Login In
2020 Volume 37 Issue 8
2020, 37(8): 855-864
doi: 10.11944/j.issn.1000-0518.2020.08.200086
Abstract:
Two-dimensional (2D) materials have attracted widespread attention due to their unique electrical, optical, and magnetic properties, and how to modify two-dimensional materials is a research hotspot. The intercalation method is one of the main methods of improving the properties of 2D materials. During the intercalation process, guest particles are inserted between the van der Waals layers of the host material, causing changes in the physical and chemical properties of the 2D materials. Gas phase intercalation, liquid phase intercalation, and solid phase intercalation can improve properties of 2D materials. This article mainly introduces the intercalation methods of 2D materials, analyzes their advantages and drawbacks, and proposes how to apply intercalation methods to improve electrical, optical properties of 2D materials.
Two-dimensional (2D) materials have attracted widespread attention due to their unique electrical, optical, and magnetic properties, and how to modify two-dimensional materials is a research hotspot. The intercalation method is one of the main methods of improving the properties of 2D materials. During the intercalation process, guest particles are inserted between the van der Waals layers of the host material, causing changes in the physical and chemical properties of the 2D materials. Gas phase intercalation, liquid phase intercalation, and solid phase intercalation can improve properties of 2D materials. This article mainly introduces the intercalation methods of 2D materials, analyzes their advantages and drawbacks, and proposes how to apply intercalation methods to improve electrical, optical properties of 2D materials.
2020, 37(8): 865-876
doi: 10.11944/j.issn.1000-0518.2020.08.200145
Abstract:
Antimicrobial peptides (AMP) have been extensively studied due to their rapid-acting, broad-spectrum activities and low possibility to develop resistance to bacteria. A potential approach to combating device-associated infections is to construct AMP-based antibacterial coatings on biomaterial surfaces. However, traditional AMP releasing coatings show temporary action due to the inherently limited reservoirs, while direct surface-tethering of AMP on surface usually suffers from the accumulation of dead microorganisms blocking functional groups. Considering the varied and complex applications of biomaterials, it is highly required to facilely adjust its functions in service and in antibacterial cases. A generic strategy by integrating the stimuli-responsive polymers and the existing antibacterial strategies exhibits a great potential in advancing the clinical applications of the AMP-based smart antibacterial platforms. In this review, the progress in the development of smart coatings based on AMP is reviewed. The main approaches to designing AMP releasing and non-releasing coatings are described, the roles of stimuli-responsive polymers in AMP-based smart coatings are also introduced, and the switching between its functions in service and antibacterial function is discussed. Furthermore, the future development of AMP-based smart coatings are prospected.
Antimicrobial peptides (AMP) have been extensively studied due to their rapid-acting, broad-spectrum activities and low possibility to develop resistance to bacteria. A potential approach to combating device-associated infections is to construct AMP-based antibacterial coatings on biomaterial surfaces. However, traditional AMP releasing coatings show temporary action due to the inherently limited reservoirs, while direct surface-tethering of AMP on surface usually suffers from the accumulation of dead microorganisms blocking functional groups. Considering the varied and complex applications of biomaterials, it is highly required to facilely adjust its functions in service and in antibacterial cases. A generic strategy by integrating the stimuli-responsive polymers and the existing antibacterial strategies exhibits a great potential in advancing the clinical applications of the AMP-based smart antibacterial platforms. In this review, the progress in the development of smart coatings based on AMP is reviewed. The main approaches to designing AMP releasing and non-releasing coatings are described, the roles of stimuli-responsive polymers in AMP-based smart coatings are also introduced, and the switching between its functions in service and antibacterial function is discussed. Furthermore, the future development of AMP-based smart coatings are prospected.
2020, 37(8): 877-882
doi: 10.11944/j.issn.1000-0518.2020.08.200056
Abstract:
A number of aryl/heteroaryl aminomethylene bisphosphonates were synthesized by one-pot reaction of diverse aryl/heteroaryl amines with diethyl phosphite and triethyl orthoformate in the presence of I2 under solvent free conditions. The product yields are 96%~99%. When the molar fraction of I2 is 5%, the product yield is the highest. The procedure is simple and the substrate scope is large. I2 is safe and very efficient as the catalyst.
A number of aryl/heteroaryl aminomethylene bisphosphonates were synthesized by one-pot reaction of diverse aryl/heteroaryl amines with diethyl phosphite and triethyl orthoformate in the presence of I2 under solvent free conditions. The product yields are 96%~99%. When the molar fraction of I2 is 5%, the product yield is the highest. The procedure is simple and the substrate scope is large. I2 is safe and very efficient as the catalyst.
2020, 37(8): 883-888
doi: 10.11944/j.issn.1000-0518.2020.08.200062
Abstract:
Cosmetic-grade sodium polyaspartate was synthesized through the polycondensation of L-aspartic acid. The effects of polymerization temperature, time and catalyst amount on the polymerization were systematically investigated to obtain the optimal polymerization conditions. The structure and molecular weight of sodium polyaspartate were characterized by nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC). The properties of acid and alkali resistance, temperature resistance and compatibility were also evaluated. The resultant sodium polyaspartate has light color (white), low odor, few impurities and high quality, exhibits excellent acid, alkali, temperature resistance and compatibility, reaches the standard as a moisturizing additive.
Cosmetic-grade sodium polyaspartate was synthesized through the polycondensation of L-aspartic acid. The effects of polymerization temperature, time and catalyst amount on the polymerization were systematically investigated to obtain the optimal polymerization conditions. The structure and molecular weight of sodium polyaspartate were characterized by nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC). The properties of acid and alkali resistance, temperature resistance and compatibility were also evaluated. The resultant sodium polyaspartate has light color (white), low odor, few impurities and high quality, exhibits excellent acid, alkali, temperature resistance and compatibility, reaches the standard as a moisturizing additive.
2020, 37(8): 889-895
doi: 10.11944/j.issn.1000-0518.2020.08.200140
Abstract:
A new sterically hindered chiral (pyrrolidine salen)Mn(Ⅲ) complex Mn3 was synthesized and employed in the asymmetric epoxidation of alkenes in NaClO aqueous/organic biphasic system. Complex Mn3 bearing tertiary amine unit displays higher activity, comparable yield and slightly higher enantioselectivity as compared with Jacobsen's catalyst. Especially, adding excess CH3I into the catalytic system can greatly shorten the reaction time while maintaining high yield and high enantioselectivity.
A new sterically hindered chiral (pyrrolidine salen)Mn(Ⅲ) complex Mn3 was synthesized and employed in the asymmetric epoxidation of alkenes in NaClO aqueous/organic biphasic system. Complex Mn3 bearing tertiary amine unit displays higher activity, comparable yield and slightly higher enantioselectivity as compared with Jacobsen's catalyst. Especially, adding excess CH3I into the catalytic system can greatly shorten the reaction time while maintaining high yield and high enantioselectivity.
2020, 37(8): 896-903
doi: 10.11944/j.issn.1000-0518.2020.08.200050
Abstract:
In this study, the composites (PE-Al-Si) with high thermal conductivity and mechanical properties were obtained by compounding low density polyethylene (LDPE), alumina (Al2O3) and SiO2 nanoparticles through melt blending, and then further modification through electron beam radiation. When the mass fraction of SiO2 nanoparticles is 1% and the electron beam radiation (EB) dose is 120 kGy, the thermal conductivity of PE-Al-Si increases from 0.624 W/(m·K) to 0.759 W/(m·K), which is 22% increase compared with the composites without SiO2 (PE-Al). The tensile strength of PE-Al-Si is increased by 17% compared with that of PE-Al. The results prove that SiO2 improves the mechanical properties, the radiation efficiency and the thermal conductivity of the composites.
In this study, the composites (PE-Al-Si) with high thermal conductivity and mechanical properties were obtained by compounding low density polyethylene (LDPE), alumina (Al2O3) and SiO2 nanoparticles through melt blending, and then further modification through electron beam radiation. When the mass fraction of SiO2 nanoparticles is 1% and the electron beam radiation (EB) dose is 120 kGy, the thermal conductivity of PE-Al-Si increases from 0.624 W/(m·K) to 0.759 W/(m·K), which is 22% increase compared with the composites without SiO2 (PE-Al). The tensile strength of PE-Al-Si is increased by 17% compared with that of PE-Al. The results prove that SiO2 improves the mechanical properties, the radiation efficiency and the thermal conductivity of the composites.
2020, 37(8): 904-911
Abstract:
Constructing segregated structure in polypropylene (PP)/carbon nanotubes (CNTs) composites via co-extrusion coating-compression molding technique is an effective way to achieve high electromagnetic interference shielding with low percolation threshold. Among them, CNTs are randomly distributed inside PP matrix to form conductive composites, which is coated on the outer surface of pure PP to form a segregated structure. The results show that the PP/CNTs composites exhibit an excellent electromagnetic interference shielding effectiveness (EMI SE) of 25.6 dB at 5.6% (mass fraction) of CNTs, and high-performance electrical conductivity with a low percolation threshold of 0.28% (volume fraction) CNTs. Furthermore the PP/CNTs composites have excellent mechanical properties. In a word, the co-extrusion coating-compression molding technique is a facile and green method, which plays a role in developing high-performance electromagnetic shielding composites.
Constructing segregated structure in polypropylene (PP)/carbon nanotubes (CNTs) composites via co-extrusion coating-compression molding technique is an effective way to achieve high electromagnetic interference shielding with low percolation threshold. Among them, CNTs are randomly distributed inside PP matrix to form conductive composites, which is coated on the outer surface of pure PP to form a segregated structure. The results show that the PP/CNTs composites exhibit an excellent electromagnetic interference shielding effectiveness (EMI SE) of 25.6 dB at 5.6% (mass fraction) of CNTs, and high-performance electrical conductivity with a low percolation threshold of 0.28% (volume fraction) CNTs. Furthermore the PP/CNTs composites have excellent mechanical properties. In a word, the co-extrusion coating-compression molding technique is a facile and green method, which plays a role in developing high-performance electromagnetic shielding composites.
2020, 37(8): 912-922
doi: 10.11944/j.issn.1000-0518.2020.08.200022
Abstract:
Poly(ether ether ketone) (PEEK) containing methyl groups was synthesized by the aromatic nucleophilic polycondensation reaction of bisphenol fluorene unit, 4, 4'-(Hexafluoroisopropylidene)diphenol, and 4, 4'-difluoro-benzophenone. Poly(ether ether ketone) proton exchange membranes were post-sulfonated using concentrated sulfuric acid to give highly proton conductive sulfonic fluorenyl groups (SF-PEEK). The structure and morphology of SF-PEEK membranes were characterized by Fourier transform infrared spectroscopy (FTIR), hydrogen nuclear magnetic resonance spectroscopy (1H NMR), thermal gravimetric analyzer (TGA), atomic force microscope (AFM) and scanning electron microscopy (SEM). The SF-PEEK membranes have strong hydrophilic/hydrophobic phase separation. The conductivity of the SF80-PFEK608 membrane (IEC=1.97 mmol/g) is 4.15×10-2 S/cm which is lower than that of Nafion membrane (5.67×10-2 S/cm). SF-PEEK membranes show much lower vanadium ions permeability (3.15×10-7~1.48×10-6 cm2/min) than that of Nafion 117 membrane (7.04×10-6 cm2/min). As a result, the self-discharge duration of the vanadium redox flow battery (VRFB) cell with SF80-PEEK608 membrane (90 h) is longer than that of VRFB cell with Nafion 117 membrane (57 h). Furthermore, the VRFB cell with SF80-PEEK608 (IEC=1.97 mmol/g) membrane exhibits higher coulombic efficiency of 80.9% compare with that of VRFB cell with Nafion 117 membrane (coulombic efficiency of 78.8%) at current density of 40 mA/cm2. The results indicate that SF-PEEK membrane is high-performance and low-cost alternative membrane for VRFB application.
Poly(ether ether ketone) (PEEK) containing methyl groups was synthesized by the aromatic nucleophilic polycondensation reaction of bisphenol fluorene unit, 4, 4'-(Hexafluoroisopropylidene)diphenol, and 4, 4'-difluoro-benzophenone. Poly(ether ether ketone) proton exchange membranes were post-sulfonated using concentrated sulfuric acid to give highly proton conductive sulfonic fluorenyl groups (SF-PEEK). The structure and morphology of SF-PEEK membranes were characterized by Fourier transform infrared spectroscopy (FTIR), hydrogen nuclear magnetic resonance spectroscopy (1H NMR), thermal gravimetric analyzer (TGA), atomic force microscope (AFM) and scanning electron microscopy (SEM). The SF-PEEK membranes have strong hydrophilic/hydrophobic phase separation. The conductivity of the SF80-PFEK608 membrane (IEC=1.97 mmol/g) is 4.15×10-2 S/cm which is lower than that of Nafion membrane (5.67×10-2 S/cm). SF-PEEK membranes show much lower vanadium ions permeability (3.15×10-7~1.48×10-6 cm2/min) than that of Nafion 117 membrane (7.04×10-6 cm2/min). As a result, the self-discharge duration of the vanadium redox flow battery (VRFB) cell with SF80-PEEK608 membrane (90 h) is longer than that of VRFB cell with Nafion 117 membrane (57 h). Furthermore, the VRFB cell with SF80-PEEK608 (IEC=1.97 mmol/g) membrane exhibits higher coulombic efficiency of 80.9% compare with that of VRFB cell with Nafion 117 membrane (coulombic efficiency of 78.8%) at current density of 40 mA/cm2. The results indicate that SF-PEEK membrane is high-performance and low-cost alternative membrane for VRFB application.
2020, 37(8): 923-929
doi: 10.11944/j.issn.1000-0518.2020.08.200034
Abstract:
Ultrafine silver powder has shown wide applications in the fields of communication, electronics and front electrode of solar cells. Its size distribution, dispersion and surface state have close relationship with its performance. In this paper, in order to obtain ultrafine silver composite with narrow size distribution, good dispersibility and high conductivity, graphene oxide (GO) was introduced in the later period of silver particles synthesized by liquid phase reduction. The structure and morphology of the composite silver powder were characterized by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. The results show that the ultrafine silver powders obtained by this method possess good dispersion and narrow size distribution. Furthermore, the interaction between GO and silver particles was explored by UV-visible spectroscopy. It is also found that by fixing the concentration of silver nitrate solution, and increasing the content of GO, the conductivity of silver powder first increases, and then decreases. When the mass percentage of GO is 2.5%, due to more effective contact among silver particles, its interfacial resistance is lower and photocurrent is higher. It will provide important data and valuable reference for the application of ultrafine silver.
Ultrafine silver powder has shown wide applications in the fields of communication, electronics and front electrode of solar cells. Its size distribution, dispersion and surface state have close relationship with its performance. In this paper, in order to obtain ultrafine silver composite with narrow size distribution, good dispersibility and high conductivity, graphene oxide (GO) was introduced in the later period of silver particles synthesized by liquid phase reduction. The structure and morphology of the composite silver powder were characterized by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. The results show that the ultrafine silver powders obtained by this method possess good dispersion and narrow size distribution. Furthermore, the interaction between GO and silver particles was explored by UV-visible spectroscopy. It is also found that by fixing the concentration of silver nitrate solution, and increasing the content of GO, the conductivity of silver powder first increases, and then decreases. When the mass percentage of GO is 2.5%, due to more effective contact among silver particles, its interfacial resistance is lower and photocurrent is higher. It will provide important data and valuable reference for the application of ultrafine silver.
2020, 37(8): 930-938
doi: 10.11944/j.issn.1000-0518.2020.00.200037
Abstract:
Compared with the Haber-Bosch process, electrochemical nitrogen fixation can directly convert N2 to NH3 under mild environmental conditions, which is the building block of fertilizer for agricultural production. However, the screening of nitrogen reduction electrocatalyst with high activity and high stability is the most important. Here, vanadium doped ZIF-8 was synthesized by the sol-gel method, and used as the precursor to prepare mesoporous carbon electrochemical N2 reduction reaction (NRR) catalysts at high temperature. The catalysts were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy, etc. The catalyst shows a highly disordered three-dimensional carbon structure. The presence of appropriate amount of V5+, nitrogen carbide and pyridine nitrogen in the catalyst can promote NRR significantly. In the 0.1 mol/L KOH electrolyte solution, with V doped amount of 1/8 and the applied potential of -0.4 V, the catalyst has the best NRR performance at the calcination temperature of 1100 ℃. The ammonia production rate can reach 7.092 mol/(cm2·h) and the Faraday efficiency (FE%) is 23.88%. Meanwhile, its current density has a slight fluctuation at -0.4 V for 18 h electrochemical reaction, further suggesting that V-N co-doped carbon based mesoporous nanomaterials has high durability.
Compared with the Haber-Bosch process, electrochemical nitrogen fixation can directly convert N2 to NH3 under mild environmental conditions, which is the building block of fertilizer for agricultural production. However, the screening of nitrogen reduction electrocatalyst with high activity and high stability is the most important. Here, vanadium doped ZIF-8 was synthesized by the sol-gel method, and used as the precursor to prepare mesoporous carbon electrochemical N2 reduction reaction (NRR) catalysts at high temperature. The catalysts were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy, etc. The catalyst shows a highly disordered three-dimensional carbon structure. The presence of appropriate amount of V5+, nitrogen carbide and pyridine nitrogen in the catalyst can promote NRR significantly. In the 0.1 mol/L KOH electrolyte solution, with V doped amount of 1/8 and the applied potential of -0.4 V, the catalyst has the best NRR performance at the calcination temperature of 1100 ℃. The ammonia production rate can reach 7.092 mol/(cm2·h) and the Faraday efficiency (FE%) is 23.88%. Meanwhile, its current density has a slight fluctuation at -0.4 V for 18 h electrochemical reaction, further suggesting that V-N co-doped carbon based mesoporous nanomaterials has high durability.
2020, 37(8): 952-959
doi: 10.11944/j.issn.1000-0518.2020.08.200046
Abstract:
Nano titanium silicalite-1 (TS-1) zeolite catalysts loaded with a series of molybdenum-containing polyoxometalate (POM) were synthesized by the impregnation method. These catalysts were characterized by SEM, UV-vis, BET, XRD, 31P MAS-NMR and 29Si MAS-NMR spectroscopy. The characterization results show that the Keggin structure in the catalysts can be remained after calcination or drying under the low temperature, but ammonium molybdate changed into molybdenum trioxide after calcination at 550 ℃. A model of oil (n-octane solution of thiophene, benzothiophene and dibenzothiophene) was used to value catalytic oxidation desulfurization performance of these catalysts. It is found that the oxidative desulfurization efficiencies decrease in the order of Mo-POM (Keggin type) > Mo-POM (Anderson type) > Mo-POM (Dawson type) > molybdenum trioxide. When the reaction conditions are the model of V(simulated oil)=V(ethanol)=10.0 mL, m(catalyst)=0.2 g, n(H2O2):n(S)=10:1, temperature=60 ℃, the desulfurization activity order of sulfur compounds is thiophene > dibenzothiophene > benzothiophene, which is obviously different from that of either TS-1 zeolite or POM. This may be derived from the synergy of the shape selectivity of nano-TS-1 zeolite and the electron cloud density of POM on the oxidation activity of organic sulfur molecules. Furthermore, the Keggin type Mo-POM-TS-1 catalysts show excellent recycling stability. All of which cause Mo-POM (Keggin type)-TS-1 catalysts to become a kind of environmental-friendly catalysts with simple preparation method, high catalytic activity and good stability.
Nano titanium silicalite-1 (TS-1) zeolite catalysts loaded with a series of molybdenum-containing polyoxometalate (POM) were synthesized by the impregnation method. These catalysts were characterized by SEM, UV-vis, BET, XRD, 31P MAS-NMR and 29Si MAS-NMR spectroscopy. The characterization results show that the Keggin structure in the catalysts can be remained after calcination or drying under the low temperature, but ammonium molybdate changed into molybdenum trioxide after calcination at 550 ℃. A model of oil (n-octane solution of thiophene, benzothiophene and dibenzothiophene) was used to value catalytic oxidation desulfurization performance of these catalysts. It is found that the oxidative desulfurization efficiencies decrease in the order of Mo-POM (Keggin type) > Mo-POM (Anderson type) > Mo-POM (Dawson type) > molybdenum trioxide. When the reaction conditions are the model of V(simulated oil)=V(ethanol)=10.0 mL, m(catalyst)=0.2 g, n(H2O2):n(S)=10:1, temperature=60 ℃, the desulfurization activity order of sulfur compounds is thiophene > dibenzothiophene > benzothiophene, which is obviously different from that of either TS-1 zeolite or POM. This may be derived from the synergy of the shape selectivity of nano-TS-1 zeolite and the electron cloud density of POM on the oxidation activity of organic sulfur molecules. Furthermore, the Keggin type Mo-POM-TS-1 catalysts show excellent recycling stability. All of which cause Mo-POM (Keggin type)-TS-1 catalysts to become a kind of environmental-friendly catalysts with simple preparation method, high catalytic activity and good stability.
2020, 37(8): 960-968
doi: 10.11944/j.issn.1000-0518.2020.08.200013
Abstract:
The synergistic inhibition effect of potassium sorbate (PS) and Zn2+ ions on the corrosion of Q235 steel in 0.5 mol/L NaCl solution was studied by weight loss method, electrochemical method, X-ray photoelectron spectroscopy (XPS) and scanning electronic microscopy (SEM). The results of weight loss measurement show that potassium sorbate has some inhibition of corrosion of Q235 steel in 0.5 mol/L NaCl solution, the inhibition efficiency increases with the increase of concentration. When the added PS concentration is 25.0 g/L, the maximum inhibition efficiency is 38.37%. The combination of PS and Zn2+ ions has a significantly synergistic inhibition effect, the corrosion inhibition efficiency is as high as 91.03%. Potentiodynamic polarization shows that the mixture of PS and Zn2+ ions can simultaneously inhibit the cathodic, anodic corrosion reactions of Q235 steel, belonging to an anodic-type corrosion inhibitors. Impedance spectroscopy shows that the mixture can form a dense corrosion inhibitor film on the electrode surface. XPS analysis confirms that the corrosion inhibitor film consists of potassium sorbate, iron oxide/hydroxide and Zn(OH)2 precipitate.
The synergistic inhibition effect of potassium sorbate (PS) and Zn2+ ions on the corrosion of Q235 steel in 0.5 mol/L NaCl solution was studied by weight loss method, electrochemical method, X-ray photoelectron spectroscopy (XPS) and scanning electronic microscopy (SEM). The results of weight loss measurement show that potassium sorbate has some inhibition of corrosion of Q235 steel in 0.5 mol/L NaCl solution, the inhibition efficiency increases with the increase of concentration. When the added PS concentration is 25.0 g/L, the maximum inhibition efficiency is 38.37%. The combination of PS and Zn2+ ions has a significantly synergistic inhibition effect, the corrosion inhibition efficiency is as high as 91.03%. Potentiodynamic polarization shows that the mixture of PS and Zn2+ ions can simultaneously inhibit the cathodic, anodic corrosion reactions of Q235 steel, belonging to an anodic-type corrosion inhibitors. Impedance spectroscopy shows that the mixture can form a dense corrosion inhibitor film on the electrode surface. XPS analysis confirms that the corrosion inhibitor film consists of potassium sorbate, iron oxide/hydroxide and Zn(OH)2 precipitate.
2020, 37(8): 969-976
doi: 10.11944/j.issn.1000-0518.2020.08.200134
Abstract:
An analytical method based on enhanced matrix removal(EMR)-Lipid column purified/liquid chromatography-tandem mass spectrometry was developed for the determination of amitraz (AMZ) and their metabolites 2, 4-xylidine (DMA), semiamitraz (DMPF) and N-(2, 4-dimethylphenyl)formamide (DMF) residues in pork and porcine liver. The pork and porcine liver samples were precipitated with acetonitrile and salting out with extraction. The acetonitrile supernatant was cleaned up with Captiva EMR-Lipid cartridge, and then the supernatant solution was filtered through a nylon membrane into a glass LC sample vial for LC-MS/MS analysis. The solution was separated on an Agilent ZORBAX Eclipse Plus C18 column (50 mm×2.1mm, 1.8 μm) with 0.1% formic acid acetonitrile-0.1% formic acid solution as mobile phases by gradient elution, then determined by LC-MS/MS with electrospray ionization (ESI) in positive ion scanning mode under multiple reaction monitoring (MRM) mode. The results show that the linear range of AMZ, DMA in pig liver and pork is 1~200 μg/kg, while the linear range of DMPF and DMF is 0.1~200 μg/kg, The correlation coefficient (R2) is greater than 0.991; The quantitative limits of AMZ, DMA, DMPF and DMF are 0.6, 0.6, 0.05, 0.05 μg/kg, respectively; The spiked recoveries at four levels of 0.1, 1, 5, and 50 μg/kg are in the range of 60.2%~127.4% with relative standard deviations (RSD) lower than 12%. This method provides an easy and fast detection technique for the analysis of AMZ and its metabolites residues in pork and porcine liver samples.
An analytical method based on enhanced matrix removal(EMR)-Lipid column purified/liquid chromatography-tandem mass spectrometry was developed for the determination of amitraz (AMZ) and their metabolites 2, 4-xylidine (DMA), semiamitraz (DMPF) and N-(2, 4-dimethylphenyl)formamide (DMF) residues in pork and porcine liver. The pork and porcine liver samples were precipitated with acetonitrile and salting out with extraction. The acetonitrile supernatant was cleaned up with Captiva EMR-Lipid cartridge, and then the supernatant solution was filtered through a nylon membrane into a glass LC sample vial for LC-MS/MS analysis. The solution was separated on an Agilent ZORBAX Eclipse Plus C18 column (50 mm×2.1mm, 1.8 μm) with 0.1% formic acid acetonitrile-0.1% formic acid solution as mobile phases by gradient elution, then determined by LC-MS/MS with electrospray ionization (ESI) in positive ion scanning mode under multiple reaction monitoring (MRM) mode. The results show that the linear range of AMZ, DMA in pig liver and pork is 1~200 μg/kg, while the linear range of DMPF and DMF is 0.1~200 μg/kg, The correlation coefficient (R2) is greater than 0.991; The quantitative limits of AMZ, DMA, DMPF and DMF are 0.6, 0.6, 0.05, 0.05 μg/kg, respectively; The spiked recoveries at four levels of 0.1, 1, 5, and 50 μg/kg are in the range of 60.2%~127.4% with relative standard deviations (RSD) lower than 12%. This method provides an easy and fast detection technique for the analysis of AMZ and its metabolites residues in pork and porcine liver samples.
2020, 37(8): 939-951
doi: 10.11944/j.issn.1000-0518.2020.08.200044
Abstract:
Tuning the existing cathode surface to construct a hetero-interface configuration has been widely applied to improve its oxygen reduction reaction (ORR) activity. Here we report our findings on effective acceleration of the ORR kinetics of La2NiO4+δ (LNO) cathode by conformal Pr2NiO4+δ (PNO) modification. Meanwhile, the mechanism of the surface modification on ORR activity is revealed. Firstly, a highly active (110) plane for oxygen reduction emerges under LNO deposition. Secondly, the PNO modified layer with~5 nm thick displays the smallest polarization resistance, which is 21 times less than that of LNO (~5 nm) referenced cathode. Meanwhile, PNO (~5 nm) heterojunction exhibits an alerted ORR kinetics because of different oxygen defect chemistries of the top layer, in which the porous LNO backbone provides a pathway to favorably transport both of oxygen ions and electrons, while the PNO decorating offers rich surface oxygen defects to further enhance the ORR activity.
Tuning the existing cathode surface to construct a hetero-interface configuration has been widely applied to improve its oxygen reduction reaction (ORR) activity. Here we report our findings on effective acceleration of the ORR kinetics of La2NiO4+δ (LNO) cathode by conformal Pr2NiO4+δ (PNO) modification. Meanwhile, the mechanism of the surface modification on ORR activity is revealed. Firstly, a highly active (110) plane for oxygen reduction emerges under LNO deposition. Secondly, the PNO modified layer with~5 nm thick displays the smallest polarization resistance, which is 21 times less than that of LNO (~5 nm) referenced cathode. Meanwhile, PNO (~5 nm) heterojunction exhibits an alerted ORR kinetics because of different oxygen defect chemistries of the top layer, in which the porous LNO backbone provides a pathway to favorably transport both of oxygen ions and electrons, while the PNO decorating offers rich surface oxygen defects to further enhance the ORR activity.
