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2020 Volume 37 Issue 6
2020, 37(6): 611-619
doi: 10.11944/j.issn.1000-0518.2020.06.190336
Abstract:
Porphyrins have been widely used to construct new photocatalytic and photosensitizing materials because of their strong absorption of visible light. The photophysical and photochemical properties of porphyrin units could be easily modulated in frameworks materials, with the aid of the large surface area and tunable pore structure of the frameworks, leading to an improved photocatalytic quantum yield and selectivity. In this review, the recent advances of porphyrin-based frameworks materials, including metal organic framework materials (MOFs) and covalent organic framework materials (COFs) as well as covalent organic polymers (COPs) have been briefly summarized in the field of photocatalysis. Moreover, the key problems faced by designing high-performance porphyrin-based photocatalysts were analyzed in order to give some advice for the future development.
Porphyrins have been widely used to construct new photocatalytic and photosensitizing materials because of their strong absorption of visible light. The photophysical and photochemical properties of porphyrin units could be easily modulated in frameworks materials, with the aid of the large surface area and tunable pore structure of the frameworks, leading to an improved photocatalytic quantum yield and selectivity. In this review, the recent advances of porphyrin-based frameworks materials, including metal organic framework materials (MOFs) and covalent organic framework materials (COFs) as well as covalent organic polymers (COPs) have been briefly summarized in the field of photocatalysis. Moreover, the key problems faced by designing high-performance porphyrin-based photocatalysts were analyzed in order to give some advice for the future development.
2020, 37(6): 620-626
doi: 10.11944/j.issn.1000-0518.2020.06.200092
Abstract:
The photodynamic bactericidal performance of a reversibly activated asymmetric cyanine (Acy) was studied. The results show that Acy can be specifically activated to produce singlet oxygen in the weakly acidic microenvironment of bacteria under the irradiation of 808 nm laser, and shows excellent photodynamic bactericidal effect on both E.coli and S.aureus, but has no photodynamic antibacterial effect under normal physiological condition. The specifically activated photodynamic feature of Acy effectively overcomes the shortcoming of non-specific damage to normal tissues in previous "always on" photosensitizers, making Acy promising for specific antibacteria.
The photodynamic bactericidal performance of a reversibly activated asymmetric cyanine (Acy) was studied. The results show that Acy can be specifically activated to produce singlet oxygen in the weakly acidic microenvironment of bacteria under the irradiation of 808 nm laser, and shows excellent photodynamic bactericidal effect on both E.coli and S.aureus, but has no photodynamic antibacterial effect under normal physiological condition. The specifically activated photodynamic feature of Acy effectively overcomes the shortcoming of non-specific damage to normal tissues in previous "always on" photosensitizers, making Acy promising for specific antibacteria.
2020, 37(6): 627-634
doi: 10.11944/j.issn.1000-0518.2020.06.190322
Abstract:
Photon therapy is a new selective cancer treatment technology which has been developed rapidly in recent years. It has the advantages of small trauma, good selectivity, low toxicity and no drug resistance. In this paper, we used hydrothermal synthesis method to prepare a new kind of layered Co-Fe double hydroxide nanosheet (Co-Fe-LDH) which has the characteristics of large specific surface area, high stability and good biocompatibility and is used to load photosensitizer IR783 (LDH-IR783) to realize the photothermal/photodynamic cooperative phototherapy of cancer under the stimulation of near-infrared laser. We characterized the composition, morphology, optical property, reactive oxygen species (ROS) generation and heat release of LDH-IR783 and tested its anticancer activity at the cellular and in vivo levels. The results indicate that the nanocomposite has a stable structure, high IR783 loading efficiency and good dispersibility, exhibits excellent photothermal/photodynamic effects under near-infrared light irradiation through producing considerable ROS and releasing heat rapidly to induce severe phototoxicity to cancer cells. Both in vitro and in vivo experiments display that the nanocomposite can effectively induce apoptosis of HeLa cells and significantly inhibit the growth of solid tumors without obvious side effects and damage to normal tissue. The preliminary results will provide new ideas for the design and application of photo-thermal/photodynamic synergistic drugs.
Photon therapy is a new selective cancer treatment technology which has been developed rapidly in recent years. It has the advantages of small trauma, good selectivity, low toxicity and no drug resistance. In this paper, we used hydrothermal synthesis method to prepare a new kind of layered Co-Fe double hydroxide nanosheet (Co-Fe-LDH) which has the characteristics of large specific surface area, high stability and good biocompatibility and is used to load photosensitizer IR783 (LDH-IR783) to realize the photothermal/photodynamic cooperative phototherapy of cancer under the stimulation of near-infrared laser. We characterized the composition, morphology, optical property, reactive oxygen species (ROS) generation and heat release of LDH-IR783 and tested its anticancer activity at the cellular and in vivo levels. The results indicate that the nanocomposite has a stable structure, high IR783 loading efficiency and good dispersibility, exhibits excellent photothermal/photodynamic effects under near-infrared light irradiation through producing considerable ROS and releasing heat rapidly to induce severe phototoxicity to cancer cells. Both in vitro and in vivo experiments display that the nanocomposite can effectively induce apoptosis of HeLa cells and significantly inhibit the growth of solid tumors without obvious side effects and damage to normal tissue. The preliminary results will provide new ideas for the design and application of photo-thermal/photodynamic synergistic drugs.
2020, 37(6): 635-641
doi: 10.11944/j.issn.1000-0518.2020.06.190338
Abstract:
Nitrous pentoxide, a new type of green nitrating agent, can replace the traditional highly polluting mixed acid. However, the conversion of direct nitrification by N2O5 is low. In this paper, three methods were used to modify HZSM-5 zeolite molecular sieve. Then, the catalyst was used to nitrate toluene with N2O5, and pyridine Fourier-transform infrared (FT-IR) and X-ray diffraction (XRD) were used for characterization. Experimental results show that the yield of mononitrotoluene is significantly improved after the introduction of the catalyst. Among them, the modification effect of the impregnation method is superior to the ion exchange method. Compared to the unmodified (45.2%), the yield increases by 22.5%; After 5 different concentrations of NaOH modification, it is found that the best modification concentration is 0.2 mol/L, and the nitrification yield reaches 58.5%.
Nitrous pentoxide, a new type of green nitrating agent, can replace the traditional highly polluting mixed acid. However, the conversion of direct nitrification by N2O5 is low. In this paper, three methods were used to modify HZSM-5 zeolite molecular sieve. Then, the catalyst was used to nitrate toluene with N2O5, and pyridine Fourier-transform infrared (FT-IR) and X-ray diffraction (XRD) were used for characterization. Experimental results show that the yield of mononitrotoluene is significantly improved after the introduction of the catalyst. Among them, the modification effect of the impregnation method is superior to the ion exchange method. Compared to the unmodified (45.2%), the yield increases by 22.5%; After 5 different concentrations of NaOH modification, it is found that the best modification concentration is 0.2 mol/L, and the nitrification yield reaches 58.5%.
2020, 37(6): 642-649
doi: 10.11944/j.issn.1000-0518.2020.06.190359
Abstract:
The crystallization and melting behavior of poly(1, 4-cyclohexylene dimethylene terephthalate) (PCT) was studied by fast scanning calorimetry (FSC) combined with traditional differential scanning calorimetry (DSC) in the range of near glass transition temperature and melting temperature (100~270 ℃). The crystallization rate of PCT is faster when the supercooling degree is larger. FSC can effectively inhibit the crystallization of PCT during the cooling process while the traditional DSC can avoid the influence of sample degradation on the experimental results under the lower supercooling degrees. The combination of FSC and DSC can well measure the crystallization kinetics of PCT. The experimental results show that the crystallization rate is the fastest at 175 ℃. FSC is also used to measure the melting point dependence of heating rate after isothermal crystallization, and calibrated on the basis of the modeling of melting kinetics for the determination of the melting point at zero heating rate Tm. The Hoffman-Weeks plot of Tm against Tc with the intersection of Tc=Tm suggested the equilibrium melting point Tmo≅315 ℃ of chain-extended infinite-size crystals of PCT.
The crystallization and melting behavior of poly(1, 4-cyclohexylene dimethylene terephthalate) (PCT) was studied by fast scanning calorimetry (FSC) combined with traditional differential scanning calorimetry (DSC) in the range of near glass transition temperature and melting temperature (100~270 ℃). The crystallization rate of PCT is faster when the supercooling degree is larger. FSC can effectively inhibit the crystallization of PCT during the cooling process while the traditional DSC can avoid the influence of sample degradation on the experimental results under the lower supercooling degrees. The combination of FSC and DSC can well measure the crystallization kinetics of PCT. The experimental results show that the crystallization rate is the fastest at 175 ℃. FSC is also used to measure the melting point dependence of heating rate after isothermal crystallization, and calibrated on the basis of the modeling of melting kinetics for the determination of the melting point at zero heating rate Tm. The Hoffman-Weeks plot of Tm against Tc with the intersection of Tc=Tm suggested the equilibrium melting point Tmo≅315 ℃ of chain-extended infinite-size crystals of PCT.
2020, 37(6): 650-657
doi: 10.11944/j.issn.1000-0518.2020.06.200031
Abstract:
In this paper, polyethylene glycol/boron nitride (PEG/BN) phase change composite was prepared by molten blending method and the influence of the flake size of BN on the thermal conductivity and crystallization behavior of phase change composites was studied. The microstructure, thermal conductivity and phase transition performance of the prepared composites were investigated by scanning electron microscope (SEM), thermal constant analyzer, infrared thermal imaging analyzer and differential scanning calorimeter (DSC). The DSC results of were analyzed by Mo Zhishen method. Results show that larger diameter (50 μm) BN can improve the thermal conductivity of PEG more effectively. When the weight fraction of BN filler content is 40%, the thermal conductivity of phase change composite can reach 5.04 W/(m·K). Under conditions of rapid cooling, BN filler with a diameter of 50 μm can shorten the semi crystallization time and increase the crystallization rate of PEG, and make the phase change composites have a large phase change enthalpy.
In this paper, polyethylene glycol/boron nitride (PEG/BN) phase change composite was prepared by molten blending method and the influence of the flake size of BN on the thermal conductivity and crystallization behavior of phase change composites was studied. The microstructure, thermal conductivity and phase transition performance of the prepared composites were investigated by scanning electron microscope (SEM), thermal constant analyzer, infrared thermal imaging analyzer and differential scanning calorimeter (DSC). The DSC results of were analyzed by Mo Zhishen method. Results show that larger diameter (50 μm) BN can improve the thermal conductivity of PEG more effectively. When the weight fraction of BN filler content is 40%, the thermal conductivity of phase change composite can reach 5.04 W/(m·K). Under conditions of rapid cooling, BN filler with a diameter of 50 μm can shorten the semi crystallization time and increase the crystallization rate of PEG, and make the phase change composites have a large phase change enthalpy.
2020, 37(6): 658-665
doi: 10.11944/j.issn.1000-0518.2020.06.190355
Abstract:
Ethyl isocyanate polysulfone (PS-SA) was prepared by introducing the —NCO active group onto the main chain of bisphenol A polysulfones matrix by the Friedel-Crafts alkylation reaction. Naphthalene sulfonic acid modified polysulfone (PS-NS) was obtained by using 2-naphthol-6, 8-disulfonic acid dipotassium as the nucleophilic reagent in one pot. The PS-NS proton exchange membranes(PEMs) were fabricated by solution casting. The relationship between temperature and the basic properties including water uptake, swelling ratio and proton conductivity were explored. PS-NS exhibits excellent dimensional stability at high water sorption because they can form phase separation structure by locating the hydrophilic group far away from the main chain of polysulfones. The water uptake of PS-NS-4 PEMs(the bonding amount of sulfonic groups is 1.42 mmol/g) is as high as 27.2% at 25 ℃ and 40.3% at 85 ℃, but the corresponding swelling ratio is only 25.2% and 57.2%. The properties are very close to that of Nafion115 membrane under the same condition.
Ethyl isocyanate polysulfone (PS-SA) was prepared by introducing the —NCO active group onto the main chain of bisphenol A polysulfones matrix by the Friedel-Crafts alkylation reaction. Naphthalene sulfonic acid modified polysulfone (PS-NS) was obtained by using 2-naphthol-6, 8-disulfonic acid dipotassium as the nucleophilic reagent in one pot. The PS-NS proton exchange membranes(PEMs) were fabricated by solution casting. The relationship between temperature and the basic properties including water uptake, swelling ratio and proton conductivity were explored. PS-NS exhibits excellent dimensional stability at high water sorption because they can form phase separation structure by locating the hydrophilic group far away from the main chain of polysulfones. The water uptake of PS-NS-4 PEMs(the bonding amount of sulfonic groups is 1.42 mmol/g) is as high as 27.2% at 25 ℃ and 40.3% at 85 ℃, but the corresponding swelling ratio is only 25.2% and 57.2%. The properties are very close to that of Nafion115 membrane under the same condition.
2020, 37(6): 666-672
doi: 10.11944/j.issn.1000-0518.2020.06.190354
Abstract:
Incorporation of inorganic nanoparticles to polyimides is an important strategy to improve corona resistance. The improvement of corona-resistant characteristics is closely related to the dispersion of nano fillers. The controllable distribution of nanoparticles in polymer matrix has always been a challenge. In this paper, The Al2O3/polyimide(PI) composites were synthesised via in situ polymerization in the solution of two-dimensional nano-sheets exfoliated from layered double hydroxides (LDH). In the process of the film formation, the two-dimensional nano-sheets tend to aggregate and orientate towards the substrates with the solvent volatilization, which would affect the distribution of Al2O3 in the polymer matrix, and furthermore improve the corona resistance of the Al2O3/LDH/PI composites. The corona resistance time of Al2O3/LDH/PI composites is 180 min, and improves by twelve-fold when 2% (mass fraction) LDH is added into 10% (mass fraction) Al2O3/PI composites, and the tensile strength increases by 37.8%. Due to the different morphologies, the combination of two-dimensional nanosheets and nanoparticles can effectively improve the corona resistance and mechanical properties of Al2O3/LDH/PI composite films.
Incorporation of inorganic nanoparticles to polyimides is an important strategy to improve corona resistance. The improvement of corona-resistant characteristics is closely related to the dispersion of nano fillers. The controllable distribution of nanoparticles in polymer matrix has always been a challenge. In this paper, The Al2O3/polyimide(PI) composites were synthesised via in situ polymerization in the solution of two-dimensional nano-sheets exfoliated from layered double hydroxides (LDH). In the process of the film formation, the two-dimensional nano-sheets tend to aggregate and orientate towards the substrates with the solvent volatilization, which would affect the distribution of Al2O3 in the polymer matrix, and furthermore improve the corona resistance of the Al2O3/LDH/PI composites. The corona resistance time of Al2O3/LDH/PI composites is 180 min, and improves by twelve-fold when 2% (mass fraction) LDH is added into 10% (mass fraction) Al2O3/PI composites, and the tensile strength increases by 37.8%. Due to the different morphologies, the combination of two-dimensional nanosheets and nanoparticles can effectively improve the corona resistance and mechanical properties of Al2O3/LDH/PI composite films.
2020, 37(6): 673-682
doi: 10.11944/j.issn.1000-0518.2020.06.190325
Abstract:
In order to improve the present situation of phosphorus pollution in environmental water, the chitosan iron (CS-Fe) composite gel beads were prepared by sol-titration-vacuum freeze drying method to remove phosphate from water. The morphology and structure of CS-Fe gel beads were characterized, and the factors affecting the adsorption of phosphate and the reaction mechanism were explored. The results show that the adsorption of phosphate by CS-Fe is a spontaneous, endothermic and entropy-increasing process, the adsorption process is in accordance with the pseudo first-order kinetic equation, the adsorption equilibrium time is 50 min, the maximum adsorption capacity calculated by Langmuir model is 23.97 mg/g, and the desorption efficiency is more than 90%. Fourier transform infrared (FT-IR), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), Zeta potential analysis and X-ray photoelectron spectroscopy show that CS-Fe forms a honeycomb structure which is favorable for the rapid adsorption of phosphate, and the adsorption mechanism includes electrostatic adsorption and ion exchange. The adsorbent combines the adsorption properties of metal compounds with the characteristics of chitosan macromolecule, which is conducive to the construction of porous materials and improvement of the adsorption effect. Gel beads materials are more conducive to recovery, avoid secondary pollution, and have potential applications.
In order to improve the present situation of phosphorus pollution in environmental water, the chitosan iron (CS-Fe) composite gel beads were prepared by sol-titration-vacuum freeze drying method to remove phosphate from water. The morphology and structure of CS-Fe gel beads were characterized, and the factors affecting the adsorption of phosphate and the reaction mechanism were explored. The results show that the adsorption of phosphate by CS-Fe is a spontaneous, endothermic and entropy-increasing process, the adsorption process is in accordance with the pseudo first-order kinetic equation, the adsorption equilibrium time is 50 min, the maximum adsorption capacity calculated by Langmuir model is 23.97 mg/g, and the desorption efficiency is more than 90%. Fourier transform infrared (FT-IR), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), Zeta potential analysis and X-ray photoelectron spectroscopy show that CS-Fe forms a honeycomb structure which is favorable for the rapid adsorption of phosphate, and the adsorption mechanism includes electrostatic adsorption and ion exchange. The adsorbent combines the adsorption properties of metal compounds with the characteristics of chitosan macromolecule, which is conducive to the construction of porous materials and improvement of the adsorption effect. Gel beads materials are more conducive to recovery, avoid secondary pollution, and have potential applications.
2020, 37(6): 683-694
doi: 10.11944/j.issn.1000-0518.2020.06.190330
Abstract:
A novel hollow composite of NiCo-layered double hydroxide and zeolitic imidazolate framework-67 (NiCo-LDH@ZIF-67) adsorbent with high adsorption capacity for pollutants, high adsorption selectivity of methyl orange (MO) and great regenerability was synthesized using ZIF-67 as a template. The sample was characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectrometer (FT-IR), N2 adsorption desorption and X-ray photoelectron spectroscopy (XPS). The effect of solution pH, the initial MO concentration and the contact time with the mixture solution on the adsorption property of NiCo-LDH@ZIF-67 was studied. The results indicate that its adsorption kinetics for MO can be well simulated by a pseudo-second-order model and its adsorption isotherm for MO follows the Langmuir equation. The optimized adsorption condition is pH=4, contact time of 15 minutes, and adsorbent dosage of 2400 mg/L. Its maximum adsorption capacity for MO can reach as high as 1766 mg/g and is higher than those reported for all similar adsorbents in the literature. In addition, NiCo-LDH@ZIF-67 can selectively adsorb MO from a mixed solution of MO and methylene blue (MB).
A novel hollow composite of NiCo-layered double hydroxide and zeolitic imidazolate framework-67 (NiCo-LDH@ZIF-67) adsorbent with high adsorption capacity for pollutants, high adsorption selectivity of methyl orange (MO) and great regenerability was synthesized using ZIF-67 as a template. The sample was characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectrometer (FT-IR), N2 adsorption desorption and X-ray photoelectron spectroscopy (XPS). The effect of solution pH, the initial MO concentration and the contact time with the mixture solution on the adsorption property of NiCo-LDH@ZIF-67 was studied. The results indicate that its adsorption kinetics for MO can be well simulated by a pseudo-second-order model and its adsorption isotherm for MO follows the Langmuir equation. The optimized adsorption condition is pH=4, contact time of 15 minutes, and adsorbent dosage of 2400 mg/L. Its maximum adsorption capacity for MO can reach as high as 1766 mg/g and is higher than those reported for all similar adsorbents in the literature. In addition, NiCo-LDH@ZIF-67 can selectively adsorb MO from a mixed solution of MO and methylene blue (MB).
2020, 37(6): 695-702
doi: 10.11944/j.issn.1000-0518.2020.06.190329
Abstract:
TiO2 nanorod arrays (NRA) and branched TiO2 nanorod arrays (B-NRA) were prepared on conducting glass (FTO) by one-step hydrothermal method and two-step hydrothermal method, respectively. Sb2S3 nanoparticles (NPs) are deposited on TiO2 NRA and TiO2 B-NRA substrates by low temperature chemical bath deposition (CBD). Poly(3-hexylthiophene-2, 5-diyl) and 2, 2', 7, 7'-tetrakis-(N, N-di-p-methoxyphenylamine)-9, 9'-spirobifluorene (P3HT and Spiro-OMeTAD) are spin-coated on the TiO2/Sb2S3 composite membrane successively to form TiO2(NRA)/Sb2S3/P3HT/Spiro-OMeTAD films and TiO2(B-NRA)/Sb2S3/P3HT/Spiro-OMeTAD films as photoactive layers of hybrid solar cells. The results show that the power conversion efficiency (PCE) of the hybrid solar cell assembled with TiO2(B-NRA)/Sb2S3/P3HT/Spiro-OMeTAD composite membrane structure is 2.92%, and the PCE of the hybrid solar cell assembled with TiO2(B-NRA)/Sb2S3/P3HT/Spiro-OMeTAD composite membrane structure is improved to 4.67%.
TiO2 nanorod arrays (NRA) and branched TiO2 nanorod arrays (B-NRA) were prepared on conducting glass (FTO) by one-step hydrothermal method and two-step hydrothermal method, respectively. Sb2S3 nanoparticles (NPs) are deposited on TiO2 NRA and TiO2 B-NRA substrates by low temperature chemical bath deposition (CBD). Poly(3-hexylthiophene-2, 5-diyl) and 2, 2', 7, 7'-tetrakis-(N, N-di-p-methoxyphenylamine)-9, 9'-spirobifluorene (P3HT and Spiro-OMeTAD) are spin-coated on the TiO2/Sb2S3 composite membrane successively to form TiO2(NRA)/Sb2S3/P3HT/Spiro-OMeTAD films and TiO2(B-NRA)/Sb2S3/P3HT/Spiro-OMeTAD films as photoactive layers of hybrid solar cells. The results show that the power conversion efficiency (PCE) of the hybrid solar cell assembled with TiO2(B-NRA)/Sb2S3/P3HT/Spiro-OMeTAD composite membrane structure is 2.92%, and the PCE of the hybrid solar cell assembled with TiO2(B-NRA)/Sb2S3/P3HT/Spiro-OMeTAD composite membrane structure is improved to 4.67%.
2020, 37(6): 703-708
doi: 10.11944/j.issn.1000-0518.2020.06.190285
Abstract:
To avoid the performance fading and safety problem of lithium batteries caused by dendrite growth on the surface of lithium anode, the mesoporous carbon matrix (MCM) was prepared using the zeolitic imidazolate framework-8 (ZIF-8) as the template and precursor. X-ray powder diffraction (XRD) and Raman spectroscopy indicate that the MCM has a certain degree of graphitization, and the N2 adsorption-desorption test (BET) proves that MCM has typical mesoporous characteristics. The XRD, Raman and BET test results suggest that the optimum annealing temperature is 900 ℃. The optimized MCM is used to study the surface modification of lithium anode. After the charge and discharge cycle test, the XRD and scanning electron microscopy (SEM) tests show that the orientation deposition of lithium metal is avoided and the growth of lithium dendrites is suppressed because MCM can balance the charge distribution on the lithium anode surface. This work reveals a facile but efficient synthesis approach of the surface modification agent to extend the cycle life and enhance the safety for high performance lithium batteries.
To avoid the performance fading and safety problem of lithium batteries caused by dendrite growth on the surface of lithium anode, the mesoporous carbon matrix (MCM) was prepared using the zeolitic imidazolate framework-8 (ZIF-8) as the template and precursor. X-ray powder diffraction (XRD) and Raman spectroscopy indicate that the MCM has a certain degree of graphitization, and the N2 adsorption-desorption test (BET) proves that MCM has typical mesoporous characteristics. The XRD, Raman and BET test results suggest that the optimum annealing temperature is 900 ℃. The optimized MCM is used to study the surface modification of lithium anode. After the charge and discharge cycle test, the XRD and scanning electron microscopy (SEM) tests show that the orientation deposition of lithium metal is avoided and the growth of lithium dendrites is suppressed because MCM can balance the charge distribution on the lithium anode surface. This work reveals a facile but efficient synthesis approach of the surface modification agent to extend the cycle life and enhance the safety for high performance lithium batteries.
2020, 37(6): 709-718
doi: 10.11944/j.issn.1000-0518.2020.06.190333
Abstract:
Although ferrochrome electrolysis technology is a novel method for preparing sodium chromate, the electrochemical oxidation of high carbon ferrochrome in NaOH aqueous solution is still unclear. The electrochemical oxidation of chromium in NaOH aqueous solution was studied by cyclic voltammetry(CV). The electrochemical oxidation of high carbon ferrochrome in NaOH aqueous solution was studied by cyclic voltammetry and linear sweep voltammetry (LSV). Scanning electron microscope (SEM), energy dispersive spectrometry (EDS) and X-ray photoelectron spectroscopy (XPS) were used to characterize the composition of solid phase products after electrolysis of high carbon ferrochrome electrode. The results are as follows:metal chromium has two ways of electrochemical oxidation to form sodium chromate in NaOH aqueous solution: Cr(0)→Cr(Ⅵ) and Cr(0)→Cr(Ⅲ)→Cr(Ⅵ). The electrochemical oxidation of high carbon ferrochrome in NaOH is different from the metal chromium. It directly generates sodium chromite by Cr(0). Cr(OH)3 occurs electrochemical reaction with Fe(0) to form stable FeCr2O4. Fe(OH)3 is formed by the strong hydrolysis of FeO2-. As the concentration of NaOH aqueous solutions increases, the high carbon ferrochrome is easily passivated in NaOH aqueous solution under low potential range due to the influence of Fe(0). The passive films are Fe3O4 and Fe2O3. The passivation films dissolve at high potential. Then high carbon ferrochrome occurs electrochemical reaction to form Na2CrO4, Fe(OH)3 and FeCr2O4. At the same time, a large amount of oxygen is deposited on the positive electrode surface. As the concentration of NaOH aqueous solutions increases, the amount of Na2CrO4 and Fe(OH)3 increases. The conditions are as follows: alkaline concentration ≥2 mol/L, anodic potential ≥1.6 V(vs.SCE).
Although ferrochrome electrolysis technology is a novel method for preparing sodium chromate, the electrochemical oxidation of high carbon ferrochrome in NaOH aqueous solution is still unclear. The electrochemical oxidation of chromium in NaOH aqueous solution was studied by cyclic voltammetry(CV). The electrochemical oxidation of high carbon ferrochrome in NaOH aqueous solution was studied by cyclic voltammetry and linear sweep voltammetry (LSV). Scanning electron microscope (SEM), energy dispersive spectrometry (EDS) and X-ray photoelectron spectroscopy (XPS) were used to characterize the composition of solid phase products after electrolysis of high carbon ferrochrome electrode. The results are as follows:metal chromium has two ways of electrochemical oxidation to form sodium chromate in NaOH aqueous solution: Cr(0)→Cr(Ⅵ) and Cr(0)→Cr(Ⅲ)→Cr(Ⅵ). The electrochemical oxidation of high carbon ferrochrome in NaOH is different from the metal chromium. It directly generates sodium chromite by Cr(0). Cr(OH)3 occurs electrochemical reaction with Fe(0) to form stable FeCr2O4. Fe(OH)3 is formed by the strong hydrolysis of FeO2-. As the concentration of NaOH aqueous solutions increases, the high carbon ferrochrome is easily passivated in NaOH aqueous solution under low potential range due to the influence of Fe(0). The passive films are Fe3O4 and Fe2O3. The passivation films dissolve at high potential. Then high carbon ferrochrome occurs electrochemical reaction to form Na2CrO4, Fe(OH)3 and FeCr2O4. At the same time, a large amount of oxygen is deposited on the positive electrode surface. As the concentration of NaOH aqueous solutions increases, the amount of Na2CrO4 and Fe(OH)3 increases. The conditions are as follows: alkaline concentration ≥2 mol/L, anodic potential ≥1.6 V(vs.SCE).
2020, 37(6): 719-725
doi: 10.11944/j.issn.1000-0518.2020.06.190347
Abstract:
Red fluorescent carbon dots (R-CDs) were synthesized by one-step solvothermal method by using p-phenylenediamine and ethanol. The synthesized R-CDs were characterized by transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and fluorescence spectroscopy, respectively. The results indicate that the R-CDs are uniform with an average size of (3.63±0.20) nm. Abundant groups like hydroxyl and amine groups are linked on the surface of the synthesized R-CDs. The as-prepared R-CDs show excitation-independent property and the maximum excitation and emission wavelengths are 480 and 620 nm, respectively. Based on static quenching between R-CDs and persulfate, the fluorescence of R-CDs could be effectively quenched by persulfate. A fluorescent strategy is developed for detection of persulfate. The method showed a linear range of 2.5~120 μmol/L with a correlation coefficient (R2) of 0.9970. The limit of detection was 1.2 μmol/L, showing excellent sensitivity and selectivity. Meanwhile, the as-proposed sensing system is successfully applied to the analysis of persulfate in tap water and lake water samples with satisfactory results.
Red fluorescent carbon dots (R-CDs) were synthesized by one-step solvothermal method by using p-phenylenediamine and ethanol. The synthesized R-CDs were characterized by transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and fluorescence spectroscopy, respectively. The results indicate that the R-CDs are uniform with an average size of (3.63±0.20) nm. Abundant groups like hydroxyl and amine groups are linked on the surface of the synthesized R-CDs. The as-prepared R-CDs show excitation-independent property and the maximum excitation and emission wavelengths are 480 and 620 nm, respectively. Based on static quenching between R-CDs and persulfate, the fluorescence of R-CDs could be effectively quenched by persulfate. A fluorescent strategy is developed for detection of persulfate. The method showed a linear range of 2.5~120 μmol/L with a correlation coefficient (R2) of 0.9970. The limit of detection was 1.2 μmol/L, showing excellent sensitivity and selectivity. Meanwhile, the as-proposed sensing system is successfully applied to the analysis of persulfate in tap water and lake water samples with satisfactory results.
2020, 37(6): 726-732
doi: 10.11944/j.issn.1000-0518.2020.06.190332
Abstract:
A simple, rapid and sensitive electrochemical analysis method with a poly(p-aminobenzene sulfonic acid)/graphene modified glassy carbon electrode (pABSA/GR/GCE) for the determination of ofloxacin (OFL) is established based on GR nanomaterials and cyclic voltammetry (CV) in this study. Compared with the glassy carbon electrode, the peak current of OFL increases significantly using pABSA/GR/GCE. Under optimized experimental conditions, the pABSA/GR/GCE shows a good linear relationship with the concentration of OFL in the range of 1~600 μmol/L and a detection limit (S/N=3) of 0.33 μmol/L. The pABSA/GR/GCE is easy to be prepared with good reproducibility and stability. It has been used in the determination of ofloxacin eye drops with satisfactory results.
A simple, rapid and sensitive electrochemical analysis method with a poly(p-aminobenzene sulfonic acid)/graphene modified glassy carbon electrode (pABSA/GR/GCE) for the determination of ofloxacin (OFL) is established based on GR nanomaterials and cyclic voltammetry (CV) in this study. Compared with the glassy carbon electrode, the peak current of OFL increases significantly using pABSA/GR/GCE. Under optimized experimental conditions, the pABSA/GR/GCE shows a good linear relationship with the concentration of OFL in the range of 1~600 μmol/L and a detection limit (S/N=3) of 0.33 μmol/L. The pABSA/GR/GCE is easy to be prepared with good reproducibility and stability. It has been used in the determination of ofloxacin eye drops with satisfactory results.
