Dendritic Ni3C1–x nanoparticles (NPs) with controlled branching have been synthesized through the thermolysis (230 °C) of nickel acetylacetonate using oleylamine as a reducing agent and 1-octadecene (ODE) as the solvent. Addition of trioctylphosphine (TOP) as a ligand inhibits formation of dendritic shapes and prevents incorporation of C, resulting in spherical Ni NPs. In comparison, when using octadecane (ODA) or trioctylphosphine oxide (TOPO) as the solvent, Ni NPs are obtained at 230 °C that have fewer, larger branches than when using ODE. Higher temperatures are required for incorporation of C from ODA or TOPO into Ni NPs, resulting in Ni3C1–x NPs. Therefore, the allyl group in ODE facilitates formation of Ni3C1–x NPs at lower temperatures. Conversion of dendritic Ni3C1–x NPs into Ni12P5 NPs after adding TOP and heating to 300 °C results in the formation of multiple voids in the branches, rather than yolk-in-shell structures or unfilled single voids observed for spherical NPs.

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Vanadium substituted nickel ferrite nanoparticles (NPs), NiFe 2−x V x O 4 (0.0 ≤ x ≤ 0.3) were prepared by sol-gel approach. The influence of calcination on the magnetic and optical properties of NiFe 2−x V x O 4 (0.0 ≤ x ≤ 0.3) NPs were investigated deeply. The lattice parameters 'a' are almost constant with V-substitution for as-prepared and calcined samples. It was found that the calcination process both increased the crystallites size and removed the impurity phases in all products. The values of optical energy band gap, E g , are in range of 1.38-1.69 eV and 1.39-1.56 eV for as-prepared and calcined samples, respectively. The specific magnetic parameters such as saturation magnetization M s , remanence M r , coercivity H c , squareness ratio (SQR) and magnetic moment n B were determined from magnetization versus applied field measurements. The various M(H) curves exhibit ferromagnetic behavior at room temperature and 10 K. A decrease in M s , M r and n B values was observed with Vanadium substitution. However, an increase in H c value was observed. The obtained magnetic results are primarily resulted from the substitution of Fe ions with V ions that will weaken the A-B super-exchange interactions. Besides, the calcination step leads to an improvement in the various M s , M r and n B parameters. This enhancement is due to the enlargement of crystallites size (or grains size) and the strengthening of the A-B exchange interactions caused by the calcination effect. Nevertheless, the enlargement in the crystallites size is followed by a reduction in H c values.

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Vertically aligned carbon nanofibers (VACNFs) were synthesized using ligand-stabilized Ni nanoparticle (NP) catalysts and plasma-enhanced chemical vapor deposition. Using chemically synthesized Ni NPs enables facile preparation of VACNF arrays with monodisperse diameters below the size limit of thin film lithography. During pregrowth heating, the ligands catalytically convert into graphitic shells that prevent the catalyst NPs from agglomerating and coalescing, resulting in a monodisperse VACNF size distribution. In comparison, significant agglomeration occurs when the ligands are removed before VACNF growth, giving a broad distribution of VACNF sizes. The ligand shells are also promising for patterning the NPs and synthesizing complex VACNF arrays.