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Hydrothermal synthesis of titanate nanostructures with high UV absorption characteristics
Nawin Viriya-Empikul,Noriaki Sano,Takeyuki Kikuchi,Sareeya Bureekaew,Wiwut Tanthapanichakoon,Tawatchai Charinpanitkul 한국공업화학회 2010 Journal of Industrial and Engineering Chemistry Vol.16 No.1
The titanate nanostructures with high UV absorption characteristics could be fabricated by hydrothermal method within a temperature range of 90–150 8C. TEM, XRD, BET analyses, and UV–vis spectroscopy were employed to elucidate the synthesized titanate nanostructure characteristics which were microstructure, phase transformation, specific surface area, and band gap energy, respectively. With an increase in the hydrothermal treating temperature from 90 to 120 8C, the specific surface area of titanate nanostructures was increased from 83 to 258 m2/g,while the band gap energy of titanate nanostructures was increased from 3.44 to 3.84 eV and then slightly decreased to 3.81 eV at 150 8C. The fabricated titanate nanostructures could exhibit higher UV adsorption capability but lower photocatalytic activity when compared with that of commercial TiO2 powders.
Pornlada Daorattanachai,Supawadee Namuangruk,Nawin Viriya-empikul,Navadol Laosiripojana,Kajornsak Faungnawakij 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.6
The conversion of glucose, fructose, and cellulose to 5-hydroxymethylfurfural (HMF) was studied under hot compressed water. The effect of acid (H3PO4) and base (NaOH) catalysts was examined by combining experimental and theoretical studies. The experimental results showed that formation of HMF from fructose is more facile than that from glucose and cellulose. The density functional calculations explained the effect of catalysts on reaction mechanism and energy profile of glucose transformation. The ring-opening of b-glucose is predicted as the rate-limiting step in non-catalytic system, while the tautomerization or the hydride-shift is the rate-limiting step in the basic and acidic conditions, respectively.
Facile strategy for stability control of gold nanoparticles synthesized by aqueous reduction method
Tanyakorn Muangnapoh,Noriaki Sano,Shin-Ichi Yusa,Nawin Viriya-empikul,Tawatchai Charinpanitkul 한국물리학회 2010 Current Applied Physics Vol.10 No.2
A facile strategy for controlling sizes and stabilities of gold nanoparticles synthesized by aqueous reduction method was experimentally examined and reported. When pH of the solution of HAuCl4 and Na3C6H5O7 was controlled by introducing either NaOH or HCl with different concentration, the zeta potential of suspension of gold nanoparticles changed accordingly. With the strategy using a control of pH in a range of 5–9, the zeta potential of synthesized gold nanoparticles was regulated in a range of -60 to -40 mV, resulting in a stable red suspension of gold nanoparticles. Under a condition with pH < 5.0, gold nanoparticles could agglomerate after being kept quiescently for a day due to an adsorption of H+ on their surface, which in turn enhanced the attractive van der Waals interaction. On the other hand, synthesis of gold nanoparticles with pH > 9.1 would provide a lower amount of gold nanoparticles due to the formation of NaAuO2. Based on these results, a potential mechanism of gold nanoparticle synthesis was also discussed.