Color-tunable phosphors Sr0.94MoO4：xEu^3＋, （0.06 - x）Tb^3＋ were synthesized rapidly by microwave ra- diation method with active carbon particle as microwave absorbent. The synthesized phosphors were investigated ...Color-tunable phosphors Sr0.94MoO4：xEu^3＋, （0.06 - x）Tb^3＋ were synthesized rapidly by microwave ra- diation method with active carbon particle as microwave absorbent. The synthesized phosphors were investigated by X-ray powder diffraction （XRD） and fluorescence spec- trophotometer. The effects of the ratio of Eu^3＋ and Tb^3＋ on the phase structure and luminescent properties of the phos- phors were discussed. The results show that Eu^3＋,Tb^3＋-doped samples can be well indexed to the pure tetragonal scheelite- type SrMoO4, indicating that Eu^3＋ and Tb^3＋ are effectively doped into the SrMoO4 host lattices. The as-synthesized Sro.94MoO4：xEu^3＋,（0.06 - x）Tb^3＋ phosphors have two luminescent centers （Eu^3＋ and Tb^3＋）, which can show red and green emissions under ultraviolet light excitation, respec- tively. Doping concentration of Eu^3＋ and Tb^3＋ has great effect on the intensity of emission peaks and the chromaticity of the samples, and the full color between green and red light can be achieved by adjusting the relative concentration of Eu^3＋ and Tb^3＋.展开更多
SrMoO4 nanoplates were synthesized by a facile reverse microemulsion method at room temperature.Energy evolution of this in situ growth process was monitored by means of a microcalorimeter.A sharp exothermic peak for ...SrMoO4 nanoplates were synthesized by a facile reverse microemulsion method at room temperature.Energy evolution of this in situ growth process was monitored by means of a microcalorimeter.A sharp exothermic peak for the initial reaction and two discontinuous relatively weak exothermic peaks for the subsequent crystal growth emerged on the microcalorimetric heat flow curve.Based on the in situ thermokinetic data,the rate constants of the nucleation process and crystallization process at 298.15 K were calculated to be 4.078×10-3 and 5.033×10-4 s-1,respectively.The growth mechanism and energy evolution were investigated.展开更多
To probe the potential utilities in the photocatalyst and luminescent materials, a series of SrMoO4 samples have been prepared via the hydrothermal preparation with different stirring speeds. These SrMoO4 samples were...To probe the potential utilities in the photocatalyst and luminescent materials, a series of SrMoO4 samples have been prepared via the hydrothermal preparation with different stirring speeds. These SrMoO4 samples were characterized using X-ray diffraction analysis, scanning electron microscopy, UV-diffuse reflection spectroscopy （UV-vis）. It has been found that the lattice parameters and [MOO4] tetrahedmn distortion of SrMoO4 samples are increased with the increased stirring speed in the process of bydrothermal preparation. By changing the stirring speeds, spindle and succulent-like morphologies have been obtained. UV-vis results show that the band gaps of SrMoO4 samples are sensitive to the stirring speed. As for the luminescent and photocatalytic properties, our experimental results clearly suggest that, compared with those samples without stirring, the luminescent and photocatalytic activities are enhanced with stirring in the hydrothermal preparation. The photodegradation of methyl blue （MB） over SrMoO4 system increases from 30% to 50%; with stirring, which may be related to small band gaps and porous surfaces. Our results indicate that stirring may he one important technique to improve the photocatalytic properties, especially in the process of hydrothermal method.展开更多
SrMoO4：Eu^3＋（10%） phosphors were produced via hydrothermal synthesis and co-precipitation.We systematically analyzed how the morphology and luminescence properties of the phosphors were affected by the synthesis c...SrMoO4：Eu^3＋（10%） phosphors were produced via hydrothermal synthesis and co-precipitation.We systematically analyzed how the morphology and luminescence properties of the phosphors were affected by the synthesis conditions,including the p H of the precursor solution,stirring speed,and postsintering temperature.The samples synthesized at p H = 8 and 9 were spindle-like rods with a core-shell structure.When the stirring speed increased to Vs = 150 r/min,the core-shell structure disappeared.Photoluminescence measurements indicated that the Sr Mo O4：Eu^3＋samples under ultraviolet radiation produced strong red emission centered at 616 nm.The luminescence properties were greatly affected by the p H,stirring during hydrothermal reaction,and use of post-annealing.The related mechansim is discussed.展开更多
Well-dispersed uniform SrMoO4 nanocrystals were synthesized by thermal decomposition of a metalorganic salt in the organic solvent under different temperatures（80, 100, 120, 140, and 160？C）. The smallest diameter o...Well-dispersed uniform SrMoO4 nanocrystals were synthesized by thermal decomposition of a metalorganic salt in the organic solvent under different temperatures（80, 100, 120, 140, and 160？C）. The smallest diameter of these SrMoO4 nanocrystals is only about 2 nm, which is regarded as the smallest values to date. The UV–vis absorbance spectra present that the larger absorption of our samples is mainly distributed in the visible light region and UV light region. The lowest energy gap is found to be 2.71 e V.Such a small gap is ascribed to the introduction of intermediate energy levels, which are due to the surface defects with decreasing the size of nanostrcutrues. The photoluminescence measurement suggests that all these samples exhibit a board and strong emission band in the range from 500 to 700 nm. Through the deconvolution of the photoluminescence spectra, the emission profiles are found to be associated with three various components（green, yellow, and red）. Moreover, the photodegration of methyl blue over our SrMoO4 samples reaches nearly 100% in 120 min. Such a high photodegration may be related to the following aspects. One is related to the size and morphology. Larger surface area leads to more absorption of methyl blue, and the small size nanoparticles lead to the efficient separation of these photogenerated electron-hole pairs. The other is related to the narrow band gap. The small gap is beneficial to more electrons to be excited from the valence band to the conduction band, and eventually more electron-hole pairs are created. Our investigations clearly suggest that thermal decomposition of one metal-organic salt in organic solvent will be a good choice to synthesize the nanoparticles with small size and uniform distribution. Our results also indicate that these SrMoO4 nanoparticles possibly have great potential utilities in photocatalysts.展开更多
Photocatalytic nitrogen reduction for the green synthesis of ammonia at ambient conditions has been slowed by the narrow light harvesting range,low activity and high charge recombination of photocatalysts.Plasmonic se...Photocatalytic nitrogen reduction for the green synthesis of ammonia at ambient conditions has been slowed by the narrow light harvesting range,low activity and high charge recombination of photocatalysts.Plasmonic semiconducting nanomaterials are becoming the promising candidates for nitrogen photofixation because of the broad absorption spectrum,rich defects and hot carriers.In the present study,plasmonic SrMoO_(4) is developed by regulating the concentration of oxygen vacancies that are accompanied in the reduction process from Mo^(6+) to Mo^(5+).The stable and tunable localized surface plasmon resonance(LSPR)absorption in visible and near infrared light range makes the wide bandgap SrMoO_(4) utilize the solar energy more efficiently.Energetic electrons from both the intrinsic band excitation and the LSPR excitation enable the reduction of dinitrogen molecules thermodynamically in ultrapure water to ammonia.This work provides a unique clue to design efficient photocatalysts for nitrogen fixation.展开更多
基金financially supported by the National Natural Science Foundation of China (No.21301046)
文摘Color-tunable phosphors Sr0.94MoO4：xEu^3＋, （0.06 - x）Tb^3＋ were synthesized rapidly by microwave ra- diation method with active carbon particle as microwave absorbent. The synthesized phosphors were investigated by X-ray powder diffraction （XRD） and fluorescence spec- trophotometer. The effects of the ratio of Eu^3＋ and Tb^3＋ on the phase structure and luminescent properties of the phos- phors were discussed. The results show that Eu^3＋,Tb^3＋-doped samples can be well indexed to the pure tetragonal scheelite- type SrMoO4, indicating that Eu^3＋ and Tb^3＋ are effectively doped into the SrMoO4 host lattices. The as-synthesized Sro.94MoO4：xEu^3＋,（0.06 - x）Tb^3＋ phosphors have two luminescent centers （Eu^3＋ and Tb^3＋）, which can show red and green emissions under ultraviolet light excitation, respec- tively. Doping concentration of Eu^3＋ and Tb^3＋ has great effect on the intensity of emission peaks and the chromaticity of the samples, and the full color between green and red light can be achieved by adjusting the relative concentration of Eu^3＋ and Tb^3＋.
基金Supported by the National Natural Science Foundation of China(No.20963001)the Major Project of Natural Science Foundation of Guangxi Province,China(No.0991001Z)
文摘SrMoO4 nanoplates were synthesized by a facile reverse microemulsion method at room temperature.Energy evolution of this in situ growth process was monitored by means of a microcalorimeter.A sharp exothermic peak for the initial reaction and two discontinuous relatively weak exothermic peaks for the subsequent crystal growth emerged on the microcalorimetric heat flow curve.Based on the in situ thermokinetic data,the rate constants of the nucleation process and crystallization process at 298.15 K were calculated to be 4.078×10-3 and 5.033×10-4 s-1,respectively.The growth mechanism and energy evolution were investigated.
基金financially supported by the National Natural Science Foundation of China under Grant Nos.11204001 and 51471001supported by the Anhui University Scientific Research Fund No.201610357120the Collaborative Innovation Research Center for Weak Signal Sensitive Materials and Devices Integration
文摘To probe the potential utilities in the photocatalyst and luminescent materials, a series of SrMoO4 samples have been prepared via the hydrothermal preparation with different stirring speeds. These SrMoO4 samples were characterized using X-ray diffraction analysis, scanning electron microscopy, UV-diffuse reflection spectroscopy （UV-vis）. It has been found that the lattice parameters and [MOO4] tetrahedmn distortion of SrMoO4 samples are increased with the increased stirring speed in the process of bydrothermal preparation. By changing the stirring speeds, spindle and succulent-like morphologies have been obtained. UV-vis results show that the band gaps of SrMoO4 samples are sensitive to the stirring speed. As for the luminescent and photocatalytic properties, our experimental results clearly suggest that, compared with those samples without stirring, the luminescent and photocatalytic activities are enhanced with stirring in the hydrothermal preparation. The photodegradation of methyl blue （MB） over SrMoO4 system increases from 30% to 50%; with stirring, which may be related to small band gaps and porous surfaces. Our results indicate that stirring may he one important technique to improve the photocatalytic properties, especially in the process of hydrothermal method.
基金financially supported by the National Natural Science Foundation of China under Grant No.11204001the Anhui Provincial Natural Science Foundation(No.1308085MA04)+3 种基金the Higher Educational Natural Science Foundation of Anhui Province(No.KJ2013A031)supported by Anhui University Scientific Research Fund No.KYXL2013009"211 Project" of Anhui University(No.SZJYKC2013020)the National Training Programs of Innovation and Entrepreneurship for Undergraduates(No.201410357005)
文摘SrMoO4：Eu^3＋（10%） phosphors were produced via hydrothermal synthesis and co-precipitation.We systematically analyzed how the morphology and luminescence properties of the phosphors were affected by the synthesis conditions,including the p H of the precursor solution,stirring speed,and postsintering temperature.The samples synthesized at p H = 8 and 9 were spindle-like rods with a core-shell structure.When the stirring speed increased to Vs = 150 r/min,the core-shell structure disappeared.Photoluminescence measurements indicated that the Sr Mo O4：Eu^3＋samples under ultraviolet radiation produced strong red emission centered at 616 nm.The luminescence properties were greatly affected by the p H,stirring during hydrothermal reaction,and use of post-annealing.The related mechansim is discussed.
基金supported by the National Science Foundation of China(Nos.11204001 and 51471001)supported by the Anhui University Scientific Research Fund(No.201610357120)the Collaborative Innovation Research Center for Weak Signal Sensitive Materials and Devices Integration
文摘Well-dispersed uniform SrMoO4 nanocrystals were synthesized by thermal decomposition of a metalorganic salt in the organic solvent under different temperatures（80, 100, 120, 140, and 160？C）. The smallest diameter of these SrMoO4 nanocrystals is only about 2 nm, which is regarded as the smallest values to date. The UV–vis absorbance spectra present that the larger absorption of our samples is mainly distributed in the visible light region and UV light region. The lowest energy gap is found to be 2.71 e V.Such a small gap is ascribed to the introduction of intermediate energy levels, which are due to the surface defects with decreasing the size of nanostrcutrues. The photoluminescence measurement suggests that all these samples exhibit a board and strong emission band in the range from 500 to 700 nm. Through the deconvolution of the photoluminescence spectra, the emission profiles are found to be associated with three various components（green, yellow, and red）. Moreover, the photodegration of methyl blue over our SrMoO4 samples reaches nearly 100% in 120 min. Such a high photodegration may be related to the following aspects. One is related to the size and morphology. Larger surface area leads to more absorption of methyl blue, and the small size nanoparticles lead to the efficient separation of these photogenerated electron-hole pairs. The other is related to the narrow band gap. The small gap is beneficial to more electrons to be excited from the valence band to the conduction band, and eventually more electron-hole pairs are created. Our investigations clearly suggest that thermal decomposition of one metal-organic salt in organic solvent will be a good choice to synthesize the nanoparticles with small size and uniform distribution. Our results also indicate that these SrMoO4 nanoparticles possibly have great potential utilities in photocatalysts.
文摘Photocatalytic nitrogen reduction for the green synthesis of ammonia at ambient conditions has been slowed by the narrow light harvesting range,low activity and high charge recombination of photocatalysts.Plasmonic semiconducting nanomaterials are becoming the promising candidates for nitrogen photofixation because of the broad absorption spectrum,rich defects and hot carriers.In the present study,plasmonic SrMoO_(4) is developed by regulating the concentration of oxygen vacancies that are accompanied in the reduction process from Mo^(6+) to Mo^(5+).The stable and tunable localized surface plasmon resonance(LSPR)absorption in visible and near infrared light range makes the wide bandgap SrMoO_(4) utilize the solar energy more efficiently.Energetic electrons from both the intrinsic band excitation and the LSPR excitation enable the reduction of dinitrogen molecules thermodynamically in ultrapure water to ammonia.This work provides a unique clue to design efficient photocatalysts for nitrogen fixation.
