Microwave-assisted synthesis and prototype oxygen reduction electrocatalyst application of N-doped carbon-coated Fe3O4 nanorods

Efficient Gold Recovery from Cyanide Solution Using Magnetic Activated Carbon

Activated carbon has been used for gold recovery in the gold mining industry commercially for decades. The high specific surface area and porosity, good affinity to aurocyanide ions, and abundant resources make activated carbon an efficient and economical material for the adsorption of aurocyanide. However, the separation of activated carbon from the slurry is usually a challenge, and the adsorption rate of activated carbon is limited by the coarse particle size. Herein, a simple and sustainable way to recover gold from cyanide solution using magnetic activated carbon synthesized via a solvothermal method has been developed. The synthesized magnetic activated carbon possesses good magnetism (44.57 emu/g) and specific surface area equal to 249.7 m²/g. The magnetic activated carbon showed 99.1% recovery efficiency of gold from 10 mg/L solution within 5 h, which is much faster compared to the commercial granular activated carbon, and the magnetic activated carbon can be easily separated from the solution with an external magnet. The adsorption ability of this magnetic activated carbon has been tested under different conditions in the cyanide solution, the adsorption isotherm and kinetics are also investigated. The magnetic activated carbon was also recycled in the adsorption-desorption tests and showed good reusability.

Biomedical response under visible-light irradiation promoted by new hydrothermally synthesized SiO2-Zn@Fe2O3 nanofibers

In the presence of Fe₃O₄ nano-fibers, we prepared SiO₂-Zn@Fe₂O₃ hybrid Nano-fibers through a novel and simple one-pot redox reaction between ZnSO₄ & SiO₂. The Fe₃O₄ exterior nano-fibers would be homogenously covered by SiO₂ coating to arrange a distinctive core-shell construction and then Zn nanoparticles are intercalated in the covering of SiO₂. The synthesized nanofibers were tested for photodegradation of methylene blue (MB). The result showed that 99 % MB was degraded in 60 min. Furthermore, the antibacterial potential of SiO₂-Zn@Fe₂O₃ nanofibers was tested against E. coli and S. aureus bacteria both in light and dark. The impact of different analysis such as Reactive oxygen species (ROS) analysis, irradiation effect on bacterial inhibition, concentration effect of SiO₂-Zn@Fe₂O₃ nanofibers and reduction of DPPH studied. The findings clearly demonstrate that ROS is produced in the presence of SiO₂-Zn@Fe₂O₃ nanofibers in bacterial cells and is responsible for their inhibition. Findings have shown that synthesized nanostructures can also increase the stability of DPPH radicals with increasing concentrations of nanomaterials, making them a strong candidate for DPPH reduction. The overall results show that the efficacy of SiO₂-Zn@Fe₂O₃ nanofibers for inhibition was more pronounced than that of individual iron oxides.

Surface Modification of Magnetic Iron Oxide Nanoparticles

Functionalized iron oxide nanoparticles (IONPs) are of great interest due to wide range applications, especially in nanomedicine. However, they face challenges preventing their further applications such as rapid agglomeration, oxidation, etc. Appropriate surface modification of IONPs can conquer these barriers with improved physicochemical properties. This review summarizes recent advances in the surface modification of IONPs with small organic molecules, polymers and inorganic materials. The preparation methods, mechanisms and applications of surface-modified IONPs with different materials are discussed. Finally, the technical barriers of IONPs and their limitations in practical applications are pointed out, and the development trends and prospects are discussed.

Nanoscale Carbon Modified α-MnO2 Nanowires: Highly Active and Stable Oxygen Reduction Electrocatalysts with Low Carbon Content

Carbon-coated α-MnO₂ nanowires (C-MnO₂ NWs) were prepared from α-MnO₂ NWs by a two-step sucrose coating and pyrolysis method. This method resulted in the formation of a thin, porous, low mass-percentage amorphous carbon coating (<5 nm, ≤1.2 wt % C) on the nanowire with an increase in single-nanowire electronic conductivity of roughly 5 orders of magnitude (α-MnO₂, 3.2 × 10^-6 S cm^-1; C-MnO₂, 0.52 S cm^-1) and an increase in surface Mn³⁺ (average oxidation state: α-MnO₂, 3.88; C-MnO₂, 3.66) while suppressing a phase change to Mn₃O₄ at high temperature. The enhanced physical and electronic properties of the C-MnO₂ NWs-enriched surface Mn³⁺ and high conductivity-are manifested in the electrocatalytic activity toward the oxygen reduction reaction (ORR), where a 13-fold increase in specific activity (α-MnO₂, 0.13 A m^-2; C-MnO₂, 1.70 A m^-2) and 6-fold decrease in charge transfer resistance (α-MnO₂, 6.2 kΩ; C-MnO₂, 0.9 kΩ) were observed relative to the precursor α-MnO₂ NWs. The C-MnO₂ NWs, composed of ∼99 wt % MnO₂ and ∼1 wt % carbon coating, also demonstrated an ORR onset potential within 20 mV of commercial 20% Pt/C and a chronoamperometric current/stability equal to or greater than 20% Pt/C at high overpotential (0.4 V vs RHE) and high temperature (60 °C) with no additional conductive carbon.

Magnetic N-containing carbon spheres derived from sustainable chitin for the selective oxidation of C–H bonds

Magnetic N-containing carbon spheres were synthesized using sustainable N-acetyl-d-glucosamine (NAG) and iron nitrate as raw materials. This carbon material exhibited excellent catalytic performance in the C–H bond oxidation.