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2019 Volume 77 Issue 3
2019, 77(3): 205-212
doi: 10.6023/A18120486
Abstract:
Carbonate radical, nitrate radical, phosphate radical and sulfate radical are all important intermediates of chemical reactions with oxidizing ability. They have a significant effect on the transfer of pollutants in natural environment. In this review, the redox potential, modes of production, detection methods of these radicals and the mechanisms of their reactions with organic compounds are introduced. It can be found that:these four radicals have different reaction rates with organic compounds because of their various redox potential; Carbonate radical is not a scavenger of hydroxyl radical. For some easily oxidized compounds, carbonate radical shows higher oxidizing ability than hydroxyl radical; Hydroxyl radicals can be converted into other four types of radicals. Meanwhile, these four types of radicals react with organic matters by electron transfer, hydrogen abstraction and addition, which is basically consistent with hydroxyl radicals. It can be predicted that the mechanism of organic compounds degradation by these four types of free radicals is similar with that of hydroxyl radicals. In the future, it is necessary to study the mutual conversion principles between these free radicals and hydroxyl radicals and the degradation mechanism of these radicals when reacting with some representative organic compounds.
Carbonate radical, nitrate radical, phosphate radical and sulfate radical are all important intermediates of chemical reactions with oxidizing ability. They have a significant effect on the transfer of pollutants in natural environment. In this review, the redox potential, modes of production, detection methods of these radicals and the mechanisms of their reactions with organic compounds are introduced. It can be found that:these four radicals have different reaction rates with organic compounds because of their various redox potential; Carbonate radical is not a scavenger of hydroxyl radical. For some easily oxidized compounds, carbonate radical shows higher oxidizing ability than hydroxyl radical; Hydroxyl radicals can be converted into other four types of radicals. Meanwhile, these four types of radicals react with organic matters by electron transfer, hydrogen abstraction and addition, which is basically consistent with hydroxyl radicals. It can be predicted that the mechanism of organic compounds degradation by these four types of free radicals is similar with that of hydroxyl radicals. In the future, it is necessary to study the mutual conversion principles between these free radicals and hydroxyl radicals and the degradation mechanism of these radicals when reacting with some representative organic compounds.
2019, 77(3): 213-230
doi: 10.6023/A18110470
Abstract:
Hypervalent iodine chemistry has arose as an important field in organic chemistry in the past decades. Hypervalent iodine compounds, with reactivities similarly to transition metals in many different types of transformations, have attracted broad interests in organic community due to their practical advantages in the mild conditions, low costs, environmental benign and low toxicity. Great progresses have been made in this field. Chiral hypervalent iodine reagents or precursors have also been developed and utilized in a variety of asymmetric reactions in a stoichiometric or catalytic way. Important advances have been witnessed in the field of chiral hypervalent iodine chemistry in recent years. However, great limitations still exist. In this review, we have made a summary of different types of chiral hypervalent iodine reagents and precursors according to the characteristics of these compounds and the timeline. It may be helpful for the researchers to better understand the development and limitations of chiral hypervalent iodine chemistry.
Hypervalent iodine chemistry has arose as an important field in organic chemistry in the past decades. Hypervalent iodine compounds, with reactivities similarly to transition metals in many different types of transformations, have attracted broad interests in organic community due to their practical advantages in the mild conditions, low costs, environmental benign and low toxicity. Great progresses have been made in this field. Chiral hypervalent iodine reagents or precursors have also been developed and utilized in a variety of asymmetric reactions in a stoichiometric or catalytic way. Important advances have been witnessed in the field of chiral hypervalent iodine chemistry in recent years. However, great limitations still exist. In this review, we have made a summary of different types of chiral hypervalent iodine reagents and precursors according to the characteristics of these compounds and the timeline. It may be helpful for the researchers to better understand the development and limitations of chiral hypervalent iodine chemistry.
2019, 77(3): 231-241
doi: 10.6023/A18100429
Abstract:
Carbohydrates, along with proteins and nucleic acids are known as basic life substances, which not only are the energy source and structure material, but also play an extremely important role in many biochemical processes, such as molecules recognition, information transformation in cells, interactions in immune response, differentiation and apoptosis of cells, etc. Compared to proteins and nucleic acids, the synthesis of oligosaccharides in chemical or enzymatic ways is more difficult, due to their diversified and complicated structures. Recently photo especially visible light promoted organic synthesis has become one of the fastest growing fields in organic chemistry attributed to its environmental friendliness, easy availability and low cost. This chemistry has also been applied to the photo-mediated glycosylation reactions by using various light sources (ultraviolet, visible light), photosensitizers (or photocatalysts), and additives (oxidants, reductants etc.), which provides milder and more effective ways for oligosaccharide assembly. To help chemists understand this field, we briefly reviewed recent advances and potential applications of photo-mediated glycosylation reactions according to their types (e.g. light sources, photosensitizers). In this review, we also detailly described the mechanisms and highlighted the advantages and limitations of these reactions. In addition, the further prospects of this area are proposed.
Carbohydrates, along with proteins and nucleic acids are known as basic life substances, which not only are the energy source and structure material, but also play an extremely important role in many biochemical processes, such as molecules recognition, information transformation in cells, interactions in immune response, differentiation and apoptosis of cells, etc. Compared to proteins and nucleic acids, the synthesis of oligosaccharides in chemical or enzymatic ways is more difficult, due to their diversified and complicated structures. Recently photo especially visible light promoted organic synthesis has become one of the fastest growing fields in organic chemistry attributed to its environmental friendliness, easy availability and low cost. This chemistry has also been applied to the photo-mediated glycosylation reactions by using various light sources (ultraviolet, visible light), photosensitizers (or photocatalysts), and additives (oxidants, reductants etc.), which provides milder and more effective ways for oligosaccharide assembly. To help chemists understand this field, we briefly reviewed recent advances and potential applications of photo-mediated glycosylation reactions according to their types (e.g. light sources, photosensitizers). In this review, we also detailly described the mechanisms and highlighted the advantages and limitations of these reactions. In addition, the further prospects of this area are proposed.
2019, 77(3): 242-252
doi: 10.6023/A18100440
Abstract:
The worldwide climate issues such as the global warming and the sea level rising are becoming serious. In order to relieve the stress of environment, a lot of attempts have been made to reduce the emission of CO2, which is the main component of greenhouse gases. CO2 capture and conversion (C3) is an emerging technology, which directly converts the captured CO2 into high value-added compounds or fuels such as formic acid, methanol and methane. Porphyrin metal-organic frameworks (PMOFs) are based on porphyrin or metalloporphyrin ligands and metal nodes. The combination of excellent thermal/chemical stability, strong absorption of visible light and long lifetime of excited state, and high CO2 capture capacity paves the way for the applications of PMOFs in C3. In this review, we have firstly introduced the synthesis strategies of PMOFs, which are guided by framework topology, pillar-layer and metal-organic cage (MOC). With the good control of the pore sizes and thermal/chemical stability, the catalytic performances of PMOFs can be easily tuned:PMOFs that are prepared via the pillar-layer and MOC strategies are of relatively lower stability, and the ones that are guided by framework topology are of higher stability. Next, we have classified the types of PMOFs according to the secondary building units (SBUs). There are four types of PMOFs, and the SBUs include (1) the low-valence metal ions such as Cu2+ and Cd2+; (2) the paddle-wheel M2(COO)4 (M=Cu2+, Zn2+) units; (3) the infinite metal (such as Al3+, Ga3+ and In3+) oxide chains; (4) the hard metal (such as Cr3+, Fe3+, Ti4+, Zr4+, Hf4+, and rare earth metals) oxide clusters. The structure characters and stability have been described afterwards. The coordination bonds in the first and second types of SBUs are relatively weak. For comparison, most of the PMOFs based on the infinite metal oxide chains and hard metal oxide cluster exhibit high thermal/chemical stabilities, which could be used for practical applications towards C3. Then, we have summarized the recent works about applications of PMOFs in C3, which are divided into four parts, including the selective capture of CO2, organic transformations with CO2, CO2 photoreduction and CO2 electroreduction. Selective capture of CO2 from a mixture of gases is one of the most important applications, considering that less energy and lower temperatures/pressures are required. Through the catalytic cycloaddition reaction of CO2 and epoxides, the important products of cyclic carbonates can be produced. Some of the catalytic reactions can be carried out at 0.1 MPa and room temperature with high yields. With the assistance of environmentally friendly visible light, CO2 can be photoreduced into fuels such as formate ion, methanol and methane. In addition, two typical examples of CO2 electroreduction have been discussed in this review. Through the process of photoreduction and electroreduction, clean energies such as solar light and electricity can be employed to help transfer the green gas CO2 into fuels. At the end, we have discussed the merits and challenges of PMOFs in the applications of C3. Selective adsorption of CO2 from other gases, especially NOx, SOx and other flue gases, is highly required. The efficiency of the catalytic cycloaddition reaction should be further improved, especially cutting down the reaction time. Reaction efficiency and product selectivity of photoreduction and electroreduction should be improved. Photoelectrocatalytic reduction of CO2, which combines both advantages of photoreduction and electroreduction, should be a hot topic in the future. The ideal system should include both a photoanode for water oxidation and a photocathode for CO2 reduction that are linked by a wire without external applied bias, achieving the dream of artificial photosynthesis.
The worldwide climate issues such as the global warming and the sea level rising are becoming serious. In order to relieve the stress of environment, a lot of attempts have been made to reduce the emission of CO2, which is the main component of greenhouse gases. CO2 capture and conversion (C3) is an emerging technology, which directly converts the captured CO2 into high value-added compounds or fuels such as formic acid, methanol and methane. Porphyrin metal-organic frameworks (PMOFs) are based on porphyrin or metalloporphyrin ligands and metal nodes. The combination of excellent thermal/chemical stability, strong absorption of visible light and long lifetime of excited state, and high CO2 capture capacity paves the way for the applications of PMOFs in C3. In this review, we have firstly introduced the synthesis strategies of PMOFs, which are guided by framework topology, pillar-layer and metal-organic cage (MOC). With the good control of the pore sizes and thermal/chemical stability, the catalytic performances of PMOFs can be easily tuned:PMOFs that are prepared via the pillar-layer and MOC strategies are of relatively lower stability, and the ones that are guided by framework topology are of higher stability. Next, we have classified the types of PMOFs according to the secondary building units (SBUs). There are four types of PMOFs, and the SBUs include (1) the low-valence metal ions such as Cu2+ and Cd2+; (2) the paddle-wheel M2(COO)4 (M=Cu2+, Zn2+) units; (3) the infinite metal (such as Al3+, Ga3+ and In3+) oxide chains; (4) the hard metal (such as Cr3+, Fe3+, Ti4+, Zr4+, Hf4+, and rare earth metals) oxide clusters. The structure characters and stability have been described afterwards. The coordination bonds in the first and second types of SBUs are relatively weak. For comparison, most of the PMOFs based on the infinite metal oxide chains and hard metal oxide cluster exhibit high thermal/chemical stabilities, which could be used for practical applications towards C3. Then, we have summarized the recent works about applications of PMOFs in C3, which are divided into four parts, including the selective capture of CO2, organic transformations with CO2, CO2 photoreduction and CO2 electroreduction. Selective capture of CO2 from a mixture of gases is one of the most important applications, considering that less energy and lower temperatures/pressures are required. Through the catalytic cycloaddition reaction of CO2 and epoxides, the important products of cyclic carbonates can be produced. Some of the catalytic reactions can be carried out at 0.1 MPa and room temperature with high yields. With the assistance of environmentally friendly visible light, CO2 can be photoreduced into fuels such as formate ion, methanol and methane. In addition, two typical examples of CO2 electroreduction have been discussed in this review. Through the process of photoreduction and electroreduction, clean energies such as solar light and electricity can be employed to help transfer the green gas CO2 into fuels. At the end, we have discussed the merits and challenges of PMOFs in the applications of C3. Selective adsorption of CO2 from other gases, especially NOx, SOx and other flue gases, is highly required. The efficiency of the catalytic cycloaddition reaction should be further improved, especially cutting down the reaction time. Reaction efficiency and product selectivity of photoreduction and electroreduction should be improved. Photoelectrocatalytic reduction of CO2, which combines both advantages of photoreduction and electroreduction, should be a hot topic in the future. The ideal system should include both a photoanode for water oxidation and a photocathode for CO2 reduction that are linked by a wire without external applied bias, achieving the dream of artificial photosynthesis.
2019, 77(3): 253-256
doi: 10.6023/A18100433
Abstract:
A label free and rapid fluorescent method for quantitative detection of chloramphenicol (CAP) based on graphene oxide (GO) fluorescence functional G-quadruplex probe (FGP) was developed. The FGP consisted of a choramphenicol aptamer and a G-rich sequence. The aptamer was used to bind CAP and the G-quadruplex formed by G-rich sequence was employed as a signal reporter after binding to Thioflavin T (ThT). In the absence of CAP, the FGP was absorbed onto the surface of GO through π-π stacking interactions, which restrained the G-rich sequence to form a G-quadruplex structure. Thus, the fluorescent intensity of background was low. In the addition of the CAP, the aptamer part of FGP could recognize and bind CAP to form a target-FGP complex, which led to the desorption of the complex from GO. Therefore, the free G-rich sequence could form G-quadruplex structure and bind to ThT, resulting a increase in the fluorescence intensity of the solution. We observed that the fluorescence increasement of the sensing platform had a linear relationship with the concentrations of CAP in the range of 2~20 nmol/L, and the limit of detection was 1.45 nmol/L. Besides, this detection system was applied for detecting CAP in the spiked milk, the recovery rate was between 93.2%~103.3%. These results indicated that this developed method can be used to efficiently recognize CAP in real samples.
A label free and rapid fluorescent method for quantitative detection of chloramphenicol (CAP) based on graphene oxide (GO) fluorescence functional G-quadruplex probe (FGP) was developed. The FGP consisted of a choramphenicol aptamer and a G-rich sequence. The aptamer was used to bind CAP and the G-quadruplex formed by G-rich sequence was employed as a signal reporter after binding to Thioflavin T (ThT). In the absence of CAP, the FGP was absorbed onto the surface of GO through π-π stacking interactions, which restrained the G-rich sequence to form a G-quadruplex structure. Thus, the fluorescent intensity of background was low. In the addition of the CAP, the aptamer part of FGP could recognize and bind CAP to form a target-FGP complex, which led to the desorption of the complex from GO. Therefore, the free G-rich sequence could form G-quadruplex structure and bind to ThT, resulting a increase in the fluorescence intensity of the solution. We observed that the fluorescence increasement of the sensing platform had a linear relationship with the concentrations of CAP in the range of 2~20 nmol/L, and the limit of detection was 1.45 nmol/L. Besides, this detection system was applied for detecting CAP in the spiked milk, the recovery rate was between 93.2%~103.3%. These results indicated that this developed method can be used to efficiently recognize CAP in real samples.
2019, 77(3): 257-262
doi: 10.6023/A18100434
Abstract:
Surface Enhanced Raman Spectroscopy (SERS) has been developed as one of powerful tools for monitoring the organic reaction due to its extremely high sensitivity. Moreover, SERS provided the abundant fingerprint spectroscopic information for the structure analysis, and it could be integrated with other techniques to achieve the on-line detection. Microfluidic technology, due to its significant role in the miniaturization, integration and portability of instrument, exhibits the promising application in biomedicine, high throughput drug screening, the environment monitoring and protection. In recent years, the microfluidic chip as one of the modern technology for analyzing various substances at the same time has been rapidly developed. Compared with the conventional technique, it has the significant advantage and convenience, such as low reagent consumption, short reaction time, high reaction efficiency and so on. Herein, the microfluidic chip was employed as the microreactor for organic reaction with the ultralow dosage, and the SERS detection was integrated into the microreactor to realize the continuous monitoring on the substrates and products. The magnetic core-shell nanoparticles Fe3O4@Ag acted as the SERS substrate with reasonable magnetism and SERS activities, and it demonstrated that the magnetic nanoparticles was flowed in the microchannel of microfluidic chip and was enriched by the external magnetic field. The introduction of magnetic nanoparticles is beneficial to improve the detection sensitivity by the magnetic aggregation and to reach the continuous SERS detection by applying and retracting external magnetic field. At the same time, it exhibited the significant advantages of low amount of reactants, high efficiency and easy to realize on-line detection and high throughput screening in organic synthesis. The micro-synthesis of α-phenylethanol and the real-time monitoring of SERS are performed by the alternative enrichment and de-enrichment of magnetic nanoparticles in the present case. By changing the flow rate of reactants in the channel of microfluidic chip, different concentrations of reactants and products were obtained in a certain duration. The influence of the spectral features from the reactants was eliminated by differential spectrum technique, and the distinctive SERS spectrum of α-phenylethanol was presented accordingly. It demonstrated that the integration of microfluidic chip and SERS technique could be developed as a powerful tool for on-line monitoring organic reactions and exhibits the promising application in high throughput screening of organic chemical reactions.
Surface Enhanced Raman Spectroscopy (SERS) has been developed as one of powerful tools for monitoring the organic reaction due to its extremely high sensitivity. Moreover, SERS provided the abundant fingerprint spectroscopic information for the structure analysis, and it could be integrated with other techniques to achieve the on-line detection. Microfluidic technology, due to its significant role in the miniaturization, integration and portability of instrument, exhibits the promising application in biomedicine, high throughput drug screening, the environment monitoring and protection. In recent years, the microfluidic chip as one of the modern technology for analyzing various substances at the same time has been rapidly developed. Compared with the conventional technique, it has the significant advantage and convenience, such as low reagent consumption, short reaction time, high reaction efficiency and so on. Herein, the microfluidic chip was employed as the microreactor for organic reaction with the ultralow dosage, and the SERS detection was integrated into the microreactor to realize the continuous monitoring on the substrates and products. The magnetic core-shell nanoparticles Fe3O4@Ag acted as the SERS substrate with reasonable magnetism and SERS activities, and it demonstrated that the magnetic nanoparticles was flowed in the microchannel of microfluidic chip and was enriched by the external magnetic field. The introduction of magnetic nanoparticles is beneficial to improve the detection sensitivity by the magnetic aggregation and to reach the continuous SERS detection by applying and retracting external magnetic field. At the same time, it exhibited the significant advantages of low amount of reactants, high efficiency and easy to realize on-line detection and high throughput screening in organic synthesis. The micro-synthesis of α-phenylethanol and the real-time monitoring of SERS are performed by the alternative enrichment and de-enrichment of magnetic nanoparticles in the present case. By changing the flow rate of reactants in the channel of microfluidic chip, different concentrations of reactants and products were obtained in a certain duration. The influence of the spectral features from the reactants was eliminated by differential spectrum technique, and the distinctive SERS spectrum of α-phenylethanol was presented accordingly. It demonstrated that the integration of microfluidic chip and SERS technique could be developed as a powerful tool for on-line monitoring organic reactions and exhibits the promising application in high throughput screening of organic chemical reactions.
2019, 77(3): 263-268
doi: 10.6023/A18100437
Abstract:
A novel yellow thermally activated delayed fluorescence emitter pPBPXZ was successfully synthesized using phenoxazine as electron-donor and pyrimidine as electron-acceptor by Buchwald-Hartwig and Suzuki coupling reactions. Density functional theory calculations show that pPBPXZ has highly twisted structure with the dihedrals of nearly 90° between phenoxazine and pyrimidine units, while the dihedrals between benzene ring and adjacent pyrimidine rings are almost 0°. The highest occupied molecular orbital (HOMO) is mainly confined on two phenoxazine segments, the lowest unoccupied molecular orbital (LUMO) is mainly located on the central pyrimidine and benzene segments, and there is only a slight overlap between HOMO and LUMO. Cyclic voltammetry investigation show pPBPXZ has reversible redox process, and the HOMO and LUMO energy levels were estimated to be -5.43 eV and -3.23 eV, respectively, from the onsets of oxidation and reduction curves. In diluted toluene solution, pPBPXZ exhibits the absorption band assigned to intramolecular charge-transfer transition and yellow fluorescence with a structureless emission peak at 535 nm. From the onsets of the fluorescence and phosphorescence spectra of pPBPXZ in 2Me-THF at 77 K, the lowest singlet (S1) and the lowest triplet (T1) energy levels are calculated to be 2.57 eV and 2.48 eV, respectively, and thus △EST is only 0.09 eV. The doped electroluminescence devices using pPBPXZ as guest emitter were prepared by vacuum evaporation method. These devices with doping ratios (w) of 6%, 11%, 16% and 23% show yellow emission at 552~560 nm and low turn-on voltages of 3.1~3.3 V. The device with a doping ratio of 11% exhibits the highest maximum forward-viewing efficiencies of a maximum current efficiency of 49.9 cd/A, a maximum power efficiency of 49.0 lm/W and a maximum external quantum efficiency of 15.7% without any light out-coupling enhancement. Particularly, the efficiencies of these devices are not sensitive to the doping ratios of pPBPXZ, which would benefit the further practical application.
A novel yellow thermally activated delayed fluorescence emitter pPBPXZ was successfully synthesized using phenoxazine as electron-donor and pyrimidine as electron-acceptor by Buchwald-Hartwig and Suzuki coupling reactions. Density functional theory calculations show that pPBPXZ has highly twisted structure with the dihedrals of nearly 90° between phenoxazine and pyrimidine units, while the dihedrals between benzene ring and adjacent pyrimidine rings are almost 0°. The highest occupied molecular orbital (HOMO) is mainly confined on two phenoxazine segments, the lowest unoccupied molecular orbital (LUMO) is mainly located on the central pyrimidine and benzene segments, and there is only a slight overlap between HOMO and LUMO. Cyclic voltammetry investigation show pPBPXZ has reversible redox process, and the HOMO and LUMO energy levels were estimated to be -5.43 eV and -3.23 eV, respectively, from the onsets of oxidation and reduction curves. In diluted toluene solution, pPBPXZ exhibits the absorption band assigned to intramolecular charge-transfer transition and yellow fluorescence with a structureless emission peak at 535 nm. From the onsets of the fluorescence and phosphorescence spectra of pPBPXZ in 2Me-THF at 77 K, the lowest singlet (S1) and the lowest triplet (T1) energy levels are calculated to be 2.57 eV and 2.48 eV, respectively, and thus △EST is only 0.09 eV. The doped electroluminescence devices using pPBPXZ as guest emitter were prepared by vacuum evaporation method. These devices with doping ratios (w) of 6%, 11%, 16% and 23% show yellow emission at 552~560 nm and low turn-on voltages of 3.1~3.3 V. The device with a doping ratio of 11% exhibits the highest maximum forward-viewing efficiencies of a maximum current efficiency of 49.9 cd/A, a maximum power efficiency of 49.0 lm/W and a maximum external quantum efficiency of 15.7% without any light out-coupling enhancement. Particularly, the efficiencies of these devices are not sensitive to the doping ratios of pPBPXZ, which would benefit the further practical application.
2019, 77(3): 269-277
doi: 10.6023/A18100430
Abstract:
The special wettability of superhydrophobic surface usually has high contact angles (CA>150°) and low contact angle hysteresis (CAH < 5°), which has been exploited for many potential applications. It is well known that wettability is mainly determined by micro/nano structure and surface composition, and various types of natural superhydrophobic surface could exhibit different wetting states, showing different wetting properties, such as low adhesive lotus leaf; the anisotropic superhydrophobic rice leaf; high adhesive rose petal. Therefore, the relationship between the wetting state and the surface structure should have a deeper understanding, especially in the design preliminary stage. The "droplet-superhydrophobic surface" system is taken as the research objects, four stable wetting state expressions are analyzed based on the principle of minimum energy. Wetting state transitions are studied on superhydrophobic surface coverd with micro/nano structured pillars of different distributions. The calculation formula of intrinsic contact angle is derived and the intrinsic contact angle of common materials is investigated. Based on the four wetting state of apparent contact angle equations, wetting diagrams were drew for investigating the wetting behavior, which include "one point, three lines, six areas, four state". The influence of the relative structure spacing and relative structure height on the wetting state is analyzed. It is found that the larger relative structure height, the smaller relative structure spacing, which can reduce the critical parameters of the transition state of the infiltration state, thereby expanding the range of the superhydrophobic surface, the more design options are available. It is also beneficial to the stability of the superhydrophobic surface, but should be controlled within certain scales because of mechanical stability. The simulation results accurately reflect the wetting state with the changes of the relative structure spacing and relative structure height. Finally, the general design of the superhydrophobic surface is refined. The results can provide theoretical guidance and technical fundament for the design of superhydrophobic surfaces.
The special wettability of superhydrophobic surface usually has high contact angles (CA>150°) and low contact angle hysteresis (CAH < 5°), which has been exploited for many potential applications. It is well known that wettability is mainly determined by micro/nano structure and surface composition, and various types of natural superhydrophobic surface could exhibit different wetting states, showing different wetting properties, such as low adhesive lotus leaf; the anisotropic superhydrophobic rice leaf; high adhesive rose petal. Therefore, the relationship between the wetting state and the surface structure should have a deeper understanding, especially in the design preliminary stage. The "droplet-superhydrophobic surface" system is taken as the research objects, four stable wetting state expressions are analyzed based on the principle of minimum energy. Wetting state transitions are studied on superhydrophobic surface coverd with micro/nano structured pillars of different distributions. The calculation formula of intrinsic contact angle is derived and the intrinsic contact angle of common materials is investigated. Based on the four wetting state of apparent contact angle equations, wetting diagrams were drew for investigating the wetting behavior, which include "one point, three lines, six areas, four state". The influence of the relative structure spacing and relative structure height on the wetting state is analyzed. It is found that the larger relative structure height, the smaller relative structure spacing, which can reduce the critical parameters of the transition state of the infiltration state, thereby expanding the range of the superhydrophobic surface, the more design options are available. It is also beneficial to the stability of the superhydrophobic surface, but should be controlled within certain scales because of mechanical stability. The simulation results accurately reflect the wetting state with the changes of the relative structure spacing and relative structure height. Finally, the general design of the superhydrophobic surface is refined. The results can provide theoretical guidance and technical fundament for the design of superhydrophobic surfaces.
2019, 77(3): 278-286
doi: 10.6023/A18110461
Abstract:
Due to the different reactivity of hydrogenation reaction by metal-free FLPs catalyst for 2, 3-disubstituted 2H-1, 4-benzoxazine, we explored the reaction mechanism by density functional theory calculations. We have chosen three kinds of substrates with different hydrogenation reactivity as the prototype substrates and toluene as the solvent to calculate the potential energy profile for the FLPs-catalysed hydrogenation reaction at M06-2X/6-311++G(d, p) level with polarized continuum model (PCM) to simulate the solvent effect. From the potential energy profile, we found that when B(C6F5)3 encounters with 2, 3-diphenyl 2H-1, 4-benzoxazine (1o) or 2-methyl-3-phenyl 2H-1, 4-benzoxazine (1p) in toluene, it mainly generates the mixture of Lewis acid-base adducts and Frustrated Lewis Pairs, which has almost similar stability suggesting the transformation of each other by intermolecular rearrangement. However, it reveals big difference when the B(C6F5)3 encounters with 2, 3-dimethyl 2H-1, 4-benzoxazine (1q), where the Lewis acid-base adducts is the preference rather than the mixture of Lewis acid-base adducts and Frustrated Lewis Pairs or Frustrated Lewis Pairs since the lower stability energy. Due to the big energy gap (10.9 kcal/mol) between Lewis acid-base adducts and Frustrated Lewis Pairs, the generated Lewis acid-base adducts could not transform into Frustrated Lewis Pairs in the FLPs-catalysed hydrogenation of 1q at 298 K. That is the main reason why 1q is an inert substrate for the hydrogenation catalysed by FLPs. Natural Bond Orbital, Mulliken charge analysis and the proton affinity energy of N4 site was carried out to assess the electric effect of substituent at C3 on N4 site. It reveals negligible effect of substituent at C3 on N4 charge (basicity) and thus proposes that steric hindrance effect is the major factor affecting the stability energy of Lewis acid-base adducts and Frustrated Lewis Pairs. This is confirmed further by calculative investigation about the substituent effect (-CH2CH3, -CH(CH3)2 and C(CH3)3) on the stability of Lewis acid-base adducts and Frustrated Lewis Pairs in 2-methyl-3-substituted 2H-1, 4-benzoxazine, where with the increased steric hindrance effect, Lewis acid-base adducts tend to have similar stability with Frustrated Lewis Pairs even though less stability. These results clearly illustrate the elusive phenomenon in our previous experiment and may provide new insight for the design of another novel FLPs-catalysed hydrogenation reaction.
Due to the different reactivity of hydrogenation reaction by metal-free FLPs catalyst for 2, 3-disubstituted 2H-1, 4-benzoxazine, we explored the reaction mechanism by density functional theory calculations. We have chosen three kinds of substrates with different hydrogenation reactivity as the prototype substrates and toluene as the solvent to calculate the potential energy profile for the FLPs-catalysed hydrogenation reaction at M06-2X/6-311++G(d, p) level with polarized continuum model (PCM) to simulate the solvent effect. From the potential energy profile, we found that when B(C6F5)3 encounters with 2, 3-diphenyl 2H-1, 4-benzoxazine (1o) or 2-methyl-3-phenyl 2H-1, 4-benzoxazine (1p) in toluene, it mainly generates the mixture of Lewis acid-base adducts and Frustrated Lewis Pairs, which has almost similar stability suggesting the transformation of each other by intermolecular rearrangement. However, it reveals big difference when the B(C6F5)3 encounters with 2, 3-dimethyl 2H-1, 4-benzoxazine (1q), where the Lewis acid-base adducts is the preference rather than the mixture of Lewis acid-base adducts and Frustrated Lewis Pairs or Frustrated Lewis Pairs since the lower stability energy. Due to the big energy gap (10.9 kcal/mol) between Lewis acid-base adducts and Frustrated Lewis Pairs, the generated Lewis acid-base adducts could not transform into Frustrated Lewis Pairs in the FLPs-catalysed hydrogenation of 1q at 298 K. That is the main reason why 1q is an inert substrate for the hydrogenation catalysed by FLPs. Natural Bond Orbital, Mulliken charge analysis and the proton affinity energy of N4 site was carried out to assess the electric effect of substituent at C3 on N4 site. It reveals negligible effect of substituent at C3 on N4 charge (basicity) and thus proposes that steric hindrance effect is the major factor affecting the stability energy of Lewis acid-base adducts and Frustrated Lewis Pairs. This is confirmed further by calculative investigation about the substituent effect (-CH2CH3, -CH(CH3)2 and C(CH3)3) on the stability of Lewis acid-base adducts and Frustrated Lewis Pairs in 2-methyl-3-substituted 2H-1, 4-benzoxazine, where with the increased steric hindrance effect, Lewis acid-base adducts tend to have similar stability with Frustrated Lewis Pairs even though less stability. These results clearly illustrate the elusive phenomenon in our previous experiment and may provide new insight for the design of another novel FLPs-catalysed hydrogenation reaction.
2019, 77(3): 287-292
doi: 10.6023/A18110472
Abstract:
Immunotherapy for cancer is a method to treat cancer by using the body's own immune system. Programmed death receptor 1 (PD-1) is one of the checkpoints in the immunotherapy. The signal pathway PD-1 (programmed death receptor 1)/PD-L1 (ligand of PD-1) is closely related to the immune escape of the cancer cells. The inhibitor drugs for PD-1 checkpoint, essentially the monoclonal antibodies of PD-1 or PD-L1 which is essentially the immune checkpoints inhibitors could block the PD-1/PD-L1 pathway and reactivate T-cells to kill cancer cells, and as a result, the immunotherapy for cancer is realized. In order to study the binding process of PD-1 drugs and PD-1 antigen in vivo, in this work, solid-state nanopore as a single molecule method is used to detect the binding of PD-1 antibody and antigen. The PD-1 antibody as well as antigen is driven though the same nanopore under the same experimental condition by the external electric field. Since the antibody's block is about 0.01297 while the antigen's block is 0.00404, the PD-1 antibody is distinguished with the PD-1 antigen according to the theoretical formula. Driving the PD-1 antigen though the nanopore modified by PD-1 antibody (a series of experiments are conducted for characterization) under the same temperature and buffer concentration, the antibody-antigen complexes are detected and distinguished with PD-1 protein and its antibody through the relative current drop analysis and the current drop achieved before. The results suggest that the antibody and antigen have a specific binding (the smaller peak represents the free PD-1 antibody and antigen) and the binding process can be detected by nano-sensors. So the nanopore is able to distinguish the antibody, the antigen and the complexes without any labling. And in the future, the nanopore technology may be a rapid and label-free way for patients and doctors to evaluate the drugs' efficiency.
Immunotherapy for cancer is a method to treat cancer by using the body's own immune system. Programmed death receptor 1 (PD-1) is one of the checkpoints in the immunotherapy. The signal pathway PD-1 (programmed death receptor 1)/PD-L1 (ligand of PD-1) is closely related to the immune escape of the cancer cells. The inhibitor drugs for PD-1 checkpoint, essentially the monoclonal antibodies of PD-1 or PD-L1 which is essentially the immune checkpoints inhibitors could block the PD-1/PD-L1 pathway and reactivate T-cells to kill cancer cells, and as a result, the immunotherapy for cancer is realized. In order to study the binding process of PD-1 drugs and PD-1 antigen in vivo, in this work, solid-state nanopore as a single molecule method is used to detect the binding of PD-1 antibody and antigen. The PD-1 antibody as well as antigen is driven though the same nanopore under the same experimental condition by the external electric field. Since the antibody's block is about 0.01297 while the antigen's block is 0.00404, the PD-1 antibody is distinguished with the PD-1 antigen according to the theoretical formula. Driving the PD-1 antigen though the nanopore modified by PD-1 antibody (a series of experiments are conducted for characterization) under the same temperature and buffer concentration, the antibody-antigen complexes are detected and distinguished with PD-1 protein and its antibody through the relative current drop analysis and the current drop achieved before. The results suggest that the antibody and antigen have a specific binding (the smaller peak represents the free PD-1 antibody and antigen) and the binding process can be detected by nano-sensors. So the nanopore is able to distinguish the antibody, the antigen and the complexes without any labling. And in the future, the nanopore technology may be a rapid and label-free way for patients and doctors to evaluate the drugs' efficiency.
