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2017 Volume 75 Issue 4
2017, 75(4): 339-350
doi: 10.6023/A16110592
Abstract:
In recent years, with the continuously deep and expanded researches of two-dimensional (2D) nanomaterials rep-resented by graphene, 2D framework materials represented by 2D metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have attracted great research interests and extensive attention. Compared with other mesoporous or mi-croporous nanomaterials, these organic framework materials provide uniformly nano-sized pores. And as compared to graphene, 2D organic framework materials can be expected to design and assemble the functionalized building units. For example, carboxyl group, amino group, hydroxyl group, etc. can be grafted onto the frameworks through various chemical reactions. These advantages are hopeful to make 2D organic framework materials a new generation of functional materials to improve the sensitivity and stability of the sensing interfaces. This review simply summarized 2D MOFs and COFs respectively, and generalized the current methods for preparing 2D MOFs and COFs nanomaterials based on "bottom-up" and "top-down" strategies and made simple comments. In addition, the applications of (2D) MOFs and COFs materials in chemical sensing and biosensing fields were introduced, and the potential and key problems of 2D MOFs and COFs in sensing applications were also discussed. And at last, this review gives some outlook for the future applications of 2D MOFs and COFs nanomaterials.
In recent years, with the continuously deep and expanded researches of two-dimensional (2D) nanomaterials rep-resented by graphene, 2D framework materials represented by 2D metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have attracted great research interests and extensive attention. Compared with other mesoporous or mi-croporous nanomaterials, these organic framework materials provide uniformly nano-sized pores. And as compared to graphene, 2D organic framework materials can be expected to design and assemble the functionalized building units. For example, carboxyl group, amino group, hydroxyl group, etc. can be grafted onto the frameworks through various chemical reactions. These advantages are hopeful to make 2D organic framework materials a new generation of functional materials to improve the sensitivity and stability of the sensing interfaces. This review simply summarized 2D MOFs and COFs respectively, and generalized the current methods for preparing 2D MOFs and COFs nanomaterials based on "bottom-up" and "top-down" strategies and made simple comments. In addition, the applications of (2D) MOFs and COFs materials in chemical sensing and biosensing fields were introduced, and the potential and key problems of 2D MOFs and COFs in sensing applications were also discussed. And at last, this review gives some outlook for the future applications of 2D MOFs and COFs nanomaterials.
Total Synthesis of (±)-Hongoquercin A via Visible-Light-Mediated Organocatalytic Polyene Cyclization
2017, 75(4): 351-354
doi: 10.6023/A16110591
Abstract:
Advances in the strategy and methodology of visible light photocatalysis have begun to alter the way how organic chemists address the synthetic problems. These powerful methods have enabled the development of novel reaction schemes and approaches (mostly via radical path) for the total synthesis of nature products under visible light photoredox catalysis. Terpenoids, possessing intriguing biological activities together with their structural diversity, have remained as attractive targets for chemists. On the basis of their biogenetic pathways, polyene cyclization is the most straightforward pathway to attain terpenoid skeletons. Most recently, a few examples of stereoselective radical polyene cyclizations have been developed. However, most of the radical approaches suffer from the requirement for stoichiometric loading of metals or radical initiators. And in many cases, low yields are obtained with complicated reaction mixtures, which cumber further development along this line especially in nature products synthesis. In our previous work, we have developed a visible-light-mediated, stereoselective organocatalytic cyclization of polyenes. The wide scope as well as the high chemoselectivity inspires us to apply this method in the total synthesis of terpenoid natural products. Thus we report here total synthesis of (±)-Hongoquercin A (1), starting from trans, trans-farnesol (4) in 7 steps and with overall 14.4% yield. Our developed visible-light-mediated redox organocatalytic methodology is employed as the key step to construct multiple ring-fused skeleton of 1 in one step.[To a flame-dried Schlenk tube equipped with a magnetic stir bar was added 3-hydroxy-5-methyl-2-((2E, 6E)-3, 7, 11-trimethyl-dodeca-2, 6, 10-trien-1-yl) cyclohex-2-enone (3) (0.20 g, 0.61 mmol) and Eosin Y (4.0 mg, 0.0061 mmol). The mixture was diluted with 1.5 mL of anhydrous hexafluoroisopropanol. The reaction was irradiated with Green LEDs at room temperature for 2 h. Upon completion, the reaction mixture was concentrated in vacuo. The residue was purified by silica gel chromatography (10% EtOAc in Petroleum ether) to give 2 (ca. 60% yield, colorless oil) containing all the skeleton carbons of Hongoquercin A.
Advances in the strategy and methodology of visible light photocatalysis have begun to alter the way how organic chemists address the synthetic problems. These powerful methods have enabled the development of novel reaction schemes and approaches (mostly via radical path) for the total synthesis of nature products under visible light photoredox catalysis. Terpenoids, possessing intriguing biological activities together with their structural diversity, have remained as attractive targets for chemists. On the basis of their biogenetic pathways, polyene cyclization is the most straightforward pathway to attain terpenoid skeletons. Most recently, a few examples of stereoselective radical polyene cyclizations have been developed. However, most of the radical approaches suffer from the requirement for stoichiometric loading of metals or radical initiators. And in many cases, low yields are obtained with complicated reaction mixtures, which cumber further development along this line especially in nature products synthesis. In our previous work, we have developed a visible-light-mediated, stereoselective organocatalytic cyclization of polyenes. The wide scope as well as the high chemoselectivity inspires us to apply this method in the total synthesis of terpenoid natural products. Thus we report here total synthesis of (±)-Hongoquercin A (1), starting from trans, trans-farnesol (4) in 7 steps and with overall 14.4% yield. Our developed visible-light-mediated redox organocatalytic methodology is employed as the key step to construct multiple ring-fused skeleton of 1 in one step.[To a flame-dried Schlenk tube equipped with a magnetic stir bar was added 3-hydroxy-5-methyl-2-((2E, 6E)-3, 7, 11-trimethyl-dodeca-2, 6, 10-trien-1-yl) cyclohex-2-enone (3) (0.20 g, 0.61 mmol) and Eosin Y (4.0 mg, 0.0061 mmol). The mixture was diluted with 1.5 mL of anhydrous hexafluoroisopropanol. The reaction was irradiated with Green LEDs at room temperature for 2 h. Upon completion, the reaction mixture was concentrated in vacuo. The residue was purified by silica gel chromatography (10% EtOAc in Petroleum ether) to give 2 (ca. 60% yield, colorless oil) containing all the skeleton carbons of Hongoquercin A.
2017, 75(4): 355-359
doi: 10.6023/A16110598
Abstract:
Cortisol in the human hair is a clinical biomarker of long-term social-and-work-related mental stress, which is of high morbidity rate in the current modern society. This study developed a sensitive hair cortisol assay, featuring sur-face-enhanced Raman spectroscopy, immunoreaction, and a double-layer paper microdevice. The first layer of the paper mi-crodevice was used to remove the hair residue in the hair extract by filtration (sample pretreatment). The second layer was used for competitive immunoreaction and detection. Standard cortisol antigen immobilized in the second layer and the free cortisol in hair extract competed to bind the spiked Raman-active cortisol monoclonal antibody solution. The hair cortisol can be quantitated by the intensity of Raman signal of monoclonal antibody bound on the paper. We found the Raman signal decreased as the cortisol concentration increases in hair samples. The relative Raman intensity measured was linearly proportional to the logarithmic value of the cortisol concentration in hair samples we measured. The detection of limit (LOD) was 1 pg/mL with the portable Raman spectrometer. The RSD of measurement was 8.38% (n=6). In addition, we used LC-MS to measure two real samples as a comparison with our method as above. The results are 0.771 and 0.153 ng/mL by LC-MS method and 0.63 and 0.247 ng/mL by the proposed method. It can be observed that the results are in same order, demonstrating the validity of the proposed method. In addition, 48 samples can be measured in a single chip. These results showed that this method is sensitive, specific, and suitable for large-scale screening of hair cortisol samples.
Cortisol in the human hair is a clinical biomarker of long-term social-and-work-related mental stress, which is of high morbidity rate in the current modern society. This study developed a sensitive hair cortisol assay, featuring sur-face-enhanced Raman spectroscopy, immunoreaction, and a double-layer paper microdevice. The first layer of the paper mi-crodevice was used to remove the hair residue in the hair extract by filtration (sample pretreatment). The second layer was used for competitive immunoreaction and detection. Standard cortisol antigen immobilized in the second layer and the free cortisol in hair extract competed to bind the spiked Raman-active cortisol monoclonal antibody solution. The hair cortisol can be quantitated by the intensity of Raman signal of monoclonal antibody bound on the paper. We found the Raman signal decreased as the cortisol concentration increases in hair samples. The relative Raman intensity measured was linearly proportional to the logarithmic value of the cortisol concentration in hair samples we measured. The detection of limit (LOD) was 1 pg/mL with the portable Raman spectrometer. The RSD of measurement was 8.38% (n=6). In addition, we used LC-MS to measure two real samples as a comparison with our method as above. The results are 0.771 and 0.153 ng/mL by LC-MS method and 0.63 and 0.247 ng/mL by the proposed method. It can be observed that the results are in same order, demonstrating the validity of the proposed method. In addition, 48 samples can be measured in a single chip. These results showed that this method is sensitive, specific, and suitable for large-scale screening of hair cortisol samples.
2017, 75(4): 360-366
doi: 10.6023/A16100549
Abstract:
Depletion of crude oil resources and environmental concerns have spurred worldwide interest in finding un-oil route for liquid fuels. Fischer-Tropsch synthesis is an effective progress for a wide spectrum of hydrocarbon chains from synthesis gas. The use of iron-based catalysts would be preferred in the industry. Here we present a strategy to produce highly dispersed active component embedded in a matrix of porous carbon. Through the carbonization of iron-containing metal-organic frameworks (Fe-MIL-100) at different temperature in N2, four kinds of Fe@C catalysts were prepared. Glucose was used as additional carbon precursor for the synthesis catalyst samples to prevent particle agglomeration. Our strategy avoids the particle agglomeration in the weak metal-support interaction Fe@C catalysts during calcination, reduction and reaction. The structure and morphology of prepared catalysts were characterized by X-ray diffraction (XRD), N2 physical adsorption, transmission electron microscopy (TEM), inductively coupled plasma-atomic emission spectrometer (ICP-AES). It is demonstrated that the iron loading, the particle size, and the Fe phase structure of Fe@C catalysts can be controlled by changing the carbonization temperature of Fe-MIL-100. With increasing the temperature, the iron loading and the particle size increase gradually. Depending on the carbonization temperature, the Fe3O4 phase is dominant at 400 and 500℃. The FeO and Fe phase appear at 600℃. The Fe3C phase prevails at 700℃. The high dispersion of the metal phase and its encapsulation in a highly porous carbon matrix result in an unrivalled FTS activity. The spatial restriction created by encapsulation seems to minimize sintering and oxidation of the active Hägg carbide phase. When the reaction conditions were set at 260℃, 3 MPa, the space velocity of 8000 h-1, the conversion of CO is up to 68%. The Fe time yield (FTY) of the Fe@C-500 catalyst were as high as 164 μmolCO·gFe-1·s-1, which surpasses that of most F-T catalysts reported in the literature in middle-temperature Fischer-Tropsch synthesis.
Depletion of crude oil resources and environmental concerns have spurred worldwide interest in finding un-oil route for liquid fuels. Fischer-Tropsch synthesis is an effective progress for a wide spectrum of hydrocarbon chains from synthesis gas. The use of iron-based catalysts would be preferred in the industry. Here we present a strategy to produce highly dispersed active component embedded in a matrix of porous carbon. Through the carbonization of iron-containing metal-organic frameworks (Fe-MIL-100) at different temperature in N2, four kinds of Fe@C catalysts were prepared. Glucose was used as additional carbon precursor for the synthesis catalyst samples to prevent particle agglomeration. Our strategy avoids the particle agglomeration in the weak metal-support interaction Fe@C catalysts during calcination, reduction and reaction. The structure and morphology of prepared catalysts were characterized by X-ray diffraction (XRD), N2 physical adsorption, transmission electron microscopy (TEM), inductively coupled plasma-atomic emission spectrometer (ICP-AES). It is demonstrated that the iron loading, the particle size, and the Fe phase structure of Fe@C catalysts can be controlled by changing the carbonization temperature of Fe-MIL-100. With increasing the temperature, the iron loading and the particle size increase gradually. Depending on the carbonization temperature, the Fe3O4 phase is dominant at 400 and 500℃. The FeO and Fe phase appear at 600℃. The Fe3C phase prevails at 700℃. The high dispersion of the metal phase and its encapsulation in a highly porous carbon matrix result in an unrivalled FTS activity. The spatial restriction created by encapsulation seems to minimize sintering and oxidation of the active Hägg carbide phase. When the reaction conditions were set at 260℃, 3 MPa, the space velocity of 8000 h-1, the conversion of CO is up to 68%. The Fe time yield (FTY) of the Fe@C-500 catalyst were as high as 164 μmolCO·gFe-1·s-1, which surpasses that of most F-T catalysts reported in the literature in middle-temperature Fischer-Tropsch synthesis.
2017, 75(4): 367-374
doi: 10.6023/A17010015
Abstract:
The exploitation of high-performance solution-processable phosphorescence organic light-emitting diode (PhOLED) materials is of great significance for the realization of large-area, low-cost and flexible display. On the basis of our previous findings that the para-phenylation (phenyl or 4-methoxyphenyl, with respect to the C-Ir bond) on the cyclometalated ligand (C.N ligand) of bis[2-phenylbenzothiazolato-N, C2']iridium (Ⅲ)(acetylacetonate) can result in compounds with drastically enhanced film amorphism hence much improved electroluminescence (EL) performance, herein, this para-phenylation strategy was applied to Ir (Ⅲ) complexes bearing a molecular platform of orange-emissive bis[2-(6-diphenylamino) phenylbenzothiazolato-N, C2']iridium (Ⅲ)(acetylacetonate)[(Nbt)2Ir (acac)] to afford two new Ir (Ⅲ) complexes, namely (3PhNbt)2Ir (acac) and (3OMePhNbt)2Ir (acac). X-ray diffraction (XRD) characterization results revealed that both the two objective compounds possess much enhanced film amorphism than their parent compound (Nbt)2Ir (acac), validating the efficacy of this para-phenylation strategy in achieving Ir (Ⅲ) complexes with enhanced film amorphism. Addi-tionally, in comparison with (Nbt)2Ir (acac), both (3PhNbt)2Ir (acac) and (3OMePhNbt)2Ir (acac) show much enhanced solubility in common organic solvents, together with 5~10 nm bathochromic-shifted phosphorescence band to red region. As a consequence, (3PhNbt)2Ir (acac) and (3OMePhNbt)2Ir (acac) were expected to be promising guest materials for the fabrication of high-performance solution-processed red PhOLEDs. EL characterization results indicated that for single-layer red solu-tion-processed PhOLEDs using (3PhNbt)2Ir (acac) and (3OMePhNbt)2Ir (acac) as the guest dopant, they show peak current efficiency of 2.4 cd·A-1 and 8.7 cd·A-1, maximum brightness of 1830 cd·m-2 and 6630 cd·m-2, and CIE coordinates of (0.61, 0.39) and (0.62, 0.38), respectively. In contrast, the contral device based on the orange-emissive (Nbt)2Ir (acac) only shows a peak current efficiency of 1.5 cd·A-1, maximum brightness of 1620 cd·m-2, and CIE coordinates of (0.59, 0.41). These results confirmed that para-phenyl modification on the C.N ligand (with respect to the C-Ir bond) is indeed an effective approach to acquiring high-performance solution-processable PhOLED Ir (Ⅲ) complexes with simultaneously red-shifted emission band.
The exploitation of high-performance solution-processable phosphorescence organic light-emitting diode (PhOLED) materials is of great significance for the realization of large-area, low-cost and flexible display. On the basis of our previous findings that the para-phenylation (phenyl or 4-methoxyphenyl, with respect to the C-Ir bond) on the cyclometalated ligand (C.N ligand) of bis[2-phenylbenzothiazolato-N, C2']iridium (Ⅲ)(acetylacetonate) can result in compounds with drastically enhanced film amorphism hence much improved electroluminescence (EL) performance, herein, this para-phenylation strategy was applied to Ir (Ⅲ) complexes bearing a molecular platform of orange-emissive bis[2-(6-diphenylamino) phenylbenzothiazolato-N, C2']iridium (Ⅲ)(acetylacetonate)[(Nbt)2Ir (acac)] to afford two new Ir (Ⅲ) complexes, namely (3PhNbt)2Ir (acac) and (3OMePhNbt)2Ir (acac). X-ray diffraction (XRD) characterization results revealed that both the two objective compounds possess much enhanced film amorphism than their parent compound (Nbt)2Ir (acac), validating the efficacy of this para-phenylation strategy in achieving Ir (Ⅲ) complexes with enhanced film amorphism. Addi-tionally, in comparison with (Nbt)2Ir (acac), both (3PhNbt)2Ir (acac) and (3OMePhNbt)2Ir (acac) show much enhanced solubility in common organic solvents, together with 5~10 nm bathochromic-shifted phosphorescence band to red region. As a consequence, (3PhNbt)2Ir (acac) and (3OMePhNbt)2Ir (acac) were expected to be promising guest materials for the fabrication of high-performance solution-processed red PhOLEDs. EL characterization results indicated that for single-layer red solu-tion-processed PhOLEDs using (3PhNbt)2Ir (acac) and (3OMePhNbt)2Ir (acac) as the guest dopant, they show peak current efficiency of 2.4 cd·A-1 and 8.7 cd·A-1, maximum brightness of 1830 cd·m-2 and 6630 cd·m-2, and CIE coordinates of (0.61, 0.39) and (0.62, 0.38), respectively. In contrast, the contral device based on the orange-emissive (Nbt)2Ir (acac) only shows a peak current efficiency of 1.5 cd·A-1, maximum brightness of 1620 cd·m-2, and CIE coordinates of (0.59, 0.41). These results confirmed that para-phenyl modification on the C.N ligand (with respect to the C-Ir bond) is indeed an effective approach to acquiring high-performance solution-processable PhOLED Ir (Ⅲ) complexes with simultaneously red-shifted emission band.
2017, 75(4): 375-382
doi: 10.6023/A16120656
Abstract:
In order to investigate the ignition characteristic of ethylene combustion at low-to-medium temperature, contem-porary detailed kinetic mechanisms for ethylene combustion, including AramcoMech_1.3 mechanism, Creck mechanism, Glarborg's mechanism, San Diego (UCSD) mechanism and Wang's mechanism, were used to simulate ignition delay times of ethylene combustion by Chemkin Pro software reflected shock tube model and closed homogeneous reactor under the as-sumption of constant-volume, homogeneous and adiabatic conditions. Simulated ignition delay times of ethylene combustion using these mechanisms disagree with the experimental data from literatures at low-to-medium temperature.Sensitivity analysis was carried out to identify the controlling steps of C2H4 ignition at 800~1300 K. The sensitivity of ig-nition delay time was calculated by the formula Sensitivity=[τign(2ki)-τign(ki)]/τign(ki)×100%. Here τign(ki) is ignition delay time based on the original combustion mechanism, τign(2ki) is ignition delay time simulated using this mechanism in which the rate constant of reaction i is doubled through multiplying the pre-exponential factor of reaction i by 2. It was demonstrated that C2H3+O2=CH2CHO+O(R1), C2H3+O2=CH2O+HCO(R2) have great sensitivity to the ignition of C2H4 over a wide temperature range, while those reactions involved HO2 (including H2-O2 and C2H4+HO2 system) are important for C2H4 ignition process at low temperature.By modifying these rate constants of R1 and R2 with more accurate calculated results and adding C2H3+O2=C2H3OO reaction and those reactions involved C2H4+HO2 system, one revised mechanism (UCSD-R2) was obtained. UCSD-R2 mechanism can produce better agreement with recent ethylene ignition delay time experimental data from literatures at low-to-medium temperature compared with UCSD mechanism.When UCSD-R2 mechanism was adopted to simulate the ignition delay time of ethylene combustion, the first stage ignition delay time at low temperature (800~950 K) and negative temperature coefficient at medium temperature (950~1100 K) were found. They were explained by using sensitivity analysis and rate-of-production analysis. The method of rate-of-production analysis can be employed to calculate the contribution of each reaction to the production and consumption of every species or to calculate total rate-of-production of every species, by Chemkin Pro software closed homogeneous reactor under the assumption of constant-volume, homogeneous and adiabatic conditions. It was demonstrated that C2H4+HO2 system can shorten the ignition delay time obviously, the production and consumption of HO2 radical play a significant role for first stage ignition of C2H4 at low temperature, the consumption of C2H3 radical results in the negative temperature coefficient at medium temperature.
In order to investigate the ignition characteristic of ethylene combustion at low-to-medium temperature, contem-porary detailed kinetic mechanisms for ethylene combustion, including AramcoMech_1.3 mechanism, Creck mechanism, Glarborg's mechanism, San Diego (UCSD) mechanism and Wang's mechanism, were used to simulate ignition delay times of ethylene combustion by Chemkin Pro software reflected shock tube model and closed homogeneous reactor under the as-sumption of constant-volume, homogeneous and adiabatic conditions. Simulated ignition delay times of ethylene combustion using these mechanisms disagree with the experimental data from literatures at low-to-medium temperature.Sensitivity analysis was carried out to identify the controlling steps of C2H4 ignition at 800~1300 K. The sensitivity of ig-nition delay time was calculated by the formula Sensitivity=[τign(2ki)-τign(ki)]/τign(ki)×100%. Here τign(ki) is ignition delay time based on the original combustion mechanism, τign(2ki) is ignition delay time simulated using this mechanism in which the rate constant of reaction i is doubled through multiplying the pre-exponential factor of reaction i by 2. It was demonstrated that C2H3+O2=CH2CHO+O(R1), C2H3+O2=CH2O+HCO(R2) have great sensitivity to the ignition of C2H4 over a wide temperature range, while those reactions involved HO2 (including H2-O2 and C2H4+HO2 system) are important for C2H4 ignition process at low temperature.By modifying these rate constants of R1 and R2 with more accurate calculated results and adding C2H3+O2=C2H3OO reaction and those reactions involved C2H4+HO2 system, one revised mechanism (UCSD-R2) was obtained. UCSD-R2 mechanism can produce better agreement with recent ethylene ignition delay time experimental data from literatures at low-to-medium temperature compared with UCSD mechanism.When UCSD-R2 mechanism was adopted to simulate the ignition delay time of ethylene combustion, the first stage ignition delay time at low temperature (800~950 K) and negative temperature coefficient at medium temperature (950~1100 K) were found. They were explained by using sensitivity analysis and rate-of-production analysis. The method of rate-of-production analysis can be employed to calculate the contribution of each reaction to the production and consumption of every species or to calculate total rate-of-production of every species, by Chemkin Pro software closed homogeneous reactor under the assumption of constant-volume, homogeneous and adiabatic conditions. It was demonstrated that C2H4+HO2 system can shorten the ignition delay time obviously, the production and consumption of HO2 radical play a significant role for first stage ignition of C2H4 at low temperature, the consumption of C2H3 radical results in the negative temperature coefficient at medium temperature.
2017, 75(4): 383-390
doi: 10.6023/A17010029
Abstract:
Fluoride, the smallest anion, is one of the most important anions in the human body which is involved in many diseases and many life activities can be displayed by its situation. It is necessary to detect fluoride ions and determine its concentration in organism. Compared to the traditional detection methods, fluorescence probes exhibit high sensitivity, high selectivity and potential for real-time detection. Because coumarin derivatives have strong emission in the visible region, high quantum yield, high photostability and excellent bioactivity, we choose them as fluorophore to prepare new fluorescent probes. Based on the mechanism of intramolecular charge transfer (ICT), the fluorescent probes CS1, CS2 and CS3 that are coumarin-based derivatives were designed, synthesized and utilized in fluoride ions detection. Their structures were confirmed by 1H NMR, 13C NMR, IR and HRMS. Meanwhile, the crystals of CS3 were obtained by slow evaporation of an ether solution at room temperature over a period of a few days. The detection limits of CS1, CS2 and CS3 for fluoride ions were respectively determined as 21.77, 3.52 and 1.99 μmol/L, indicating that probes have a good sensitivity to the detection of fluoride. The selectivity experiment results demonstrated that the three probes were highly selective for fluoride ions over other competitive. The recognition mechanism of the fluorescent response to fluoride ions was verified by HRMS and NMR experiment in this work. A lot of detailed experiment results indicated that the fluorescent response of probes to fluoride ions attributed to the specific fluoride promoted Si-O cleavage. The study of the effect of probes on viability of cells were carried out using the methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay. The experimental results indicated that the three probes had low cytotoxicity. Then the three probes were successfully used to fluorescent detect and image fluoride ions in MCF-7 cells by fluorescence spectrum and confocal fluorescence microscopic imaging, respectively.
Fluoride, the smallest anion, is one of the most important anions in the human body which is involved in many diseases and many life activities can be displayed by its situation. It is necessary to detect fluoride ions and determine its concentration in organism. Compared to the traditional detection methods, fluorescence probes exhibit high sensitivity, high selectivity and potential for real-time detection. Because coumarin derivatives have strong emission in the visible region, high quantum yield, high photostability and excellent bioactivity, we choose them as fluorophore to prepare new fluorescent probes. Based on the mechanism of intramolecular charge transfer (ICT), the fluorescent probes CS1, CS2 and CS3 that are coumarin-based derivatives were designed, synthesized and utilized in fluoride ions detection. Their structures were confirmed by 1H NMR, 13C NMR, IR and HRMS. Meanwhile, the crystals of CS3 were obtained by slow evaporation of an ether solution at room temperature over a period of a few days. The detection limits of CS1, CS2 and CS3 for fluoride ions were respectively determined as 21.77, 3.52 and 1.99 μmol/L, indicating that probes have a good sensitivity to the detection of fluoride. The selectivity experiment results demonstrated that the three probes were highly selective for fluoride ions over other competitive. The recognition mechanism of the fluorescent response to fluoride ions was verified by HRMS and NMR experiment in this work. A lot of detailed experiment results indicated that the fluorescent response of probes to fluoride ions attributed to the specific fluoride promoted Si-O cleavage. The study of the effect of probes on viability of cells were carried out using the methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay. The experimental results indicated that the three probes had low cytotoxicity. Then the three probes were successfully used to fluorescent detect and image fluoride ions in MCF-7 cells by fluorescence spectrum and confocal fluorescence microscopic imaging, respectively.
2017, 75(4): 391-397
doi: 10.6023/A16110624
Abstract:
In recent years, hybrid nanomaterials of graphene and polyaniline have attracted extensive interest and have been considered as promising electrode materials for supercapacitor combining the advantages of both materials with synergistic effects. In contrast to the well-developed two-dimensional planar structure of graphene-PANI, the pursuit of hollow gra-phene-PANI hybrid structure is relatively less investigated. The hollow micro/nanostructured graphene-PANI materials with the nanoscale shell, inner cavity and pore structures, is highly expected to exhibit remarkable enhanced supercapacitor performance owing to the enhanced specific surface area and shortened diffusion length for both charge and mass transport. In this work, a novel kind of graphene-polyaniline hollow capsules (PANI-SGR HS) was prepared via Pickering emulsion polymerization using sulfonated graphene (SGR) as Pickering stabilizer. Amphiphilic sulfonated graphene is prepared by a covalent modification and used to stabilize oil phase containing aniline monomer. Aniline molecules were adsorbed to the oil-water interface owing to the electrostatic interaction between amino groups of aniline and sulfonic groups of SGR, which subsequently underwent interfacial polymerization at the oil/water interface upon the addition of initiator ammonium persulfate (APS). The effects of the sulfonation degree of graphene, the SGR concentration as well as the oil/water volume ratio on the stability and morphology of SGR stabilized emulsions were investigated in detail. The SGR with appropriate sulfonation degree can produce stable emulsions. The average diameter of the emulsion droplet decreased with the increasing concentration of SGR stabilizer. The emulsion stability can be improved with the increased water phase infraction. After polymerization of aniline and removal of the oil phase, three-dimensional hollow graphene-polyaniline sphere (PANI-SGR HS) was obtained. The morphology of PANI-SGR HS was observed by scanning electron microscopy (SEM). The special hollow sphere structure not only enlarged the liquid contact area but also improved charge carrier mobility. The hollow sphere modified electrode exhibited excellent performance with a specific capacitance of 480.59 F·g-1 at 1 A·g-1, which is much higher than 251 F·g-1 of the common two-dimensional stacked graphene-polyaniline film. This novel three-dimensional PANI-SGR HS material may have potential applications in energy storage.
In recent years, hybrid nanomaterials of graphene and polyaniline have attracted extensive interest and have been considered as promising electrode materials for supercapacitor combining the advantages of both materials with synergistic effects. In contrast to the well-developed two-dimensional planar structure of graphene-PANI, the pursuit of hollow gra-phene-PANI hybrid structure is relatively less investigated. The hollow micro/nanostructured graphene-PANI materials with the nanoscale shell, inner cavity and pore structures, is highly expected to exhibit remarkable enhanced supercapacitor performance owing to the enhanced specific surface area and shortened diffusion length for both charge and mass transport. In this work, a novel kind of graphene-polyaniline hollow capsules (PANI-SGR HS) was prepared via Pickering emulsion polymerization using sulfonated graphene (SGR) as Pickering stabilizer. Amphiphilic sulfonated graphene is prepared by a covalent modification and used to stabilize oil phase containing aniline monomer. Aniline molecules were adsorbed to the oil-water interface owing to the electrostatic interaction between amino groups of aniline and sulfonic groups of SGR, which subsequently underwent interfacial polymerization at the oil/water interface upon the addition of initiator ammonium persulfate (APS). The effects of the sulfonation degree of graphene, the SGR concentration as well as the oil/water volume ratio on the stability and morphology of SGR stabilized emulsions were investigated in detail. The SGR with appropriate sulfonation degree can produce stable emulsions. The average diameter of the emulsion droplet decreased with the increasing concentration of SGR stabilizer. The emulsion stability can be improved with the increased water phase infraction. After polymerization of aniline and removal of the oil phase, three-dimensional hollow graphene-polyaniline sphere (PANI-SGR HS) was obtained. The morphology of PANI-SGR HS was observed by scanning electron microscopy (SEM). The special hollow sphere structure not only enlarged the liquid contact area but also improved charge carrier mobility. The hollow sphere modified electrode exhibited excellent performance with a specific capacitance of 480.59 F·g-1 at 1 A·g-1, which is much higher than 251 F·g-1 of the common two-dimensional stacked graphene-polyaniline film. This novel three-dimensional PANI-SGR HS material may have potential applications in energy storage.
2017, 75(4): 398-402
doi: 10.6023/A16110619
Abstract:
The aim of this study is to establish a biotin-avidin system and time-resolved fluorimmunoassay (BAS-TRFIA) for quantitative analysis of Aeromonas Hydrophila. First, A. Hydrophila strain B18 isolated from diseased Anguilla rostrata, was used for rabbit anti-serum preparation by injecting the formalin-inactivated bacteria. The rabbit immunoglobulin (IgG) was purified by SPA affinity column. Then, a 96-well microtiter plate precoated with the rabbit IgG was incubated with the strain B18, and biotinylated IgG was pipette to the wells to form a typical double-antibody-sandwich immune complex. Finally, Eu3+-labeled streptavidin was added the wells to produce affinity reaction. Time-resolved fluorescence (TRF) of Eu3+ was measured in enhancement solution to reflect the quantity of the strain B18. This assay showed a good relationship between TRF and the concentration of the strain B18. The limit of detection (LOD) was 1.0×102 cfu/mL, and the LOD of BAS-TRFIA was improved 400-fold compared to the already reported ELISA. The established sandwich BAS-TRFIA showed a good sixth order polynomial fitting from 1.0×10 to 1.0×106 cfu/mL for the strain B18 with the correlation coefficient 0.9716. The strain B18 was positive in BAS-TRFIA, while 19 other contrast strains of Aeromonas eucrenophila, Aeromonas jandaei, Aeromonas enteropelogenes, Escherichia coli, Aeromonas bestiarum and Aeromonas media etc. were negative in the assay, indicating that the antibody had high specificity. The intra-assay and inter-assay standard deviation were less than 5.00% and 9.00%, respectively. The TRF didn't change obviously after the related reagents were placed at 37℃ for 6 days. The method was used to detect the tissues including liver, kidney, intestine, gill and muscle from A. rostrata infected artificial with the strain B18. The result showed 98.33% of 60 samples were positive. BAS-TRFIA for A. hydrophila strain B18 was sensitive, specific and simple. The results indicate that the established BAS-TRFIA has potential application for screening A. hydrophila in aquaculture.
The aim of this study is to establish a biotin-avidin system and time-resolved fluorimmunoassay (BAS-TRFIA) for quantitative analysis of Aeromonas Hydrophila. First, A. Hydrophila strain B18 isolated from diseased Anguilla rostrata, was used for rabbit anti-serum preparation by injecting the formalin-inactivated bacteria. The rabbit immunoglobulin (IgG) was purified by SPA affinity column. Then, a 96-well microtiter plate precoated with the rabbit IgG was incubated with the strain B18, and biotinylated IgG was pipette to the wells to form a typical double-antibody-sandwich immune complex. Finally, Eu3+-labeled streptavidin was added the wells to produce affinity reaction. Time-resolved fluorescence (TRF) of Eu3+ was measured in enhancement solution to reflect the quantity of the strain B18. This assay showed a good relationship between TRF and the concentration of the strain B18. The limit of detection (LOD) was 1.0×102 cfu/mL, and the LOD of BAS-TRFIA was improved 400-fold compared to the already reported ELISA. The established sandwich BAS-TRFIA showed a good sixth order polynomial fitting from 1.0×10 to 1.0×106 cfu/mL for the strain B18 with the correlation coefficient 0.9716. The strain B18 was positive in BAS-TRFIA, while 19 other contrast strains of Aeromonas eucrenophila, Aeromonas jandaei, Aeromonas enteropelogenes, Escherichia coli, Aeromonas bestiarum and Aeromonas media etc. were negative in the assay, indicating that the antibody had high specificity. The intra-assay and inter-assay standard deviation were less than 5.00% and 9.00%, respectively. The TRF didn't change obviously after the related reagents were placed at 37℃ for 6 days. The method was used to detect the tissues including liver, kidney, intestine, gill and muscle from A. rostrata infected artificial with the strain B18. The result showed 98.33% of 60 samples were positive. BAS-TRFIA for A. hydrophila strain B18 was sensitive, specific and simple. The results indicate that the established BAS-TRFIA has potential application for screening A. hydrophila in aquaculture.
2017, 75(4): 403-407
doi: 10.6023/A16110599
Abstract:
Brevetoxins (BTXs) are highly toxic biotoxin and can cause human intoxication through food chain. The detection of brevetoxins is very difficult due to lack of optical and electrochemical (EC) signal. In this work, we developed an ultrasensitive capillary electrophoresis (CE) immunoassay and EC method for the determination of BTX-B by gold nanoparticles (AuNPs) assisted signal generation and sequential stacking concentration. The AuNPs were synthesized by sodium citrate reduction of HAuCl4 in water. The AuNPs were conjugated with horseradish peroxidase (HRP) and antibody (Ab) to immobilize the HRP and Ab on the AuNPs surface with the molar ratio of HRP/Ab of 9/1. The Ab conjugated on the AuNPs surface incubated with limited amount of BTX-B in standard solution or shellfish samples to produce immunocomplex on the basis of the noncompetitive immunoreactions. Before sample injection, a NaOH plug with 10 cm height difference for 150 s was hydrodynamically injected into the separation capillary. After incubation for 40 min at room temperature, the immune sample was then electrokinetically injected into the capillary at 10 kV for 330 s. The positively charged analytes migrated rapidly into the capillary and were neutralized and stacked at the boundary between sample and NaOH plug, which led to the first preconcentration. After sample loading, the capillary inlet vial was changed to low-pH buffer solution, and H+ in the buffer solution moved rapidly into the capillary toward cathode across the neutral analytes zone. The neutralized analytes were positively charged again and the injected analytes were further condensed. Next, the formed immunocomplex, unbound HRP-Au-Ab probe and the excess HRP were separated by CE and sensitively detected by EC detection. AuNPs were used as carriers of HRP and Ab in order to carry out EC detection with the EC signals derived from catalytic reaction of the carried HRP to the H2O2/o-aminophenol system. Simultaneously, the EC signal was highly amplified by improving the HRP/Ab molar ratio on the surface of AuNPs. The proposed method by AuNPs assisted signal generation and on-line sequential concentration realized the sensitive and rapid determination of BTX-B in shellfish samples. In the range between 0.1 and 120 ng/mL, the assay allowed quantitative determination of BTX-B and the limit of detection (LOD) was 26 ng/L. The LOD was 365-fold lower than ELISA method. The amplified sensitivity was enhanced by high HRP/Ab ratio at AuNPs surface and sequential preconcentration. The proposed method provides a convenient and sensitive analytical approach for the determination of trace BTX in complex samples.
Brevetoxins (BTXs) are highly toxic biotoxin and can cause human intoxication through food chain. The detection of brevetoxins is very difficult due to lack of optical and electrochemical (EC) signal. In this work, we developed an ultrasensitive capillary electrophoresis (CE) immunoassay and EC method for the determination of BTX-B by gold nanoparticles (AuNPs) assisted signal generation and sequential stacking concentration. The AuNPs were synthesized by sodium citrate reduction of HAuCl4 in water. The AuNPs were conjugated with horseradish peroxidase (HRP) and antibody (Ab) to immobilize the HRP and Ab on the AuNPs surface with the molar ratio of HRP/Ab of 9/1. The Ab conjugated on the AuNPs surface incubated with limited amount of BTX-B in standard solution or shellfish samples to produce immunocomplex on the basis of the noncompetitive immunoreactions. Before sample injection, a NaOH plug with 10 cm height difference for 150 s was hydrodynamically injected into the separation capillary. After incubation for 40 min at room temperature, the immune sample was then electrokinetically injected into the capillary at 10 kV for 330 s. The positively charged analytes migrated rapidly into the capillary and were neutralized and stacked at the boundary between sample and NaOH plug, which led to the first preconcentration. After sample loading, the capillary inlet vial was changed to low-pH buffer solution, and H+ in the buffer solution moved rapidly into the capillary toward cathode across the neutral analytes zone. The neutralized analytes were positively charged again and the injected analytes were further condensed. Next, the formed immunocomplex, unbound HRP-Au-Ab probe and the excess HRP were separated by CE and sensitively detected by EC detection. AuNPs were used as carriers of HRP and Ab in order to carry out EC detection with the EC signals derived from catalytic reaction of the carried HRP to the H2O2/o-aminophenol system. Simultaneously, the EC signal was highly amplified by improving the HRP/Ab molar ratio on the surface of AuNPs. The proposed method by AuNPs assisted signal generation and on-line sequential concentration realized the sensitive and rapid determination of BTX-B in shellfish samples. In the range between 0.1 and 120 ng/mL, the assay allowed quantitative determination of BTX-B and the limit of detection (LOD) was 26 ng/L. The LOD was 365-fold lower than ELISA method. The amplified sensitivity was enhanced by high HRP/Ab ratio at AuNPs surface and sequential preconcentration. The proposed method provides a convenient and sensitive analytical approach for the determination of trace BTX in complex samples.
