Sorapong Pavasupree

Natural rutile-derived titanate nanofibers prepared by direct hydrothermal processing

Long titanate nanofibers (typically 10–500 μm in length and 20–50 nm in diameter) were successfully prepared in high yield by the direct hydrothermal processing using natural rutile as a starting material. Fourier transform infrared spectroscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy, electron diffraction, and x-ray diffraction demonstrated that the as-synthesized nanofibers presumably consisted of sodium hydrogen trititanate [(Na,H) 2 Ti 3 O 7, e.g., Na 0.4 H 1.6 Ti 3 O 7 ] including some hexatitanate-type defects [(Na,H) 2 Ti 6 O 13 ]. A partial topotactic condensation model explained their nanostructure well. Although the as-synthesized fibers are defective, they can be cured by a post-heat-treatment in air. The direct hydrothermal treatment for natural rutile will be a promising low-cost process for one-dimensional nanomaterials, which can act not only as a reaction step but also as a purification step.

Synthesis and characterization of nanoporous, nanorods, nanowires metal oxides

Abstract Mesoporous high surface area and high crystallinity MO2 (M=Ti, Ce, Zr, and Hf) and their mixed oxides powders were synthesized by a modified sol–gel method using laurylamine hydrochloride, metal alkoxide and acetylacetone. The prepared powders had a crystalline size of about 5–15 nm, a specific surface area of 44–80 m2/g, and a narrow pore size distribution with average pore diameter of about 3–6 nm. One-dimensional (1D) nanostructured (nanorods and nanowires) metal oxides were also successfully synthesized. These synthesis methods provide simple routes to fabricate nanostructured materials under mild conditions. These materials are promising forchemical and energy-related applications such as catalysts, and semiconductors in dye-sensitized solar cell.

Synthesis of TiO2 Nanotubes and Its Photocatalytic Activity for H2 Evolution

TiO2-derived nanotubes were prepared by hydrothermal treatment in 10 M NaOH(aq) by using commercially available TiO2 (Degussa P-25) as starting material. N2-adsorption/desorption analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) observations of the obtained product revealed the formation of titanate nanotube structure with its diameter of about 10–20 nm. The effect of post-heat-treatment on the phase structure, morphology, specific surface area and photocatalytic activity was investigated. The TiO2 (B) nanotubes could be observed at post-heat-treatment of 300 °C. As post-heat-treatment was increased to 400 °C, the nanotubes began to transform into nanoparticles of anatase phase, producing a bi-crystalline mixture of TiO2 (B) nanotubes and anatase nanoparticles. Moreover, the particles changed into rutile phase through the post-heat-treatment at higher temperatures over 700 °C. The photocatalytic activity of prepared samples was evaluated with photocatalytic H2 evolution. The results showed that the TiO2-derived nanotubes treated at appropriate temperature exhibited high H2 evolution.

Fabrication and Utilization of Titania Nanofibers from Natural Leucoxene Mineral in Photovoltaic Applications

TiO2 nanofibers were synthesized from natural leucoxene mineral via a hydrothermal process. The shapes, crystalline structure, shape transformation, phase transformation, and specific surface area of the resulting nanostructured materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer–Emmett–Teller (BET) surface area measurements. The size of prepared nanofibers was about 12–58 nm in width and about 3–22 µm in length. The BET surface area of the prepared sample was about 55 m2/g. Obtained nanofibers were preliminarily applied as photocatalysts for hydrogen evolution and electrodes for dye-sensitized solar cells (DSSCs).

The Effect of Molar Ratio of TiO2/WO3 Nanocomposites on Visible Light Prepared by Hydrothermal Method

The coupled TiO2/WO3 nanocomposites were synthesized by hydrothermal method by using hydrogen titanate and ammonium metatungstate hydrate as the precursors of TiO2 and WO3, respectively. The effects of hydrothermal conditions to prepare hydrogen titanate powders were studied. It was found that the hydrothermal condition at 130 °C for 24h shown the best result. The TiO2/WO3 nanocomposites were carried out as a function of varied molar ratio of TiO2/WO3 for 1:1, 3:1 and 1:3. The coupled TiO2/WO3 nanocomposites are characterized by transmission electron microscopy, UV-vis absorption spectra by UV–VIS spectrometer and photocatalytic activity by degradation of MB solution under visible light. The results show that the absorption spectra of the coupled TiO2/WO3 nanocomposites can be seen in visible light region which higher than pure TiO2 (from hydrothermal method) and P25-Degussa.

Hydrothermal Synthesis of Nanorods/Nanoparticles TiO 2 for Photocatalytic Activity and Dye-sensitized Solar Cell Applications

Nanorods/nanoparticles TiO 2 with mesoporous structure were synthesized by hydrothermal method at 150 °C for 20 h. The samples characterized by XRD, SEM, TEM, SAED, HRTEM, and BET surface area. The nanorods had diameter about 10-20 nm and the lengths of 100-200 nm, the nanoparticles had diameter about 5-10 nm. The prepared material had average pore diameter about 7-12 nm. The BET surface area and pore volume of the sample are about 203 m 2 /g and 0.655 cm 3 /g, respectively. The nanorods/nanoparticles TiO 2 with mesoporous structure showed higher photocatalytic activity (I 3 − concentration) than the nanorods TiO 2 , nanofibers TiO 2 , mesoporous TiO 2 , and commercial TiO 2 (ST-01, P-25, JRC-01, and JRC-03). The solar energy conversion efficiency (η) of the cell using nanorods/nanoparticles TiO 2 with mesoporous structure was about 7.12 % with Jsc of 13.97 mA/cm 2 , Voc of 0.73 V and ff of 0.70; while η of the cell using P-25 reached 5.82 % with Jsc of 12.74 mA/cm 2 , Voc of 0.704 V and ff of 0.649.

The Production of Poly(L-lactic acid) from 2-Steps Direct Polycondensation in 100 Kg Scale

Synthesis of poly(L-lactic acid), PLLA, in a mass scale production using 2-steps direct polycondensation methods was investigated. One hundred kilogram of L-lactic acid was esterified in a designed reactor under reduced pressure at elevated temperature in the first step, followed solid state polymerization, SSP. The synthesized PLLA from both laboratory (5 g) and mass (100 L) scales show comparable melting temperature, Tm (151 – 172 oC) and molecular weight (Mn) (10,000 -32,000) at the similar polymerization conditions. The appearances of synthesized PLLA are yellow-white solid powder. The results show high potential to produce environmental friendly polymer, PLLA, using non-complex facilities process.

Fabrication of Size-controllable Flower-like TiO2 and its Photocatalytic Activity

Size-controllable flower-like titante superstructure was prepared by simple hydrothermal method from amorphous TiO2 sphere precursor without any template. By changing concentration of electrolyte (KCl), the size of amorphous TiO2 sphere precursor could be controlled. N2-sorption analysis, scanning electron microscopy (SEM), and X-ray diffraction (XRD) observation of as-prepared samples revealed the formation of titanate nanosheet structure with high surface area of 350.7 mg. Upon thermal treatment at 500 C, the titanate nanosheets were converted into anatase TiO2 with deformation of their structures. The as-prepared flower-like titanate showed high photocatalytic activity for H2 evolution from water splitting reaction. Moreover, the sample heat treated at 500 C exhibited higher photocatalytic activity than that of commercial TiO2 anatase powder (ST-01).

Hydrothermal Synthesis of Nanofibers from Natural Ilmenite Mineral and Their Utilization for Dye-Sensitized Solar Cell

Titanate nanofibers were synthesized by a hydrothermal method using a low-cost ilmenite mineral as the starting material. The crystalline structure of the as-synthesized nanofibers demonstrated titanate structure (H2TixO2x+1). The bi-crystalline mixture consisting of TiO2 (B) and anatase TiO2 nanofibers was obtained by heat treatment at 500°C for 2 h. Dye-sensitized solar cells (DSSCs) with photoanode consisting of the nanocomposite of nanoparticles and nanofibers (5%) rendered a light-to-electricity conversion efficiency (η) of 0.28%. In contrast, the cells with photoanodes consisting of only nanoparticles and nanofibers exhibited η of 0.25% and 0.15%, respectively.

Photocatalytic Hydrogen Evolution over Tantalate Photocatalysts

Tantalate and titanate photocatalysts were prepared by solid-state reaction at 1273 K using various ratios of SrCO 3 , Ta 2 O 5 , and TiO 2 as starting materials. The prepared solid photocatalysts were characterized using XRD and SEM analysis. These prepared tantalate and titanate photocatalysts showed high photocatalytic H 2 evolution activity by water splitting without co-catalyst loading. The highest H 2 evolution rate of prepared photocatalysts was found to be 138 μmolh −1 with the starting materials ratio of 2/0.5/1.5 (Sr/Ta/Ti; mol). Furthermore, this photocatalyst showed photocatalytic activity for H 2 evolution from distilled water.