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Abstract:
In this research, electrophoretic deposition (EPD) was employed to prepare a porous composite film (ACF electrode) consisting of 90 wt% activated carbon particles, 10 wt% iron oxide nanoparticles, and a chitosan as binder in a facile, fast, and sustainable manner. This micro-mesoporous composite film, with a thickness of ∼45 µm and a surface area of ∼208.1 m2g−1, was coated on a stainless steel substrate. The SEM and TEM investigations proved the homogeneous distribution of carbon microparticles and iron oxide nanoparticles in the deposit, while the EDX, XRD, Raman spectroscopy, and XPS confirmed the chemical composition. ACF electrodes were also used in a symmetric two-electrode cell configuration with a sandwiched gel polymer electrolyte - PVdF(HFP)-PC-Mg(ClO4)2 and revealed a specific capacitance of ∼54.4 F g−1, along with satisfactory energy and power density of ∼4.7 Wh kg−1 and 1.2 kW kg−1, respectively, and excellent electrochemical stability up to ∼10,000 cycles (with merely 8.5% decay by the 5000th cycle). Obtained results confirmed the stability of the used system and its possible application in the field of energy storage and conversion.

Keywords:
Adsorption,Thermal desorption,Gd-doped Fe3O4,Methotrexate

Abstract:
Porous carbons find various applications, including as adsorbents for clean water production and as electrode materials in energy storage devices such as supercapacitors. While supercapacitors reach higher power densities than batteries, they are less widely used, as their energy density is lower. We present a low-temperature wet ultrasonochemical synthesis technique to modify the surface of activated carbon with 1 wt% Cu nanoparticles. We analyzed the modified carbon using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy and confirmed the composite formation by N2 adsorption–desorption isotherms at 77 K. For comparison, we did the same tests on pristine carbon. We used the modified carbon as an electrode material in a homebuilt supercapacitor filled with gel polymer electrolyte and as an absorbent of Malachite green dye. In both applications, the modified carbon performed substantially better than its pristine counterpart. The modified-carbon supercapacitor exhibited a single electrode-specific capacitance of approximately 68.9 F g1. It also demonstrated an energy density of 9.8 W h kg1 and a power density of 1.4 kW kg1. These values represent improvements over the pristine-carbon supercapacitor, with increases of 25.7 F g1 in capacitance, 3.8 W h kg1 in energy density, and 0.5 kW kg1 in power density. After 10 000 charging–discharging cycles, the capacitance of the modified-carbon supercapacitor decreased by approximately 10%, indicating good durability of the material. We found that the modified carbon’s absorbance capacity for Malachite dye is more than that of the pristine carbon; the adsorption capacity value was B153.16 mg g1 for modified carbon with pseudo-second kinetic order, in accordance with the Redlich–Peterson adsorption model.

Abstract:
The electrochemical properties of metal oxides are very attractive and fascinating in general, making them a potential candidate for supercapacitor application. Vanadium oxide is of particular interest because it possesses a variety of valence states and is also cost effective with low toxicity and a wide voltage window. In the present study, vanadium oxide nanorods were synthesized using a modified sol–gel technique at low temperature. Surface morphology and crystallinity studies were carried out by using scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy analysis. To the best of our knowledge, the as-prepared nanorods were tested with magnesium ion based polymer gel electrolyte for the first time. The prepared supercapacitor cell exhibits high capacitance values of the order of ~ 141.8 F g−1 with power density of ~ 2.3 kW kg−1 and energy density of ~ 19.1 Wh kg−1. The cells show excellent rate capability and good cycling stability.

Abstract:
The structural, electronic, and magnetic properties of low-energy rhenium implanted c-Si are examined for the first time. The damage created by rhenium ions and the following partial reconstruction of the silicon host matrix after rapid thermal annealing (RTA) are investigated as a function of the fluence. Rutherford backscattering spectrometry (RBS) results reveal that the implanted ions are located in the near-surface region with the distribution maximum at about 23 nm below the surface. The analysis of rhenium-depth distribution using the McChasy code shows that the implanted Re-ions are located in the interstitial lattice positions. The RTA leads to a partial recovery of the silicon crystal structure. According to the RBS results, the formed inclusions are not coherent with the silicon host matrix causing an increase of the lattice distortion. Analysis of channeled RBS/c spectra carried out by the McChasy code revealed different levels of bent channels in damaged regions suggesting bimodal distribution of inclusions in the silicon. Studies of high-resolution X-ray photoelectron spectroscopy (XPS) conducted after the RTA showed the shift of Re 4f7/2 binding energy (BE) by +0.68 and + 0.85 eV with respect to metallic rhenium for the samples with lower/higher fluencies, respectively. Complex XPS, density functional theory (DFT) simulations, and transmission electron microscopy (TEM) data analysis allowed us to conclude that the near-surface layer of the sample (~10 nm) consists of nanoinclusions with cubic and/or hexagonal ReSi. In the middle area of the samples, much larger nanoinclusions (>10/20 nm for higher/lower fluencies, respectively) containing pure metallic rhenium inside are formed. The RTA increases the magnetic moment of the sample with the lower dose nearly 20-fold, whereas in the sample with the higher dose a 3-fold increment is observed only. The magnetic response of the examined systems after the RTA indicates a presence of magnetic interactions between the nanoinclusions resulting in the system exhibiting super-spin glass or super-ferromagnetism.

Keywords:
rhenium-implanted silicon, RBS, XPS, RTA, TEM, DFT

Abstract:
Comprehensive studies of drug transport in nanofibres based mats have been performed to predict drug release kinetics. The paper presents our approach to analyze the impact of fibers arrangement, one of the parameters varied in our parallel experimental studies. Drug encapsulation in submicron fibers and subsequent controlled release of drugs is a tedious task due to the large number of process and material parameters involved. In the numerical study we constructed a 3D finite element geometry representing nanofibrous cubic element. COMSOL Multiphysics has been used to assess the impact of the various purposed arrangements of fibers within the mat. Drug release from nanofibers was modeled by adsorption -desorption and diffusion equation, where drug diffusion coefficient in the fluid between the fibers was altered depending on porosity of the material. Our study shows that for the same material porosity drug release from the matrix of regularly oriented fibers is slower than from randomly oriented, isotropic nanofibrous material. Also by decreasing distance between the fibers drug transport rate is reduced.

Keywords:
Electrospinning, ZnO nanofibers, ZnFeO, Room temperature ferromagnetism, Magnetic oxides