Transfer Diffusion Coefficient Research Articles

Voltammetric and electro-kinetic assessment of prucalopride at MnO2-rGO fabricated pencil graphite electrode

Development and design of rGO-based nanocomposite-modified carbon-based electrodes are necessary to enhance the selectivity and desired selectivity of the voltammetric sensors. In this work, a manganese dioxide-reduced graphene oxide (MnO2-rGO) fabricated pencil graphite electrode is described for the detection of prucalopride (PRU), which is used to treat chronic idiopathic constipation. A simple cost effective hydrothermal method was used to synthesize the needle-shaped MnO2. The MnO2-rGO nanocomposite was characterized using XRD, SEM, and FTIR spectroscopy to examine its microstructure and morphology. The results revealed that MnO2 needles are distributed on the flakes of the rGO, thereby enhancing the electro-catalytic activity of MnO2-rGO/PGE. The electrochemical performance of the developed MnO2-rGO/PGE was examined using CV, chronocoulometry, SWSV, and DPSV methods. The diffusion-controlled oxidation of the PRU at the MnO2-rGO/PGE produces an irreversible peak in all the voltammograms which were used to calculate several electro-kinetic parameters like electron transfer coefficient (α = 0.598), diffusion coefficient (Do = 1.62 × 10−5 cm2s−1), surface coverage (Γo = 1.55 × 10−9 molcm−2), and effective surface area. Furthermore, advanced SWSV and DPSV methods are proposed for the accurate, selective, and sensitive detection of the PRU in pharmaceutical samples. The reported values of detection limit (LOD) for the proposed SWSV and DPSV methods are 20.39 μM and 14.53 μM, respectively, which make them eco-friendly and affordable alternative tools for the quantification of the PRU in pharmaceutical samples.

Improving CO2 adsorption efficiency of an amine-modified MOF-808 through the synthesis of its graphene oxide composites

This research developed a novel composite of MOF-NH2 and graphene oxide (GO) for enhanced CO2 capture. Employing the response surface methodology-central composite design (RSM-CCD) for experiments design, various MOF-NH2/GO samples with GO loadings from 0 to 30 wt% were synthesized. The results of SEM, XRD, EDS, and BET analysis revealed that the materials maintained their MOF crystal structure, confirmed by X-ray diffraction, and exhibited unique texture, high porosity, and oxygen-enriched surface chemistry. The influence of temperature (25–65 °C) and pressure (1–9 bar) on CO2 adsorption capacity was assessed using a volumetric adsorption system. Optimum conditions were obtained at weight percent of 22.6 wt% GO, temperature of 25 °C, and pressure of 9 bar with maximum adsorption capacity of 303.61 mg/g. The incorporation of amino groups enhanced the CO2 adsorption capacity. Isotherm and kinetic analyses indicated that Freundlich and Fractional-order models best described CO2 adsorption behavior. Thermodynamic analysis showed the process was exothermic, spontaneous, and physical, with enthalpy changes of − 16.905 kJ/mol, entropy changes of − 0.030 kJ/mol K, and Gibs changes energy of − 7.904 kJ/mol. Mass transfer diffusion coefficients increased with higher GO loadings. Regenerability tests demonstrated high performance and resilience, with only a 5.79% decrease in efficiency after fifteen cycles. These findings suggest significant potential for these composites in CO2 capture technologies.

Electrochemical Charge Transfer Kinetics of Ferrocene in the Light of Different Working Electrodes.

Ferrocene is an accidentally discovered organometallic compound that serves as a crucial redox probe in investigating electrochemical charge transfer dynamics. Besides solution phase studies, ferrocene derivatives are well-explored in molecular thin films, including self-assembled monolayers on various electrodes for understanding on-surface redox behavior, and in molecular electronics, and charge storage applications. Heterogeneous charge transfer is an imperative parameter for efficient charge transport in spin-dependent electrochemistry, photoelectrochemistry, and molecular electronic devices. In this work, we aim to study the electrochemical charge transfer of ferrocene on various electrodes such as commercially obtained glassy carbon, graphite rod, indium tin oxide (ITO), and as-prepared gold, and nickel to determine the impact of the nature of the working electrode on the electron transfer rate, diffusion coefficient, and reversibility of the redox process. Both the direct current and alternating current-based electrochemical experiments are performed, followed by digitization of the experimental results. The kinetics of electron transfer and electrochemical reversibility reveal a strong dependence on the nature of the working electrode, as the electrochemically driven oxidation and reduction of the material of interest are directly related to the Fermi energy and electronic structure of the working electrode.

Visible Light as a Promising Signal Amplification Tool for the Efficient Electrochemical Detection of Azithromycin Antibiotic by Using Photoactive Spinel Nickel Ferrite Nanoflakes

An efficient photoactive spinel NiFe2O4 nanoflakes (NFO NFs) was successfully prepared and integrated into an electrochemical sensor for the sensitive determination of Azithromycin (AZM) under visible light illumination. With the introduction of 532 nm laser illumination, NFO NFs could be easily excited and induce the charge-separation state with electrons in the conduction band and holes in the valence band. Upon illumination, the low band gap value in combination with edge-to-flat-surface/edge-to-edge conjunctions of NFO NFs could form the electron transfer pathway for transferring photogenerated electron-hole pairs to the AZM analyte-NFO electrode interface. Hence, the fabricated visible light-assisted NFO-based electrochemical sensor shows remarkable enhanced analytical performance, with calculated values of electron transfer rate constant, adsorption capacity, diffusion coefficient, and catalytic rate constant under visible light illumination of 1.29, 1.27, 2.08, and 3.40 times higher than in the dark condition, respectively. As a result, the NFO-based electrochemical sensing platform in the presence of visible light illumination possessed a high electrochemical sensitivity of 0.070 μA μM−1 in a wide linear dynamic range of 2.5–150 μM and a detection limit of 1.67 μM and also exhibited excellent anti-interference ability, repeatability, storage stability, reproducibility, and practical feasibility for AZM detection in pharmaceutical tablets.

Comparison of Different Electrochemical Methodologies for Electrode Reactions: A Case Study of Paracetamol

Understanding electrochemical reactions at the surface of electrodes requires the accurate calculation of key parameters—the transfer coefficient (α), diffusion coefficient (D0), and heterogeneous electron transfer rate constant (k0). The choice of method to calculate these parameters requires careful consideration based on the nature of the electrochemical reaction. In this study, we conducted the cyclic voltammetry of paracetamol to calculate the values of these parameters using different methods and present a comparative analysis. Our results demonstrate that the Ep − Ep/2 equation for α and the modified Randles–Ševčík equation for D0 is particularly effective for the calculations of these two parameters. The Kochi and Gileadi methods are reliable alternatives for the calculation of k0. Nicholson and Shain’s method using the equation k0 = Ψ(πnD0Fν/RT)1/2 gives the overestimated values of k0. However, the value of k0 calculated using the plot of ν−1/2 versus Ψ (from the Nicholson and Shain equation, where ν is scan rate) agrees well with the values calculated from the Kochi and Gilaedi methods. This study not only identifies optimal methodologies for quasi-reversible reactions but also contributes to a deeper understanding of electrochemical reactions involving complex electron transfer and coupled chemical reactions, which can be broadly applicable in various electrochemical studies.

Precise analyses of photoelectrochemical reactions on particulate Zn0.25Cd0.75Se photoanodes in nonaqueous electrolytes using Ru bipyridyl complexes as a probe.

Recombination of photoexcited carriers at interface states is generally believed to strongly govern the photoelectrochemical (PEC) performance of semiconductors in electrolytes. Sacrificial reagents (e.g., methanol or Na2SO3) are often used to assess the ideal PEC performance of photoanodes in cases of minimised interfacial recombination kinetics as well as accelerated surface reaction kinetics. However, varying the sacrificial reagents in the electrolyte means simultaneously changing the equilibrium potential and the number of electrons required to perform the sacrificial reaction, and thus the thermodynamic and kinetic aspects of the PEC reactions cannot be distinguished. In the present study, we propose an alternative methodology to experimentally evaluate the energy levels of interfacial recombination centres that can reduce PEC performance. We prepare nonaqueous electrolytes containing three different Ru complexes with different bipyridyl ligands; redox reactions of Ru complexes represent one-electron processes with similar charge transfer rates and diffusion coefficients. Therefore, the Ru complexes can serve as a probe to isolate and evaluate only the thermodynamic aspects of PEC reactions. Recombination centres at the interface between a nonaqueous electrolyte and a Zn0.25Cd0.75Se particulate photoanode are elucidated using this method as a model case. The energy level at which photocorrosion proceeds is also determined.

Nitrogen Defect-Rich Graphitic Carbon Nitride for Highly Sensitive Voltammetric Determination of Tryptophan.

Here, a highly sensitive electrochemical sensor for detection of tryptophan (Trp) using a nitrogen defect graphitic carbon nitride-modified glassy carbon electrode (ND-CN/GCE) was introduced. ND-CN/GCE showed a higher oxidation current for Trp than the graphitic carbon nitride-modified glassy carbon electrode (g-CN/GCE) and bare glassy carbon electrode (BGCE). The synthesized nitrogen defect-rich graphitic carbon nitride (ND-CN) was characterized using X-ray photoelectron spectroscopy, X-ray diffraction spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. Electrochemical impedance spectroscopy and cyclic voltammetry were used to further analyze the electrochemical properties of BGCE, g-CN/GCE, and ND-CN/GCE. The oxidation of Trp at ND-CN/GCE is a diffusion-controlled process at pH 3.0. It was calculated that the transfer coefficient, rate constant, and diffusion coefficient of Trp were 0.53, 2.24 × 103 M-1 s-1, and 8.3 × 10-3 cm2 s-1, respectively, at ND-CN/GCE. Trp was detected using square wave voltammetry, which had a linear range from 0.01 to 40 μM at pH 3.0 and a limit of detection of about 0.0034 μM (3σ/m). Analyzing the presence of Trp in a milk and multivitamin tablet sample with a percentage recovery in the range of 97.0-108% satisfactorily demonstrated the practical usability of the electrochemical sensor. The ND-CN/GCE additionally displays good repeatability and reproducibility and satisfactory selectivity.

Effects of uniaxial tensile strain on the release of small molecules from silicone rubber

AbstractSilicone rubber materials may be subject to mechanical strains which can affect the transport properties of small molecules loaded in the materials such as plasticizers and active molecules, hence deteriorating their intended mechanical properties or affecting their performance as carriers of active molecules. Therefore, it is important to understand the effects of mechanical strains on transport of small molecules in the silicone rubber matrix. In this work, silicone rubber sheets loaded with 2 wt% triacetin were stretched and held at four different lengths up to 125% engineering strain. The mass transfer coefficients and diffusion coefficients of triacetin in the strained silicone rubber were determined by monitoring the release of triacetin using headspace gas chromatography–mass spectrometry. It was found that there was no significant change of diffusion coefficient as the applied strain increased, which might result from two microstructure changes that had conflicting effects on diffusion: chain orientation and free volume deformation.

Temperature instantaneous online monitoring methods of thermal runaway based on electrode process principle

With the properties of suitable operating voltage, high energy density and stable structure, sodium-ion batteries are widely used in energy storage systems as the most promising alternative to lithium-ion batteries. However, the thermal runaway of sodium ion battery has occurred easily, which poses a great threat to the whole safety system of battery. This paper discusses a method to predict and prevent thermal runaway of sodium-ion batteries by measuring electrochemical impedance of battery. Based on the electrode material with the role of temperature control detector, the working temperature inside the battery can be directly reflected and monitored in real time, and the method is not only simple, fast, accurate, efficient, but also low-cost, which can achieve real-time on-line monitoring of the temperature inside the battery. In this work, using the sodium-ion batteries for study, it has been found that the charge transfer resistance (Rct), peak current (Ip), diffusion coefficient (D0) and cell internal temperature rare the key factors in battery effeciency. Therefore, the corresponding functional relationship can be established to effectively control the normal operation of the battery by exploring instantaneous detection of temperature sensitive electrochemical parameters, and timely disposes the battery with abnormal temperature to avoid the thermal runaway.

Modeling and thermodynamic analysis of the hydration and germination of triticale seeds

We investigated the hydration and germination of triticale seeds to improve process efficiency and product quality. The grains were hydrated in a water bath at 20–50 °C for 15 h. Temperatures of 20 °C–30 °C and process times as of 660 min provided the best hydration rates without hindering the germination capacity of the seeds. Throughout processing, we monitored the moisture uptake and volumetric expansion of the samples by gravimetric methods. A tracer pigment added to the hydration water and the images obtained with scaning electron microscopy elucidated the mechanisms of moisture uptake throughout the grains. The water penetrated the grain primarily through the micropyle, a region of high porosity. The mass transfer (diffusion coefficient) and thermodynamic properties (enthalpy, entropy, and Gibbs free energy) indicated the process is non-spontaneous and endothermic. Such piece of information is helpful in equipment design. We also proposed mathematical models, based on Fick's Law of Diffusion, that predict the moisture content of cereal seeds hydrated at 20–50 °C for up to 15 h with great accuracy (P ≤ 3.36% and RMSE≤1.54%).

Effects of carbon to nitrogen ratio on oxygen mass transfer characteristics in wastewater and biofilms

Systematic elucidation of the oxygen mass transfer (OMT) mechanism is the key to improving aeration and oxygenation efficiency. In this study, an aerobic fluidized bed biofilm reactor (AFBBR) was established to evaluate the OMT in the wastewater phase [macroscopic (reactor) scale] and diffusion kinetic parameters in the biofilm phase (microbiological scale) under different carbon-nitrogen(C:N) ratios. A model relating the oxygen concentration and the aerobic layer thickness of the biofilm was established based on oxygen mass balance theory and Fick's second law. The results showed that the average DO concentration decreased from 7.68 mg/L to 5.85 mg/L with increasing C:N ratio (from 4.79 to 13.94). The oxygen transfer rate (OTR) was consistent with the distribution of the total biomass (total suspended solids, TSS), which was the largest (9.74 ± 0.33 mg/(L·h) and 8178 ± 87 mg/L) under the highest C:N ratio (13.94). Additionally, the α-factor, as a key parameter for evaluating OMT efficiency, had an exponential correlation with chemical oxygen demand (CODcr). The oxygen concentration exhibited in a Gaussian distribution (0.9963 ≤R2 ≤0.9998) relative to the thickness of the aerobic layer. The mass transfer efficiency (ki) and diffusion coefficient (Di) of oxygen in the boundary layer both reached maxima [(8.1 ± 3.2)× 10−5 cm2/s and (2.0 ± 0.1)× 10−3 cm/s] under the condition of C:N = 9.49. However, under the lowest C:N ratio, the biofilm thickness (LF=2422 ± 411 µm) and oxygen diffusion coefficient (Db) both reached maxima. These results have important theoretical significance for improving OMT theory and reducing the energy consumption of the aeration process.

Chitosan Supports Boosting NiCo2O4 for Catalyzed Urea Electrochemical Removal Application.

Currently, wastewater containing high urea levels poses a significant risk to human health. Else, electrocatalytic methodologies have the potential to transform urea present in urea-rich wastewater into hydrogen, thereby contributing towards environmental conservation and facilitating the production of sustainable energy. The characterization of the NiCo2O4@chitosan catalyst was performed by various analytical techniques, including scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Furthermore, the activity of electrodes toward urea removal was investigated by several electrochemical techniques. As a function of current density, the performance of the modified NiCo2O4@chitosan surface was employed to remove urea using electrochemical oxidation. Consequently, the current density measurement was 43 mA cm-2 in a solution of 1.0 M urea and 1.0 M KOH. Different kinetic characteristics were investigated, including charge transfer coefficient (α), Tafel slope (29 mV dec-1), diffusion coefficient (1.87 × 10-5 cm2 s-1), and surface coverage 4.29 × 10-9 mol cm-2. The electrode showed high stability whereas it lost 10.4% of its initial current after 5 h of urea oxidation.

Analysis of Diffusion Coefficients of Iron Monoboride and Diiron Boride Coating Formed on the Surface of AISI 420 Steel by Two Different Models: Experiments and Modelling.

In the present work, two mathematical diffusion models have been used to estimate the growth of the iron monoboride and diiron boride coating formed on AISI 420 steel. The boronizing of the steel was carried out with the solid diffusion packing method at a boronizing temperature of 1123 K-1273 K. Experimental results show the two-coating system consists of an outer monoboride and an inner diiron boride coating with a predominantly planar structure at the propagation front. The depth of the boride coating increases according to temperature and treatment time. A parabolic curve characterizes the propagation of the boride coatings. The two proposed mathematical models of mass transfer diffusion are founded on the solution corresponding to Fick's second fundamental law. The first is based on a linear boron concentration-penetration profile without time dependence, and the second model with time dependence (exact solution). For both models, the theoretical law of parabolic propagation and the average flux of boron atoms (Fick's first fundamental law) at the growth interfaces (monoboride/diiron boride and diiron boride/substrate) are considered to estimate the propagation of the boride coatings (monoboride and diiron boride). To validate the mathematical models, a programming code is written in the MATLAB program (adaptation 7.5) designed to simulate the growth of the boride coatings (monoboride and diiron boride). The following parameters are used as input data for this computer code: (the layer thicknesses of the FeB and Fe2B phases, the operating temperature, the boronizing time, initial formation time of the boride coating, the surface boron concentration limits, FeB/Fe2B and Fe2B/Fe growth interfaces, and the mass transfer diffusion coefficient of boron in the iron monoboride and diiron boride phases). The outputs of the computer code are the constants εFeB and εFe2B. The assessment of activation energies of AISI 420 steel for the two mathematical models of mass transfer is coincident (QFeB=221.9 kJ∙mol-1 and QFe2B=209.1 kJ∙mol-1). A numerical analysis was performed using a standard Taylor series for clarification of the proximity between the two models. SEM micrographs exhibited a strong propensity toward a flat-fronted composition at expansion interfaces of the iron monoboride and diiron boride coating, confirmed by XRD analysis. Tribological characterizations included the Vickers hardness test method, pin-on-disc, and Daimler-Benz Rockwell-C indentation adhesion tests. After thorough analysis, the energies were compared to the existing literature to validate our experiment. We found that our models and experimental results agreed. The diffusion models we utilized were crucial in gaining a deeper understanding of the boronizing behavior of AISI 420 steel, and they also allowed us to predict the thicknesses of the iron monoboride and diiron boride coating. These models provide helpful approaches for predicting the behavior of these steels.

Enhanced microorganism attachment and flavin excretion in microbial fuel cells via an N,S-codoped carbon microflower anode

Commonly used dense arrays of nanomaterials on carbon cloth (CC) are not suitable to accommodate microorganisms in microbial fuel cells (MFCs) due to their unmatched size. To simultaneously enrich exoelectrogens and accelerate the extracellular electron transfer (EET) process, SnS2 nanosheets were selected as sacrificial templates to prepare binder-free N,S-codoped carbon microflowers (N,S-CMF@CC) by polymer coating and pyrolysis. N,S-CMF@CC showed a cumulative total charge of 125.70C/m2, approximately 2.11 times higher than that of CC, indicating its better electricity storage capacity. Moreover, the interface transfer resistance and diffusion coefficient in bioanodes were 42.68 Ω and 9.27 × 10-10 cm2/s, respectively, superior to CC (141.3 Ω and 1.06 × 10-11 cm2/s). Remarkably, N,S-codoped carbon microflowers excreted more flavin than CC, as confirmed by continuous fluorescence monitoring. Biofilm and 16S rRNA gene sequence analysis revealed that exoelectrogens were enriched, and nanoconduits were generated on the N,S-CMF@CC anode. In particular, flavin excretion was also promoted on our hierarchical electrode, effectively driving the EET process. MFCs equipped with the N,S-CMF@CC anode could deliver a power density of 2.50 W/m2, coulombic efficiency of 22.77 %, and chemical oxygen demand (COD) removal amount of 90.72 mg/L/d, higher than that of bare CC. These findings not only demonstrate that our anode is capable of solving the cell enrichment issue, but it may also increase EET rates by bound flavin with outer membrane c-type cytochromes (OMCs) to simultaneously boost the power generation and wastewater treatment performance of MFCs.

Semi-empirical modeling of the temporal variation of indoor radon concentration over short periods

The time rate of change of the indoor radon concentration is studied in a semi-empirical frame. The differential equation that describes the radon mass-balance inside a room is used, with taking into account all sources of indoor radon. Rather than solving the equation numerically, an analytical form is obtained with applying some approximations that are based on experimental observations. This makes the describing model more realistic and updatable. After fitting some of the parameters to the experimental data, the model is found to be successful for describing the indoor radon concentration over a couple of days. Moreover, the model predicts some important characteristics of the radon flow to the indoors from the soil and from the building materials. For the room considered in this study, it is found that the radon diffusion transfer coefficient inside the building material is while the radon diffusion and advection transfer coefficients inside the soil are and respectively. The model can also predict the amount of contribution to the indoor radon by any sources that may be unknown. It was found to be The obtained results show the feasibility and convenience of the model.

Transport of Small Molecules in Loaded Natural Rubber: Experimental Measurement and Numerical Simulation

Small organic molecules such as plasticizers, antioxidants, and some active molecules such as scent/fragrance compounds and drug molecules are incorporated into natural rubber materials to modify their properties and processability or utilize them as carriers in delivery systems. The transport of those small molecules within the rubber can greatly alter the properties and performances of the loaded rubber materials. Thus, it is important to study the transport properties of those molecules in natural rubber matrices and the factors influencing how fast the molecules diffuse. In this work, vulcanized rubber sheets with three different cross-link densities loaded with eight small molecules with different boiling points, molecular weights, and chemical moieties were prepared. Desorption experiments were performed to determine the mass transfer coefficients and diffusion coefficients of those molecules, and the corresponding numerical models were built. Good agreements between experiments and numerical simulation were observed. It was found that the mass transfer coefficients of those small molecules decreased with increasing boiling points but remained practically constant among rubber sheets with different cross-link densities. The diffusion coefficients of those small molecules did not show evident correlation with their molecular weights, but their relationships with cross-link densities indicated that for some molecules there might be an optimal cross-link density where a small molecule reached its maximum diffusion coefficient. The resulting findings could be applied to a wide range of fields.

Автоматизоване розпаралелювання програми моделювання внутрішньочастинкової дифузії й абсорбції в неоднорідних нанопористих середовищах

Heterogeneous media consisting of thin layers of particles of forked porous structure with different physical-chemical properties are widely used in science-intensive technologies and priority sectors of industry, medicine, ecology, etc. Such layers are distributed systems of pores consisting of two main spaces: micro- and nanopores of particles and macropores and cavities between particles. Mass transfer in the system of heterogeneous media causes two types of mass transfer: diffusion in macropores, owing to interparticle space, and diffusion in the system of micro- and nanopores inside particles of the heterogeneous medium. Intraparticle space has a higher level of adsorptive capacity, and at the same time, has a lower velocity of diffusion intrusion in comparison with interparticle space. In modeling concentra- tion and gradient fields for various diffusible components, an important scientific problem is the identification of kinetic parameters of a transfer, predetermining mass transfer velocity on macro- and micro levels, and also equilibrium conditions. The results of designing and parallelization of a program implementing a Crank-Nicolson scheme using algebra-algorithmic specifications represented in a natural- linguistic form are given. The tools for automated design, synthesis and auto-tuning of programs were applied that provided the translation of algebra-algorithmic schemes into source code in a target programming language and its tuning for execution environment to increase the program performance. Numerical distributions of values of diffusion coefficients for intraparticle transfer along coordinate of medium thickness for various time snapshots were obtained. Based on the results of the identification, the models were checked for adequacy and numerical modeling and analysis of concentration and gradient fields of mass transfer were carried out. The experiment results of auto- tuning the software implementation demonstrated high multiprocessor speedup on test data input.

A Layered Electrochemical Sensor for Epinephrine Based on a Nitrogen‐Doped Reduced Graphene Oxide‐ZnFe2O4/β‐Cyclodextrin‐Modified Platinum Electrode

AbstractA novel nanocomposite of nitrogen‐doped reduced graphene oxide‐ZnFe2O4/β‐cyclodextrin (NRGO‐ZnFe2O4/β‐CD) was synthesised for electrocatalytic applications on platinum electrode. The structural and morphological characterisation of the synthesised nanocomposite was carried out using FTIR, XRD, EDAX, FESEM, HRTEM etc. The electrochemical characterisation was performed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). NRGO‐ZnFe2O4/β‐CD proved to be an excellent electrocatalyst for the electrochemical detection of epinephrine on platinum electrode and the optimum pH for the response was found to be 7. The electrochemical characteristics of the oxidation of epinephrine was found to be quasi reversible and diffusion controlled with charge transfer coefficient and diffusion coefficient of 0.55 and 1.03×10−5 cm2/s respectively. Detection limit in the micromolar range of epinephrine was achieved with specific recognition in presence of other structurally similar catecholamines like norepinephrine and dopamine even in their ten‐fold excess concentration at β‐CD/NRGO‐ZnFe2O4/Pt electrode and the electrode exhibited good repeatability, excellent reproducibility and stability for the oxidation of epinephrine. Recognition of epinephrine with high selectivity could be attained in presence of other common substances present in biological fluids.

Performance analysis of heat exchanger- evacuated tube assisted drying system (HE-ETADS) under unload condition

A prototype heat exchanger-evacuated tube assisted drying system (HE-ETADS) has been fabricated and tested under unload conditions in active mode at different water flow rates (10, 20, and 30Ltr/hr). Experimental work was conducted in three different categories. Category-I: drying system in stagnation condition, Category-II: all fans are in operating condition and Category-III: ventilation window is open. Coefficient of performance, heat consumption factor, convective heat transfer coefficient (CHTC) and diffusion coefficient have been calculated in thermal performance analysis of advanced system. Highest coefficient of diffusivity (0.19) was on third day of experimentation under Category-III at 30Ltr/hr water flow rate. Maximum heat consumption factor (0.60) was calculated during the second day for Category-I at 20Ltr/hr and for Category-II it was 0.775 during third day of experimentation at 30Ltr/hr, whereas in Category-III it was 0.782 at 10Ltr/hr water flow rate during first day of experiment. Higher coefficient of performance was 0.902 on third day of experiment for Category-I at 30Ltr/hr water flow rate whereas 0.940 was on first day of experimentation for Category-II at 10Ltr/hr flow rate. Category-III achieved 0.97 at 10Ltr/hr water flow rate during first day of experiment. CHTC of north wall insulated greenhouse dryer (NWIGHD) for ground to drying cabin air was 46.622 W/m2℃, while for advanced HE-ETADS it was found 47.542 W/m2℃, which is 1.98% greater than NWIGHD. Hence, HE-ETADS has potential to enhance drying rate and reduce payback period.

Ionic liquid crystals/nano-nickel oxide-decorated carbon nanotubes composite for electrocatalytic treatment of urea-contaminated water

Electrochemical treatment is an efficient approach for urea-decontamination from aqueous media. Reliable electro-catalysts are therefore crucial for water decontamination applications. We introduce in this work a newly developed composite by modifying a nickel substrate with nickel oxide nanoparticles (NiO), multiwalled carbon nanotubes (CNTs) and ionic liquid crystals (ILCs). The composite modifier (Ni/NiO + CNTs) exhibit an outstanding specific catalytic current for 0.33 M urea electro-oxidation in 1 M KOH of 1303 A·g−1·cm−2. The optimum regime of the catalyst administration to the substrate surface is a layer of ILCs followed by a mixture of CNTs and NiO with a ratio of 1:1 by mass (Ni/ILCs/NiO + CNTs (1:1)). The inclusions of ILCs assist the ionic exchange of the electrode surface and increase substantially the performance of the catalyst. The change in the carbon-based component of the catalyst affects the electro-catalytic current; reduced graphene oxide (RGO) exhibit relatively lower value compared to CNTs. The Tafel slope, the exchange current density, charge transfer coefficient, diffusion coefficient, and heterogeneous rate constant in 0.33 M urea/1.0 M KOH for the optimized electrode (Ni/ILCs/NiO + CNTs (1:1)) are: 33.0 mV·dec−1, 2.89 × 10−5 A·cm−2, 0.91, 1.70 × 10−3 cm2·s−1, 1.51 × 105 mol−1·L·s−1, respectively. The calculated activation energy of the electrochemical conversion of urea is 5.28 kJ·mol−1. The electrode shows high stability when used for extended time to constant applied potential of about +0.5 V for urea electro-oxidation. The conversion efficiency increased in the order Ni/ILCs/NiO + CNTs > Ni/NiO + CNTs > Ni/NiO compared to the Ni surface.