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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.
Shibayama Naoyuki,Kanda Hiroyuki,Yusa Shin-ichi,Fukumoto Shota,Baranwal Ajay K.,Segawa Hiroshi,Miyasaka Tsutomu,Ito Seigo 나노기술연구협의회 2017 Nano Convergence Vol.4 No.18
We confirmed the influence of ZnO nanoparticle size and residual water on performance of all inorganic perovskite solar cells. By decreasing the size of the ZnO nanoparticles, the short-circuit current density (Jsc) and open circuit photovoltage (Voc) values are increased and the conversion efficiency is improved. Although the Voc value is not affected by the influence of residual water in the solution for preparing the ZnO layer, the Jsc value drops greatly. As a result, it was found that it is important to use the oxide nanoparticles with a small particle diameter and to reduce the water content in the oxide forming material in order to manufacture a highly efficient all inorganic perovskite solar cells.
Gold nanoparticles supported on mesoporous iron oxide for enhanced CO oxidation reaction
Tanaka, Shunsuke,Lin, Jianjian,Kaneti, Yusuf Valentino,Yusa, Shin-ichi,Jikihara, Yohei,Nakayama, Tsuruo,Zakaria, Mohamed Barakat,Alshehri, Abdulmohsen Ali,You, Jungmok,Hossain, Md. Shahriar A.,Yamauch The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.10
<P>Herein, we report the synthesis of gold (Au)-loaded mesoporous iron oxide (Fe2O3) as a catalyst for both CO and NH3 oxidation. The mesoporous Fe2O3 is firstly prepared using polymeric micelles made of an asymmetric triblock copolymer poly(styrene-<I>b</I>-acrylic acid-<I>b</I>-ethylene glycol) (PS-<I>b</I>-PAA-<I>b</I>-PEG). Owing to its unique porous structure and large surface area (87.0 m<SUP>2</SUP> g<SUP>−1</SUP>), the as-prepared mesoporous Fe2O3 can be loaded with a considerably higher amount of Au nanoparticles (Au NPs) (7.9 wt%) compared to the commercial Fe2O3 powder (0.8 wt%). Following the Au loading, the mesoporous Fe2O3 structure is still well-retained and Au NPs with varying sizes of 3-10 nm are dispersed throughout the mesoporous support. When evaluated for CO oxidation, the Au-loaded mesoporous Fe2O3 catalyst shows up to 20% higher CO conversion efficiency compared to the commercial Au/Fe2O3 catalyst, especially at lower temperatures (25-150 °C), suggesting the promising potential of this catalyst for low-temperature CO oxidation. Furthermore, the Au-loaded mesoporous Fe2O3 catalyst also displays a higher catalytic activity for NH3 oxidation with a respectable conversion efficiency of 37.4% compared to the commercial Au/Fe2O3 catalyst (15.6%) at 200 °C. The significant enhancement in the catalytic performance of the Au-loaded mesoporous Fe2O3 catalyst for both CO and NH3 oxidation may be attributed to the improved dispersion of the Au NPs and enhanced diffusivity of the reactant molecules due to the presence of mesopores and a higher oxygen activation rate contributed by the increased number of active sites, respectively.</P>