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2018 Volume 76 Issue 7
2018, 76(7): 501-514
doi: 10.6023/A18040138
Abstract:
In view of the depletion of fossil fuels, the development and utilization of environment-friendly and sustainable resources widely play an indispensable role in alleviating and resolving problems about resources and environment. Biomass could be utilized as biofuels and renewable platform chemicals. However, biomass-derived molecules are fairly oxygen-rich and hyperfunctionalized. Therefore, new synthetic routes for the regenerative production of chemicals, fuels, and energy from renewable biomass sources are currently investigated especially the routes of transforming high-oxygen-content biomassderived vicinal diols and poly vicinal alcohols into fuels and value-added chemicals. A range of reductive deoxygenation methods consisting of direct deoxygenation, pyrolysis, hydrogenolysis, decarbonylation, decarboxylation, hydrodeoxygenation, and deoxydehydration (DODH) are under investigation. In this review, we detail the recent-evolutionary and efficient strategies of transition metal-catalyzed DODH of vicinal diols into corresponding alkenes, including rhenium, molybdenum, vanadium, and ruthenium catalysts. Rhenium-catalyzed DODH reactions are very selective and active to provide high yields of olefin products, which keep important functionality in place as well as can be readily functionalized. Recent efforts in rhenium-mediated systems include the development of new rhenium catalysts, the application of cheaper and more available reductants, and growing mechanistic understandings owing to both theoretical and experimental studies. A new emerging trend within DODH is the development of heterogeneous rhenium-based catalysts which demonstrates their ability to rival and in some cases surpass their homogeneous counterparts. Furthermore, catalysts based on the transition metals molybdenum, vanadium and ruthenium show great potential as inexpensive alternatives to rhenium catalysts.
In view of the depletion of fossil fuels, the development and utilization of environment-friendly and sustainable resources widely play an indispensable role in alleviating and resolving problems about resources and environment. Biomass could be utilized as biofuels and renewable platform chemicals. However, biomass-derived molecules are fairly oxygen-rich and hyperfunctionalized. Therefore, new synthetic routes for the regenerative production of chemicals, fuels, and energy from renewable biomass sources are currently investigated especially the routes of transforming high-oxygen-content biomassderived vicinal diols and poly vicinal alcohols into fuels and value-added chemicals. A range of reductive deoxygenation methods consisting of direct deoxygenation, pyrolysis, hydrogenolysis, decarbonylation, decarboxylation, hydrodeoxygenation, and deoxydehydration (DODH) are under investigation. In this review, we detail the recent-evolutionary and efficient strategies of transition metal-catalyzed DODH of vicinal diols into corresponding alkenes, including rhenium, molybdenum, vanadium, and ruthenium catalysts. Rhenium-catalyzed DODH reactions are very selective and active to provide high yields of olefin products, which keep important functionality in place as well as can be readily functionalized. Recent efforts in rhenium-mediated systems include the development of new rhenium catalysts, the application of cheaper and more available reductants, and growing mechanistic understandings owing to both theoretical and experimental studies. A new emerging trend within DODH is the development of heterogeneous rhenium-based catalysts which demonstrates their ability to rival and in some cases surpass their homogeneous counterparts. Furthermore, catalysts based on the transition metals molybdenum, vanadium and ruthenium show great potential as inexpensive alternatives to rhenium catalysts.
2018, 76(7): 515-525
doi: 10.6023/A18030125
Abstract:
Due to the heavy use of fossil fuels, the emission of carbon dioxide has been steadily increased and the climate has been deteriorated severely. In order to solve these problems, various physical and chemical methods were used to reduce the amount of carbon dioxide in the atmosphere, but the result is not so effective. Metal carbon dioxide batteries not only can capture carbon dioxide, but also can be used as clean energy storage devices. At the same time, the development and research of metal carbon dioxide batteries also promote the development of the electric vehicle industry towards a more economical, environmentally friendly and sustainable direction. Based on these advantages, metal carbon dioxide battery has developed rapidly in recent years. Li-CO2 batteries exhibit an extremely high discharge capacity of 17625 mAh/g and a cut-off capacity of 1000 mAh/g at a current density of 100 mA/g, running for 100 cycles at low overpotentials. Quasi-solid state Na-CO2 batteries are non-flammable and have strong electrolyte-locking ability. It can run 400 cycles at 500 mA/g with a fixed capacity of 1000 mAh/g in pure CO2. Its electrochemical performance has the potential to be further improved. Al-CO2 battery has good application prospects and economic benefits due to the low cost of Al as well as great economic value of the sodium aluminate as discharge product. Mg-CO2 battery shows a discharge voltage plateau of 0.9 V when the volume ratio of CO2/O2 is 1:1, which is higher than that of pure O2. This paper mainly introduces the research progress of metal (lithium, sodium, aluminum, and magnesium) carbon dioxide battery, and compares the electrochemical performance of metal (lithium, sodium) carbon dioxide battery with metal (lithium, sodium) oxygen battery, puts forward the current problems of metal carbon dioxide batteries, and provides the solutions. Finally, the future development of metal carbon dioxide batteries is reviewed.
Due to the heavy use of fossil fuels, the emission of carbon dioxide has been steadily increased and the climate has been deteriorated severely. In order to solve these problems, various physical and chemical methods were used to reduce the amount of carbon dioxide in the atmosphere, but the result is not so effective. Metal carbon dioxide batteries not only can capture carbon dioxide, but also can be used as clean energy storage devices. At the same time, the development and research of metal carbon dioxide batteries also promote the development of the electric vehicle industry towards a more economical, environmentally friendly and sustainable direction. Based on these advantages, metal carbon dioxide battery has developed rapidly in recent years. Li-CO2 batteries exhibit an extremely high discharge capacity of 17625 mAh/g and a cut-off capacity of 1000 mAh/g at a current density of 100 mA/g, running for 100 cycles at low overpotentials. Quasi-solid state Na-CO2 batteries are non-flammable and have strong electrolyte-locking ability. It can run 400 cycles at 500 mA/g with a fixed capacity of 1000 mAh/g in pure CO2. Its electrochemical performance has the potential to be further improved. Al-CO2 battery has good application prospects and economic benefits due to the low cost of Al as well as great economic value of the sodium aluminate as discharge product. Mg-CO2 battery shows a discharge voltage plateau of 0.9 V when the volume ratio of CO2/O2 is 1:1, which is higher than that of pure O2. This paper mainly introduces the research progress of metal (lithium, sodium, aluminum, and magnesium) carbon dioxide battery, and compares the electrochemical performance of metal (lithium, sodium) carbon dioxide battery with metal (lithium, sodium) oxygen battery, puts forward the current problems of metal carbon dioxide batteries, and provides the solutions. Finally, the future development of metal carbon dioxide batteries is reviewed.
2018, 76(7): 526-530
doi: 10.6023/A18040163
Abstract:
The surface enhanced Raman spectroscopy (SERS) has been employed in the structural characterization successfully due to its ultra-high sensitivity. However, it is still remained the significant difficulties in the precise interpretation of spectroscopy. Thus, it was not developed as the promising tool for monitoring the organic reaction directly. Herein, by using the two dimensional Au nanoparticles array film as substrate, the SERS was hyphenated with high performance liquid chromatography (HPLC). The individual advantages of high sensitivity of SERS and high efficiency in separation of HPLC were combined together, and it was extended successfully to real-time monitor of a Suzuki coupling reaction between 3-bromopyridine and phenylboronic acid. Firstly, the retention time and SERS spectra of standard solution of 3-bromopyridine and phenylboronic acid were performed respectively. It was beneficial for distinguishing the reactants of the current Suzuki reaction. After the reaction was proceeded for about 5 min, the mixture was sampled for the HPLC-SERS detection. It demonstrated that the chromatogram peaks located at 2.1 min and 2.8 min were contributed to phenylboronic acid and 3-bromopyridine, while 3.6 min and 15.3 min were originated from the reaction products. The solution collected at different retention times were then flowed through the catheter and dropped to the surface of Au nanoparticles arrays sequentially. The SERS spectra features were well agreement with that of 3-bromopyridine at 2.8 min, while the SERS spectra was absent for phenylboronic acid at 2.1 min due to its weak adsorption on Au surface. For the products, the typical vibrational modes of 3-phenylpyridine and diphenyl were observed in the SERS spectra, suggesting the composition of the product and byproduct. Meanwhile, the final product was confirmed by NMR spectroscopy, proving a structure of 3-phenylpyridine. Finally, the SERS results were well associated with the chromatographic peaks in a certain duration. It indicated that the HPLC-SERS technique would be a promising tool as a complementary approach to traditional techniques (such as LC-MS) for on line monitoring the organic reaction processes.
The surface enhanced Raman spectroscopy (SERS) has been employed in the structural characterization successfully due to its ultra-high sensitivity. However, it is still remained the significant difficulties in the precise interpretation of spectroscopy. Thus, it was not developed as the promising tool for monitoring the organic reaction directly. Herein, by using the two dimensional Au nanoparticles array film as substrate, the SERS was hyphenated with high performance liquid chromatography (HPLC). The individual advantages of high sensitivity of SERS and high efficiency in separation of HPLC were combined together, and it was extended successfully to real-time monitor of a Suzuki coupling reaction between 3-bromopyridine and phenylboronic acid. Firstly, the retention time and SERS spectra of standard solution of 3-bromopyridine and phenylboronic acid were performed respectively. It was beneficial for distinguishing the reactants of the current Suzuki reaction. After the reaction was proceeded for about 5 min, the mixture was sampled for the HPLC-SERS detection. It demonstrated that the chromatogram peaks located at 2.1 min and 2.8 min were contributed to phenylboronic acid and 3-bromopyridine, while 3.6 min and 15.3 min were originated from the reaction products. The solution collected at different retention times were then flowed through the catheter and dropped to the surface of Au nanoparticles arrays sequentially. The SERS spectra features were well agreement with that of 3-bromopyridine at 2.8 min, while the SERS spectra was absent for phenylboronic acid at 2.1 min due to its weak adsorption on Au surface. For the products, the typical vibrational modes of 3-phenylpyridine and diphenyl were observed in the SERS spectra, suggesting the composition of the product and byproduct. Meanwhile, the final product was confirmed by NMR spectroscopy, proving a structure of 3-phenylpyridine. Finally, the SERS results were well associated with the chromatographic peaks in a certain duration. It indicated that the HPLC-SERS technique would be a promising tool as a complementary approach to traditional techniques (such as LC-MS) for on line monitoring the organic reaction processes.
2018, 76(7): 531-536
doi: 10.6023/A18040157
Abstract:
Organic electron donors with planar configuration, moderate redox potential and favorable flexibility are the foundation of the molecular material science and self-assembly chemistry. A series of TTF derivatives (TTF1~TTF8) with well molecule flexibility have been synthesized employing a copper-mediated C—S coupling reaction of 1, 2-diiodophenyl groups and a zinc-thiolate complex, (TBA)2[Zn(DMIT)2] (TBA=tetrabutyl ammonium, DMIT=1, 3-dithiole-2-thione-4, 5-dithiolate) as the key step. The physicochemical properties and crystal structures of these TTFs are fully investigated by UV/Vis absorption spectra, cyclic voltammetry, single crystal X-ray diffraction. The ethylenedioxy/ethylenedithio group and sulfur attached phenyl groups lead to unusual properties of TTFs. In comparison with TTF5~TTF8 containing ethylenedithio groups, TTF1~TTF4 substituted by ethylenedioxy groups exhibit stronger absorbance, due to the different electronegative of oxygen and sulfur atom. In addition the absorbance is reducing progressively as the electron donating ability of the respective aryl groups increasing. By introducing fused aryls, the first half redox potential (E1/21) used to estimate the electrochemical stability of different organic electron donors of the TTF derivatives are much higher than that of BEDT-TTF and TTF itself. The aryls ensure the stability of TTF-core via dispersing its electrons. By hot recrystallization or slowly evaporating the solvent, single crystals of eight TTFs suitable for single-crystal X-ray diffraction measurement were obtained. All these TTF derivatives adopt boat conformation with various dihedral angles between the central C2S4 plane with the terminal C2O2 and C2S2 plane of the TTF framework. Complicated aryls leads to larger dihedral angles. TTF5~TTF8 with ethylenedithio groups have more dominant curving configuration with respect to TTF1~TTF4 functionalized by ethylenedioxy groups. Additionally, the stereo-hindrance effects due to the fused phenyl groups prolong the distance from one molecule to another. As a typical example of crystal structure of TTF4, the two methoxy groups make the distance much longer than that in TTF1. Furthermore, the flexible TTFs exhibit unique behavior on self-assembling when the C—S bond vibrate upon and down the TTF-skeleton plane. Single crystals of the complex (TTF4)(C60) are obtained via slowly evaporating chlorobenzene at room temperature after the mixture was heated and refluxed for five minutes. The dihedral angles of TTF4 enlarges to some extent from 24.30° in monomer to 30.17° in complex. Two electron donor molecules produced a cavity and a C60 molecule filled the cavity with C—C and C—S contacts.
Organic electron donors with planar configuration, moderate redox potential and favorable flexibility are the foundation of the molecular material science and self-assembly chemistry. A series of TTF derivatives (TTF1~TTF8) with well molecule flexibility have been synthesized employing a copper-mediated C—S coupling reaction of 1, 2-diiodophenyl groups and a zinc-thiolate complex, (TBA)2[Zn(DMIT)2] (TBA=tetrabutyl ammonium, DMIT=1, 3-dithiole-2-thione-4, 5-dithiolate) as the key step. The physicochemical properties and crystal structures of these TTFs are fully investigated by UV/Vis absorption spectra, cyclic voltammetry, single crystal X-ray diffraction. The ethylenedioxy/ethylenedithio group and sulfur attached phenyl groups lead to unusual properties of TTFs. In comparison with TTF5~TTF8 containing ethylenedithio groups, TTF1~TTF4 substituted by ethylenedioxy groups exhibit stronger absorbance, due to the different electronegative of oxygen and sulfur atom. In addition the absorbance is reducing progressively as the electron donating ability of the respective aryl groups increasing. By introducing fused aryls, the first half redox potential (E1/21) used to estimate the electrochemical stability of different organic electron donors of the TTF derivatives are much higher than that of BEDT-TTF and TTF itself. The aryls ensure the stability of TTF-core via dispersing its electrons. By hot recrystallization or slowly evaporating the solvent, single crystals of eight TTFs suitable for single-crystal X-ray diffraction measurement were obtained. All these TTF derivatives adopt boat conformation with various dihedral angles between the central C2S4 plane with the terminal C2O2 and C2S2 plane of the TTF framework. Complicated aryls leads to larger dihedral angles. TTF5~TTF8 with ethylenedithio groups have more dominant curving configuration with respect to TTF1~TTF4 functionalized by ethylenedioxy groups. Additionally, the stereo-hindrance effects due to the fused phenyl groups prolong the distance from one molecule to another. As a typical example of crystal structure of TTF4, the two methoxy groups make the distance much longer than that in TTF1. Furthermore, the flexible TTFs exhibit unique behavior on self-assembling when the C—S bond vibrate upon and down the TTF-skeleton plane. Single crystals of the complex (TTF4)(C60) are obtained via slowly evaporating chlorobenzene at room temperature after the mixture was heated and refluxed for five minutes. The dihedral angles of TTF4 enlarges to some extent from 24.30° in monomer to 30.17° in complex. Two electron donor molecules produced a cavity and a C60 molecule filled the cavity with C—C and C—S contacts.
2018, 76(7): 537-542
doi: 10.6023/A18040175
Abstract:
Black phosphorus has attracted broad interest because of their low-dimensional effect, and has become a new kind of two-dimensional (2D) materials. Phosphorus has several allotropes. Black phosphorus is the most thermodynamic stable in them. As a kind of two-dimensional materials, black phosphorus has high carrier mobility and on/off ratio. The band gap of black phosphorus can be adjusted by its number of layers from 0.3 to 2 eV. It is of great significance to the development of new infrared and near-infrared optoelectronic devices. Currently, the main methods for preparing black phosphorus are chemical vapor transfer and high energy ball milling methods. In this paper, black phosphorus was successfully synthesized from red phosphorus via chemical vapor transfer and high energy ball milling methods. Then black phosphorus was put in ethanol for 10 min to liquid exfoliation, in which the ultrasonic power was 400 W. The microstructures and stability of black phosphorus synthesized by two methods were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and differential scanning calorimeter (DSC). In situ electrical measurements of black phosphorus prepared by chemical vapor transfer were performed using a commercial scanning tunnelling microscope-transmission electron microscope probing system (STM-TEM, Nanofactory Instruments) inserted into a JEOL-2010F TEM. The microstructural characterization results show that there is some red phosphorus and amorphous phases in black phosphorus prepared by high energy ball milling method. On the contrary, the black phosphorus prepared by chemical vapor transfer method has no amorphous phases. The XRD results show that black phosphorus synthesized by chemical vapor transfer method did not change significantly after keeping in the air for 16 days. The DSC results show that the volatile points of the black phosphorus prepared by high energy ball milling and chemical vapor transfer methods are respectively 394.5 and 432.2℃, which means the latter has better thermal stability. The TEM results show that a layer or two layers of phosphorene via liquid exfoliation had been obtained, which is large in size and clean in surface. After being irradiated in TEM with a dose of 0.8 eV/(Å2·s) at 200 kV for 60 min, few new diffraction spots appeared in black phosphorus synthesized by chemical vapor transfer method, which indicates it is relatively stable under electron radiation in vacuum. In a word, the black phosphorus prepared by chemical vapor transfer method has large size, good crystallinity, high purity, and high stability. It can be used to prepare two-dimensional black phosphorus by mechanical exfoliation and liquid exfoliation, and then be applied to advanced microelectronic devices.
Black phosphorus has attracted broad interest because of their low-dimensional effect, and has become a new kind of two-dimensional (2D) materials. Phosphorus has several allotropes. Black phosphorus is the most thermodynamic stable in them. As a kind of two-dimensional materials, black phosphorus has high carrier mobility and on/off ratio. The band gap of black phosphorus can be adjusted by its number of layers from 0.3 to 2 eV. It is of great significance to the development of new infrared and near-infrared optoelectronic devices. Currently, the main methods for preparing black phosphorus are chemical vapor transfer and high energy ball milling methods. In this paper, black phosphorus was successfully synthesized from red phosphorus via chemical vapor transfer and high energy ball milling methods. Then black phosphorus was put in ethanol for 10 min to liquid exfoliation, in which the ultrasonic power was 400 W. The microstructures and stability of black phosphorus synthesized by two methods were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and differential scanning calorimeter (DSC). In situ electrical measurements of black phosphorus prepared by chemical vapor transfer were performed using a commercial scanning tunnelling microscope-transmission electron microscope probing system (STM-TEM, Nanofactory Instruments) inserted into a JEOL-2010F TEM. The microstructural characterization results show that there is some red phosphorus and amorphous phases in black phosphorus prepared by high energy ball milling method. On the contrary, the black phosphorus prepared by chemical vapor transfer method has no amorphous phases. The XRD results show that black phosphorus synthesized by chemical vapor transfer method did not change significantly after keeping in the air for 16 days. The DSC results show that the volatile points of the black phosphorus prepared by high energy ball milling and chemical vapor transfer methods are respectively 394.5 and 432.2℃, which means the latter has better thermal stability. The TEM results show that a layer or two layers of phosphorene via liquid exfoliation had been obtained, which is large in size and clean in surface. After being irradiated in TEM with a dose of 0.8 eV/(Å2·s) at 200 kV for 60 min, few new diffraction spots appeared in black phosphorus synthesized by chemical vapor transfer method, which indicates it is relatively stable under electron radiation in vacuum. In a word, the black phosphorus prepared by chemical vapor transfer method has large size, good crystallinity, high purity, and high stability. It can be used to prepare two-dimensional black phosphorus by mechanical exfoliation and liquid exfoliation, and then be applied to advanced microelectronic devices.
2018, 76(7): 543-548
doi: 10.6023/A18030111
Abstract:
The geochemical cycle of heavy metal ion driven by microbes is widespread in nature. Previous studies are focused on the removal efficiency in the treatment of Cd in the bioelectrochemical systems; however, little is reported regarding the reduction mechanism of Cd on the electrode surface in the neutral physiological environment. In this work, we investigated the microbiological influence of Shewanella oneidensis MR-1 wild type and its mutant △omcA-△mtrc for Cd electrodeposition on a glassy carbon electrode (GCE) surface by using cyclic voltammetric (CV) and chronoamperometric methods. The CVs and I-t curves were carried out in a three-electrode system in the present of MR-1 cells (the value of optical density at 600 nm was 0.5) under nitrogen atmosphere. Much results were found in the present of MR-1 wild type:(1) the reducing peak potentials for Cd electrodeposition obviously negative shifted from CVs; (2) when the scan rate was comparatively slow (20 mV·s-1 vs. saturated calomel electrode), the Cd electrodeposition process contained two steps in the second scan in CVs which were Cd(Ⅱ)-Cd(Ⅰ)-Cd; (3) the average diffusion coefficient of Cd(Ⅱ) from bulk solution to GCE surface (0.93×10-6 cm·s-1), calculated from I-t curves, was slightly slower than that without MR-1 wild type (1.1×10-6 cm·s-1); (4) the progressive nucleation mechanism for Cd electrodeposition changed into an instantaneous three-dimensional nucleation by compared with their actual nucleation curves. Once the Cd electrodeposition process was performed in the solution with △omcA-△mtrc mutant, the diffusion of Cd(Ⅱ) from bulk solution to GCE surface (the average diffusion coefficient was 0.84×10-6 cm·s-1) changed much slower than before; nonetheless, the Cd electrodeposition was also consistent with the instantaneous three-dimensional nucleation. On the other hand, inhomogeneous Cd particles were observed on GCE surfaces at different stepping potentials from scanning electron microscopy (SEM) images. In contrast, the homogeneous Cd particles were found in the present of MR-1 wild type and △omcA-△mtrc mutant when the reduction potentials were higher than -0.9 V. These SEM results regarding the surface morphology of electrodeposited Cd particles also well agreed with three-dimensional nucleation mechanisms.
The geochemical cycle of heavy metal ion driven by microbes is widespread in nature. Previous studies are focused on the removal efficiency in the treatment of Cd in the bioelectrochemical systems; however, little is reported regarding the reduction mechanism of Cd on the electrode surface in the neutral physiological environment. In this work, we investigated the microbiological influence of Shewanella oneidensis MR-1 wild type and its mutant △omcA-△mtrc for Cd electrodeposition on a glassy carbon electrode (GCE) surface by using cyclic voltammetric (CV) and chronoamperometric methods. The CVs and I-t curves were carried out in a three-electrode system in the present of MR-1 cells (the value of optical density at 600 nm was 0.5) under nitrogen atmosphere. Much results were found in the present of MR-1 wild type:(1) the reducing peak potentials for Cd electrodeposition obviously negative shifted from CVs; (2) when the scan rate was comparatively slow (20 mV·s-1 vs. saturated calomel electrode), the Cd electrodeposition process contained two steps in the second scan in CVs which were Cd(Ⅱ)-Cd(Ⅰ)-Cd; (3) the average diffusion coefficient of Cd(Ⅱ) from bulk solution to GCE surface (0.93×10-6 cm·s-1), calculated from I-t curves, was slightly slower than that without MR-1 wild type (1.1×10-6 cm·s-1); (4) the progressive nucleation mechanism for Cd electrodeposition changed into an instantaneous three-dimensional nucleation by compared with their actual nucleation curves. Once the Cd electrodeposition process was performed in the solution with △omcA-△mtrc mutant, the diffusion of Cd(Ⅱ) from bulk solution to GCE surface (the average diffusion coefficient was 0.84×10-6 cm·s-1) changed much slower than before; nonetheless, the Cd electrodeposition was also consistent with the instantaneous three-dimensional nucleation. On the other hand, inhomogeneous Cd particles were observed on GCE surfaces at different stepping potentials from scanning electron microscopy (SEM) images. In contrast, the homogeneous Cd particles were found in the present of MR-1 wild type and △omcA-△mtrc mutant when the reduction potentials were higher than -0.9 V. These SEM results regarding the surface morphology of electrodeposited Cd particles also well agreed with three-dimensional nucleation mechanisms.
2018, 76(7): 549-555
doi: 10.6023/A18030100
Abstract:
Synthesis of large scale ultrathin 2D structural TiO2 is challenging and meaningful in many fields of science and technology, because of their larger surface area and higher electron-hole pairs separation efficiency. In this work, a "bottomup" method is used to synthesize the large-size ultrathin TiO2 nanosheets at low temperature by liquid-phase. The mixture of tetrabutyl titanate and ethanol could hydrolyze in a dilute nitric acid solution with an ice-water bath and the obtained hydrolysates could peptize. After peptized, the hydrolysis products become to be very small TiO2 nanoclusters and they form a two-dimensional network structure via the orientation bonding formed by hydrogen bond. Continue to be aged at low temperature, the crystallization degree of samples will increase, and the networks eventually turn into TiO2 nanosheets. Effects of the concentration of nitric acid, ambient temperature and reactant concentration on the formation of two-dimensional structure TiO2 are studied in this work. The transmission electron microscope (TEM), ultraviolet-visible (UV-Vis) absorbance spectra, X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier Transform infrared spectroscopy (FTIR) are used to analyze the morphology, microstructure and properties of the samples, and the experiment of photocatalytic reduction of Cr(Ⅵ) is conducted to observe the photocatalytic activity of samples as well as to verify the effects of system parameters on the microstructure of TiO2 nanosheets. The results show that when the concentration of nitric acid is during 0.0217~0.0721 mol·L-1, the anatase TiO2 nanosheets that thinner than 1 nm could be obtained by peptizing and aging at 0~4℃. Excess nitric acid leads to crystalline and morphology transformation of TiO2, but lower concentration of nitric acid could prolong the peptizing time; increasing the ambient temperature will undermine the formation of two-dimensional structure; improving the amount of ethanol in the reactant will be helpful to disperse the hydrolysis products, and promote the process of the peptizing and formation of the two-dimensional structure.
Synthesis of large scale ultrathin 2D structural TiO2 is challenging and meaningful in many fields of science and technology, because of their larger surface area and higher electron-hole pairs separation efficiency. In this work, a "bottomup" method is used to synthesize the large-size ultrathin TiO2 nanosheets at low temperature by liquid-phase. The mixture of tetrabutyl titanate and ethanol could hydrolyze in a dilute nitric acid solution with an ice-water bath and the obtained hydrolysates could peptize. After peptized, the hydrolysis products become to be very small TiO2 nanoclusters and they form a two-dimensional network structure via the orientation bonding formed by hydrogen bond. Continue to be aged at low temperature, the crystallization degree of samples will increase, and the networks eventually turn into TiO2 nanosheets. Effects of the concentration of nitric acid, ambient temperature and reactant concentration on the formation of two-dimensional structure TiO2 are studied in this work. The transmission electron microscope (TEM), ultraviolet-visible (UV-Vis) absorbance spectra, X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier Transform infrared spectroscopy (FTIR) are used to analyze the morphology, microstructure and properties of the samples, and the experiment of photocatalytic reduction of Cr(Ⅵ) is conducted to observe the photocatalytic activity of samples as well as to verify the effects of system parameters on the microstructure of TiO2 nanosheets. The results show that when the concentration of nitric acid is during 0.0217~0.0721 mol·L-1, the anatase TiO2 nanosheets that thinner than 1 nm could be obtained by peptizing and aging at 0~4℃. Excess nitric acid leads to crystalline and morphology transformation of TiO2, but lower concentration of nitric acid could prolong the peptizing time; increasing the ambient temperature will undermine the formation of two-dimensional structure; improving the amount of ethanol in the reactant will be helpful to disperse the hydrolysis products, and promote the process of the peptizing and formation of the two-dimensional structure.
2018, 76(7): 556-563
doi: 10.6023/A18040153
Abstract:
The clusters can be seen in carbon-rich explosives during detonation. However, we can't directly observe the formation of clusters by experimental methods. The thermal decomposition of TNT at various temperatures are studied using ReaxFF/lg molecular dynamics simulations. The ReaxFF/lg force field provides detailed information on the formation of cluster from atomic level, the stability of the clusters and the graphite-like structures. The results show that clusters formed slowly at the initial reaction with increasing the relative molecular mass of a TNT approximately one time. As the reaction proceeding, the mass of clusters increases rapidly, and the molecular weight of max cluster can reach 8000~10000 (amu), accounting over about 18% of the system mass. Analysis of the structure of the clusters reveal that some benzene rings in the clusters were broken, and five-membered rings and the six-membered rings which contain N and O atoms were formed, and the more complex seven-membered rings structure were formed under the 3500 K condition. Through the method of linear expansion and direct cooling, the stability of the clusters was studied:the clusters decomposed rapidly by the method of linear expansion, while the clusters aggregated into larger clusters by the method of direct cooling. Through the analysis of graphite-like structures, we obtain that it is an essential step to first expand and the cool down second by analysis the production process of graphite-like structures. The mass ratio of C atoms in the clusters has been increasing during the reaction process by comparing the ratio of the mass of each atom in the clusters and TNT molecules, while the mass ratio of N atoms and H atoms in the clusters decrease and the mass ratio of O atoms show more complicated during the whole reaction. This study can provide a good basis for the preparation of new nanomaterials for detonation of TNT.
The clusters can be seen in carbon-rich explosives during detonation. However, we can't directly observe the formation of clusters by experimental methods. The thermal decomposition of TNT at various temperatures are studied using ReaxFF/lg molecular dynamics simulations. The ReaxFF/lg force field provides detailed information on the formation of cluster from atomic level, the stability of the clusters and the graphite-like structures. The results show that clusters formed slowly at the initial reaction with increasing the relative molecular mass of a TNT approximately one time. As the reaction proceeding, the mass of clusters increases rapidly, and the molecular weight of max cluster can reach 8000~10000 (amu), accounting over about 18% of the system mass. Analysis of the structure of the clusters reveal that some benzene rings in the clusters were broken, and five-membered rings and the six-membered rings which contain N and O atoms were formed, and the more complex seven-membered rings structure were formed under the 3500 K condition. Through the method of linear expansion and direct cooling, the stability of the clusters was studied:the clusters decomposed rapidly by the method of linear expansion, while the clusters aggregated into larger clusters by the method of direct cooling. Through the analysis of graphite-like structures, we obtain that it is an essential step to first expand and the cool down second by analysis the production process of graphite-like structures. The mass ratio of C atoms in the clusters has been increasing during the reaction process by comparing the ratio of the mass of each atom in the clusters and TNT molecules, while the mass ratio of N atoms and H atoms in the clusters decrease and the mass ratio of O atoms show more complicated during the whole reaction. This study can provide a good basis for the preparation of new nanomaterials for detonation of TNT.
2018, 76(7): 564-574
doi: 10.6023/A18030086
Abstract:
Understanding the effects of molecules with branched structures on surface activities and micellization of star-shaped oligomeric surfactants will promote the applications of oligomeric surfactants. The present work has studied the interactions and aggregation of branched carboxylate 2-hexyldecanoic acid (HDA) and 2, 2, 4, 8, 10, 10-hexamethylundecane-5-carboxylic acid (HMLCA) with single chain sodium dodecyl sulfonate (SDoS) and star-shaped tetrameric sulfonate surfactant (EDA-(C12SO3Na)4) in aqueous solution of pH 11 by surface tension, ζ-Potential and small angle neutron scattering (SANS). Surface tension measurements have shown that the addition of HDA or HMLCA can significantly reduce the surface tension at critical micellar concentration (CMC), meanwhile, the CMC values increase slightly as the mole fraction of HDA or HMLCA increases. The interaction parameter (β), calculated according to the non-ideal mixed solution model, indicate that different interaction degrees exist between branched carboxylate and sulfonate surfactant on surface activities and micellization. The four mixtures all exhibit synergism in surface tension reduction efficiency. The mixtures of single chain sulfonate surfactant and branched carboxylate also exhibit synergism in micelle formation, whereas the mixtures of tetrameric sulfonate surfactant and branched carboxylate do not, although the attractive interaction of HDA/EDA-(C12SO3Na)4 and HMLCA/EDA-(C12SO3Na)4 is stronger than that of HDA/SDoS and HMLCA/SDoS in mixed micelles. Taking HDA as a representative, SANS and ζ-Potential results reveal that the addition of HDA into these two sulfonate surfactants leads to different aggregate transitions in the solution. For HDA/SDoS, when the molar fraction of HDA (XHDA) is constant and the total surfactant concentration increases, spherical micelles transfer into rod-like micelles. For the HDA/EDA-(C12SO3Na)4 mixture, the rod-like micelles become shorter as XHDA increases at a fixed total surfactant concentration, while the rod-like micelles are growing longer with increasing XHDA at a fixed total surfactant concentration. This observation suggests that the branched structure of carboxylates can improve the aggregation ability of the mixed system. In addition these mixtures show excellent performance at emulsifying dodecane, and HDA or HMLCA can greatly reduce the dosage of sulfonate surfactants.
Understanding the effects of molecules with branched structures on surface activities and micellization of star-shaped oligomeric surfactants will promote the applications of oligomeric surfactants. The present work has studied the interactions and aggregation of branched carboxylate 2-hexyldecanoic acid (HDA) and 2, 2, 4, 8, 10, 10-hexamethylundecane-5-carboxylic acid (HMLCA) with single chain sodium dodecyl sulfonate (SDoS) and star-shaped tetrameric sulfonate surfactant (EDA-(C12SO3Na)4) in aqueous solution of pH 11 by surface tension, ζ-Potential and small angle neutron scattering (SANS). Surface tension measurements have shown that the addition of HDA or HMLCA can significantly reduce the surface tension at critical micellar concentration (CMC), meanwhile, the CMC values increase slightly as the mole fraction of HDA or HMLCA increases. The interaction parameter (β), calculated according to the non-ideal mixed solution model, indicate that different interaction degrees exist between branched carboxylate and sulfonate surfactant on surface activities and micellization. The four mixtures all exhibit synergism in surface tension reduction efficiency. The mixtures of single chain sulfonate surfactant and branched carboxylate also exhibit synergism in micelle formation, whereas the mixtures of tetrameric sulfonate surfactant and branched carboxylate do not, although the attractive interaction of HDA/EDA-(C12SO3Na)4 and HMLCA/EDA-(C12SO3Na)4 is stronger than that of HDA/SDoS and HMLCA/SDoS in mixed micelles. Taking HDA as a representative, SANS and ζ-Potential results reveal that the addition of HDA into these two sulfonate surfactants leads to different aggregate transitions in the solution. For HDA/SDoS, when the molar fraction of HDA (XHDA) is constant and the total surfactant concentration increases, spherical micelles transfer into rod-like micelles. For the HDA/EDA-(C12SO3Na)4 mixture, the rod-like micelles become shorter as XHDA increases at a fixed total surfactant concentration, while the rod-like micelles are growing longer with increasing XHDA at a fixed total surfactant concentration. This observation suggests that the branched structure of carboxylates can improve the aggregation ability of the mixed system. In addition these mixtures show excellent performance at emulsifying dodecane, and HDA or HMLCA can greatly reduce the dosage of sulfonate surfactants.
