[en] In situ potassium (K)-doped single-walled carbon nanotube (SWCNT) was synthesized using a hydrogen arc-discharge method. X-ray photoelectron spectroscopy analysis showed that the K-doped SWCNTs consisted of 0.12% K mass composition. The K-doped SWCNTs showed the lower turn-on electric field of 2.0 V/μm at a current density of 10^-9 A/cm² and the higher emission current density of 3.0 mA/cm² at an applied field of 4.6 V/μm compared with the undoped SWCNTs. The improved field emission performance of K-doped SWCNTs was mainly attributed to the decreased work function and the increased density of state near the Fermi energy

[en] Single-walled carbon nanotubes (SWCNTs) were directly synthesized by a hydrogen arc discharge method using only Fe catalyst. The synthesized carbon materials indicated high-purity SWCNTs with Fe catalyst encapsulated with several graphite layers. The diameter of Fe catalysts encapsulated with graphene layers is 1.5-2.0 nm. From the ferromagnetic resonance measurements, the as-synthesized SWCNTs show the ferromagnetic properties at room temperature. The ferromagnetic properties of SWCNTs would be attributed to Fe catalysts encapsulated by graphite layers.

[en] Sodium (Na)-doped C₆₀ thin films were grown by using a high vacuum evaporation system. Ultraviolet photoelectron spectroscopy showed that the electronic density of states (DOS) of Na-doped C₆₀ films is higher than that of undoped C₆₀ films at 0-0.1 eV and 0.7-13.7 eV binding energy. We consider that the high electronic DOS near Fermi energy due to the Na-dopants contributes to the n-type semiconductor properties with electrical resistance of 1.5 x 10⁵ Ω. We also observed that the electronic DOS of the C₆₀ films/Cu substrate near Fermi level is higher than that of the C₆₀ films/Si substrate indicating charge transfer at the interface

[en] Highlights: ► FeO_x embedded in carbon (FeEC) was prepared as a platinum-free cathode catalyst. ► Fe oxides and Fe metal were the main active catalytic sites in FeEC. ► The higher ORR activity of FeEC was from the higher electronic density of states near Fermi level. ► The improved stability of FeEC stemmed from the carbon layers covering the composite particles. - Abstract: Composite FeO_x nanoparticles embedded in carbon were prepared by the chemical vapor deposition of CH₄ on iron phthalocyanine. They showed relatively high catalytic activity towards oxygen reduction, demonstrating their potential applicability as inexpensive platinum-free cathode catalysts for use in low-temperature fuel cells. Fe oxides and Fe metal embedded in porous carbon, not nitrogen-coordinated iron compounds, were shown to be the active catalytic sites in composite FeO_x nanoparticles embedded in carbon.