Search

Microbial fuel cell (MFC) is a promising technology for simultaneous wastewater treatment and energy harvesting. The properties of the anode material play a critical role in the performance of the MFC. In this study, graphene oxide was prepared by a modified hummer's method. A thin layer of graphene oxide was incorporated on the carbon brush using an electrophoretic technique. The deoxygenated graphene oxide formed on the surface of the carbon brush (RGO-CB) was investigated as a bio-anode in MFC operated with real wastewater. The performance of the MFC using the RGO-CB was compared with that using plain carbon brush anode (PCB). Results showed that electrophoretic deposition of graphene oxide on the surface of carbon brush significantly enhanced the performance of the MFC, where the power density increased more than 10 times (from 33 mWm−2 to 381 mWm−2). Although the COD removal was nearly similar for the two MFCs, i.e., with PCB and RGO-CB; the columbic efficiency significantly increased in the case of RGO-CB anode. The improved performance in the case of the modified electrode was related to the role of the graphene in improving the electron transfer from the microorganism to the anode surface, as confirmed from the electrochemical impedance spectroscopy measurements.

In this work, Cu2O nanoparticles were successfully prepared onto the surface of two-dimensional graphitic carbon nitride (g-C3N4) by using a simple solution chemistry approach. An environment-friendly reducing agent, glucose, was used for the synthesis of Cu2O NPs onto the surface of g-C3N4 without using any surfactant or additives. The surface composition, crystalline structure, morphology, as well as other properties have been investigated using XPS, XRD, SEM, FTIR, FESEM, EDS, etc. The electrochemical measurements of the prepared materials demonstrated that Cu2O exhibited a weak oxidation activity towards urea, while g-C3N4 has no activity towards urea oxidation. The Cu2O supported on the surface of g-C3N4 (Cu2O-g-C3N4) demonstrated a significant activity towards urea oxidation that reached two times that of the unsupported one. The significant increase in the performance was related to the synergetic effect between the Cu2O and g-C3N4 support. The prepared composite materials demonstrated high stability towards urea oxidation as confirmed from the stable current discharge for around 3 h without any noticeable degradation performance.

A g-C3N4/VC composite material comprising of graphitic carbon nitride (g-C3N4) and Vulcan carbon (VC) with different ratios, i.e., 2:1, 1:1, and 1:2 were prepared through hydrothermal method without using any additives. These composite materials were further utilized as a support for Ni(OH)2 nanoparticles. These materials formed new type of Ni/(g-C3N4/VC) composite materials. The SEM images show the sheet-like structure of the graphitic carbon nitride. Although Ni nanoparticles' electrochemical activity over the surface for graphitic carbon nitride was slightly more compared to Ni supported on the Vulcan carbon, the Ni supported on the different composite supports demonstrated an outstanding activity compared with that over the single supports. Among the different composite ratios of the graphitic carbon nitride to the Vulcan carbon, the one with high Vulcan carbon, i.e., 2:1, exhibited the best performance that is nine-times the current density in comparison to that of Ni over Vulcan carbon at 0.5 V using 2 M urea in 1 M potassium hydroxide. The stability for the prepared Ni over the composite support was high, where the degradation in the current density for more than 2 hours was negligible.

In this work, standalone cobalt dendrites are prepared then doped with graphene flakes by a simple electroplating technique. Microstructural examination using SEM with EDX, as well as Raman spectroscopy measurements, verified the successful formation of graphene. The prepared material exhibit a favorably high electrochemical methanol oxidation activity with an onset oxidation potential of 0.07 V vs. Ag/AgCl, which is significantly lower than that of the Ni (0.35 V vs. Ag/AgCl). The doping process causes a decrease in the ohmic resistance of the material from 3.2 Ohm cm−2 to 2 Ohm cm−2, which consequently resulted in a significant increase in the current density from 35 mA cm−2 to 62 mA cm−2 using 1 M methanol at 0.5 V vs. Ag/AgCl. After two hours of current discharge at 0.5 V vs. Ag/AgCl, the catalyst doped with graphene showed a current density of 62 mA cm−2. This is an eight-times higher than that obtained in the case of the Ni nano-powder. An electrode prepared by depositing the catalyst on the surface of a highly conductive porous Ni foam was successfully used as the anode of a passive air cathode direct methanol fuel cell, demonstrating an open circuit voltage of 0.75 V using 0.25 M methanol in 1 M KOH.

A simple electrodeposition technique has been used to synthesize Co nanoparticles with a 3D leaf-like morphology at room temperature. The prepared Co material has a layered sheet structure of a few nanometers thickness. The surface area of the Co leaf-like structure is three times higher than that of the Co nanoparticles. The prepared nanoparticles exhibit high activity towards ethanol oxidation in alkaline media with an onset potential of 0 V vs Ag/AgCl, which is one of the lowest reported potentials for a non-precious catalyst. The current density is observed to increase with increasing ethanol concentration from 0.1 M to 2 M, after which it plateaus. Mixing the Co catalyst with Vulcan carbon (20 wt%) resulted in a 50% increase in current discharge at different ethanol concentrations due to the improvement in mass and charge transfer rates as confirmed by EIS measurements. Also, Co deposited in situ on the surface of nickel foam (NF) exhibited a high activity towards ethanol oxidation as a standalone electrode that is 10 times that of bare NF.

We report a density functional theory study of ZnO cluster doped with Eu and Mg along with native point defects using the generalized gradient approximation including the Hubbard parameter. The Zn atomic positions are found to be energetically more favorable doping sites than O. The Eu has a lower formation energy than Zn and O vacancies, helps in lowering the formation energy of point defects and induces spin polarization. Mg is less favorable dopant energetically and is not inducing any magnetism in the cluster. Presence of Eu and point defects along with Mg can help in sustaining spin polarization, implying that transition metal and rare earth dopant is a favorable combination to invoke desirable properties in ZnO based materials. Eu–Eu doping pair prefers ferromagnetic orientation and a spin flip is induced by Eu in the Eu–Mg configuration. Further, Eu doping increases the value of static refractive index and optical absorption in the UV region compared to the undoped ZnO cluster.

The quest for high performance supercapacitors from the energy-power point of view is commonly addressed from the constituting electrode materials and/or the electrolyte. Carbon-based double-layer capacitors are known for their high power density, whereas pseudocapacitors which use transition metal oxides/nitrides/sulfides or conductive polymers are known for their high energy density. In this work we show that one can modulate the energy storage capability of supercapacitors by mixing at preset ratios two types of carbon materials having two different energy storage capabilities. The time-domain and frequency-domain electrochemical characterization of five symmetric devices, in which electrodes made of carbon nanofibers (CNF) are mixed with cobalt-modified CNF (Co-CNF) at different mass proportions, show that as the Co-CNF content is increased, the effective capacitance, and hence the restored energy, is increased without affecting the power performance of the device. This opens up new opportunities for the modular design of supercapacitor electrodes using a small set of electric double-layer capacitive materials.

Direct urea fuel cell (DUFC) is an attractive and inexpensive method for the simultaneous wastewater treatment (urine and urea-contaminated water) and electricity generation. Many efforts have been made to increase the catalytic activity of Ni-based DUFC anodic catalyst toward urea oxidation, which is considered to be the best non-precious catalyst in alkaline media so far. Alloying Ni with other metals and/or non-metals, and increasing its surface area demonstrated a power of up to 26.9 mW cm−2 at room temperature, which is comparable to that obtained in direct alcoholic fuel cells using high loading of precious catalyst. However, this is still viewed as low-performance. This review presents a comprehensive picture of the mechanism of urea oxidation on Ni-based catalysts, the poisoning effect of catalysts and its possible remedies, as well as the different approaches in preparing highly active catalysts. We also analyze the performance and associated issues of DUFC using newly applied strategies to increase its open-circuit voltage and power output via alternative oxidants and re-designed chemical conditions in the cell.

International audience; Severe acute respiratory syndrome SARS-CoV-2 virus led to notable challenges amongst researchers in view of development of new and fast detecting techniques. In this regard, surface-enhanced Raman spectroscopy (SERS) technique, providing a fingerprint characteristic for each material, would be an interesting approach. The current study encompasses the fabrication of a SERS sensor to study the SARS-CoV-2 S1 (RBD) spike protein of the SARS-CoV-2 virus family. The SERS sensor consists of a silicon nanowires (SiNWs) substrate decorated with plasmonic silver nanoparticles (AgNPs). Both SiNWs fabrication and AgNPs decoration were achieved by a relatively simple wet chemical processing method. The study deliberately projects the factors that influence the growth of silicon nanowires, uniform decoration of AgNPs onto the SiNWs matrix along with detection of Rhodamine-6G (R6G) to optimize the best conditions for enhanced sensing of the spike protein. Increasing the time period of etching process resulted in enhanced SiNWs’ length from 0.55 to 7.34 µm. Furthermore, the variation of the immersion time in the decoration process of AgNPs onto SiNWs ensued the optimum time period for the enhancement in the sensitivity of detection. Tremendous increase in sensitivity of R6G detection was perceived on SiNWs etched for 2 min (length=0.90 µm), followed by 30s of immersion time for their optimal decoration by AgNPs. These SiNWs/AgNPs SERS-based sensors were able to detect the spike protein at a concentration down to 9.3 × 10−12 M. Strong and dominant peaks at 1280, 1404, 1495, 1541 and 1609 cm−1 were spotted at a fraction of a minute. Moreover, direct, ultra-fast, facile, and affordable optoelectronic SiNWs/AgNPs sensors tuned to function as a biosensor for detecting the spike protein even at a trace level (pico molar concentration). The current findings hold great promise for the utilization of SERS as an innovative approach in the diagnosis domain of infections at very early stages.

Generating true random bits of high quality at high data rates is usually viewed as a challenging task. To do so, physical sources of entropy with wide bandwidth are required which are able to provide truly random bits and not pseudorandom bits, as it is the case with deterministic algorithms and chaotic systems. In this work we demonstrate a reliable high-speed true random bit generator (TRBG) device based on the unpredictable electrical current time series of atmospheric pressure air microplasma (APAMP). After binarization of the sampled current time series, no further post-processing was needed in order for the bitstreams to pass all 15 tests of the NIST SP 800-22 statistical test suite. Several configurations of the system have been successfully tested at different sampling rates up to 100 MS/s, and with different inter-electrode distances giving visible/non-visible optical emissions. The cost-effectiveness, simplicity and ease of implementation of the proposed APAMP system compared to others makes it a very promising solution for portable TRBGs.

We report the synthesis of aryldiazonium tetrachloroaurate(III) salts [X-4-C6H4N≡N]AuCl4 (X = F, Cl, Br, I, CN, NO2) and their mild reduction to covalently functionalized nanoparticles. The synthesis of the salts was carried out by the oxidation of anilines, dissolved in HCl, using sodium nitrite followed by the exchange of the counter anion with [AuCl4]- in water. In another procedure, the anilines were protonated with H[AuCl4] in acetonitrile followed by one-electron oxidation using nitrosonium salt [NO]X (X = BF4−, PF6−). Raman and ATR-FTIR spectroscopy displayed the diazonium νN≡N and Raman showed the tetrachloroaurate νAu-Cl stretching frequencies. X-ray crystal structure of [NO2-4-C6H4N≡N]AuCl4 salt showed N≡N bond distance typical of a triple bond. Gold-aryl nanoparticles were constructed by the mild chemical reduction of the diazonium gold(III) salts using 9-borabicyclo[3.3.1]nonane (9-BBN). Nanoparticles hydrodynamic diameter, elemental composition, dynamics information, and stability data were determined. Transmission electron microscopy (TEM) measurements showed limited aggregation due to the small suppressing organic shell. However, dynamic light scattering (DLS) measurements showed considerable aggregation in acetonitrile. X-ray photoelectron spectrometry (XPS) showed the gold core in zero oxidation state and manifested the gold-organic shell connectivity. The –N=N-aryl interfacial formation on the gold surface can be ruled out since the N1s peak assigned to the diazonium moiety showed no sign in the XPS nitrogen area in addition to its absence in the ATR-FTIR spectra. Raman spectroscopy measurements showed a peak assigned to gold-carbon bonding supported by density functional calculations (DFT) on Au20-C6H4-CN model.

There is a tremendous interest in the fabrication of novel hemocompatible nanoparticles for applications in theranostics. In this context, bovine serum albumin (BSA) conjugates with the water-soluble and super robust gold-aryl nanoparticles truncated with carboxylic functionals were synthesized. The gold-aryl nanoparticles were fabricated by the mild reduction of the diazonium gold(III) salt [HOOC-4-C6H4N≡N]AuCl4. The gold core size and the presence of BSA sheath encapsulating Au−COOH nanoparticles were concluded from transmission electron microscopy (TEM). Clear spectral changes supported by quantitative X-ray photoelectron spectrometry (XPS) surface analysis are visible: the C1s/Au4d intensity ratio increased sharply and the gold features were very well attenuated after BSA attachment, which brings more nitrogen essentially due to NH-C = O peptide links. The conjugation of BSA with Au−COOH nanoparticles resulted in the isoelectric point (pI) change from 4.7 to a range of 4.1-5.0. The robustness of the bioconjugates can be concluded based on the high ζ-potential values and the resistance to drastic pH conditions. The high encapsulation efficiency percentage (EE%) calculated using Bradford protein assay was in a range of 90.0–94.6% under physiological pH values. Taken together, overall studies imply the presence of interaction between the Au−COOH nanoparticles and BSA. In this study we investigated the interaction of gold nanoparticles and their BSA conjugates with human red blood cells (RBCs), which might cause cell deformity and hemolysis. To elaborate on the uniqueness of the bioconjugates, they showed negligible hemolysis or morphology deformation to cells membrane visualized using light and phase contrast microscopes. Quantitative measurements of hemoglobin leached out of the cell membrane using UV–vis showed negligible hemolysis. The high physiological stability of the conjugates fosters their applications in intravenous drug delivery supported by the long blood circulation half-life.

This work presents the simple synthesis and simultaneous deposition of graphene nanoplatelets onto pure copper substrates for use as capacitive deionization electrodes. Copper is cheap and abundant material that can easily be fabricated into electrodes but suffers from high reactivity in solution with unpredictable consequences. The deposition of turbostratic graphene layer using the proposed high energy centrifugal milling technique introduces a chemically inert, but electrically conductive surface layer that extends the operational lifetime of the copper working electrode many folds compared to the bare pure copper one. In the trials presented here the operation of the pure copper electrode degraded almost instantly as the electrochemical cell was activated, compared to a smooth 60-minute operation of its graphene-coated counterpart. The graphene electrode was successful in reducing the solution conductance by more than 12% for the test period, which renews the interest in copper as an effective counter electrode for capacitive deionization applications. The quality of graphene deposition is verified via Raman spectroscopy, while the characterization of the copper chloride is done via X-ray Diffraction. The deionization process resulted in the production of Cu2Cl(OH)3 deposits on the copper electrode, which is mentioned as a viable method of producing it, although it is an unexpected result of this work.

This study unravels the soft chemical synthesis of Bi2O3/ZnO (BZO) nanocomposites having nano-cones like morphology with tunable optical and luminescent properties. The prepared BZO samples with varying Bi2O3 concentrations have been characterized for structural, morphological, band gap energy, photoluminescence (PL) and antibacterial characteristics. Structural and morphological investigations revealed the separate single wurtzite phase of ZnO and monoclinic phase of Bi2O3 without any undesired phases with dominant nano-cones like morphology. Optical and PL analysis have depicted the band gap widening, enhanced ultra-violet (UV) emission and decreased defects densities of BZO nanocomposites as compared to pristine ZnO nano-cones. Interestingly, a good correlation between defects and antibacterial activity of ZnO nanostructures has been found.

This paper presents the results obtained for incorporating the Al65Cu24Fe11material with the conventional TiO2 as the electron injection layer in dye-sensitized solar cells. The icosahedral phase of the Al-Cu-Fe system has attractive physical and optical properties at the target composition, and is obtained by synthesizing the material via the facile high energy ball milling process to ensures the highest possible interdiffusion of elemental powders, followed by heat treatment. The evolution of the i-phase is confirmed via X-ray diffraction, scanning electron microscopy and energy dispersive x-ray spectroscopy. The optical absorption and electrical properties of the compound are investigated by spectrometry, four probe measurement and Mott-Schottky analysis, respectively. Different cells with different percentages (x value) of (TiO2)1-x/(Al65Cu24Fe11)xare constructed and tested to obtain the electrical characteristic curves, efficiency and fill factor to quantify the effect of the proposed material mixture.

Carbon-based nanofluids are viewed as promising thermal fluids for heat transfer applications. However, other properties, such as electrical conductivity and electrochemical behavior, are usually overlooked and rarely investigated despite their importance for the overall performance characterization of a given application. In this study, we synthesized PAN-based carbon nanofibers (CNF) by electrospinning, and characterized them using electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and thermogravimetric analysis. Thermoelectrical and electrochemical measurements were carried out on nanofluids. We found that, although CNF nanofluids exhibit good thermal and electrical properties with a negligible corrosive effect, the suspensions tend to sediment within a few days. However, acid treatment of CNF (F-CNF), which resulted in the shortening of the fibers and the appearance of surface-oxygenated species, made F-CNF-based nanofluids exhibit superior stability in water that extended for more than 90 days, with consistent and superior thermal and electrical properties.

One of the main challenges facing the development of urea fuel cells is the low catalytic activity of the anode. Ni decorated carbon nano-fiber is a promising anode catalyst in urea fuel cells. In this study, we have investigated the effect of Cd doping of Ni decorated carbon nano-fiber on catalytic activity for urea oxidation. The catalyst was prepared by heat treatment of electrospun nano-fibers containing different percentages of Ni and Cd acetates in poly(vinyl alcohol) under an inert atmosphere at 850 °C. The initial percentages of the Cd acetate to Ni acetate in the polymer solution was set at 5, 10, 30, 50 and 70 wt.%. The introduction of Cd significantly improved the electro-catalytic activity for urea oxidation. The sample that was prepared with initial 50 wt.% Cd acetate showed the best activity for urea oxidation activity using different urea concentrations, 0.33 M–3 M. The introduction of Cd improved both the quality and the number of active sites for the urea oxidation as seen from the shift of the anodic peak potential and anodic peak current density, respectively.

Graphene nanosheets (GNS) reinforced Al2O3 nanocomposites were prepared by a rapid sintering route. The microhardness and fracture toughness values of the resulting nanocomposites simultaneously increased due to efficient graphene nanosheet incorporation and chemical interaction with the Al2O3 matrix grains. The properties enhancement is attributed to uniformly dispersed graphene nanosheet in the consolidated structure promoted by high surface roughness and ability of graphene nanosheet to decorate Al2O3 nanoparticles, strong GNS/Al2O3 chemical interaction during colloidal mixing and pullout/crack bridging toughening mechanisms during mechanical testing. The GNS/Al2O3 interaction during different processing stages was thoroughly examined by thermal and structural investigation of the interfacial area. We report formation of an intermediate aluminum oxycarbide phase via a confined carbothermal reduction reaction at the GNS/Al2O3 interface. The graphene nanosheet surface roughness improves GNS/Al2O3 mechanical attachment and chemical compatibility. The Al2O3/GNS interface phase facilitates efficient load transfer, thus delaying failure through impediment of crack propagation. The resulting nanocomposites, therefore, offer superior toughness.

Bipolar electrochemistry is used as an economical, single-step, and scalable process for the oxidation of a wireless graphite substrate, and the subsequent electrophoretic deposition of graphene oxide thin film on a second wireless substrate. An all-solid-state symmetric double-layer capacitor (EDLC) using binderless reduced graphene oxide electrodes exhibited outstanding reversibility and capacitance retention over 18000 cycles, as well as superior capacitive behavior at far-from-dc frequencies (for example 45 and 47 μ F cm-2 ), effective capacitances at 75 and 189 Hz, respectively (computed using a series resonance network with ideal inductors), compared to 55 μ F cm-2 at close-to-dc (computed from cyclic voltammetry at 10 mV s-1 ). This makes the device well-suited for ac filtering applications. A one-hour thermal treatment of the electrodes at 900 °C under vacuum increased the capacitance 13-fold (719 μ F cm-2 ) at close-to-dc, which decreased to 185 and 150 μ F cm-2 as the frequency was increased to 37 and 106 Hz, respectively These properties make this device suitable for both reasonable dc energy storage and higher frequency applications.

Graphene is a 2-D carbon material showing considerable prominence in a wide range of optoelectronics, energy storage, thermal and mechanical applications. However, due to its unique features which are typically associated with difficulty in handling (ultra-thin thickness and hydrophobic surface, to name a few), synthesis and subsequent deposition processes are thus critical to the material properties of the prepared graphene films. While existing synthesis approaches such as chemical vapor deposition and epitaxial growth can grow graphene with high degree of order, the costly high temperature and/or high vacuum process prohibit the widespread usage, and the subsequent graphene transfer from the growth substrates for deposition proves to be challenging. Herein, a low-cost one-step synthesis and deposition approach for preparing few-layer graphene (FLG) on flexible copper substrates based on dry ball-free milling of graphite powder is proposed. Different from previous reports, copper substrates are inserted into the milling crucible, thus accomplishing simultaneous synthesis and deposition of FLG and eliminating further deposition step. Furthermore, while all previously reported high energy milling processes involve using balls of various sizes, we adopt a ball-free milling process relying only on centrifugal forces, which significantly reduces the surface damage of the deposition substrates. Sample characterization indicates that the process yields FLG deposited uniformly across all tested specimens. Consequently, this work takes graphene synthesis and deposition a step closer to full automation with simple and low-cost process.

Nanoparticle (NP) synthesis by biological systems is more cost-effective, safe, and environmentally friendly when compared to currently used chemical and physical methods. Although many studies have utilized different plant extracts to synthesize NPs, few studies have incorporated living plants. In this study, silver nanoparticles (AgNPs) were synthesized exogenously by Tephrosia apollinea living plant system under the combined stresses of silver nitrate and different levels of drought stress simulated by Polyethylene glycol (PEG) (0, &minus, 0.1, &minus, 0.2, and &minus, 0.4 MPa for three and six days). Biomass, cell death, and H2O2 content were evaluated to determine the toxicological effect of the treatments on the plant. More severe effects were detected in day 6 plants compared to day 3 plants, and at higher drought levels. UV-visible spectrum, energy dispersive X-ray spectroscopy, X-ray diffraction, scanning electron microscope, and Fourier transform infrared spectroscopy were used to detect and characterize the T. apollinea synthesized NPs. The shapes of the NPs were spherical and cubic with different phytochemicals being the possible capping agents. Broth microdilution was used to determine the antimicrobial activity of the NPs against Escherichia coli and Staphylococcus aureus. In this case, antimicrobial activity increased at higher PEG concentrations. Bactericidal effects were observed against E. coli, while only bacteriostatic effects were detected against S. aureus.

Mesoporous Co dendrites prepared by electroplating have a surface area of 145 m2g−1, which is three times that of Co nanoparticles. The Co dendrites demonstrate superior urea oxidation activity compared to Ni or Co nanoparticles prepared using chemical reduction. The onset potential with Co dendrites is around 0 V “vs. Ag/AgCl” using 2 M urea, that is remarkably lower than 0.35 V “vs. Ag/AgCl” for Ni catalyst at optimum urea concentration of 0.5 M. The current produced in case of the Co dendrites using 2 M urea at 0.5 V “vs. Ag/AgCl” was six times that obtained using Ni. The in-situ measurements using Co dendrites on the Ni foam as anode and Prussian blue as cathode catalyst demonstrated a 21 mWcm−2 at 20 °C. These are the first reported results for a complete Ni-free nonprecious anode and cathode catalysts under real fuel cell operation with high performance comparable to those obtained using precious catalyst under same conditions.

This paper presents the results obtained for dye-sensitized solar cells with an Al65Cu24Fe11 mesoporous layer replacing the conventional TiO2 layer. The synthesis of the icosahedral quasicrystalline Al-Cu-Fe compound is done by high energy ball milling to ensure the highest possible diffusion of the starting powder elemental materials, and the evolution of the desired microstructure is monitored via X-ray diffraction, scanning electron microscopy and energy dispersive x-ray spectroscopy. The optical absorption and electrical properties of the compound was characterized by spectrometry, four probe measurement, as well as Mott-Schottky analysis, respectively, and compared with those of TiO2. Natural beetroot dye sensitizer was used in this, where its optical absorptivity property has been investigated. A natural organic dye extracted from beetroot is selected for the application as it has the widest absorption at the UV-Vis range. Two identical cells are constructed, one with the reference TiO2 material and the other with Al-Cu-Fe icosahedral compound as the mesoporous layer. The electrical characteristic curves, efficiency and fill factor were calculated for both. Power conversion efficiency enhancement from 0.4% to 0.827% was shown.

In this work, we show the results of our investigation on the photoelectric properties of heterojunction solar cells based on Au/PS/mc-Si/Al and Au/TiO2/PS/mc-Si/Al structures. Porous silicon (PS) were prepared by an electrochemical etching process with different values of current density. The surface porosity was found to increase with the increase of current density. Pulsed laser deposition was used to deposit 80 nm TiO2 thin films. Surface morphology and structural properties of TiO2/PS were characterized by using scanning electron microscopy (SEM) and atomic force microscopy (AFM). An enhancement of the electrical properties of the TiO2/PS/mc-Si heterojunction was observed after coating with TiO2. As a consequence, the solar cell efficiencies increased from 1.4% for the uncoated PS/mc-Si structure to 5% for the TiO2 coated one. Impedance spectroscopy confirmed the passivation effect of TiO2 through the improvement of the elaborated cells’ electron lifetime and the formation of a TiO2/PS/Au heterojunction with the appearance of a second semi-circle in the Nyquist plot.

This paper investigates the effect of applying static and dynamic magnetic fields on the deposition of Fe-Cu compound on the working electrode of a dye-sensitized solar cell. The deposition of this compound on glass is complicated due to the fact that it cannot be evaporated or sintered beyond the dissociation temperature of 973 K (700 °C), and the doctor blade technique causes detrimental layer inconsistencies. The Fe-Cu compound is relatively easy to produce and is significantly cheaper and more absorptive (>81 pct) in the Vis–NIR than the standard TiO2 mesoporous material used for solar cells. It also behaves as a semiconductor due to the high diffusion of the Fe into the Cu lattice that a bandgap of 1.8 eV is obtained. The use of a Schiff base dye with a compatible bandgap of 1.68 eV is used as a sensitizer for the production of a test cell that generated more photocurrent than its TiO2 counterpart, which is a promising result for an alternative mesoporous layer in solar cells.

Surface enhanced Raman scattering (SERS) is an important analytical tool for the optochemical detection of molecules. The enhancement is commonly achieved by engineering (i) novel types and morphologies of plasmonic nanomaterials, and (ii) patterned or roughened supporting substrates of high surface area for increased light scattering and molecule adsorption. Si substrates can be easily and reproducibly textured for effective SERS applications. In this work, silver nanoprisms (AgNPr) coated silicon nanowire (SiNWs) of different morphologies have been prepared by metal-assisted chemical etching and tested for SERS detection of R6G dye. By varying the etching time from 5 to 30 min, the nanowires' lengths increased from 2.4 to 10.5 µm and resulted in a variable topological morphology of the substrates in terms of bundles and valleys. We found that an optimum of 10 min etching time led to the highest SERS enhancement of R6G on AgNPr/SiNWs at 612 cm-1 Raman shift (30× compared to R6G/Si and 2× compared to R6G/AgNPr/Si), with a detection limit comparable to that of state-of-the-art performances (down to 5×10-10 M of R6G). Such an enhancement is attributed to a middle ground between increased overall surface area of SiNWs, and the available bundle tops trapping the AgNPr and R6G molecules.

With the increased use of metal nanoparticles (NPs), their access to the food chain has become a main concern to scientists and holds controversial social implications. This research particularly sheds light on copper nanoparticles (CuNP), as they have been commonly used in several industries nowadays. In this study, we investigated the phytotoxicity of CuNP on cucumber (Cucumis sativus) plants grown hydroponically. Atomic Absorption Spectroscopy (AAS), X-Ray Fluorescence (XRF), and Scanning Electron Microscopy (SEM) analysis confirmed that C. sativus treated with CuNP accumulated CuNP in the plant tissues, with higher levels in roots, with amounts that were concentration dependent. Furthermore, genotoxicity was assessed using Random amplified polymorphic DNA (RAPD) technique, and our results showed that CuNP caused genomic alterations in C. sativus. Phenotypical, physiological, and biochemical changes were assessed by determining the CuNP treated plant's total biomass, chlorophyll, H2O2 and MDA contents, and electrolyte leakage percentage. The results revealed notable adverse phenotypical changes along with decreased biomass and decreased levels of the photosynthetic pigments (Chlorophyll a and b) in a concentration-dependent manner. Moreover, CuNP induced damage to the root plasma membrane as determined by the increased electrolyte leakage. A significant increase in H2O2 and MDA contents were detected in C. sativus CuNP treated plants. Additionally, copper-zinc superoxide dismutase (Cu-Zn SOD) gene expression was induced under CuNP treatment. Overall, our results demonstrated that CuNP of 10-30 nm size were toxic to C. sativus plants. This finding will encourage the safe production and disposal NPs. Thus, reducing nano-metallic bioaccumulation into our food chain through crop plants; that possesses a threat to the ecological system.

ZnO was prepared using room temperature bipolar electrochemical process in deionized water. Electron microscopy, powder X-ray diffraction, and micro-Raman spectroscopy showed crystallization of the material into the wurtzite hexagonal structure of ZnO, self-organized in micro-sized flower-like shapes that are formed out of individual nanorods preferentially grown along the direction. The intrinsic electronic properties were evaluated by potentiodynamic electrochemical impedance spectroscopy using Mott–Schottky analysis of semiconductor/liquid junctions. Because the flat band and carrier density are frequency-dependent, we used an approximation based on fractional order capacitance fitting, and subsequently three different ways to calculate the frequency-independent effective capacitance of the system. The capacitance computed using the four parameters of single-dispersion Randle's model, i.e., pseudocapacitance, dispersion coefficient, and series and parallel resistances, is more recommended for the characterization of the electrochemical system.

To develop operative surface-enhanced Raman spectroscopy (SERS) sensors, nanostructures with high signal enhancement and ease of production are highly desired. The SERS-active nanoparticle-gap-film (NGF) sandwich substrate using graphene as the gap nanospacer is of particular interest due to its strong local field enhancement associated with the atomically thin graphene gap. However, the complexity in fabricating such nanostructures, especially the often involved high-temperature and vacuum processes, ultimately hampers practical applications. Here, a simple and low-cost SERS-active NGF sensor is demonstrated in which a graphene-based nanospacer was prepared by a one-step transfer-free mechanical milling process under amiable conditions. Notably, the milling process can readily produce and deposit the graphene nanospacer in a single fabrication step onto the desired metal substrates. To further enhance SERS performance, shape-anisotropic triangular silver nanoprisms were introduced into the NGF system, which offered enhanced Raman gain compared to spherical silver nanoparticles. Using Rhodamine 6G as the probe, the NGF SERS sensors exhibited a high sensitivity with a low detection limit of 5 × 10−9M with an enhancement factor of 2.7 × 105. This study opens up a new route for the facile production of cost-effective graphene-based NGF substrates for various SERS sensing applications.

Random bit generators (RBGs) in today's digital information and communication systems employ a high rate physical entropy sources such as electronic, photonic, or thermal time series signals. However, the proper functioning of such physical systems is bound by specific constrains that make them in some cases weak and susceptible to external attacks. In this study, we show that the electrical current time series of contact glow discharge electrolysis, which is a dc voltage-powered micro-plasma in liquids, can be used for generating random bit sequences in a wide range of high dc voltages. The current signal is quantized into a binary stream by first using a simple moving average function which makes the distribution centered around zero, and then applying logical operations which enables the binarized data to pass all tests in industry-standard randomness test suite by the National Institute of Standard Technology. Furthermore, the robustness of this RBG against power supply attacks has been examined and verified.

International audience