure, depleted, and fractured oil and gas reservoirs.