H2 is an important energy carrier for replacing fossil fuel in the future due to its high energy density and environmental friendliness.As a sustainable H2-generation method,photocatalytic H2 production by water split...H2 is an important energy carrier for replacing fossil fuel in the future due to its high energy density and environmental friendliness.As a sustainable H2-generation method,photocatalytic H2 production by water splitting has attracted much interest.Here,oil-soluble ZnxCd1-xS quantum dot(ZCS QD)with a uniform particle size distribution were prepared by a hot-injection method.However,no photocatalytic H2-production activity was observed for the oil-soluble ZCS QD due to its hydrophobicity.Thus,the oil-soluble ZCS QD was converted into a water-soluble ZCS QD by a ligand-exchange method.The water-soluble ZCS QD exhibited excellent photocatalytic H2-production performance in the presence of glycerin and Ni^2+,with an apparent quantum efficiency of 15.9%under irradiation of 420 nm light.Further,the photocatalytic H2-generation activity of the ZCS QD was~10.7 times higher than that of the ZnxCd1-xS relative samples prepared by the conventional co-precipitation method.This work will inspire the design and fabrication of other semiconductor QD photocatalysts because QD exhibits excellent separation efficiency for photogenerated electron-hole pairs due to its small crystallite size.展开更多
Ho^（3＋） doped La_（2（1-x））Yb_（2x）TiO_5 samples were prepared by sol-gel method. Pyrochlore structured powders were obtained under the annealing of the as-prepared samples at 1100 °C for 3 h in the air. Al...Ho^（3＋） doped La_（2（1-x））Yb_（2x）TiO_5 samples were prepared by sol-gel method. Pyrochlore structured powders were obtained under the annealing of the as-prepared samples at 1100 °C for 3 h in the air. All the samples were characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM） and photoluminescent spectroscopy. When x=0, we obtained La_2TiO_5 phosphors. Monitored at 546 nm, the excitation spectrum of Ho^（3＋） activated La_2TiO_5 phosphors consisted of a broad band originating from the charge-transfer band（CTB） between Ho^（3＋） ions and the nearest neighboring O^（2-） ions at 250-280 nm and four sharp bands associated to f-f transitions of Ho^（3＋） ions at 350-500 nm. Under the blue light excitation at 461 nm, Ho^（3＋） ion in La_2TiO_5 emitted an intense green emission band at 546 nm due to the transition of ~5S_2, ~5F_4→~5I_8. Two intense bands were observed at 490 nm（blue, ~5F_3→I_8） and 663 nm（red, ~5F_5→~5I_8） in the up-conversion（UC） spectrum under 980 nm NIR laser excitation in La_2TiO_5 phosphors activated with Ho^（3＋） alone, whereas they were much different from the down-conversion（DC） luminescent samples. When x=7.5 mol.%-17.5 mol.%, the UC emission spectra of them dominated at 546 nm（green, ~5S_2, ~5F_4→~5I_8） and enhanced significantly with the dose of Yb^（3＋） ion. The decay curve also confirmed that the transitions of ~5F_4→~5I_8 and ~5S_2→~5I_8 were merged into one emission band at 546 nm.展开更多
文摘H2 is an important energy carrier for replacing fossil fuel in the future due to its high energy density and environmental friendliness.As a sustainable H2-generation method,photocatalytic H2 production by water splitting has attracted much interest.Here,oil-soluble ZnxCd1-xS quantum dot(ZCS QD)with a uniform particle size distribution were prepared by a hot-injection method.However,no photocatalytic H2-production activity was observed for the oil-soluble ZCS QD due to its hydrophobicity.Thus,the oil-soluble ZCS QD was converted into a water-soluble ZCS QD by a ligand-exchange method.The water-soluble ZCS QD exhibited excellent photocatalytic H2-production performance in the presence of glycerin and Ni^2+,with an apparent quantum efficiency of 15.9%under irradiation of 420 nm light.Further,the photocatalytic H2-generation activity of the ZCS QD was~10.7 times higher than that of the ZnxCd1-xS relative samples prepared by the conventional co-precipitation method.This work will inspire the design and fabrication of other semiconductor QD photocatalysts because QD exhibits excellent separation efficiency for photogenerated electron-hole pairs due to its small crystallite size.
基金supported by the National Natural Science Foundation of China(51401130)the Natural Science Foundation of Liaoning Province(2014028015)Fundamental Research Foundation of Central Universities(N142304007)
文摘Ho^（3＋） doped La_（2（1-x））Yb_（2x）TiO_5 samples were prepared by sol-gel method. Pyrochlore structured powders were obtained under the annealing of the as-prepared samples at 1100 °C for 3 h in the air. All the samples were characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM） and photoluminescent spectroscopy. When x=0, we obtained La_2TiO_5 phosphors. Monitored at 546 nm, the excitation spectrum of Ho^（3＋） activated La_2TiO_5 phosphors consisted of a broad band originating from the charge-transfer band（CTB） between Ho^（3＋） ions and the nearest neighboring O^（2-） ions at 250-280 nm and four sharp bands associated to f-f transitions of Ho^（3＋） ions at 350-500 nm. Under the blue light excitation at 461 nm, Ho^（3＋） ion in La_2TiO_5 emitted an intense green emission band at 546 nm due to the transition of ~5S_2, ~5F_4→~5I_8. Two intense bands were observed at 490 nm（blue, ~5F_3→I_8） and 663 nm（red, ~5F_5→~5I_8） in the up-conversion（UC） spectrum under 980 nm NIR laser excitation in La_2TiO_5 phosphors activated with Ho^（3＋） alone, whereas they were much different from the down-conversion（DC） luminescent samples. When x=7.5 mol.%-17.5 mol.%, the UC emission spectra of them dominated at 546 nm（green, ~5S_2, ~5F_4→~5I_8） and enhanced significantly with the dose of Yb^（3＋） ion. The decay curve also confirmed that the transitions of ~5F_4→~5I_8 and ~5S_2→~5I_8 were merged into one emission band at 546 nm.
