Chemical state

About: Chemical state is a research topic. Over the lifetime, 2378 publications have been published within this topic receiving 78183 citations.

Preparation of visible-light active N-doped nano-TiO 2 photocatalyst by hydrothermal method

Abstract: The nitrogen doping nano-titania (TiO 2 ) photocatalyst was synthesized through a hydrothermal method. Ethylene Diamine Tetraacetic Acid (EDTA) was selected as the nitrogen resource to combine with titanium sulfate (Ti(SO 4 ) 2 ) via chemical complexation. The crystal size and phase, morphology, chemical state and photocatalytic ability were analyzed and characterized by X-ray diffraction (XRD), UV-visible spectrophotometer(UV-Vis), field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS). A strong absorption in visible light region was observed. The results showed that the nitrogen was doped effectively and the chemical state of the nitrogen was Ti-N-O and Ti-O-N. Furthermore, the nitrogen doping TiO 2 was expressed as TiO 1.9697 N 0.0303 by calculating the concentration of nitrogen. The photocatalytic ability in visible light region could be improved by nitrogen doping in comparison with commercial P25 through the photodegradaton of organic pollutant methylene blue (MB), demonstrating its promising potential in environmental application.

Surface structure - catalytic function in nanophase gold catalysts

Abstract: Catalysts consisting of ultra-fine gold particles supported on iron oxide have been synthesized by the coprecipitation method. Subsequent to preparation, each sample was heat treated in air at four different temperatures, ranging from 473 K to 773 K. Steady state carbon monoxide oxidation was carried out over each sample. Upon extended reaction, catalyst deactivation took place over three of the catalysts whose respective surface compositions (e.g., gold to iron atomic ratio) were altered appreciably from their initial state. Surface structure analyses performed on all the unreacted catalysts have revealed variations in physical properties (e.g., degree of crystallinity and particle size). In addition, lattice parameters of gold were observed to increase up to 20 % from the bulk value. In contrast, XPS showed both gold and iron to be in essentially the same chemical states for all catalysts, irrespective of heat treatment temperatures. The importance of surface sensitive parameters to catalytic function are discussed.

Chemical state analysis of sulfur in hair samples by high resolution XRF.

Abstract: 生体試料の分析の分野においても,定性・定量分析だけでなく,含まれている元素の状態分析の必要性が高まっている.本研究では,ヒトの毛髪を試料に取り上げ,高分解能XRF法により試料に含まれる硫黄の状態分析が可能であることを示した.高分解能蛍光X線スペクトルは,二結晶型分光器{分光結晶:Ge(111)×2}を用いて測定した.更に得られた高分解能SKαスペクトルに対し,最小二乗法によるピーク分離法を適用して解析を行い,定量的な状態分析を行った.22種の標準物質の測定と,試料の測定及び解析から,ヒトの毛髪中の硫黄はS2-(有機物)が主成分であり(95～96%),S6+(無機物)がわずかに存在することが分かった.この二つの状態以外は存在しないことも分かった.中国人と日本人,男性と女性を対照させて検討した結果,硫黄の量,状態共に国籍の差が認められた.又,女性のほうがS6+がわずかながら多いことも認められた.一方黒髪と白髪を対比して検討したところ,白髪は黒髪に対しS2-が減少する傾向にあることが分かった.X線照射による損傷については.本研究での条件程度のX線(Cr,35kV,30mA)であれば,1時間強程度の照射ならば硫黄の状態が変化することはないことが明らかになった.

Control of the chemical state change of sulfur in solid compound targets during high-resolution PIXE measurements

Abstract: A high-energy-resolution wavelength-dispersive (WD) X-ray spectrometer in the Johansson geometry, which allowed energy resolution below the natural linewidth of the Kα lines was employed in measurements of the proton-induced Kα X-ray emission spectra for six typical sulfur compounds (CdS, Na2SO3, Na2 S2O5, NaHSO3, (NH4)2SO4, and Na2SO4) to investigate the chemical state change during 2.4-MeV proton irradiation with a current density of 7.5 nA/mm2. We found that the chemical state change of each compound depended on the various factors affecting the surface temperature increase, such as target thickness, mounting method, and existence of active cooling during the measurement. The chemical state of sulfur on the target surface of S4+ compounds was gradually changed into S6+ without exception through irradiation under poor cooling conditions. Sulfur compounds of the S0 and S6+ states with closed shell structures were proven to be chemically stable against proton bombardment, as expected. However, (NH4)2SO4 was found to be most sensitive to proton irradiation among the sulfur compounds, and S0, one of the reaction products, became a major element at doses higher than 3 × 108 Gy. If thick targets were mounted by using a carbon adhesive tape, chemical state change could be observed in some cases even with lowtemperature cooling down to −80 °C, however, the chemical state change seemed to be remarkably suppressed by using very thin targets mounted with a silver paste even without active cooling. In conclusion, the chemical states of sulfur compounds could be preserved without significant change for an accumulated dose of about 3 × 107 Gy, equivalent to a typical high-resolution PIXE scanning period, by adopting a proper target preparation scheme to discharge proton-induced thermal energy effectively from the irradiated target surface.