No abstract

The graphite encapsulated iron nanoparticles were fabricated by using arc discharge method. The synthesized nanoparticles were pre-treated by an inductively coupled RF Ar plasma and then post-treated by NH 3 plasma under various gas pressures and treatment times. Analyses of XPS spectra have been carried out to study the effect of the plasma treatment on the surface modification of nitrogen-containing groups. The morphological changes of the particles surface by plasma treatment have also been analyzed by using HR-TEM. Present results show that the highest values of N/C atomic ratio of 4.4 % is obtained by applying 10 min of Ar plasma pre-treatment and 2 min of NH 3 plasma post treatment conducted in RF power of 80 Watt and gas pressure of 50 Pa.

A high-efficiency surface modification of graphite-encapsulated iron compounds magnetic nanoparticles using an inductively coupled radio-frequency plasma with a pulsed particle explosion technique was studied. A significant increase in N 1s peak intensity in the X-ray photoelectron spectroscopy spectra was obtained by applying a negative pulsed bias voltage of −1 kV to the substrate stage for 15 s or less at a repetition frequency of 1 kHz and a duty ratio of 50% in ammonia plasma. The intensity of the N 1s peak and the N/C ratio of the nanoparticles treated in a pulsed particle explosion system were 3–4 times higher than those of the particles treated without bias. The amino group population of nanoparticles treated using the present technique was determined to be about 8.2 × 104 molecules per nanoparticle, roughly four times higher than that of particles treated without bias. The dispersion of the plasma-treated nanoparticles was significantly improved compared with those of the untreated and treated particles in the nonbiasing system. The surface structure analysis by transmission electron microscopy showed no significant damage on the structure or morphology of the treated nanoparticles, indicating that the present technique is applicable to the high-efficiency surface modification of magnetic nanoparticles.

C 60 fullerene exhibits unique optical properties that have high potential for wide photooptical applications. To analyze the optical properties of C 60 , its excitation and emission properties were studied using UV-Vis absorption and photoluminescence (PL) spectroscopy, which were performed in various, nonpolar organic solvents such as toluene, xylene, and trichloroethylene (TCE). The C 60 solutions in toluene, xylene, and TCE displayed similar excitation bands at 625, 591, 570, 535, and 404 nm corresponding to A g → T 1u and A g → T 1g transitions. However, these bands differed from the solid C 60 observed by UV-Vis diffuse reflectance spectroscopy. The two emission band energies of C 60 solution in toluene and xylene were nearly the same (1.78 and 1.69 eV), whereas the C 60 solution in TCE was shifted to 1.72 and 1.65 eV. Because the polarity of TCE is higher than that of toluene and xylene, the PL spectrum of the C 60 solution in TCE was red-shifted. The PL spectroscopy had a better capability than UV-Vis absorbance spectroscopy to distinguish the different interactions between C 60 and the organic solvents due to their different solvent polarities.