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Metallic Co nanowires with a mean diameter of about 190 nm and lengths up to 160 µm are prepared by electroless deposition (solution reduction) in propylene glycol at room temperature under external magnetic field. Co deposition behavior in propylene glycol is investigated by in situ monitoring of mixed potentials in conjunction with linear sweep voltammetry and the oxidation-reduction potential of the Co(II)/Co redox pair is determined to be about −0.54 V vs Ag/AgCl. When the mixed potential drops below the oxidation-reduction potential of the Co(II)/Co redox pair, small Co nanoparticles are generated in the solution and are magnetized in the presence of external magnetic field. Strong attractive dipolar interactions are induced along the magnetic field direction, which results in the assembly of Co nanoparticles to nanowires. The Co nanowires exhibit ferromagnetic properties at room temperature, with an enhanced coercivity of about 700 Oe possibly due to shape anisotropy.

Metallic Co nanowires with a mean diameter of about 190 nm and lengths up to 160 µm are prepared by electroless deposition (solution reduction) in propylene glycol at room temperature under external magnetic field. Co deposition behavior in propylene glycol is investigated by in situ monitoring of mixed potentials in conjunction with linear sweep voltammetry and the oxidation-reduction potential of the Co(II)/Co redox pair is determined to be about −0.54 V vs Ag/AgCl. When the mixed potential drops below the oxidation-reduction potential of the Co(II)/Co redox pair, small Co nanoparticles are generated in the solution and are magnetized in the presence of external magnetic field. Strong attractive dipolar interactions are induced along the magnetic field direction, which results in the assembly of Co nanoparticles to nanowires. The Co nanowires exhibit ferromagnetic properties at room temperature, with an enhanced coercivity of about 700 Oe possibly due to shape anisotropy.

Metallic Co nanoparticles of 24–110 nm diameters are prepared by electroless deposition (chemical reduction) in an aqueous solution at room temperature. The reduction process is monitored by an in situ measurement of a mixed potential. The mixed potential, which is above the redox potential of a Co(II)/Co redox pair, drops by the addition of the nucleating agent H2PtCl6 and also decreases with an increase in the H2PtCl6 concentration. Smaller Co nanoparticles are formed. In the smaller particle size, the fraction of the face-centered cubic Co phase increases, and the hexagonal close-packed Co phase decreases.

Metallic Co nanoparticles of 24–110 nm diameters are prepared by electroless deposition (chemical reduction) in an aqueous solution at room temperature. The reduction process is monitored by an in situ measurement of a mixed potential. The mixed potential, which is above the redox potential of a Co(II)/Co redox pair, drops by the addition of the nucleating agent H2PtCl6 and also decreases with an increase in the H2PtCl6 concentration. Smaller Co nanoparticles are formed. In the smaller particle size, the fraction of the face-centered cubic Co phase increases, and the hexagonal close-packed Co phase decreases.

Ferromagnetic Co nanoparticles with diameters of about 40–400 nm are synthesized by electroless deposition in boiling propylene glycol. The Co particle size is decreased to a certain degree by varying the concentration of starting materials and by adding nucleating agents. The electrochemical behavior of propylene glycol is investigated by in situ measurements of mixed potential to understand the formation of Co nanoparticles in polyol systems. The mixed potential decreases with an increase in temperature and in the presence of NaOH, which suggests the faster decomposition of propylene glycol. It also shifts abruptly to a more negative value when nucleating agents are added. This indicates that nucleating agents catalyze both the oxidation reaction of propylene glycol and the reduction reaction of Co(II) species, as well as aid in the formation of Co nanoparticles as heterogeneous nucleation sites.

Ferromagnetic Co nanoparticles with diameters of about 40–400 nm are synthesized by electroless deposition in boiling propylene glycol. The Co particle size is decreased to a certain degree by varying the concentration of starting materials and by adding nucleating agents. The electrochemical behavior of propylene glycol is investigated by in situ measurements of mixed potential to understand the formation of Co nanoparticles in polyol systems. The mixed potential decreases with an increase in temperature and in the presence of NaOH, which suggests the faster decomposition of propylene glycol. It also shifts abruptly to a more negative value when nucleating agents are added. This indicates that nucleating agents catalyze both the oxidation reaction of propylene glycol and the reduction reaction of Co(II) species, as well as aid in the formation of Co nanoparticles as heterogeneous nucleation sites.