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The ion beam-induced defects in carbon supports for platinum (Pt) nanoparticles have been found to enhance the catalytic activity. Highly oriented pyrolytic graphite (HOPG) was irradiated with 380 keV argon ions (Ar + ), and Pt nanoparticles were then deposited on it by a radio frequency (rf) magnetron sputtering method. The Pt nanoparticle size on Ar + -irradiated HOPG and the carbon structure at the interface were investigated by transmission electron microscope (TEM) and Raman spectroscopy, respectively. The observed size of Pt nanoparticles on the irradiated HOPG was larger than that on the non-irradiated HOPG. Raman spectra indicated that vacancy-like defects were formed on the HOPG surface by Ar + -irradiation at the fluences between 1.0 × 10 12 and 1.0 × 10 13 ions/cm 2 , and sp 3 defects were induced by irradiation more than 5.0 × 10 13 ions/cm 2 . These defective structures on the HOPG would promote the Pt particle growth. [ABSTRACT FROM AUTHOR]

Abstract Ion irradiation is well-known as a versatile tool for manipulating the physical, chemical and magnetic properties of carbon materials. Recently, the ion-beam-induced defects in carbon supports for platinum (Pt) nanoparticles have been found to enhance catalytic activity during the oxygen reduction reaction. This finding suggests that the electronic structure of the Pt nanoparticles would be affected by the ion-beam-irradiated carbon support. Raman spectroscopy was performed on the highly oriented pyrolytic graphite (HOPG) following the irradiated with 380 keV argon ions (Ar+) and the deposition of Pt nanoparticles using radio frequency (rf) magnetron sputtering. In this paper, we obtained the phonon correlation length from Raman spectrum, and estimated that approximately three point defects were present at the interface between each 5 nm Pt nanoparticle and the HOPG irradiated with Ar+ at the fluence of 1.0 × 1013 ions/cm2. [ABSTRACT FROM AUTHOR]

In this work, coherent phonons in glassy carbon using transient reflection measurements with the pump-probe spectroscopy are investigated. Detection of coherent oscillation of optical phonons in a polished glassy carbon sample is enabled by wavelength-selected measurements for reflected probe pulse. We demonstrate that the G and D mode oscillations occur at 46.8 and 38.2 THz frequency, respectively, and have approximately the same lifetime of 0.17 ps. Furthermore, we find that the D mode peak is anisotropic and spreads towards lower energies. [Display omitted] • Femtosecond transient reflection signal showed a coherent oscillation of optical phonons in a polished glassy carbon. • Wavelength selective detection with an optical bandpass filter enhanced the phonon oscillation. • Both G and D mode oscillations had approximately the same lifetime of 0.17 ps. [ABSTRACT FROM AUTHOR]