对两种颗粒吸收光谱测量方法的差异性及在二类水体中的适用性进行了研究．通过理论推导指出．颗粒后向散射是T方法（Transmittance method）较T—R方法（Transmittance and Reflectance method）测量结果偏高的首要原因，并且其偏高程...对两种颗粒吸收光谱测量方法的差异性及在二类水体中的适用性进行了研究．通过理论推导指出．颗粒后向散射是T方法（Transmittance method）较T—R方法（Transmittance and Reflectance method）测量结果偏高的首要原因，并且其偏高程度同时取决于颗粒的后向散射和吸收性质；对福建沿岸典型二类水体同时采用两种方法测量的结果表明：与T—R方法相比．T方法测量所得总颗粒、非藻类颗粒、藻类颗粒的光学密度．在400～700nm波段的平均相对误差分别为38．5％、40．0％、33．1％．根据理论推导和实际测量分析结果，提出在中国近海二类水体中需采用T—R方法来替代T方法测量颗粒吸收光谱的建议．展开更多
Cu/ZrO2/SiO2 are efficient catalysts for the selective hydrogenation of CO2 to CH3OH. In order to understand the role of ZrO2 in these mixed-oxides based catalysts, in situ X-ray absorption spectroscopy has been carri...Cu/ZrO2/SiO2 are efficient catalysts for the selective hydrogenation of CO2 to CH3OH. In order to understand the role of ZrO2 in these mixed-oxides based catalysts, in situ X-ray absorption spectroscopy has been carried out on the Cu and Zr K-edge. Under reaction conditions, Cu remains metallic, while Zr is present in three types of coordination environment associated with 1) bulk ZrO2, 2) coordinatively saturated and 3) unsaturated Zr(Ⅳ) surface sites. The amount of coordinatively unsaturated Zr surface sites can be quantified by linear combination fit of reference X-Ray absorption near edge structure (XANES) spectra and its amount correlates with CH3OH formation rates, thus indicating the importance of Zr(Ⅳ) Lewis acid surface sites in driving the selectivity toward CH3OH. This finding is consistent with the proposed mechanism, where CO2 is hydrogenated at the interface between the Cu nanoparticles that split H2 and Zr(Ⅳ) surface sites that stabilizes reaction intermediates.展开更多
The interaction between silver nanoparticles and Methylene Blue （MB） is studied by UV-Vis spectroscopy and fluorescence spec- trometry. The UV-Vis absorption of the silver nanoparticles changes dramatically with the...The interaction between silver nanoparticles and Methylene Blue （MB） is studied by UV-Vis spectroscopy and fluorescence spec- trometry. The UV-Vis absorption of the silver nanoparticles changes dramatically with the addition of MB. However, no obvious changes of absorption spectra of MB are observed when silver colloids are added into the MB solution. In the presence of surfactant SDS, the catalysis of the silver nanoparticles in the reduction of MB by sodium borohydride is exhibited by UV-Vis and fluorescence spectrosopy of MB displaying faster response compared with the absence of the silver nanoparticles. The results show that the activity of surfactant SDS modified silver nanoparticles is great and a strong physical adsorption to MB exists.展开更多
By stepwise adding of reducer N2H4.H2O, cuprous oxide （Cu2O） nanoparticles （NPs） with adjustable structures were synthe- sized. The features of Cu2O NPs were characterized by XRD, TEM and UV-Vis absorption spectra...By stepwise adding of reducer N2H4.H2O, cuprous oxide （Cu2O） nanoparticles （NPs） with adjustable structures were synthe- sized. The features of Cu2O NPs were characterized by XRD, TEM and UV-Vis absorption spectra. When the reducer was added into the reactant system at one time, the sizes of the Cu2O NPs are in the range of 120-140 nm. Most Cu2O NPs are sol- id spheres. As the reducer was divided into two equal parts and stepwisely added, almost all the NPs are hollow spheres with good size （150-170 nm） distribution and dispersity. But when the reducer was divided into three or four equal parts and stepwisely added, the NPs are hollow spheres, core-shell structures or solid spheres, and the sizes distribution of the products is deteriorated. The effect of sodium hydrate （NaOH） was also probed. Addition of NaOH speeded up the nucleation and growth processes of Cu2O NPs. With the alkalinity increase, the shells of the hollow spheres become compact and the thicknesses of the shells increase, but the size distribution of the NPs is deteriorated. The absorption spectra of the CuzO NPs are tunable. With the shell thicknesses increase, the absorption peaks have red shifts. An inside-outside growth model of Cu2O NPs was proposed to explain the results. The Cu2O single crystalline grains grow not only in the reactant solution, but also inside of the hollow nanospheres. The new Cu2O nanocrystallines can not only aggregate onto the shells of the nano hollow spheres, but also inside and outside of the hollow spheres, which leads to increasing the shell thicknesses of the hollow spheres, forming core-shell structures or small solid spheres of Cu2O NPs, respectively.展开更多
文摘对两种颗粒吸收光谱测量方法的差异性及在二类水体中的适用性进行了研究．通过理论推导指出．颗粒后向散射是T方法（Transmittance method）较T—R方法（Transmittance and Reflectance method）测量结果偏高的首要原因，并且其偏高程度同时取决于颗粒的后向散射和吸收性质；对福建沿岸典型二类水体同时采用两种方法测量的结果表明：与T—R方法相比．T方法测量所得总颗粒、非藻类颗粒、藻类颗粒的光学密度．在400～700nm波段的平均相对误差分别为38．5％、40．0％、33．1％．根据理论推导和实际测量分析结果，提出在中国近海二类水体中需采用T—R方法来替代T方法测量颗粒吸收光谱的建议．
基金E.L.,K.L.,P.W.,and S.T.are supported by the SCCER-Heat and Energy Storage program
文摘Cu/ZrO2/SiO2 are efficient catalysts for the selective hydrogenation of CO2 to CH3OH. In order to understand the role of ZrO2 in these mixed-oxides based catalysts, in situ X-ray absorption spectroscopy has been carried out on the Cu and Zr K-edge. Under reaction conditions, Cu remains metallic, while Zr is present in three types of coordination environment associated with 1) bulk ZrO2, 2) coordinatively saturated and 3) unsaturated Zr(Ⅳ) surface sites. The amount of coordinatively unsaturated Zr surface sites can be quantified by linear combination fit of reference X-Ray absorption near edge structure (XANES) spectra and its amount correlates with CH3OH formation rates, thus indicating the importance of Zr(Ⅳ) Lewis acid surface sites in driving the selectivity toward CH3OH. This finding is consistent with the proposed mechanism, where CO2 is hydrogenated at the interface between the Cu nanoparticles that split H2 and Zr(Ⅳ) surface sites that stabilizes reaction intermediates.
基金supported by the National Natural Science Foundation of China(No.20875059)
文摘The interaction between silver nanoparticles and Methylene Blue （MB） is studied by UV-Vis spectroscopy and fluorescence spec- trometry. The UV-Vis absorption of the silver nanoparticles changes dramatically with the addition of MB. However, no obvious changes of absorption spectra of MB are observed when silver colloids are added into the MB solution. In the presence of surfactant SDS, the catalysis of the silver nanoparticles in the reduction of MB by sodium borohydride is exhibited by UV-Vis and fluorescence spectrosopy of MB displaying faster response compared with the absence of the silver nanoparticles. The results show that the activity of surfactant SDS modified silver nanoparticles is great and a strong physical adsorption to MB exists.
基金supported by the National Natural Science Foundation of China(Grant Nos.41172110 and 61107090)Shandong Provincial Natural Science Foundation(Grant No.ZR2011BZ007)
文摘By stepwise adding of reducer N2H4.H2O, cuprous oxide （Cu2O） nanoparticles （NPs） with adjustable structures were synthe- sized. The features of Cu2O NPs were characterized by XRD, TEM and UV-Vis absorption spectra. When the reducer was added into the reactant system at one time, the sizes of the Cu2O NPs are in the range of 120-140 nm. Most Cu2O NPs are sol- id spheres. As the reducer was divided into two equal parts and stepwisely added, almost all the NPs are hollow spheres with good size （150-170 nm） distribution and dispersity. But when the reducer was divided into three or four equal parts and stepwisely added, the NPs are hollow spheres, core-shell structures or solid spheres, and the sizes distribution of the products is deteriorated. The effect of sodium hydrate （NaOH） was also probed. Addition of NaOH speeded up the nucleation and growth processes of Cu2O NPs. With the alkalinity increase, the shells of the hollow spheres become compact and the thicknesses of the shells increase, but the size distribution of the NPs is deteriorated. The absorption spectra of the CuzO NPs are tunable. With the shell thicknesses increase, the absorption peaks have red shifts. An inside-outside growth model of Cu2O NPs was proposed to explain the results. The Cu2O single crystalline grains grow not only in the reactant solution, but also inside of the hollow nanospheres. The new Cu2O nanocrystallines can not only aggregate onto the shells of the nano hollow spheres, but also inside and outside of the hollow spheres, which leads to increasing the shell thicknesses of the hollow spheres, forming core-shell structures or small solid spheres of Cu2O NPs, respectively.
