A series of WO3 samples with different crystalline phases were prepared by the thermal decomposition method from ammonium tungstate hydrate.X-ray diffraction（XRD）,scanning electron microscopy（SEM）,high-resolution ...A series of WO3 samples with different crystalline phases were prepared by the thermal decomposition method from ammonium tungstate hydrate.X-ray diffraction（XRD）,scanning electron microscopy（SEM）,high-resolution transmission electron microscopy（HRTEM）,X-ray photoelectron spectroscopy,and N2 adsorption-desorption were used to characterize the crystalline phase,morphology,particle size,chemical composition,and surface area of the WO3 samples.The formation of hexagonal（h-WO3） and monoclinic（m-WO3） crystal structures of WO3 at different temperatures or different times was confirmed by XRD.m-WO3 is formed at 600 ℃,while m-WO3 starts to transform into h-WO3 at 800℃.However,h-WO3,which forms at 800℃,may transform into m-WO3 by increasing the calcination temperature to 1000℃.SEM results indicate that m-WO3 particles exhibit a bulky shape with heavy aggregates,while h-WO3 particles exhibit a rod-like shape.Moreover,m-WO3 crystals are sporadically patched on the surface of the h-WO3 rod-like particles,resulting in the exposure of both m-WO3 and h-WO3 on the surface.It is observed that the monoclinic phase（m-WO3）/hexagonal phase（h-WO3） junction was fabricated by tuning the calcination temperature and calcination time.The relative ratios between m-WO3 and h-WO3 in the phase junction can readily be tailored by control of the calcination time.The photocatalytic activities of WO3 with different crystalline phases were evaluated by the photocatalytic degradation of rhodamine B as a model pollutant.A higher photocatalytic activity was observed in the WO3 sample with the m-WO3/h-WO3junction as compared with the sample with only m-WO3.The improvement of photocatalytic activity can be attributed to the reduction of the electron-hole recombination rate owing to the formation of the phase junction,whose presence has been confirmed by HRTEM and photoluminescence spectra.展开更多
A method of gradient-elution HPLC with UV detection was developed for theanalysis of nine major constituents of Salvia species, a commonly used TCM herb, namely danshensu,protocatechuic acid, protocatechualdehyde, sal...A method of gradient-elution HPLC with UV detection was developed for theanalysis of nine major constituents of Salvia species, a commonly used TCM herb, namely danshensu,protocatechuic acid, protocatechualdehyde, salviano-lic acid B, methyltanshinone, dihydrotanshinone,cryptotanshinone, tanshinoneⅠand tanshinoneⅡ_A. In the present study, a Shimadzu CLC-ODS column(150 mm x 6 mm, 5 μm) was utilized and 0.5% formic acid (A) and acetonitrile (B) were used forgradient elution at a total flow rate of 0.8 mL· min^(-1). All calibration curves showed goodlinear regression ( r > 0.999) within test ranges. Extraction was conducted by refluxing methanol(10 mL) with dried herb (0.5 g) for 1.0 h.The assay was simple, convenient and reproducible. Theproposed method was successfully applied to the determination of nine major constituents in thirteenSalvia. species and the results showed that the contents of Salvia components vary in differentspecies and origin. Tanshinone was hardly detected in S. yunnanensis and S. prionitis, thereforethey are not suitable for clinical use as Danshen.展开更多
基金supported by the National Natural Science Foundation of China (21573101)the Liaoning Provincial Natural Science Foundation(2014020107)+2 种基金the Program for Liaoning Excellent Talents in University (LJQ2014041)the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry ([2013]1792)the Opening Project of Key Laboratory of Photochemical Conversion and Optoelectronic Materials, TIPC, CAS,the Opening Project of State Key Laboratory of Catalysis, DICP, CAS (N-09-06)~~
文摘A series of WO3 samples with different crystalline phases were prepared by the thermal decomposition method from ammonium tungstate hydrate.X-ray diffraction（XRD）,scanning electron microscopy（SEM）,high-resolution transmission electron microscopy（HRTEM）,X-ray photoelectron spectroscopy,and N2 adsorption-desorption were used to characterize the crystalline phase,morphology,particle size,chemical composition,and surface area of the WO3 samples.The formation of hexagonal（h-WO3） and monoclinic（m-WO3） crystal structures of WO3 at different temperatures or different times was confirmed by XRD.m-WO3 is formed at 600 ℃,while m-WO3 starts to transform into h-WO3 at 800℃.However,h-WO3,which forms at 800℃,may transform into m-WO3 by increasing the calcination temperature to 1000℃.SEM results indicate that m-WO3 particles exhibit a bulky shape with heavy aggregates,while h-WO3 particles exhibit a rod-like shape.Moreover,m-WO3 crystals are sporadically patched on the surface of the h-WO3 rod-like particles,resulting in the exposure of both m-WO3 and h-WO3 on the surface.It is observed that the monoclinic phase（m-WO3）/hexagonal phase（h-WO3） junction was fabricated by tuning the calcination temperature and calcination time.The relative ratios between m-WO3 and h-WO3 in the phase junction can readily be tailored by control of the calcination time.The photocatalytic activities of WO3 with different crystalline phases were evaluated by the photocatalytic degradation of rhodamine B as a model pollutant.A higher photocatalytic activity was observed in the WO3 sample with the m-WO3/h-WO3junction as compared with the sample with only m-WO3.The improvement of photocatalytic activity can be attributed to the reduction of the electron-hole recombination rate owing to the formation of the phase junction,whose presence has been confirmed by HRTEM and photoluminescence spectra.
文摘A method of gradient-elution HPLC with UV detection was developed for theanalysis of nine major constituents of Salvia species, a commonly used TCM herb, namely danshensu,protocatechuic acid, protocatechualdehyde, salviano-lic acid B, methyltanshinone, dihydrotanshinone,cryptotanshinone, tanshinoneⅠand tanshinoneⅡ_A. In the present study, a Shimadzu CLC-ODS column(150 mm x 6 mm, 5 μm) was utilized and 0.5% formic acid (A) and acetonitrile (B) were used forgradient elution at a total flow rate of 0.8 mL· min^(-1). All calibration curves showed goodlinear regression ( r > 0.999) within test ranges. Extraction was conducted by refluxing methanol(10 mL) with dried herb (0.5 g) for 1.0 h.The assay was simple, convenient and reproducible. Theproposed method was successfully applied to the determination of nine major constituents in thirteenSalvia. species and the results showed that the contents of Salvia components vary in differentspecies and origin. Tanshinone was hardly detected in S. yunnanensis and S. prionitis, thereforethey are not suitable for clinical use as Danshen.
