Chemical Structure of Fe-Ni Nanoparticles for Efficient Oxygen Evolution Reaction Electrocatalysis

Binary Metal-Oxide Active Sites Derived from Cu-Doped MIL-88 with Enhanced Electroactivity for Nitrate Reduction

Nitrate-to-ammonia electrochemical conversion is important for decreasing water pollution and increasing the production of valuable ammonia. However, achieving high ammonium production without undesirable byproducts is difficult. Cu-doped MIL-88-derived bimetallic oxide catalysts with electrocatalytically active Fe-O-Cu bridges, which have high NO3- adsorption energy and facilitate N-intermediate hydrogenation, are developed for NH4+ production. Cu doping promotes hybridization between the O 2p of NO3- and Fe-Cu 3d, facilitating the adsorption and reduction of NO3- with a low Tafel slope (62.1 mV dec-1) and high ammonia yield (1698.8 μg·h-1·cm-2). The cathode efficiency is stable for seven cycles. Cu adjacent to Fe sites inhibits hydrogen evolution, promotes NO3- adsorption, and decreases the intermediate adsorption energy barrier. This study provides new opportunities for fabricating diverse binary metal oxides with new interfaces as efficient cathode materials for selective electroreduction.

Electrochemical sensor for simultaneous determination of trifluoperazine and dopamine in human serum based on graphene oxide-carbon nanotubes/iron-nickel nanoparticles

Trifluoperazine (TFLP) is an important psychiatric medication that balances the dopamine (DA) level in the brain for patients suffering from neurological disorder diseases. An efficient electrochemical sensor is developed for detecting TFLP in real human serum samples. The sensor is fabricated by casting the GC surface with two consecutive thin layers, namely a graphene oxide-carbon nanotubes mixture (GRO-CNT), and iron-nickel nanoparticles (Fe-Ni). The diffusion-controlled oxidation process of TFLP at the composite surface includes one electron transfer process. Under optimized conditions, the sensor in human serum shows excellent catalytic effect for simultaneous determination of TFLP and dopamine (DA) in the same concentration range (0.5 μM to 18 μM) with low detection limits of 0.13 μM and 0.32 μM respectively. The combined effect of a large conductive surface area and the excellent catalytic activity of the nanocomposite improves the sensor's performance. The sensor exhibits a stable current response over four weeks, excellent reproducibility, and insignificant interference from common species present in human serum samples. The reliability test of using the sensor in serum samples shows good recovery of TFLP.

Evaluation of In Vitro Cytotoxic, Genotoxic, Apoptotic, and Cell Cycle Arrest Potential of Iron-Nickel Alloy Nanoparticles

The use of iron-nickel alloy nanoparticles (Fe-Ni ANPs) is increasing daily in various fields. People are increasingly exposed to these nanoparticles for occupational and environmental reasons. Our study determined some of the effects of Fe-Ni ANP exposure and impacts on human health at the cellular level. The cytotoxic and genotoxic potentials of Fe-Ni ANPs were investigated by XTT, clonogenic, comet, and GammaH2AX analyses using Beas-2B cells. Annexin V, multicaspase, and cell cycle arrest methods were used to understand the apoptotic mechanism of action. The intracellular ROS method was used to determine the primary mechanism that leads to cytotoxic and genotoxic activity. The Fe-Ni ANPs showed cytotoxic activity with the XTT and clonogenic methods: they had genotoxic potential, as demonstrated via genotoxicity methods. It was determined that the cytotoxic effect was realized by the caspase-dependent apoptotic pathway, and the cells were stopped at the G0/G1 stage by Fe-Ni ANPs. Increased intracellular ROS due to Fe-Ni ANPs led to cytotoxic, genotoxic, and apoptotic activity. Potential risks to human health due to Fe-Ni ANPs were then demonstrated at the cellular level.

SALDI Substrate-Based FeNi Magnetic Alloy Nanoparticles for Forensic Analysis of Poisons in Human Serum

In this study, FeNi magnetic alloy nanoparticles (MANPs) were employed for the forensic analysis of four poisons—dimethametryn, napropamide, thiodicarb, and strychnine—using surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). FeNi MANPs were prepared via coprecipitation using two reducing agents, sodium borohydride (NaBH4) and hydrazine monohydrate (N2H4·H2O), to optimize the prepared MANPs and investigate their effect on the performance of SALDI-MS analysis. Thereafter, SALDI-MS analysis was carried out for the detection of three pesticides and a rodenticide. The prepared substrate offered sensitive detection of the targeted analytes with LOD values of 1 ng/mL, 100 pg/mL, 10 ng/mL, and 200 ng/mL for dimethametryn, napropamide, thiodicarb, and strychnine, respectively. The relative standard deviation (%RSD) values were in the range of 2.30–13.97% for the pesticides and 15–23.81% for strychnine, demonstrating the good spot-to-spot reproducibility of the FeNi substrate. Finally, the MANPs were successfully employed in the analysis of poison-spiked blood serum using a minute quantity of the sample with an LOD of 700 ng/mL dimethametryn and napropamide, 800 ng/mL thiodicarb, and 500 ng/mL strychnine. This study has great potential regarding the analysis of several poisons that may be found in human serum, which is significant in cases of self-harm.

Effect of Plating Variables on Oxygen Evolution Reaction of Ni–Zn–Fe Electrodes for Alkaline Water Electrolysis

In this study, we investigated the oxygen evolution reaction (OER) characteristics of Ni–Zn–Fe electrodes by varying plating current density and Ni:Fe ratio in a plating bath. The activity of the OER increased up to the plating current density of 160 mA/cm2, as the Fe content of the deposited electrode increased and electrochemical surface area (ECSA) increased after Zn dealloying. However, for the plated electrode with higher than 160 mA/cm2 of current density, the change in composition caused by underpotential deposition led to decreased activity due to decreasing Fe content and diminishing Zn dealloying. Moreover, when the Ni:Fe ratio in the plating bath was varied, outstanding OER activity was observed at Ni:Fe = 2:1. When the Fe content of the bath increased beyond this ratio, Fe could not restrain Ni oxidation and formed Fe oxides in OER reaction, and oxygen vacancy decreased. These caused a degradation of the OER activity.

The glass-like structure of iron-nickel nanochains produced by the magnetic-field-induced reduction reaction with sodium borohydride

Preparation and detailed structural characterization of iron-nickel wire-like nanochains with Fe_0.75Ni_0.25, Fe_0.50Ni_0.50, and Fe_0.25Ni_0.75 compositions are reported. The investigated nanomaterials were produced by the novel template-free magnetic-field-induced reduction reaction with NaBH₄ as the reducing agent. It is demonstrated that this method leads to the formation of Fe-Ni nanochains composed of spherical nanoparticles with an average diameter of 50-70 nm and with a very high degree of atomic disorder manifested as the lack of clearly developed bcc and fcc phases, which are usually observed for nano- and polycrystalline Fe-Ni species. The recorded wide-angle X-ray scattering data for the obtained Fe-Ni nanochains exhibit a strong resemblance to those obtained for bulk metallic glasses. The atomic scale structure of the investigated nanochains has been studied using pair distribution function analysis of the recorded total scattering data. The best fits to the experimental pair distribution functions have been achieved assuming two-phase models of hcp and bcc networks with the size of coherently scattering regions of about 2.5 nm in diameter, for each Fe-Ni composition. The transmission electron microscopy images indicate that the glass-like bimetallic alloy cores are covered by amorphous oxide/hydroxide shells with their thickness ranging from 2 to 5 nm. Moreover, electron energy loss spectroscopy, X-ray photoelectron spectroscopy, and Mössbauer spectroscopy results confirm the core-shell structure of the Fe-Ni nanochains and the complex character of the shell layer which consists of several iron- and nickel-containing phases.

Ni-Fe oxide-PEDOT modified anode coupled with BAF treating ammonia and nitrite in recirculating seawater of aquaculture system

Efficient ammonia and nitrite removal in low nutrient recirculating seawater of recirculating aquaculture system (RAS) is critical for healthy cultivation. However, it is hard for conventional biological aerated filters (BAFs) to meet this demand under short hydraulic retention time (HRT). The electrooxidation-BAFs (E-BAFs) were constructed for efficient seawater treatment in a RAS of Sebastes schlegelii, with high activity anodic catalyst Ni-Fe oxide-PEDOT. Satisfactory ammonia removal (88.2% in E-BAFs, 33.7% higher than the control, stage 3) and nitrite removal (69.9 % in E-BAFs, 45.3% in the control) were achieved at HRT of 50 min. The proportion of nitrifying bacteria (Nitrospira, Nitrosomonas and Nitrosopumilus) and nitrification/denitrification genes (amoCAB, nxrAB, narGHI, et. al) were higher in E-BAFs than the control, suggesting better potential in functional bacteria enrichment. Aerobic colony number in RAS with E-BAFs was lower and specific growth rate (SGR) of Sebastes schlegelii (3.79%) was significantly higher, indicating a better culture effect.

Size and chemical order dependence of magnetic-ordering temperature and spin structure in Fe@Ni and Ni@Fe core-shell nanoparticles

The effect of particle size and chemical order on the temperature-dependent magnetic properties of Fe@Ni and Ni@Fe core-shell nanoparticles is studied in the framework of a classical spin Hamiltonian and Monte Carlo simulations. We found that the mean temperature-dependent magnetization and magnetic-ordering temperature are strongly affected by both the particle size (in size range of 4 to 16 nm) and core-shell chemical order. As a main result, we report the depression of the magnetic ordering-temperature with decreasing size of the elemental Fe and Ni nanoparticles. More specifically, in the case of Fe and Ni nanoparticles, the magnetic-ordering temperature is lowered by 40 (195 K) to 300 (175 K) compared to the bulk value for nanoparticle diameters ranging from 16 to 4 nm, respectively, consistent with previous theoretical data. We further provide a comprehensive insight into the magnetic properties of Fe@Ni and Ni@Fe nanoparticles, unveiling a rich and distinct magnetic-ordering temperature and spin structure that emphatically depends on the core/shell ratio.