Suttinart Noothongkaew

Toward Arbitrary-Direction Energy Harvesting through Flexible Piezoelectric Nanogenerators Using Perovskite PbTiO3 Nanotube Arrays

New fiber-type piezoelectric nanogenerator devices consisting of radially aligned perovskite PbTiO3 nanotubes are designed for energy harvesting from arbitrary mechanical motion. The free-standing fiber-type nanogenerators generate constant amount of electric power by bending or wind motion regardless of direction, thus, extending the possibility of their practical applications.

Zinc Oxide Nanostructures Synthesized by Thermal Oxidation of Zinc Powder on Si Substrate

ZnO nanowhiskers were formed by a simple oxidation of metallic zinc powder 99.9% at different temperatures from 400-900 °C for 2 hours on the silicon substrate. The result can be obtained after the thermal oxidation process, the ZnO nanowhiskers with different morphologies at different temperatures in which these morphologies and composition of ZnO nanostructures were characterized by scanning electron microscope, (SEM) and X-ray diffraction, XRD. It was found that the products were nanowhiskers, the structure are triangular shapes with average width of 10-50 nm at the root, 10-30 nm at the tip and length in the range of 1-3 μm was observed by SEM. Temperature in the range of 600-700 °C was suitable for the preparation of ZnO nanowhiskers. At higher temperature of 800 °C, the concentrations of ZnO structures become lower and stronger. At the oxidized temperature of 900 °C, ZnO nanowhiskers were not found and surface morphology become to porous. These results indicate that the oxidation rate is faster than the diffusion rate of Zn vapor on the surface of ZnO nuclei.

AC-Impedance Spectroscopic Analysis on the Charge Transport in CVD-Grown Graphene Devices with Chemically Modified Substrates

A comprehensive study for the effect of interfacial buffer layers on the electrical transport behavior in CVD-grown graphene based devices has been performed by ac-impedance spectroscopy (IS) analysis. We examine the effects of the trap charges at graphene/SiO2 interface on the total capacitance by introducing self-assembled monolayers (SAMs). Furthermore, the charge transports in the polycrystalline graphene are characterized through the temperature-dependent IS measurement, which can be explained by the potential barrier model. The frequency-dependent conduction reveals that the conductivity of graphene is related with the mobility, which is limited by the scattering caused by charged adsorbates on SiO2 surface.

Synthesis of Zinc Oxide Nanowire-Nanowall-Like Hybrid Structures on Graphene

ZnO nanowire-nanowall-like hybrid structure on graphene was synthesized with a simple chemical vapor deposition technique. This was done without a template by utilizing a catalyst to control the growth time and condensation. The surface morphology of nanostructure was characterized by using a field emission scanning electron microscope (FE-SEM). We found that the ZnO nanowire-nanowall-like hybrid structure was uniformly deposited on the graphene. The extremely strong ZnO (0002) peaks were observed by using x-ray diffraction (XRD). This method showed the preferred (0001) orientation and high crystalline quality of the ZnO nanostructures. The optical properties were investigated utilizing photoluminescence (PL). These results showed the strong green-yellow emission attributed to the robust inner reflection and scattering. This simplified method has great potential in synthesizing uniform ZnO nanowire-nanowall-like hybrid structures on graphene. These nanostructures may have important applications in new types of flexible gas sensors or other fields demanding high surface area materials.

Zinc Oxide Nano Walls Synthesized by Chemical Vapor Deposition

ZnO nanowalls were synthesized by chemical vapor deposition at temperature of 650 °C for 1 hour on the silicon substrate. The morphologies of samples were characterized by scanning electron microscopy (SEM). The result from X-ray diffraction (XRD) confirmed that the ZnO nanowalls were vertical c-axis orientation. A room temperature Photoluminescence peak at 378 nm is ultraviolet emission (UV) and the broad peak at wavelengths around 450-650 nm is corresponding to the green emission of ZnO nanostructure. This synthesis may be applicable for gas sensor or solar cells.

Characterization of Anatase and Rutile Phase of TiO2 Nanostructures with Different Thermal Annealing

TiO2 nanostructures were prepared by anodization of Ti foils. The TiO2 nanostructure films were annealed at the temperature range of 500°C to 900°C for 2 h. The morphology, elemental composition, and crystallization of TiO2 nanostructures were analyzed by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Raman spectra, and X-ray spectroscopy (XPS), respectively. XRD and Raman spectra results confirm the presence of the anatase phase for TiO2 nanostructure films which were annealed at 500°C to 700°C. Furthermore, it found that anatase to rutile phase transition occurred at temperature above 700oC.

r-GO/MWCNTs Nanocomposite Film as Electrode Material for Supercapacitor

We synthesized a reduced graphene oxide (r-GO) multi-walled carbon nanotube (MWCNTs) nanocomposite film via layer by layer (LBL) assembly. This structure was prepared by vacuum filtration and heat-treated at a low temperature of 500°C. The morphology of the sample was determined by field emission electron spectroscopy (FE-SEM). The structural detail and the chemical analysis were characterized by using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The cyclic voltammetry (CV) curve of r-GO/MWCNTs nanocomposite appeared nearly rectangular in shape. The current density (A/g) was gradually increased by increasing the scan rate of the voltage, as high as a scan rate of 500 mVs-1. At a current density of 10 mAg-1, the specific capacitance of the nanocomposite, estimated by galvanostatic (GA) charge/discharge measurement, is 150 Fg-1. These nanocomposites can be developed for supercapacitor electrodes.

Synthesis and Gas Sensing Properties of SnO2-CuO Nanocomposites

SnO2-CuO nanocomposites have been synthesized with the simple co-precipitation method for gas sensing properties. Sn and CuO powder were the starting materials. The synthesized products were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that SnO2-CuO nanocomposites have a tetragonal and monoclinic structure, respectively. SEM images verify that the some microballs are up to 10 µm and nanorods have a diameter range from 10-100 nm, while length ranges a few micrometers. The nanocomposite products were highly sensitivity to CO2 gas at room temperature.