Residues of tetracycline antibiotics(TCs) in environments may be harmful to human.Due to their high polarities,it is extremely challenging to efficiently enrich TCs with low concentrations in natural waters for analys...Residues of tetracycline antibiotics(TCs) in environments may be harmful to human.Due to their high polarities,it is extremely challenging to efficiently enrich TCs with low concentrations in natural waters for analysis.In this work,a magnetic metal-organic framework Fe_(3)O_(4)@[Cu_(3)(btc)_(2)]was synthesized and applied as a dispersive micro-solid phase extraction adsorbent for TCs enrichment.Effects of dispersive micro-solid phase extraction conditions including extraction time,solution p H,and elution solvent on the extraction efficiencies of TCs were investigated.Results show that TCs could be enriched efficiently by Fe_(3)O_(4)@[Cu_(3)(btc)_(2)],and electrostatic interaction between TCs and Fe_(3)O_(4)@[Cu_(3)(btc)_(2)]dominated this process.Combined with liquid chromatography-tandem mass spectrometry,four TCs residues (oxytetracycline,tetracycline,chlortetracycline,and doxycycline) in natural waters were determined.The detection limits (LOD,S/N=3) of the four antibiotics were 0.01-0.02μg/L,and the limits of quantitation (LOQ,S/N=10)were 0.04-0.07μg/L.The recoveries obtained from river water and aquaculture water spiked with three TCs concentration levels ranged from 70.3%to 96.5%with relative standard deviations of 3.8%-12.8%.Results indicate that the magnetic metal-organic framework based dispersive micro-solid phase extraction is simple,rapid and high-loading for antibiotics enrichment from water,which further expand the practical application of metal-organic frameworks in sample pretreatment for environmental pollutant analysis.展开更多
Planar films of pure and Ti^(4+)-dopedβ-Fe_(2)O_(3)were prepared by a spray pyrolysis method.X-ray diffraction patterns and Raman spectra of the metastableβ-Fe_(2)O_(3)film showed that its thermal stability was sign...Planar films of pure and Ti^(4+)-dopedβ-Fe_(2)O_(3)were prepared by a spray pyrolysis method.X-ray diffraction patterns and Raman spectra of the metastableβ-Fe_(2)O_(3)film showed that its thermal stability was significantly improved because of covalent bonds in the interfaces between the film and substrate,while only weak Van der Waals bonds existed at the interfaces within the particle-assembledβ-Fe_(2)O_(3)film prepared by electrophoretic deposition.The as-prepared planar films were thus able to withstand higher annealing temperature and stronger laser irradiation power in comparison with theβ-Fe_(2)O_(3)particle-assembly.Ti^(4+)doping was used to increase the concentration of carriers in the metastableβ-Fe_(2)O_(3)film.Compared with pureβ-Fe_(2)O_(3)photoanodes,the highest saturated photocurrent for water splitting over the Ti^(4+)-dopedβ-Fe_(2)O_(3)photoanode was increased by a factor of approximately three.Theβ-Fe_(2)O_(3)photoanode exhibited photochemical stability for water splitting for a duration exceeding 100 h,which indicates its important potential application in solar energy conversion.展开更多
Alumina/aluminum-silicon alloy composite is manufactured by squeeze casting. The effect of the reinforcementon the morphology of the silicon phase in aluminum-silicon alloy is studied. The results indicate that an alu...Alumina/aluminum-silicon alloy composite is manufactured by squeeze casting. The effect of the reinforcementon the morphology of the silicon phase in aluminum-silicon alloy is studied. The results indicate that an alumina fiber canserve as propitious sites for the heterogeneous nucleation of the silicon phase, and the primary silicon in the compositecan nucleate on the surface of the fiber. The fiber in the composite can trigger twin during the coupled growth of thealuminum-silicon eutectic and lead to modification of the eutectic silicon near the fiber.展开更多
By means of X-ray diffraction investigations and electric resistivity measurements the tempera- ture dependence of phase structure and supercon- ductivity in YBa_2Cu_3O_(7_x) over the temperature range of 20℃-950℃ h...By means of X-ray diffraction investigations and electric resistivity measurements the tempera- ture dependence of phase structure and supercon- ductivity in YBa_2Cu_3O_(7_x) over the temperature range of 20℃-950℃ have been studied.The lattice parameters a,b and c as well as conductivity as a function of annealing temperatures can be roughly divided into three zones which are superconductive orthorhombic structure 1(a<b(?)c/3) at 20℃-500℃,normal conductive orthorhombic structure 2(a<b<c/3)from 550℃ to about 750℃ and semiconductive-like tetragonal structure (a=b<c/3)from about 800℃ to 950℃.However, the boundaries of the three zones is not much distinctive because there is a continuous transi- tion from the orthorhombic to tetragonal struc- ture.Furthermore,the processes of orthorhom- bic-tetragonal transition in the range of 350℃-950℃ are not only continuous but also reversible.The isothermal transition of orthorhombic 2 to orthorhombic 1 occurs at 350℃-500℃,while the maximum rate of transition and high T_c superconductivity can be obtained at about 460℃.This process of isothermal transition depends on the ordering of oxygen atoms or vacancies and the thermodynamic equilibrium to allow the oxygen diffusion.展开更多
基金supported by the National Natural Science Foundation of China(No.21607003).
文摘Residues of tetracycline antibiotics(TCs) in environments may be harmful to human.Due to their high polarities,it is extremely challenging to efficiently enrich TCs with low concentrations in natural waters for analysis.In this work,a magnetic metal-organic framework Fe_(3)O_(4)@[Cu_(3)(btc)_(2)]was synthesized and applied as a dispersive micro-solid phase extraction adsorbent for TCs enrichment.Effects of dispersive micro-solid phase extraction conditions including extraction time,solution p H,and elution solvent on the extraction efficiencies of TCs were investigated.Results show that TCs could be enriched efficiently by Fe_(3)O_(4)@[Cu_(3)(btc)_(2)],and electrostatic interaction between TCs and Fe_(3)O_(4)@[Cu_(3)(btc)_(2)]dominated this process.Combined with liquid chromatography-tandem mass spectrometry,four TCs residues (oxytetracycline,tetracycline,chlortetracycline,and doxycycline) in natural waters were determined.The detection limits (LOD,S/N=3) of the four antibiotics were 0.01-0.02μg/L,and the limits of quantitation (LOQ,S/N=10)were 0.04-0.07μg/L.The recoveries obtained from river water and aquaculture water spiked with three TCs concentration levels ranged from 70.3%to 96.5%with relative standard deviations of 3.8%-12.8%.Results indicate that the magnetic metal-organic framework based dispersive micro-solid phase extraction is simple,rapid and high-loading for antibiotics enrichment from water,which further expand the practical application of metal-organic frameworks in sample pretreatment for environmental pollutant analysis.
文摘Planar films of pure and Ti^(4+)-dopedβ-Fe_(2)O_(3)were prepared by a spray pyrolysis method.X-ray diffraction patterns and Raman spectra of the metastableβ-Fe_(2)O_(3)film showed that its thermal stability was significantly improved because of covalent bonds in the interfaces between the film and substrate,while only weak Van der Waals bonds existed at the interfaces within the particle-assembledβ-Fe_(2)O_(3)film prepared by electrophoretic deposition.The as-prepared planar films were thus able to withstand higher annealing temperature and stronger laser irradiation power in comparison with theβ-Fe_(2)O_(3)particle-assembly.Ti^(4+)doping was used to increase the concentration of carriers in the metastableβ-Fe_(2)O_(3)film.Compared with pureβ-Fe_(2)O_(3)photoanodes,the highest saturated photocurrent for water splitting over the Ti^(4+)-dopedβ-Fe_(2)O_(3)photoanode was increased by a factor of approximately three.Theβ-Fe_(2)O_(3)photoanode exhibited photochemical stability for water splitting for a duration exceeding 100 h,which indicates its important potential application in solar energy conversion.
文摘Alumina/aluminum-silicon alloy composite is manufactured by squeeze casting. The effect of the reinforcementon the morphology of the silicon phase in aluminum-silicon alloy is studied. The results indicate that an alumina fiber canserve as propitious sites for the heterogeneous nucleation of the silicon phase, and the primary silicon in the compositecan nucleate on the surface of the fiber. The fiber in the composite can trigger twin during the coupled growth of thealuminum-silicon eutectic and lead to modification of the eutectic silicon near the fiber.
文摘By means of X-ray diffraction investigations and electric resistivity measurements the tempera- ture dependence of phase structure and supercon- ductivity in YBa_2Cu_3O_(7_x) over the temperature range of 20℃-950℃ have been studied.The lattice parameters a,b and c as well as conductivity as a function of annealing temperatures can be roughly divided into three zones which are superconductive orthorhombic structure 1(a<b(?)c/3) at 20℃-500℃,normal conductive orthorhombic structure 2(a<b<c/3)from 550℃ to about 750℃ and semiconductive-like tetragonal structure (a=b<c/3)from about 800℃ to 950℃.However, the boundaries of the three zones is not much distinctive because there is a continuous transi- tion from the orthorhombic to tetragonal struc- ture.Furthermore,the processes of orthorhom- bic-tetragonal transition in the range of 350℃-950℃ are not only continuous but also reversible.The isothermal transition of orthorhombic 2 to orthorhombic 1 occurs at 350℃-500℃,while the maximum rate of transition and high T_c superconductivity can be obtained at about 460℃.This process of isothermal transition depends on the ordering of oxygen atoms or vacancies and the thermodynamic equilibrium to allow the oxygen diffusion.
