Effect of Cadmium on Germination Characters and Biochemical Parameters of Two Iranian Ecotypes of Cumin (Cuminum cyminum L.)

Cadmium (Cd), being a highly toxic metal pollutant of soils, it inhibits root and shoot growth and yield production, affects nutrient uptake and homeostasis. It is frequently accumulated by agriculturally important crops and then enters the food chain with a significant potential to impair animals and human’s health. Therefore, a study was conducted to evaluate the effects of various Cd levels (0 as control, 300, 450, 600, 750 and 1050 µM) on some growth and biochemical parameters of two Iranian ecotypes of cumin (Cuminum cyminum) seedlings. The results revealed that seed germination, root growth, chlorophyll content and total soluble protein of both ecotypes decreased significantly with increase in metal concentration. The proline showed an increase in lower concentrations of Cd but at higher concentrations it decreased. The present results allow us to conclude that the cumin plants adversely affected by cadmium toxicity. Decrease in the seed germination percentage, root growth, chlorophyll and protein content may be considered as circumstantial evidence for the toxicity of cadmium. The present study demonstrated that under cadmium stress, C. cyminum underwent biochemical changes to survive under high concentrations of this metal. Increase in metal chelate components (proline) proves this fact. It can be concluded that Isfahan ecotype was superior to Khorasan ecotype in most of the measured parameters and it can be suggested that Isfahan ecotype is more tolerant to Cd stress than Khorasan ecotype

Ternary transition metal chalcogenides decorated on rGO as an efficient nanocatalyst towards urea electro-oxidation reaction for biofuel cell application

A ternary transition metal chalcogenide, containing MoS2, NiS, and Co3S4 (MCNS), and MCNS/reduced graphene oxide (MCNS/rGO) composite were prepared as anode catalysts by a simple hydrothermal process for Urea electro-oxidation. It's expected that rGO with high specific surface area provides superior catalytic performance for MCNS/rGO than MCNS. Also, the synergic effect of Mo, Ni, and Co in the composite accelerates the urea oxidation and enhances the performance of the catalyst. The composites were characterized by field emission electron microscopy, transition electron microscopy, and X-ray diffraction spectroscopy. Electrochemical properties of composites were evaluated by cyclic voltammetry. The MCNS/rGO demonstrated superior electrocatalytic performance than the MCNS catalyst. The incorporating of rGO into MCNS creates a high electrochemical surface area for urea electro-oxidation that resulted in a higher current density (18 mA cm�2) than MCNS (3.7 mA cm�2) at the presence of 0.6 M urea and the scan rate of 20 mV s�1. The maximum current density obtained 43 mA cm�2 for MCNS/rGO at the scan rate of 70 mV s�1 in room temperature. Also, single cells based on MCNS and MCNS/rGO supplied a maximum power density of 7.7 mW cm�2 and 21.0 mW cm�2 at room temperature, respectively. Hence, MCNS/rGO can be a favorable electrocatalyst for application in the direct urea fuel cell. © 2019 Elsevier B.V

Preparation and characterization of a carbon-based magnetic nanostructure via co-precipitation method: Peroxidase-like activity assay with 3,3ʹ,5,5ʹ-tetramethylbenzidine

Objective(S): Natural and artificial enzymes have shown important roles in biotechnological processes. Recently, design and synthesis of artificial enzymes especially peroxidase mimics has been interested by many researchers. Due to disadvantages of natural peroxidases, there is a desirable reason of current research interest in artificial peroxidase mimics. Methods: In this study, magnetic multiwall carbon nanotubes with a structure of Fe3O4/MWCNTs as enzyme mimetic were fabricated using in situ co-precipitation method. The structure, composition, and morphology of Fe3O4/MWCNTs nanocomposite were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). The magnetic properties were investigated by the vibrating sample magnetometer (VSM). Peroxidase-like catalytic activity of nanocomposite was investigated using colorimetric and electrochemical tests with 3,3ʹ,5,5ʹ-tetramethylbenzidine (TMB) substrate. Results: The obtained data proved the synthesis of Fe3O4/MWCNTs nanocomposite. The average crystallite size of nanostructures was estimated about 12 nm by Debye–Scherer equation. It was found that Fe3O4/MWCNTs nanocomposite exhibit peroxidase-like activity. Colorimetric and electrochemical data demonstrated that prepared nanocomplex has higher catalytic activity toward H2O2 than pure MWCNT nanocatalyst. From electrochemical tests concluded that the Fe3O4/MWCNTs electrode exhibited the better redox response to H2O2, which is ~ 2 times larger than that of the MWCNTs. Conclusions: The synthesis of Fe3O4nanoparticles on MWCNTs was successfully performed by in situ co-precipitation process. Fe3O4/MWCNTs nanocatalyst exhibited a good peroxidase-like activity. These biomimetic catalysts have some advantages such as simplicity, stability and cost effectiveness that can be used in the design of enzyme-based devices for various applied fields

Electrochemical determination of rutin by using NiFe2O4 nanoparticles-loaded reduced graphene oxide

A binary transition metal oxide containing nickel and iron (NiFe2O4) and hybridization of this nanomaterial with reduced graphene oxide (rGO) are synthesized by the hydrothermal method. X-ray diffraction (XRD) and Raman spectroscopy confirm the successful synthesis of these materials. Also, scanning electron microscope (SEM) and transmission electron microscope (TEM) images illustrated the particle morphology with the particle size of 20 nm. The synthesized material is then examined as a sensor on the surface of the glassy carbon electrode to detect a very small amount of rutin. Some electrochemical tests such as cyclic voltammetry, differential pulse voltammetry (DPV), and impedance spectroscopy indicate the remarkable accuracy of this sensor and its operation in a relatively wide range of concentrations of rutin (100 nM-100 µM). The accuracy of the proposed electrochemical sensors is approximately 100 nM in 0.1 M PBS, (pH = 3) which is relatively impressive and can be reported. Also, the stability rate after 100 DPV was about 95 , which is a considerable and relatively excellent value. Considering the very good results, it seems that the NiFe2O4-rGO can be considered as a new proposal in the development of accurate and inexpensive electrochemical sensors. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature

Enhanced electrochemical performance of MnNi2O4/rGO nanocomposite as pseudocapacitor electrode material and methanol electro-oxidation catalyst

Binary transition metal oxides with encouraging electrocatalyst properties have been suggested as electrode materials for supercapacitors and methanol oxidation. Hence, in this work, a binary mixed metal oxide based on nickel and manganese (MnNi2O4) and its hybrid with reduced graphene oxide were synthesized by a one-step hydrothermal method. After physical and morphological characterization, the potential of these nanostructures was investigated for use as supercapacitor electrodes and methanol electro-oxidation. The results of the electrochemical analysis showed a substantial effect of adding rGO to the MnNi2O4. The MnNi2O4/rGO hybrid electrode supercapacitor exhibited good stability of 93% after 2000 consecutive CV cycles and specific capacitance of 631 F/g at the scan rate of 10 mV/s. Furthermore, the application of this hybrid nanomaterial in the methanol electro-oxidation reaction (MOR) indicated its appropriate electrochemical efficiency and stability in methanol oxidation. Our results show that MnNi2O4/rGO can be considered as a promising electrode material for energy applications

NiCo2O4‐rGO/Pt as a robust nanocatalyst for sorbitol electrooxidation

A ternary nanocatalyst consisting of nickel cobalt oxide (NiCo2O4), reduced graphene oxide (rGO), and platinum (Pt) was introduced as a promising catalyst for application in the sorbitol oxidation reaction (SOR) process for use in fuel cells. Other catalysts such as NiCo2O4, NiCo2O4-rGO, and NiCo2O4/Pt were prepared for comparison. The structure and morphology of the synthesized nanocatalysts were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The efficiency of the as-synthesized materials was assessed by electrochemical tests of cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (CA). The comparison of the SOR process for the synthesized nanocatalysts showed that NiCo2O4-rGO/Pt has the highest current density (57.2 mA cm2, 45.04 mA/mg) at a scan rate of 10 mV/s and the lowest peak potential (0.64 V) as well as the highest cyclic stability than other materials. The superior electrocatalytic performance is attributed to the synergistic effect of the components. Moreover, the charge transfer resistance of SOR for NiCo2O4-rGO/Pt catalyst is 702 Ω, lower than that for NiCo2O4/Pt (930 Ω). Thus, NiCo2O4-rGO/Pt constitutes an efficient and promising nanocatalyst for SOR

MoS2/Ni3S2/Reduced Graphene Oxide Nanostructure as an Electrocatalyst for Alcohol Fuel Cells

The development of active and stable catalysts is essential for the commercialization of direct alcohol fuel cells. In this work, we introduce a MoS2/Ni3S2/rGO catalyst as a cost-effective, stable, and high-performance catalyst for application in alcohol fuel cells. MoS2/Ni3S2 and its hybrid with reduced graphene oxide (rGO) are synthesized and evaluated as nanocatalysts in the alcohol (methanol and ethanol) electro-oxidation process in alkaline media. The effects of temperature and scanning rate are investigated. Voltammetry results show that MoS2/Ni3S2/rGO has good catalytic efficiency and excellent stability of 106 and 104% after 200 consecutive CV cycles for MOR and EOR, respectively. The synergic effect of starfish Ni3S2 and the coated porous MoS2 facilitates the absorption of hydroxyl ions and alcohols on the surface of the catalyst, while rGO enlarges the specific surface area and the electrical conductivity of the electrocatalyst

NiO-Co3O4-rGO as an Efficient Electrode Material for Supercapacitors and Direct Alcoholic Fuel Cells

Transition metal oxides can be performant electrode materials for supercapacitors and alcohol oxidation if their conductivity and capacity are improved. Herein, an advanced nanocomposite material made of NiO-Co3O4 on reduced graphene oxide (rGO) is synthesized by a one-step hydrothermal method for supercapacitors and methanol/ethanol oxidation. It is demonstrated that the nanocomposite is a promising material for energy storage as NiO-Co3O4-rGO supercapacitor electrodes achieve a specific capacity of 149 mAh g−1 (894 F g−1) at a current density of 0.5 A g−1, the discharge time of 689 s, and excellent stability of 95% after 6000 cycles. Moreover, NiO-Co3O4-rGO shows a current density of 15 and 10 mA cm−2 in methanol and ethanol oxidation reactions, respectively, along with excellent stability

Electrocatalytic Performance of MnMoO₄-rGO Nano-Electrocatalyst for Methanol and Ethanol Oxidation

Today, finding low-cost electro-catalysts for methanol and ethanol oxidation with high performance and stability is one of the new research topics. A nanocatalyst based on metal oxides in the form of MnMoO4 was synthesized by a hydrothermal method for methanol (MOR) and ethanol (EOR) oxidation reactions. Adding reduced graphene oxide (rGO) to the catalyst structure improved the electrocatalytic activity of MnMoO4 for the oxidation processes. The crystal structure and morphology of the MnMoO4 and MnMoO4-rGO nanocatalysts were investigated by physical analyses such as scanning electron microscopy and X-ray diffraction. Their abilities for MOR and EOR processes in an alkaline medium were evaluated by performing electrochemical tests such as cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. MnMoO4-rGO showed oxidation current densities of 60.59 and 25.39 mA/cm2 and peak potentials of 0.62 and 0.67 V in MOR and EOR processes (at a scan rate of 40 mV/s), respectively. Moreover, stabilities of 91.7% in MOR and 88.6% in EOR processes were obtained from the chronoamperometry analysis within 6 h. All these features make MnMoO4-rGO a promising electrochemical catalyst for the oxidation of alcohols