Shi-Mian Chao

Surface plasma resonant effect of gold nanoparticles on the photoelectrodes of dye-sensitized solar cells

In this study, we prepared different shapes of gold nanoparticles by seed-mediated growth method and applied them on the photoelectrodes of dye-sensitized solar cells (DSSCs) to study the surface plasma resonant (SPR) effect of gold nanoparticles on the photoelectrodes of dye-sensitized solar cells. The analyses of field emission scanning electron microscopy show that the average diameter of the spherical gold nanoparticles is 45 nm, the average length and width of the short gold nanorods were 55 and 22 nm, respectively, and the average length and width of the long gold nanorods were 55 and 14 nm, respectively. The aspect ratio of the short and long gold nanorods was about 2.5 and 4, respectively. The results of ultraviolet–visible absorption spectra show that the absorption wavelength is about 540 nm for spherical gold nanoparticles, and the absorption of the gold nanorods reveals two peaks. One is about 510 to 520 nm, and the other is about 670 and 710 nm for the short and long gold nanorods, respectively. The best conversion efficiency of the dye-sensitized solar cells with spherical gold nanoparticles and short and long gold nanorods added in is 6.77%, 7.08%, and 7.29%, respectively, and is higher than that of the cells without gold nanoparticles, which is 6.21%. This result indicates that the effect of gold nanoparticles on the photoelectrodes can increase the conductivity and reduce the recombination of charges in the photoelectrodes, resulting in the increase of conversion efficiency for DSSCs. In addition, the long gold nanorods have stronger SPR effect than the spherical gold nanoparticles and short gold nanorods at long wavelength. This may be the reason for the higher conversion efficiency of DSSCs with long gold nanorods than those of the cells with spherical gold nanoparticles and short gold nanorods.

Effect of TiO2 nanotubes with TiCl4 treatment on the photoelectrode of dye-sensitized solar cells

In this study, we used the electrochemical anodization to prepare TiO2 nanotube arrays and applied them on the photoelectrode of dye-sensitized solar cells. In the field emission scanning electron microscopy analysis, the lengths of TiO2 nanotube arrays prepared by electrochemical anodization can be obtained with approximately 10 to 30 μm. After titanium tetrachloride (TiCl4) treatment, the walls of TiO2 nanotubes were coated with TiO2 nanoparticles. XRD patterns showed that the oxygen-annealed TiO2 nanotubes have a better anatase phase. The conversion efficiency with different lengths of TiO2 nanotube photoelectrodes is 3.21%, 4.35%, and 4.34% with 10, 20, and 30 μm, respectively. After TiCl4 treatment, the efficiency of TiO2 nanotube photoelectrode for dye-sensitized solar cell can be improved up to 6.58%. In the analysis of electrochemical impedance spectroscopy, the value of Rk (charge transfer resistance related to recombination of electrons) decreases from 26.1 to 17.4 Ω when TiO2 nanotubes were treated with TiCl4. These results indicate that TiO2 nanotubes treated with TiCl4 can increase the surface area of TiO2 nanotubes, resulting in the increase of dye adsorption and have great help for the increase of the conversion efficiency of DSSCs.

Effect of Au nanoparticles added in nanocrystalline TiO2 film on the photoelectrode of dye-sensitised solar cells

In this study, we used a citrate reduction method and electrophoretic deposition (EPD) to prepare hybrid nanocrystalline TiO2/Au films and applied it to the photoelectrode of dye-sensitised solar cell. The films and solar cells were investigated by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), I-V characteristics and electrochemical impedance spectroscopy (EIS) analyses. In the FE-SEM analysis, TiO2/Au hybrid layers have the porous structure that is advantageous in the dye-loading capacity. The results of EDX reveal that the TiO2/Au hybrid layer contains 0.28 wt% gold nanoparticles. X-ray diffraction patterns show that the TiO2/Au hybrid films contain TiO2 anatase and rutile phase, and Au peaks. Under sunlight simulator (AM 1.5 100 mW/cm2) illumination, the conversion efficiency of dye-sensitised solar cell with TiO2/Au hybrid layer is obviously higher than that of TiO2 film. In the analysis of electrochemical impedance spectroscopy ...

Effects of different shaped gold nanoparticles on the photoelectrode of dye-sensitized solar cells

In this study, we prepared different shapes of gold nanoparticles by the seed-mediated growth method to apply on the photoelectrode of dye-sensitized solar cells. Analyses of field emission scanning electron microscopy and ultraviolet–visible absorption spectra show that the average diameter of spherical gold nanoparticles is 66 nm and gold nanorods in aspect ratio is 2. The best conversion efficiencies of dye-sensitized solar cell with spherical gold nanoparticles and gold nanorods added in are 6.77 and 7.08%, and are higher than that without gold nanoparticles. These results indicate that the effect of gold nanoparticles on the photoelectrode can increase the conductivity and reduce the recombination of charges in the photoelectrode, resulting in the increase of conversion efficiency for dye-sensitized solar cells. Futhermore, gold nanorods have stronger surface plasmon resonance intensity than spherical gold nanoparticles at long wavelength. This may be the reason why conversion efficiency of dye-sensitized solar cells with gold nanorods is higher than that of spherical gold nanoparticles.

Effect of hybrid nanocrystalline TiO 2 /Au film on the photoelectrode of dye-sensitized solar cell

In this study, we used a citrate reduction method and electrophoretic deposition (EPD) to prepare hybrid nanocrystalline TiO2/Au films and applied on the photoelectrode of dye-sensitized solar cell. The films and solar cells were investigated by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDX), I-V characteristics, and electrochemical impedance spectroscopy (EIS) analyses. In the FE-SEM analysis, TiO2/Au hybrid layers have the porous structure that is advantageous in the dye-loading capacity. The results of EDX reveal that the TiO2/Au hybrid layer containing 0.28 wt% gold nanoparticles. Under sunlight simulator (AM 1.5 100 mW/cm2) illumination, the conversion efficiency of dye-sensitized solar cell with TiO2/Au hybrid layer is obviously higher than TiO2 film. In the analysis of electrochemical impedance spectroscopy (EIS), the total impedance of hybrid TiO2/Au photoelectrode is 98.9 W, which is lower than that of TiO2 film photoelectrode. These results indicate that TiO2/Au hybrid layer can increase the conductivity and reduce the recombination of charges in the photoelectrode, resulting in the increase of conversion efficiency for DSSCs.

Fabrication of FePt@Au Nanoparticles by Reverse Micelle Method

In this study, magnetic iron platinum alloy-core/gold-shell (FePt@Au) nanoparticles (NPs) were synthesized using the reverse micelle technique under ambient pressure at 25°C. Gold-coated NPs are prevented FePt oxidation and allowed the samples to be manipulated without additional precautions to prevent oxidation. FePt@Au NPs were successfully fabricated and demonstrated by X-ray diffractometry (XRD) and ultraviolet-visible absorption spectra. Transmission electron microscopy (TEM) reveals the average diameter of FePt@Au NPs is about 5.7 nm. The result of superconducting quantum interference device (SQUID) magnetometry shows it was super-paramagnetic, the blocking temperature and the coercive field of 26 K and 350 Oe, respectively.

Structural and Magnetic Properties of Different Shape Gold Nanoparticles

In this study, different shape of gold nanoparticles were prepared by seed-mediate growth method and investigated by the measurements of ultraviolet-visible (UV/Vis) spectrometer, transmission electron microscopy (TEM), X-ray diffractometer (XRD), and superconducting quantum interference device (SQUID). When the dosage of gold seed (DGS) is smaller than 0.03 mL or greater than 0.03 mL, the aspect ratio of gold nanorods will diminish, and the output of gold nanoparticles will also decrease. Therefore the optional condition for preparation of gold nanorod is DGS=0.03 mL. While DGS increases to 0.5 mL, the shape of the gold nanoparticles is changed form rod to sphere. There are weak ferromagnetism observed in the results of magnetization for gold nanorods and spherical nanoparticles under -2000 to 2000 Oe at 5K, and the coercive fields are 226 Oe and 66 Oe for the gold nanorods and spherical gold nanoparticles, respectively.