Search Results (33)

Isovaleraldehyde is an important chemical raw material for the production of flavors, which is volatile and flammable and poses a health risk to humans. It is, therefore, essential to develop a rapid assay for the identification of isovaleraldehyde. In this study, octahedral NiCo₂O₄/MIL-Fe₅₃ nanocomposites were successfully fabricated for the rapid detection of isovaleraldehyde. The prepared NiCo₂O₄/MIL-Fe₅₃ nanocomposites were characterized by SEM, XRD, FTIR, and XPS to analyze the material properties. The effects of temperature, carrier gas flow rate, selectivity, and stability on the cataluminescence performance of this sensor were investigated. The results showed that NiCo₂O₄/MIL-Fe₅₃ nanocomposites have excellent selectivity to isovaleraldehyde with response and recovery times of 6 and 8 s, respectively. A linear relationship was found between the CTL signal and isovaleraldehyde concentration Y = 9.56X − 23.3 (R² = 0.99) over the concentration range of 13.66 to 437.22 ppm with a detection limit of 2.44 ppm. The relative deviation RSD = 4.18% for multiple tests of the sensor indicates good stability and longevity. Mechanistic studies have shown that the heterojunction formed by NiCo₂O₄/MIL-Fe₅₃ nanocomposites has the advantage of improving CTL sensing performance. This study may advance the application of cataluminescence sensors in the detection of isovaleraldehyde. Full article

This study explores the mechanical properties of graphene/aluminum (Gr/Al) nanocomposites through nanoindentation testing performed via molecular dynamics simulations in a large-scale atomic/molecular massively parallel simulator (LAMMPS). The simulation model was initially subjected to energy minimization at 300 K, followed by relaxation for 50 ps under the NPT ensemble, wherein the number of atoms (N), simulation temperature (T), and pressure (P) were conserved. After the model was fully relaxed, loading and unloading simulations were performed. This study focused on the effects of the Gr arrangement with a brick-and-mortar structure and incorporation of high-entropy alloy (HEA) coatings on mechanical properties. The findings revealed that Gr sheets (GSs) significantly impeded dislocation propagation, preventing the dislocation network from penetrating the Gr layer within the plastic zone. However, interactions between dislocations and GSs in the Gr/Al nanocomposites resulted in reduced hardness compared with that of pure aluminum. After modifying the arrangement of GSs and introducing HEA (FeNiCrCoAl) coatings, the elastic modulus and hardness of the Gr/Al nanocomposites were 83 and 9.5 GPa, respectively, representing increases of 21.5% and 17.3% compared with those of pure aluminum. This study demonstrates that vertically oriented GSs in combination with HEA coatings at a mass fraction of 3.4% significantly enhance the mechanical properties of the Gr/Al nanocomposites. Full article

Effluent-containing dye molecules is a significant environmental hazard. An economical and energy-saving solution is needed to combat this issue for the purpose of environmental sustainability. In this study, Fe-Ni-Co-based trimetallic nanocomposite was synthesized using the coprecipitation method. Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), and Fourier Transform Infra-Red spectroscopy were conducted to explore the physical morphology, phase structure and functional groups of the synthesized catalyst. Among dyes, methyl orange is considered as a major contaminant in textile effluent. The current study focused on the degradation of methyl orange using a trimetallic Fe-Ni-Co-based nanocomposite. A central composite design in response surface methodology was employed to analyze the independent variables including dye concentration, catalyst dose, temperature, hydrogen peroxide, irradiation time, and pH. Dye degradation has been achieved up to 81% in 20 min at the lowest initial concentration (5 mg/L) in optimized conditions. Based on ANOVA, the predicted values were in great agreement with the actual values, signifying the applicability of response surface methodology in the photocatalytic decolorization of dyeing effluents. The results gained from this research demonstrated that the synthesis method of trimetallic nanocomposite (Iron Triad) is a cost-effective and energy efficient method that can be scaled up to a higher level for industrial application. Full article

In the present study, composites incorporating NiO-Co₃O₄ (NC) and CuO-NiO-Co₃O₄ (CNC) as active electrode materials were produced through the hydrothermal method and their performance was investigated systematically. The composition, formation, and nanocomposite structure of the fabricated material were characterized by XRD, FTIR, and UV–Vis. The FE-SEM analysis revealed the presence of rod and spherical mixed morphologies. The prepared NC and CNC samples were utilized as supercapacitor electrodes, demonstrating specific capacitances of 262 Fg⁻¹ at a current density of 1 Ag⁻¹. Interestingly, the CNC composite displayed a notable long-term cyclic stability 84.9%, which was observed even after 5000 charge–discharge cycles. The exceptional electrochemical properties observed can be accredited to the harmonious effects of copper oxide addition, the hollow structure, and various metal oxides. This approach holds promise for the development of supercapacitor electrodes. These findings collectively indicate that the hydrothermally synthesized NC and CNC nanocomposites exhibit potential as high-performance electrodes for supercapacitor applications. Full article

Binary transition metal selenides (BTMSs) are more promising than single transition metal selenides (TMS) as anode materials of sodium-ion batteries (SIBs). However, it is still very challenging to prepare high-performance BTMSs in the pure phase, instead of a mixture of two TMSs. In this study, a binary metal center-based MOF derived selenization strategy was developed to prepare iron–cobalt selenide (Fe₂CoSe₄@NC) and iron–nickel selenide (Fe₂NiSe₄@NC) nanocomposites in the single phase and when wrapped with carbon layers. As the anode material of SIBs, Fe₂CoSe₄@NC exhibits higher long-term cycling performance than Fe₂NiSe₄@NC, maintaining a capacity of 352 mAh g⁻¹ after 2100 cycles at 1.0 A g⁻¹, which is ascribed to the higher percentage of the nanopores, larger lattice spacing, and faster Na+ diffusion rate in the electrode materials of the former rather than the latter. Full article

When a severe plastic deformation (SPD) process is performed at high temperatures, it becomes more versatile. Designed originally for the bulk nanoconstruction of hard-to-deform alloys, high-speed high-pressure torsion (HSHPT) is an SPD method used in this research for assembling multiple layers of shape memory nanocomposites. Three hard-to-deform magnetic alloys in the cast state were used. Soft magnetic shape memory alloys, NiFeGa and FePdMn, and a potentially hard magnetic alloy, CoZr, were assembled in various composites. Both grain refinement and strong layer bonding were achieved in ZrCo/FePdMn and ZrCo/NiFeGa composites in seconds. The very short SPD time is specific to HSHPT because of the intense friction that occurs under high pressures, which generates huge amounts of heat. After SPD, the temperature rises in bulk material like a pulse, being dissipated mostly through heat conduction. The SPD parameters were carefully controlled with an advanced automation system using a programmable logic controller. Nevertheless, the major drawbacks of high-pressure torsion were overcome, and large SPD discs were obtained. Various investigation techniques (optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and atomic force microscopy) show well-defined interfaces as well as a fine and ultrafine structure. Full article

Bimetallic FeCo and FeNi nanoparticles attract much attention due to their promising magnetic properties and a wide range of practical applications as recording and storage media, catalytic systems in fuel cells, supercapacitors, lithium batteries, etc. In this paper, we propose an original approach to the preparation of FeCo- and FeNi/N-doped carbon nanocomposites by means of a coupled process of frontal polymerization and thermolysis of molecular co-crystallized acrylamide complexes. The phase composition, structure, and microstructure of the resulting nanocomposites are studied using XRD, IR spectroscopy, elemental and thermal analysis, and electron microscopy data. The main magnetic characteristics of the synthesized nanocomposites, including the field dependences and the ZFC-FC curves peculiarities, are studied. It is shown that the obtained FeCo/N-C nanocomposites exhibit exchange bias behavior at low temperatures. In turn, FeNi/N-C nanocomposites are ferromagnetically ordered. Full article

Bimetallic nanocomposites and nanoparticles have received tremendous interest recently because they often exhibit better properties than single-component materials. Improved electron transfer rates and the synergistic interactions between individual metals are two of the most beneficial attributes of these materials. In this review, we focus on bimetallic nanoporous gold (NPG) because of its importance in the field of electrochemical sensing coupled with the ease with which it can be made. NPG is a particularly important scaffold because of its unique properties, including biofouling resistance and ease of modification. In this review, several different methods to synthesize NPG, along with varying modification approaches are described. These include the use of ternary alloys, immersion–reduction (chemical, electrochemical, hybrid), co-electrodeposition–annealing, and under-potential deposition coupled with surface-limited redox replacement of NPG with different metal nanoparticles (e.g., Pt, Cu, Pd, Ni, Co, Fe, etc.). The review also describes the importance of fully characterizing these bimetallic nanocomposites and critically analyzing their structure, surface morphology, surface composition, and application in electrochemical sensing of chemical and biochemical species. The authors attempt to highlight the most recent and advanced techniques for designing non-enzymatic bimetallic electrochemical nanosensors. The review opens up a window for readers to obtain detailed knowledge about the formation and structure of bimetallic electrodes and their applications in electrochemical sensing. Full article

Nanocomposites of polyaniline (PANI)/Fe_2.85Ni_0.15O₄ (PFN) were successfully prepared using the co-precipitation method combined with an in-situ polymerization process. The FN and PFN nanocatalysts were characterized using various methods for the photocatalytic degradation of Rhodamine B (RhB). The XRD, Raman, TEM, and DTA-DTG analyses suggest that the FN nanoparticles (NPs) were effectively coated by PANI and that there were interactions between FN and PANI. Magnetic measurements indicated that PFN nanocomposites exhibited good superparamagnetic behavior and high saturation magnetization (39.5–57.6 emu/g), which are suitable for separating photocatalysts from solution for reuse. Adsorption-desorption analysis showed that the specific surface area of PFN was higher than that of FN. The UV-vis absorption spectra of FN and PFN nanocomposites exhibited strong absorption of visible light, attributed to the doping of Ni, which resulted in the reduction of the band-gap energy (E_g) of Fe₃O₄ to 2.4 eV. PFN nanocomposites with different mass ratios of PANI demonstrated superior photocatalytic activity compared to FN NPs. Furthermore, it was observed that PFN with a 10% mass ratio of PANI exhibited the highest RhB degradation efficiency, achieving a rate of approximately 98% after 300 min of irradiation. Finally, the possible photocatalytic degradation mechanisms of the PFN nanocomposites on RhB were discussed. PFN photocatalysts with good photocatalytic activity, inexpensive materials, and easy preparation could be potential candidates for wastewater purification applications. Full article

The electrochemical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are the most critical processes in renewable energy-related technologies, such as fuel cells, water electrolyzers, and unitized regenerative fuel cells. N-doped carbon composites have been demonstrated to be promising ORR/OER catalyst candidates because of their excellent electrical properties, tunable pore structure, and environmental compatibility. In this study, we prepared porous N-doped carbon nanocomposites (NC) by combining mussel-inspired polydopamine (PDA) chemistry and transition metals using a solvothermal carbonization strategy. The complexation between dopamine catechol groups and transition metal ions (Fe, Ni, Co, Zn, Mn, Cu, and Ti) results in hybrid structures with embedded metal nanoparticles converted to metal–NC composites after the carbonization process. The influence of the transition metals on the structural, morphological, and electrochemical properties was analyzed in detail. Among them, Cu, Co, Mn, and Fe N-doped carbon nanocomposites exhibit efficient catalytic activity and excellent stability toward ORR. This method improves the homogeneous distribution of the catalytically active sites. The metal nanoparticles in reduced (MnO, Fe₃C) or metallic (Cu, Co) oxidation states are protected by the N-doped carbon layers, thus further enhancing the ORR performance of the composites. Still, only Co nanocomposite is also effective toward OER with a potential bifunctional gap (ΔE) of 0.867 V. The formation of Co-N active sites during the carbonization process, and the strong coupling between Co nanoparticles and the N-doped carbon layer could promote the formation of defects and the interfacial electron transfer between the catalyst surface, and the reaction intermediates, increasing the bifunctional ORR/OER performance. Full article

FeCo and FeNi nanoalloy particles encapsulated in a nitrogen-doped carbonized shell (FeCo/C-N and FeNi/C-N) were synthesized by thermolysis at 400 °C of polyacrylamide complexes after frontal polymerization of co-crystallizate of Fe and Co or Ni nitrates and acrylamide. During the thermolysis of polyacrylamide complexes in a self-generated atmosphere, Co(II) or Ni(II) and Fe(III) cations are reduced to form FeCo and FeNi nanoalloy particles, while polyacrylamide simultaneously forms a nitrogen-doped carbon shell layer. This unique architecture provides high chemical and thermal stability of the resulting nanocomposites. The average crystallite size of FeCo and FeNi nanoparticles is 10 and 12 nm, respectively. The nanocomposites were studied by X-ray diffraction, atomic force microscopy, scanning electron microscopy, and high-resolution transmission electron microscopy. The nanocomposites have been tested as antifriction and antiwear additives in lubricating oils. The optimal concentrations of nanoparticles were determined, at which the antifriction and antiwear properties of the lubricant manifest themselves in the best possible way. Full article

Lanthanum (La) nanocomposites LaFeO₃, LaNiO₃, and LaCoO₃ were synthesized using a sol-gel method, and different La to-metal (Fe, Ni, or Co) ratios were attained using various concentrations of salts. The resulting composites were calcined at 540 °C and characterized by XRD, SEM-EDX, FT-IR spectroscopy, XPS, thermogravimetric analysis (TGA), and PL spectroscopy. The activity of the lanthanum composites (LaFeO₃, LaNiO₃, and LaCoO₃) was studied using the photocatalytic degradation of methylene blue (MB) and ortho-toluidine blue (o-TB) under visible light with a wavelength below 420 nm. The change in the concentration of dyes was monitored by using the UV-Vis spectroscopy technique. All composites appeared to have some degree of photocatalytic activity, with composites possessing an orthorhombic crystal structure having higher photocatalytic activity. The LaCoO₃ composite is more efficient compared with LaFeO₃ and LaNiO₃ for both dyes. High degradation percentages were observed for the La composites with a 1:1 metal ratio. Full article

The hematite-based nanomaterials are involved in several catalytic organic and inorganic processes, including water decontamination from organic pollutants. In order to develop such species, a series of bimetallic hematite-based nanocomposites were obtained by some goethite composites-controlled calcination. Their composition consists of various phases such as α-FeOOH, α-Fe₂O₃ or γ-Fe₂O₃ combined with amorphous (Mn₂O₃, Co₃O₄, NiO, ZnO) or crystalline (CuO) oxides of the second transition ion from the structure. The component dimensions, either in the 10–30 or in the 100–200 nm range, together with the quasi-spherical or nanorod-like shapes, were provided by Mössbauer spectroscopy and powder X-ray diffraction as well as transmission electron microscopy data. The textural characterization showed a decrease in the specific area of the hematite-based nanocomposites compared with corresponding goethites, with the pore volume ranging between 0.219 and 0.278 cm³g⁻¹. The best catalytic activity concerning indigo carmine removal from water in hydrogen peroxide presence was exhibited by a copper-containing hematite-based nanocomposite sample that reached a dye removal extent of over 99%, which correlates with both the base/acid site ratio and pore size. Moreover, Cu-hbnc preserves its catalytic activity even after four recyclings, when it still reached a dye removal extent higher than 90%. Full article

At present, the research focus has been aimed at the pursuit of the design and synthesis of catalysts for effective photocatalytic degradation of organic pollutants in wastewater, and further exploration of novel materials of the photodegradation catalyst. In this paper, the Sol-gel route after thermal treatment was used to produce NiFe₂O₄ carbon aerogel (NiFe₂O₄-CA) nanocomposites with cotton linter cellulose as the precursor of aerogel, by co-precipitating iron and nickel salts onto its substrate. The structure and composition of these materials were characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), Raman spectra, high-resolution scanning electron microscopy (HR-SEM), high-resolution scanning electron microscope mapping (SEM-mapping), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET)’s surface area. The magnetic properties of the material were analyzed by a vibrating-sample magnetometer (VSM). Moreover, diffuse reflectance spectra (DRS), electrochemical impedance spectroscopy (EIS) and photo-luminescence spectroscopy (PL) characterized the photoelectric properties of this cellulose-aerogels-based NiFe₂O₄-CA. Methylene blue (MB) acted as the simulated pollutant, and the photocatalytic activity of NiFe₂O₄-CA nanocomposites under visible light was evaluated by adjusting H₂O₂ content and the pH value. The results showed that the optical absorption range of nickel ferrite was broadened by doping cellulose-aerogels-based carbon, which exerted more positive effects on photocatalytic reactions. This is because the doping of this aerogel carbon promoted a more uniform distribution of NiFe₂O₄ particles. Given the Methylene blue (MB) degradation reaction conformed to the first-order kinetic equation, the NiFe₂O₄-CA nanocomposites conducted excellent catalytic activity by maintaining almost 99% of the removal of MB (60 mg/L) within 180 min and upheld excellent stability over four consecutive cycles. This study indicated that NiFe₂O₄-CA nanocomposites reserved the potential as a future effective treatment of dye wastewater. Full article

Sol-gel route followed by thermal treatment was used to produce NiFe₂O₄ doped with transition metal ions (Zn²⁺, Mn²⁺, Co²⁺). The structural, morphological, and magnetic properties of the doped NiFe₂O₄ were compared with those of virgin NiFe₂O₄. The metal-glyoxylates’ formation and decomposition as well as the thermal stability of the doped and virgin ferrites were assessed by thermal analysis. The functional groups identified by Fourier-transform infrared spectroscopy confirmed the decomposition of metal nitrates, the formation and decomposition of precursors, and the formation of the SiO₂ matrix. The X-ray diffraction indicated that the sol-gel synthesis produced single-phase crystalline ferrites in case of virgin, Zn²⁺ and Co²⁺-doped Ni-ferrites. By doping with Mn²⁺, several secondary phases derived from the SiO₂ matrix accompanied the crystalline spinel ferrite. The crystallite sizes depended on the annealing temperature and type of doping ion. The gradual increase of lattice parameters suggested the uniform distribution of doping metal ions in the NiFe₂O₄ lattice. The saturation magnetization, remanent magnetizations, coercivity, and anisotropy were found to depend on the doping ion, annealing temperature, and particle size. The high saturation magnetization values of the obtained nanocomposites make them suitable for a wide range of applications in the field of sensors development and construction. Full article