Recent Trends in the Improvement of the Electrochemical Response of Screen-Printed Electrodes by Their Modification with Shaped Metal Nanoparticles

Novel sensing technologies proposed must fulfill the demands of wastewater treatment plants, the food industry, and environmental control agencies: simple, fast, inexpensive, and reliable methodologies for onsite screening, monitoring, and analysis. These represent alternatives to conventional analytical methods (ICP-MS and LC-MS) that require expensive and non-portable instrumentation. This needs to be controlled by qualified technicians, resulting moreover in a long delay between sampling and high-cost analysis. Electrochemical analysis based on screen-printed electrodes (SPEs) represents an excellent miniaturized and portable alternative due to their disposable character, good reproducibility, and low-cost commercial availability. SPEs application is widely extended, which makes it important to design functionalization strategies to improve their analytical response. In this sense, different types of nanoparticles (NPs) have been used to enhance the electrochemical features of SPEs. NPs size (1–100 nm) provides them with unique optical, mechanical, electrical, and chemical properties that give the modified SPEs increased electrode surface area, increased mass-transport rate, and faster electron transfer. Recent progress in nanoscale material science has led to the creation of reproducible, customizable, and simple synthetic procedures to obtain a wide variety of shaped NPs. This mini-review attempts to present an overview of the enhancement of the electrochemical response of SPEs when NPs with different morphologies are used for their surface modification

Irreversibility analysis in dissipative magnetohydromagnetic flow of non-Newtonian nanomaterials

The theme of this article is to scrutinize the entropy rate in hydromagnetic flow of Reiner–Philippoff nanofluid by a stretching surface. Energy equation is developed through first law of thermodynamic with dissipation and Joule heating. Furthermore, random and thermophoretic motion is discussed. Additionally, binary reaction is discussed. Physical feature of irreversibility analysis is discussed. Nonlinear expression is obtained by suitable transformation. The obtained systems are solved through the numerical method (bvp4c). Variation of entropy rate, thermal field, velocity profile, and concentration against sundry variables are discussed. Computational outcomes of thermal and mass transport rate for influential parameters are studied in tabularized form. A reverse effect holds for thermal field and velocity through magnetic variable. Higher Bingham number leads to a rise in velocity field. An intensification in thermal field and concentration is noted for thermophoretic variable. An enhancement in fluid variable leads to augments velocity. An increment in entropy analysis is seen for magnetic effect. Larger estimation of diffusion variable improves entropy rate. A reduction in concentration is noticed for reaction variable.

Heat and mass transport investigation in radiative and chemically reacting fluid over a differentially heated surface and internal heating

The aim of this study is to investigate the heat and mass transport over a stretchable surface. The analysis is prolonged to the concept of thermal radiations and chemical reaction over a differentially heated surface with internal heating. This is significant from an engineering and industrial point of view. The nonlinear model is successfully attained by adopting the similarity transforms and then further computation is done via a hybrid Runge–Kutta algorithm coupled with shooting technique. The behavior of fluid velocity and heat and mass transport are then furnished graphically for feasible ranges of parameters. A comprehensive discussion of the results is provided against multiple parameters. Foremost, the local thermal performance and mass transport rate are explained via numerical computation. The major outcomes of the study are described in the end.

Experimental Investigation and CFD Modeling of Supercritical Adsorption Process

The kinetics of the supercritical adsorption process was experimentally studied by the example of ”ibuprofen-silica aerogel” composition obtainment at various parameters: Pressure 120–200 bar and temperature 40–60 °C. Computational Fluid Dynamics (CFD) model of the supercritical adsorption process in a high-pressure apparatus based on the provisions of continuum mechanics is proposed. Using supercritical adsorption process kinetics experimental data, the dependences of the effective diffusion coefficient of active substance in the aerogel, and the maximum amount of the adsorbed active substance into the aerogel on temperature and pressure are revealed. Adequacy of the proposed model is confirmed. The proposed mathematical model allows predicting the behavior of system (fields of velocity, temperature, pressure, composition, density, etc.) at each point of the studied medium. It makes possible to predict mass transport rate of the active substance inside the porous body depending on the geometry of the apparatus, structure of flow, temperature, and pressure.

Numerical Investigation of Heat and Mass Transport in the Flow over a Magnetized Wedge by Incorporating the Effects of Cross-Diffusion Gradients: Applications in Multiple Engineering Systems

The flow over a wedge is significant and frequently occurs in civil engineering. It is significant to investigate the heat and mass transport characteristics in the wedge flow. Therefore, the analysis is presented to examine the effects of preeminent parameters by incorporating the cross-diffusion gradients in the energy and mass constitutive relations. From the analysis, it is perceived that the temperature drops against a higher Prandtl number. Due to concentration gradients in the energy equation, the temperature rises slowly. Moreover, it is examined that the mass transfer significantly reduces due to Schmidt effects and more mass transfer is pointed against the Soret number. The shear stresses increase due to stronger magnetic field effects. The local thermal performance of the fluid enhances against more dissipative fluid, and DuFour effects reduced it. Furthermore, the mass transport rate drops due to higher Soret effects and increases against multiple Schmidt number values.

Quantifying Joule Heating and Mass Transport in Metal Nanowires During Controlled Electromigration

The nanoscale heat dissipation (Joule heating) and mass transport during electromigration (EM) have attracted considerable attention in recent years. Here, the EM-driven movement of voids in gold (Au) nanowires of different shapes (width range: 50–300 nm) was directly observed by performing atomic force microscopy. Using the data, we determined the average mass transport rate to be 105 to 106 atoms/s. We investigated the heat dissipation in L-shaped, straight-shaped, and bowtie-shaped nanowires. The maximum Joule heating power of the straight-shaped nanowires was three times that of the bowtie-shaped nanowires, indicating that EM in the latter can be triggered by lower power. Based on the power dissipated by the nanowires, the local temperature during EM was estimated. Both the local temperature and junction voltage of the bowtie-shaped nanowires increased with the decrease in the Joule heating power and current, while the current density remained in the order of 108 A/cm2. The straight-shaped nanowires exhibited the same tendency. The local temperature at each feedback point could be simply estimated using the diffusive heat transport relationship. These results suggest that the EM-driven mass transport can be controlled at temperatures much lower than the melting point of Au.

Plume dynamics in Hele-Shaw porous media convection

Mass transport in multi-species porous media is through molecular diffusion and plume dynamics. Predicting the rate of mass transport has application in determining the efficiency of the storage and sequestration of carbon dioxide. We study a water and propylene–glycol system enclosed in a Hele-Shaw cell with variable permeability that represents a laboratory analogue of the general properties of porous media convection. The interface between the fluids, tracked using an optical shadowgraph technique, is used to determine the mass transport rate, the spatial separation of solutal plumes, and the velocity and width characteristics of those plumes. One finds that the plume dynamics are closely related to the mass transport rate. This article is part of the themed issue ‘Energy and the subsurface’.

Cytotoxicity of Ferulic Acid on T24 Cell Line Differentiated by Different Microenvironments

Ferulic acid (4-hydroxy-3-methoxycinnamic acid) (FA) is a ubiquitous health beneficial phenolic acid. Although FA has shown a diversity of biological activities including anti-inflammatory, antihypercholesterolemic and anticancer bioactivities, studies revealing its adverse effects are accumulating. Recently, 3D-cultures are shown to exhibit uniquely biological behaviors different from that of 2D cultures. To understand whether the cytotoxicity of FA against the T24 cell line (a bladder cancer cell line) in 2D-culture could consistently retain similar bioactivity if cultured in the 3D-systems, we conducted this experiment with 2 mM FA. Much higher cytotoxicity was found for 3D- than 2D-culture, showing (2D vs. 3D): apoptotic rates, 64% and 76%; cell killing rates,3.00×105 cells mmol−1·h−1and2.63×106cells mmol−1·h−1, attaining a 8.77-fold. FA upregulated the activities at 72 h (2D vs. 3D in folds that of control): SOD, 1.73-folds (P<0.05) versus 3.18 folds (P<0.001); and catalase, 2.58 versus 1.33-folds. Comparing to the control (without FA), Bcl-2 was prominently downregulated while Bax, caspase-3 and cleaved caspase-9 were more upregulated in 3D-cultures (P<0.05). Conclusively, different microenvironments could elicit different biological significance which in part can be ascribed to different mass transport rate.

Laser CVD of Filaments

Lasers have been used to chemically vapor deposit materials since the 1970’s. The fine focus achievable with the laser beam allows deposition to be carried out on a substrate much like hand-writing. The formation of a filament simply requires moving the filament to keep the laser beam focused on or near the depositing tip of the filament. Deposition rates can be very rapid because of the high mass transport rate that can be achieved, although the total mass deposited is low. Multiple beams can be used to increase the number of filaments being formed, but the high deposition rate would be sacrificed somewhat. However, the process is attractive for producing small amounts of new high temperature materials in the easily tested filament form. The process is also amenable to easily making more complicated shapes such as coils that could be used for heating or other applications. Deposition kinetics are different for cases where deposition is from the original deposition molecule or early formed fragment, compared to intermediates formed by subsequent gas phase reactions.