Highly sensitive methods are important for monitoring the concentration of metal ions in industrial wastewater.Here,we developed a new probe for the determination of metal ions by fluorescence quenching.The probe cons...Highly sensitive methods are important for monitoring the concentration of metal ions in industrial wastewater.Here,we developed a new probe for the determination of metal ions by fluorescence quenching.The probe consists of hydroxylated graphene quantum dots(H-GQDs),prepared from GQDs by electrochemical method followed by surface hydroxylation.It is a non-reactive indicator with high sensitivity and detection limits of 0.01μM for Cu2+,0.005μM for Al3+,0.04μM for Fe3+,and 0.02μM for Cr3+.In addition,the low biotoxicity and excellent solubility of H-GQDs make them promising for application in wastewater metal ion detection.展开更多
High-temperature nuclear magnetic resonance(NMR)has proven to be very useful for detecting the temperatureinduced structural evolution and dynamics in melts.However,the sensitivity and precision of high-temperature NM...High-temperature nuclear magnetic resonance(NMR)has proven to be very useful for detecting the temperatureinduced structural evolution and dynamics in melts.However,the sensitivity and precision of high-temperature NMR probes are limited.Here we report a sensitive and stable high-temperature NMR probe based on laser-heating,suitable for in situ studies of metallic melts,which can work stably at the temperature of up to 2000 K.In our design,a well-designed optical path and the use of a water-cooled copper radio-frequency(RF)coil significantly optimize the signal-to-noise ratio(S/NR)at high temperatures.Additionally,a precise temperature controlling system with an error of less than±1 K has been designed.After temperature calibration,the temperature measurement error is controlled within±2 K.As a performance testing,^(27)Al NMR spectra are measured in Zr-based metallic glass-forming liquid in situ.Results show that the S/NR reaches 45 within 90 s even when the sample's temperature is up to 1500 K and that the isothermal signal drift is better than0.001 ppm per hour.This high-temperature NMR probe can be used to clarify some highly debated issues about metallic liquids,such as glass transition and liquid-liquid transition.展开更多
A novel molecular probe for identifying properties of supported transition metals and metal oxides catalysts was established.The catalytic mechanism of transition metals was proposed.
Electrical conductivities of micron-scale aluminum wires were quantitatively measured by a four-point atomic force microscope (AFM) probe. This technique is a combination of the principles of the four-point probe meth...Electrical conductivities of micron-scale aluminum wires were quantitatively measured by a four-point atomic force microscope (AFM) probe. This technique is a combination of the principles of the four-point probe method and standard AFM. This technique was applied to the 99.999% aluminum wires with 350 nm thickness and different widths of 5.0, 25.0 and 50.0μm. Since the small dimensions of the wires, the geometrical effects were discussed in details. Experiment results show that the four-point AFM probe is mechanically flexible and robust. The four-point AFM probe technique is capable of measuring surface topography together with local electrical conductivity simultaneously. The repeatable measurements indicate that this technique could be used for fast in-situ electrical properties characterization of sensors and microelectromechanical system devices.展开更多
It was observed that rare earth ions (Nd 3+, Sm 3+, Eu 3+, Gd 3+, Tb 3+) have significant quenching effects on the fluorescence of anticoagulation factor I (ACF I). The results of the fluorescence titra...It was observed that rare earth ions (Nd 3+, Sm 3+, Eu 3+, Gd 3+, Tb 3+) have significant quenching effects on the fluorescence of anticoagulation factor I (ACF I). The results of the fluorescence titration of ACF I with rare earth ions demonstrate that ACF I has two RE 3+-binding sites, and the rare earth ions and Ca 2+ bind to ACF I competitively in the two similar sites. The association constants K 1 and K 2 of ACF I with each rare earth ions (Nd 3+, Sm 3+, Eu 3+, Gd 3+, Tb 3+) are close to each other, which indicates the structural similarity of the two binding sites in ACF I. Although the ionic radii of Nd 3+, Sm 3+, Eu 3+, Gd 3+ and Tb 3+ are different, both their K 1 and K 2 are similar, respectively. This reveals the conformational flexibility of the two binding sites in ACF I, which offers a possibility for Ca 2+ to take play in the inducing conformational changes of ACF I and the promoting the binding of ACF I with activated coagulation factor X.展开更多
A new type of self-assembled molecule ON-OFF fluorescence probe for toxic transition metal ions, made up of thiacalix[4]arene, micelle and fluorescence group, has been studied by DFT/TDDFT method combined with experim...A new type of self-assembled molecule ON-OFF fluorescence probe for toxic transition metal ions, made up of thiacalix[4]arene, micelle and fluorescence group, has been studied by DFT/TDDFT method combined with experiment spectra. Since the mechanism of the optical quenching signal response of such self-assembled micelle probe has always been a controversial issue of uncertainty, the spatial construction and geometric structures of the functional units of probe in the Cu2＋ ion detecting process were calculated and the mechanism was investigated by the molecular transition orbital pairs method to explore the origination of ON-OFF fluorescence sign response. The results presented that the signal response mechanism of the micelle probe is ascribed to F？rster resonance energy transfer（FRET） which provides new sights different from most of the conclusions by the related research work reported.展开更多
Transient liquid phase(TLP)bonding was investigated in Hastelloy-X samples with different filler metal thicknesses(20,35,50,65,and 100μm)and holding time(5,20,80,320,and 640 min)to obtain optimum bonding parameters.M...Transient liquid phase(TLP)bonding was investigated in Hastelloy-X samples with different filler metal thicknesses(20,35,50,65,and 100μm)and holding time(5,20,80,320,and 640 min)to obtain optimum bonding parameters.Microstructural evaluations using electron probe microanalysis(EPMA)and electron backscattered diffraction(EBSD)show that the central eutectic phases present in the athermally solidified zone(ASZ)are Ni_(3)B,Ni_(2)Si,and CrB,and the precipitates formed in the diffusion-affected zone(DAZ)are MoB,CrB_(2),and Mo_(2)B_(5).According to the results,decreasing the filler thickness as well as increasing the holding time helps realize the completion of isothermal solidification and reduction in the density of precipitates in the DAZ,leading to a joint with more uniform properties.Diffusion of boron and silicon to longer distances with increasing holding time causes the removal of Cr-rich borides in the DAZ and the formation of Mo-rich silicide at the joint interface.Decrease in hardness of ASZ and DAZ due to the elimination of brittle phases in these zones during long holding time causes more uniform hardness distribution in the joint area.The best results are obtained for the sample joined with the 35μm-thick filler metal for 640 min holding time.展开更多
基金financially supported by the National Natural Science Foundation of China (No. 21674011)Beijing Municipal Natural Science Foundation (No. 2172040)
文摘Highly sensitive methods are important for monitoring the concentration of metal ions in industrial wastewater.Here,we developed a new probe for the determination of metal ions by fluorescence quenching.The probe consists of hydroxylated graphene quantum dots(H-GQDs),prepared from GQDs by electrochemical method followed by surface hydroxylation.It is a non-reactive indicator with high sensitivity and detection limits of 0.01μM for Cu2+,0.005μM for Al3+,0.04μM for Fe3+,and 0.02μM for Cr3+.In addition,the low biotoxicity and excellent solubility of H-GQDs make them promising for application in wastewater metal ion detection.
基金Project supported by the Instrument Developing Project of the Chinese Academy of Sciences(Grant No.YZ201639)the National Key R&D Program of China(Grant No.2018YFA0703604)+1 种基金the National Natural Science Foundation of China(Grant Nos.51922102,92163108,and 52071327)the Zhejiang Provincial Natural Science Foundation of China(Grant No.LR18E010002)。
文摘High-temperature nuclear magnetic resonance(NMR)has proven to be very useful for detecting the temperatureinduced structural evolution and dynamics in melts.However,the sensitivity and precision of high-temperature NMR probes are limited.Here we report a sensitive and stable high-temperature NMR probe based on laser-heating,suitable for in situ studies of metallic melts,which can work stably at the temperature of up to 2000 K.In our design,a well-designed optical path and the use of a water-cooled copper radio-frequency(RF)coil significantly optimize the signal-to-noise ratio(S/NR)at high temperatures.Additionally,a precise temperature controlling system with an error of less than±1 K has been designed.After temperature calibration,the temperature measurement error is controlled within±2 K.As a performance testing,^(27)Al NMR spectra are measured in Zr-based metallic glass-forming liquid in situ.Results show that the S/NR reaches 45 within 90 s even when the sample's temperature is up to 1500 K and that the isothermal signal drift is better than0.001 ppm per hour.This high-temperature NMR probe can be used to clarify some highly debated issues about metallic liquids,such as glass transition and liquid-liquid transition.
文摘A novel molecular probe for identifying properties of supported transition metals and metal oxides catalysts was established.The catalytic mechanism of transition metals was proposed.
基金Project( 17206011) supported by the Japan Society for the Promotion of Science
文摘Electrical conductivities of micron-scale aluminum wires were quantitatively measured by a four-point atomic force microscope (AFM) probe. This technique is a combination of the principles of the four-point probe method and standard AFM. This technique was applied to the 99.999% aluminum wires with 350 nm thickness and different widths of 5.0, 25.0 and 50.0μm. Since the small dimensions of the wires, the geometrical effects were discussed in details. Experiment results show that the four-point AFM probe is mechanically flexible and robust. The four-point AFM probe technique is capable of measuring surface topography together with local electrical conductivity simultaneously. The repeatable measurements indicate that this technique could be used for fast in-situ electrical properties characterization of sensors and microelectromechanical system devices.
文摘It was observed that rare earth ions (Nd 3+, Sm 3+, Eu 3+, Gd 3+, Tb 3+) have significant quenching effects on the fluorescence of anticoagulation factor I (ACF I). The results of the fluorescence titration of ACF I with rare earth ions demonstrate that ACF I has two RE 3+-binding sites, and the rare earth ions and Ca 2+ bind to ACF I competitively in the two similar sites. The association constants K 1 and K 2 of ACF I with each rare earth ions (Nd 3+, Sm 3+, Eu 3+, Gd 3+, Tb 3+) are close to each other, which indicates the structural similarity of the two binding sites in ACF I. Although the ionic radii of Nd 3+, Sm 3+, Eu 3+, Gd 3+ and Tb 3+ are different, both their K 1 and K 2 are similar, respectively. This reveals the conformational flexibility of the two binding sites in ACF I, which offers a possibility for Ca 2+ to take play in the inducing conformational changes of ACF I and the promoting the binding of ACF I with activated coagulation factor X.
基金supported by the Natural Science Foundation of Liaoning Province(201602516)Shenyang Project of Young and Middle-aged Innovative Talents of Science and Technology(RC170244)
文摘A new type of self-assembled molecule ON-OFF fluorescence probe for toxic transition metal ions, made up of thiacalix[4]arene, micelle and fluorescence group, has been studied by DFT/TDDFT method combined with experiment spectra. Since the mechanism of the optical quenching signal response of such self-assembled micelle probe has always been a controversial issue of uncertainty, the spatial construction and geometric structures of the functional units of probe in the Cu2＋ ion detecting process were calculated and the mechanism was investigated by the molecular transition orbital pairs method to explore the origination of ON-OFF fluorescence sign response. The results presented that the signal response mechanism of the micelle probe is ascribed to F？rster resonance energy transfer（FRET） which provides new sights different from most of the conclusions by the related research work reported.
文摘Transient liquid phase(TLP)bonding was investigated in Hastelloy-X samples with different filler metal thicknesses(20,35,50,65,and 100μm)and holding time(5,20,80,320,and 640 min)to obtain optimum bonding parameters.Microstructural evaluations using electron probe microanalysis(EPMA)and electron backscattered diffraction(EBSD)show that the central eutectic phases present in the athermally solidified zone(ASZ)are Ni_(3)B,Ni_(2)Si,and CrB,and the precipitates formed in the diffusion-affected zone(DAZ)are MoB,CrB_(2),and Mo_(2)B_(5).According to the results,decreasing the filler thickness as well as increasing the holding time helps realize the completion of isothermal solidification and reduction in the density of precipitates in the DAZ,leading to a joint with more uniform properties.Diffusion of boron and silicon to longer distances with increasing holding time causes the removal of Cr-rich borides in the DAZ and the formation of Mo-rich silicide at the joint interface.Decrease in hardness of ASZ and DAZ due to the elimination of brittle phases in these zones during long holding time causes more uniform hardness distribution in the joint area.The best results are obtained for the sample joined with the 35μm-thick filler metal for 640 min holding time.
