Synthesis of Metallic Nanostructures Using Ionizing Radiation and Their Applications

This paper reviews the radiation-induced synthesis of metallic nanostructures and their applications. Radiolysis is a powerful method for synthesizing metallic nanoparticles in solution and heterogeneous media, and it is a clean alternative to other existing physical, chemical, and physicochemical methods. By varying parameters such as the absorbed dose, dose rate, concentrations of metallic precursors, and nature of stabilizing agents, it is possible to control the size, shape, and morphology (alloy, core-shell, etc.) of the nanostructures and, consequently, their properties. Therefore, the as-synthesized nanoparticles have many potential applications in biology, medicine, (photo)catalysis, or energy conversion.

Gamma-radiation induced synthesis of freestanding nickel nanoparticles

A versatile method to produce metallic nickel nanoparticles is demonstrated. Metallic Ni nanoparticles have been synthesized from aqueous solution of NiCl₂ using γ-radiation induced reduction. To prevent Ni re-oxidation, post-irradiation treatment was elaborated. Structural and compositional analyses were executed using X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. These studies reveal that the synthesized material consists of fcc Ni particles having size of 3.47 ± 0.71 nm. The nanoparticles have a tendency to agglomerate to the larger clusters. The latter are partially oxidized to form thin amorphous/poor-crystalline Ni(OH)₂/NiO layers at the surface. Magnetization measurements demonstrate that the nanomaterial exhibit ferromagnetic-like behaviour with magnetization 30% lower than that in bulk Ni. The large active surface area (ECSA, 39.2 m² g^-1) and good electrochemical reversibility, confirmed by the electrochemical studies, make the synthesized material a potential candidate as an active component for energy storage devices.

Niobium dioxide prepared by a novel La-reduced route as a promising catalyst support for Pd towards the oxygen reduction reaction

Electron transfer from NbO₂ to Pd enhances the ORR activity of Pd/NbO₂.

A flexible non-precious metal Fe-N/C catalyst for highly efficient oxygen reduction reaction

A novel, flexible non-precious-metal oxygen reduction reaction catalyst is fabricated by direct pyrolysis of carbon cloth decorated with an iron-coordinated aniline and pyrrole copolymer. The resultant Fe-N/C manifests superior activity, long-term stability in alkaline media and comparable activity in acidic electrolyte. The precursor carbon cloth modified with aniline and pyrrole copolymer provides high densities of carbon, nitrogen and iron-doping sites, which generates a great many active sites. Compared to the Pt/C catalyst, Fe-N/C pyrolyzed at 850 °C (Fe-N/C-850) shows excellent activity with onset and half-wave potentials of 17 mV and -174 mV in 0.1 M KOH, which are more activated than an iron-free catalyst (-29 mV and -235 mV) and comparable to those of Pt/C (28 mV and -237 mV) with the same loading. The electrocatalysis and reaction kinetics results demonstrate that Fe-N/C-850 will be a promising catalyst at low cost for applications in fuel cells.

pH-Control as a way to fine-tune the Cu/Cu2O ratio in radiation induced synthesis of Cu2O particles

In this work we have optimized the γ-radiation induced synthesis of Cu-Cu2O particles from aqueous CuSO4 solution by investigating the effect of pH. The obtained precipitate was analyzed by XRD and SEM techniques. The results indicated that at solution pH lower than 3.75, quasi-spherical Cu agglomerates can be formed while at pH higher than 4.40 only octahedron-shaped Cu2O particles are produced. At solution pH in the range from 3.75 to 4.40, a Cu-Cu2O mixture is produced. It was found that the relative amount of Cu2O in the Cu-Cu2O precipitate increases with pH in the studied range. The influence of solution pH on the Cu/Cu2O ratios in the product can be explained on the basis of pH-dependent competition kinetics between the reactions leading to either Cu or Cu2O formation. As a consequence, the composition and morphology of the Cu-Cu2O precipitate can be tuned by controlling pH of the aqueous CuSO4 solution during the γ-radiation induced synthesis.

Facile synthesis of hollow hierarchical Ni@C nanocomposites with well-dispersed high-loading Ni nanoparticles embedded in carbon for reduction of 4-nitrophenol

Hollow hierarchical Ni@C nanocomposites with highly dispersed Ni nanoparticles (NPs) embedded in well-graphitized carbon matrix have been synthesized by solid-state pyrolysis of simple, well-defined organic–inorganic layered nickel hydroxide. The integration of highly dispersed Ni NPs, high Ni NPs content (up to ∼88.01 wt%), well-graphitized carbon as well as strong Ni/carbon interaction in the Ni@C make them display excellent catalytic activity and stable magnetic recyclability toward the reduction of 4-nitrophenol by NaBH₄.

Hollow hierarchical Ni@C nanocomposites with highly dispersed Ni nanoparticles (NPs) embedded in well-graphitized carbon matrix have been synthesized by solid-state pyrolysis of simple, well-defined organic–inorganic layered nickel hydroxide.