Papers by Author: Yu Sung Liu

Abstract: Pure metal iron nanoparticles are unstable in the air. By a coating iron on nanoparticle surface with gold, these air-stable nanoparticles are protected from the oxidation and retain most of the favorable magnetic properties. However, it is difficult to prepare Fe-core/Au-shell (Fe@Au) nanoparticles under ambient pressure because iron nanoparticles are very easily to be oxidized in the air. In this study, we synthesized Fe@Au nanoparticles by modified reverse micelle method under ambient pressure and investigated them by X-ray diffraction, transmission electron microscopy (TEM), ultraviolet-visible absorption spectra, and magnetic susceptibility measurements. X-ray diffraction analysis shows that the pattern of iron is hidden under the pattern of gold. TEM image reveals that the core-shell structure is obviously observed and the average size of Fe@Au nanoparticles is about 12 nm, with about 8 nm diameter core and 2 nm shell. The absorption band of the Fe@Au nanoparticles shifts to a longer wavelength and broadens relative to that of the pure gold. The magnetic susceptibility of Fe@Au nanoparticles is measured with a SQUID magnetometer and found to be superparamagnetic with a blocking temperature Tb ~25 K.

Abstract: In this research, vertically oriented TiO2 nanotube was fabricated on ITO glass by electrochemistry method, and investigated by the measurements of X-ray diffractometer (XRD), scanning electron microscopy (SEM), and ultraviolet-visible (UV/VIS) spectrometer. X-ray diffraction patterns show that the best sintering temperature of TiO2 nanotube is 500°C, at which TiO2 anatase phase forms best. SEM images reveal that the diameter and height of TiO2 nanotube are 70 nm and 230 nm, respectively. Transmittance curves reveal that the transmittance of annealed TiO2 nanotube is about 80%~90%, and is obviously higher than non-annealed TiO2 nanotube. The absorption band of annealed TiO2 nanotube is at 330~370 nm. The results of current-voltage (I-V) characteristics analysis reveal that dye-sensitized solar cell with TiO2 nanotube electrode has better I-V characteristics and efficiency than TiO2 film electrode. This result may be due to the annealed TiO2 nanotube applied on the electrode of dye-sensitized solar cell can increase the contact area between TiO2 and dye, resulting in the enhancement of I-V characteristics and efficiency for dye-sensitized solar cell.