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2019 Volume 77 Issue 2
2019, 77(2): 121-129
doi: 10.6023/A18100412
Abstract:
The unique "core-shell" structure endows nanoscale zero-valent iron (nZVI) rich aquatic surface chemistry properties. Transformation of surface chemistry and crystal phase of nZVI affect its reactivity and environmental transport and fate. Recent advances on the surface chemistry and phase transformation of nZVI in aqueous media are highlighted in this paper focusing on a basic theory of nZVI for pollution control and environmental application. Surface chemistry and phase of both fresh and reacted nZVI are presented. The structure, composition and properties of nanoparticles are determined not only by reaction time but also by environmental conditions. Specifically, the influences of dissolved oxygen, hydraulic conditions (static and stirring), types and concentrations of heavy metals (U(Ⅵ), Cr(Ⅵ), Se(Ⅳ)) and anions (NO3-, SO42-, HPO42- and HCO3-) are investigated. In addition, the effect of surface modification with polyelectrolytes, including anionic polyacrylamide (APAM) and carboxymethylcellulose sodium (CMC), on microstructure, morphology and composition of nanoparticles in aqueous phase was discussed. Results demonstrate that environmental conditions have significant impacts on particles structure, composition and properties, consequently on nZVI performance for pollutant removal. After corrosion under different aqueous conditions, the core-shell structured nZVI are distorted and the metallic iron core is transformed into different iron oxides/hydroxides, such as γ-Fe2O3, Fe3O4 and γ-FeOOH. These iron (hydr)oxides exhibit different surface complexation and affinity proprieties, thus eventually affecting the pollutant removal performance and the environmental fate of reaction products. More research on the effect of dynamic structure transformation by different types of pollutants, and a reaction model between the surface chemistry/phase transformation and removal performance are needed to deepen our understanding on nZVI surface chemistry, and develop more effective technologies of environmental applications.
The unique "core-shell" structure endows nanoscale zero-valent iron (nZVI) rich aquatic surface chemistry properties. Transformation of surface chemistry and crystal phase of nZVI affect its reactivity and environmental transport and fate. Recent advances on the surface chemistry and phase transformation of nZVI in aqueous media are highlighted in this paper focusing on a basic theory of nZVI for pollution control and environmental application. Surface chemistry and phase of both fresh and reacted nZVI are presented. The structure, composition and properties of nanoparticles are determined not only by reaction time but also by environmental conditions. Specifically, the influences of dissolved oxygen, hydraulic conditions (static and stirring), types and concentrations of heavy metals (U(Ⅵ), Cr(Ⅵ), Se(Ⅳ)) and anions (NO3-, SO42-, HPO42- and HCO3-) are investigated. In addition, the effect of surface modification with polyelectrolytes, including anionic polyacrylamide (APAM) and carboxymethylcellulose sodium (CMC), on microstructure, morphology and composition of nanoparticles in aqueous phase was discussed. Results demonstrate that environmental conditions have significant impacts on particles structure, composition and properties, consequently on nZVI performance for pollutant removal. After corrosion under different aqueous conditions, the core-shell structured nZVI are distorted and the metallic iron core is transformed into different iron oxides/hydroxides, such as γ-Fe2O3, Fe3O4 and γ-FeOOH. These iron (hydr)oxides exhibit different surface complexation and affinity proprieties, thus eventually affecting the pollutant removal performance and the environmental fate of reaction products. More research on the effect of dynamic structure transformation by different types of pollutants, and a reaction model between the surface chemistry/phase transformation and removal performance are needed to deepen our understanding on nZVI surface chemistry, and develop more effective technologies of environmental applications.
2019, 77(2): 130-142
doi: 10.6023/A18090363
Abstract:
In the past twenty years, our knowledge on gas phase radical ion chemistry has been significantly improved due to the development of electron capture dissociation. Combined with soft ionization method, it has shown the technique can provide novel fragment ions for the structural elucidation of biomolecules, especially for protein characterization. This review aims to introduce fundamental aspects of electron capture dissociation mass spectrometry, as well as its applications in the analysis of biomolecules.
In the past twenty years, our knowledge on gas phase radical ion chemistry has been significantly improved due to the development of electron capture dissociation. Combined with soft ionization method, it has shown the technique can provide novel fragment ions for the structural elucidation of biomolecules, especially for protein characterization. This review aims to introduce fundamental aspects of electron capture dissociation mass spectrometry, as well as its applications in the analysis of biomolecules.
2019, 77(2): 143-152
doi: 10.6023/A18090404
Abstract:
With the rapid development of nuclear industry, nuclear energy, as a kind of low-carbon energy, has been widely used in the world. However, in the development and application of nuclear energy, a large amount of radionuclides, especially the radioactive uranium, have been inevitably discharged into the environment, causing serious environmental pollution and having great harm to human health. Layered double hydroxides (LDHs) have become the excellent adsorbents in environmental pollution treatments due to easy preparation, large specific surface area, the unique nanostructure and excellent ion exchange capacity. Hence, the preparation of layered double hydroxides and their composites for the efficient removal of radioactive uranium is one of the hot issues in the field of environmental science, which include coprecipitation, ion exchange, hydrothermal method, the urea hydrolysis method, aerogel, microwave-crystallization and separate nucleation/crystallization isolation method. Besides the aforementioned methods, other reported synthesis methods of LDHs include the secondary intercalation method (an intercalation method involving dissolution and the re-coprecipitation method), reconstruction method based on the "memory effect", N2 protection synthesis, mechanochemical synthesis, surface synthesis, template synthesis, and others. The modification methods of layered double hydroxides can be divided into calcination, intercalation and compounding method, which significantly increase the active sites and further improve the adsorption performance of the materials to radioactive uranium. In addition, the adsorption mechanism has been thoroughly investigated with spectroscopic analysis techniques such as Fourier transformed infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Extended X-ray absorption fine structure (EXAFS). In conclusion, the review briefly discuss the application prospects of layered double hydroxides and their composites in the treatment of water pollution, which provide definitive reference values for the further research and practical application of environmental management in the future.
With the rapid development of nuclear industry, nuclear energy, as a kind of low-carbon energy, has been widely used in the world. However, in the development and application of nuclear energy, a large amount of radionuclides, especially the radioactive uranium, have been inevitably discharged into the environment, causing serious environmental pollution and having great harm to human health. Layered double hydroxides (LDHs) have become the excellent adsorbents in environmental pollution treatments due to easy preparation, large specific surface area, the unique nanostructure and excellent ion exchange capacity. Hence, the preparation of layered double hydroxides and their composites for the efficient removal of radioactive uranium is one of the hot issues in the field of environmental science, which include coprecipitation, ion exchange, hydrothermal method, the urea hydrolysis method, aerogel, microwave-crystallization and separate nucleation/crystallization isolation method. Besides the aforementioned methods, other reported synthesis methods of LDHs include the secondary intercalation method (an intercalation method involving dissolution and the re-coprecipitation method), reconstruction method based on the "memory effect", N2 protection synthesis, mechanochemical synthesis, surface synthesis, template synthesis, and others. The modification methods of layered double hydroxides can be divided into calcination, intercalation and compounding method, which significantly increase the active sites and further improve the adsorption performance of the materials to radioactive uranium. In addition, the adsorption mechanism has been thoroughly investigated with spectroscopic analysis techniques such as Fourier transformed infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Extended X-ray absorption fine structure (EXAFS). In conclusion, the review briefly discuss the application prospects of layered double hydroxides and their composites in the treatment of water pollution, which provide definitive reference values for the further research and practical application of environmental management in the future.
2019, 77(2): 153-159
doi: 10.6023/A18090372
Abstract:
A new porous crystalline materials Zr-containing organic framework of UiO-66 has a large specific surface area, strong adsorption capacity, and the highly ordered arrangement of metal ions in its crystal structure. In this study, because UiO-66 has a good structural features, Fe-doped nano-ZrO2 photocatalyst of Fe-ZrO2 were successfully prepared by the adsorption of Fe3+ onto UiO-66, and calcination of the precursor of Fe3+/UiO-66, subsequently. The morphology and structure of the catalyst were characterized by scanning electron microscopy (SEM), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption isotherm, Fourier transform infrared spectroscopy (FT-IR) and UV-Vis absorption spectroscopy (UV-vis DRS). The electrochemical performance of the catalyst was analyzed by fluorescence (PL) and electrochemical impedance spectroscopy. Finally, the photodegradation of rhodamine B solution by the catalysis of Fe-ZrO2 was studied. The results showed that the degradation rate of rhodamine B (RhB) under visible light irritation was 83% in 120 min with the catalyst of Fe-ZrO2 from the calcination of the precursor Fe3+/UiO-66. The catalyst has a promising stability. The degradation rate to RhB could still reach 78% after three cycles.
A new porous crystalline materials Zr-containing organic framework of UiO-66 has a large specific surface area, strong adsorption capacity, and the highly ordered arrangement of metal ions in its crystal structure. In this study, because UiO-66 has a good structural features, Fe-doped nano-ZrO2 photocatalyst of Fe-ZrO2 were successfully prepared by the adsorption of Fe3+ onto UiO-66, and calcination of the precursor of Fe3+/UiO-66, subsequently. The morphology and structure of the catalyst were characterized by scanning electron microscopy (SEM), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption isotherm, Fourier transform infrared spectroscopy (FT-IR) and UV-Vis absorption spectroscopy (UV-vis DRS). The electrochemical performance of the catalyst was analyzed by fluorescence (PL) and electrochemical impedance spectroscopy. Finally, the photodegradation of rhodamine B solution by the catalysis of Fe-ZrO2 was studied. The results showed that the degradation rate of rhodamine B (RhB) under visible light irritation was 83% in 120 min with the catalyst of Fe-ZrO2 from the calcination of the precursor Fe3+/UiO-66. The catalyst has a promising stability. The degradation rate to RhB could still reach 78% after three cycles.
2019, 77(2): 160-165
doi: 10.6023/A18090401
Abstract:
The effect of NH3 concentration, reaction time and other conditions on the heterogeneous reaction of NH3 and Cl2 on the surface of γ-Al2O3 particles was investigated at the room temperature, pressure and in the presence of oxygen by ion chromatography (IC). The formation of the surface species (Cl-, NO3-, and SO42-) via both individual reaction and co-existing reaction of NH3, Cl2, SO2 and NO2 on the surface of γ-Al2O3 was investigated as well. The results revealed that NH3 (400 ppm) and Cl2 (400 ppm) had synergistic effect on the surface γ-Al2O3, and the total yield of Cl- was 589.65 μg after reaction of 2 h. The formation of the surface chlorides increased firstly and then decreased with the increase of ammonia concentration, and the maximum yield of Cl- was reached at 400 ppm of NH3. In the presence of active chlorine, NH3 significantly promoted the generation of the adsorptive species on the surface, such as Cl-, NO3- and SO42-, and the most obvious synergistic effect was induced to form on the conditions of four gases co-existence. The heterogeneous reaction mechanism of NH3 with Cl2 and the influence on the atmospheric environment were also discussed as well. Additionally, the mixing ratios used in the study are extremely high compared with ambient levels, which could be as a simulation to explore whether the synergistic effect obtained in this paper are also present in the real ambient conditions. We have studied a relatively low mixing ratios for heterogeneous reaction experiments, but the content of nitrate and chloride on the surface of γ-Al2O3 were lower than the limit of detection of ion chromatography. Therefore, other researches such as Knudsen cell and smog chamber study, field monitoring, and mode study are also worth for exploring in future study. The results of this study could provide reference data for the study of the contribution of active chlorine and ammonia to the formation of secondary inorganic particles.
The effect of NH3 concentration, reaction time and other conditions on the heterogeneous reaction of NH3 and Cl2 on the surface of γ-Al2O3 particles was investigated at the room temperature, pressure and in the presence of oxygen by ion chromatography (IC). The formation of the surface species (Cl-, NO3-, and SO42-) via both individual reaction and co-existing reaction of NH3, Cl2, SO2 and NO2 on the surface of γ-Al2O3 was investigated as well. The results revealed that NH3 (400 ppm) and Cl2 (400 ppm) had synergistic effect on the surface γ-Al2O3, and the total yield of Cl- was 589.65 μg after reaction of 2 h. The formation of the surface chlorides increased firstly and then decreased with the increase of ammonia concentration, and the maximum yield of Cl- was reached at 400 ppm of NH3. In the presence of active chlorine, NH3 significantly promoted the generation of the adsorptive species on the surface, such as Cl-, NO3- and SO42-, and the most obvious synergistic effect was induced to form on the conditions of four gases co-existence. The heterogeneous reaction mechanism of NH3 with Cl2 and the influence on the atmospheric environment were also discussed as well. Additionally, the mixing ratios used in the study are extremely high compared with ambient levels, which could be as a simulation to explore whether the synergistic effect obtained in this paper are also present in the real ambient conditions. We have studied a relatively low mixing ratios for heterogeneous reaction experiments, but the content of nitrate and chloride on the surface of γ-Al2O3 were lower than the limit of detection of ion chromatography. Therefore, other researches such as Knudsen cell and smog chamber study, field monitoring, and mode study are also worth for exploring in future study. The results of this study could provide reference data for the study of the contribution of active chlorine and ammonia to the formation of secondary inorganic particles.
2019, 77(2): 166-171
doi: 10.6023/A18100423
Abstract:
Recently, the research work concerning B(C6F5)3 catalyzed reduction of carbonyl compounds revealed that this Lewis acid B(C6F5)3 presents, actually, a rather water-tolerant system. This fact considerably broadens the scope of the water/base tolerant frustrated Lewis pairs (FLP) chemistry. In this research, an efficient chemoselective reduction of aldehydes and ketones to alcohols catalyzed by the Lewis acid B(C6F5)3 has been developed. It is the first report about the chemoselective reduction of carbonyl compounds under aqueous conditions catalyzed by FLPs with hydridosilanes as reducing agents. The selectivity and activity of different hydridosilanes and the influence of substituents in carbonyl compounds have been studied. The effect of water concentration on the chemoselectivity of the reaction has also been investigated. It has been found that a 2~3 fold excess of water relatively to hydridosilanes usually exhibits better selectivity and overall yields than in the equimolar case. The reduction reaction can even be successfully performed with pure water as a solvent without any loss of the reactivity. Such a procedure has been successfully applied to reduce 14 differently substituted aldehydes and ketones into alcohols with up to 100% yields under mild conditions, but failed in case of the diaryl substituted ketones. Both experimental and computational methods have been performed to confirm the possibility of the water mediated mechanism and the effects of different Lewis bases on the LB——H-OH——LA three-component aggregates. These mechanistic studies have revealed that such water mediation between a carbonyl compound and a catalyst advantageously (i) activates the C=O group by protonation and (ii) fixes the catalytic borane moiety by formation of a B-O bond, which to some extent prevents the direct hydrolysis of hydridosilane and makes the reaction possible under moist conditions. Detailed clarification of the actual role of water in the reduction reaction of question will promote the further development of FLP-catalyzed and related reactions in the "green" chemistry field.
Recently, the research work concerning B(C6F5)3 catalyzed reduction of carbonyl compounds revealed that this Lewis acid B(C6F5)3 presents, actually, a rather water-tolerant system. This fact considerably broadens the scope of the water/base tolerant frustrated Lewis pairs (FLP) chemistry. In this research, an efficient chemoselective reduction of aldehydes and ketones to alcohols catalyzed by the Lewis acid B(C6F5)3 has been developed. It is the first report about the chemoselective reduction of carbonyl compounds under aqueous conditions catalyzed by FLPs with hydridosilanes as reducing agents. The selectivity and activity of different hydridosilanes and the influence of substituents in carbonyl compounds have been studied. The effect of water concentration on the chemoselectivity of the reaction has also been investigated. It has been found that a 2~3 fold excess of water relatively to hydridosilanes usually exhibits better selectivity and overall yields than in the equimolar case. The reduction reaction can even be successfully performed with pure water as a solvent without any loss of the reactivity. Such a procedure has been successfully applied to reduce 14 differently substituted aldehydes and ketones into alcohols with up to 100% yields under mild conditions, but failed in case of the diaryl substituted ketones. Both experimental and computational methods have been performed to confirm the possibility of the water mediated mechanism and the effects of different Lewis bases on the LB——H-OH——LA three-component aggregates. These mechanistic studies have revealed that such water mediation between a carbonyl compound and a catalyst advantageously (i) activates the C=O group by protonation and (ii) fixes the catalytic borane moiety by formation of a B-O bond, which to some extent prevents the direct hydrolysis of hydridosilane and makes the reaction possible under moist conditions. Detailed clarification of the actual role of water in the reduction reaction of question will promote the further development of FLP-catalyzed and related reactions in the "green" chemistry field.
2019, 77(2): 172-178
doi: 10.6023/A18090410
Abstract:
Developing biocompatible, multifunctional and in-situ labeling nanoplatform is high challenging for molecular imaging. Organic derivates melanin nanoparticles (MNPs) holds great potential to be multimodal contrast agents, and have been used for photoacoustic imaging, magnetic resonance imaging, and 64Cu PET imaging with simple modifications. In order to extend MNPs application in molecular imaging, here a novel radio-nuclide was applied to in-situ labeling of MNPs. Large numbers of active dihydroxyindole/indolequinone groups and natural binding ability of MNPs enabled them to have the ability to label different types of radionuclides which have unique half-life and functions, especially long-life elemental nuclide. This project explored the in-situ labeling methods of organic melanin nanoparticles with a promising diagnostic radionuclides named Iodine-124 (124I), and using this novel multifunctional organic nanoparticles for preliminary molecular imaging studies. Generally, ultrafine particle size melanin nanoparticles (5.5 nm in diameter) were prepared by ultrasonication method using naturally occurring melanin, then PEG3500 which had amino group at both ends was used as a stabilizer agent to obtain PEG-MNP nanocarriers (7.5 nm in diameter) with better water solubility and stability. The nanoparticles were full characterized by dynamic light scattering (DLS), transmission electron microscope (TEM) and 1H NMR, respectively. Then, one kind of elemental nuclide was labeled. Classic iodine labeled method with N-Bromo Succinimide (NBS) was used as oxidant to oxidize active dihydroxyindole/indolequinone ring of PEG-MNP for electrophilic substitution reaction labeling 124I (100.8 h). This reaction rate is extremely fast (60 s reaction time) and high labelling yield (>99%). The 124I was labeled successfully and in-situ labeled PEG-MNP nanocarriers were obtained. After that, 124I and 124I-PEG-MNP were used to further preclinical evaluation by micro-PET imaging. Micro-PET images were collected at 2 h, 24 h and 48 h after intravenous injection 7.4 MBq 124I and 124I-PEG-MNP in normal Kunming mice (n=3). The ROI target area of heart, liver and thyroid were delineated for semi-quantitative analysis. Then, in order to verify the imaging ability of 124I-PEG-MNP in solid tumor. We built human pancreatic cancer BxPC3 xenograft model (n=3), and Micro-PET scans were performed at different time points. Results showed that the labeling rate of 124I on PEG-MNP was 99.9%. And the radiochemical purity in vitro stability of 124I-PEG-MNP in 96 h was more than 90%. Micro-PET images showed that 124I-PEG-MNP had no obvious thyroid uptake which indicated no de-marking in mice. The radio-distribution of 124I and 124I-PEG-MNP was substantially different in liver and thyroid (P < 0.001). In vivo semi-quantitative analysis showed that the radio uptakes of organs were consistent with the distribution of nanoparticles. And the PET imaging of xenograft mice showed that 124I-PEG-MNP can utilize the enhanced permeability and retention effect (EPR) to be significantly enriched at the tumor and retained in the tumor site for more than 48 h. PEG-MNP has the ability to label long half-life nuclide 124I. This research provides an experimental basis for further construction of long-circulation multimodal imaging probes.
Developing biocompatible, multifunctional and in-situ labeling nanoplatform is high challenging for molecular imaging. Organic derivates melanin nanoparticles (MNPs) holds great potential to be multimodal contrast agents, and have been used for photoacoustic imaging, magnetic resonance imaging, and 64Cu PET imaging with simple modifications. In order to extend MNPs application in molecular imaging, here a novel radio-nuclide was applied to in-situ labeling of MNPs. Large numbers of active dihydroxyindole/indolequinone groups and natural binding ability of MNPs enabled them to have the ability to label different types of radionuclides which have unique half-life and functions, especially long-life elemental nuclide. This project explored the in-situ labeling methods of organic melanin nanoparticles with a promising diagnostic radionuclides named Iodine-124 (124I), and using this novel multifunctional organic nanoparticles for preliminary molecular imaging studies. Generally, ultrafine particle size melanin nanoparticles (5.5 nm in diameter) were prepared by ultrasonication method using naturally occurring melanin, then PEG3500 which had amino group at both ends was used as a stabilizer agent to obtain PEG-MNP nanocarriers (7.5 nm in diameter) with better water solubility and stability. The nanoparticles were full characterized by dynamic light scattering (DLS), transmission electron microscope (TEM) and 1H NMR, respectively. Then, one kind of elemental nuclide was labeled. Classic iodine labeled method with N-Bromo Succinimide (NBS) was used as oxidant to oxidize active dihydroxyindole/indolequinone ring of PEG-MNP for electrophilic substitution reaction labeling 124I (100.8 h). This reaction rate is extremely fast (60 s reaction time) and high labelling yield (>99%). The 124I was labeled successfully and in-situ labeled PEG-MNP nanocarriers were obtained. After that, 124I and 124I-PEG-MNP were used to further preclinical evaluation by micro-PET imaging. Micro-PET images were collected at 2 h, 24 h and 48 h after intravenous injection 7.4 MBq 124I and 124I-PEG-MNP in normal Kunming mice (n=3). The ROI target area of heart, liver and thyroid were delineated for semi-quantitative analysis. Then, in order to verify the imaging ability of 124I-PEG-MNP in solid tumor. We built human pancreatic cancer BxPC3 xenograft model (n=3), and Micro-PET scans were performed at different time points. Results showed that the labeling rate of 124I on PEG-MNP was 99.9%. And the radiochemical purity in vitro stability of 124I-PEG-MNP in 96 h was more than 90%. Micro-PET images showed that 124I-PEG-MNP had no obvious thyroid uptake which indicated no de-marking in mice. The radio-distribution of 124I and 124I-PEG-MNP was substantially different in liver and thyroid (P < 0.001). In vivo semi-quantitative analysis showed that the radio uptakes of organs were consistent with the distribution of nanoparticles. And the PET imaging of xenograft mice showed that 124I-PEG-MNP can utilize the enhanced permeability and retention effect (EPR) to be significantly enriched at the tumor and retained in the tumor site for more than 48 h. PEG-MNP has the ability to label long half-life nuclide 124I. This research provides an experimental basis for further construction of long-circulation multimodal imaging probes.
2019, 77(2): 179-183
doi: 10.6023/A18090382
Abstract:
The strategy for electrochemiluminescence (ECL) sensor based on the CdSe quantum dots (QDs) to detect amines is proposed. We investigated the QDs ECL toward different amines, and found that amines could lead to the enhancement of ECL intensity. A novel amines detection platform based on micellar reversed sweeping, capillary electrophoresis (CE) separation, and quantum dots electrochemiluminescence detection was proposed for simultaneous detection of ractopamine and clenbuterol in meat samples. Firstly, the capillary was filled with running buffer containing SDS micelles. The electrophoretic velocity of SDS micelle was reverse to that of electroosmotic velocity. By controlling electroosmotic flow, the SDS-sample conjugates were at an immobile state in capillary. This immobile state was maintained for an extended period of time so that essentially unlimited volume of sample solution could be injected into the capillary. Then the sample was electrokinetically introduced into the separation capillary at 20 kV for 50 min. The negative charged SDS micelles in the buffer attracted the sample ions at the boundary of sample and buffer solution. The micellar reversed sweeping process allows introducing large amount of analytes into capillary to accumulate at the capillary inlet. After CE separation, the preconcentrated analytes sequentially enter into detection cell and lead to the enhancement of ECL intensity of QDs. The micellar reversed sweeping allows a large number of analytes trapped by SDS micelles, which could significantly amplify the QD's ECL signal for 6000-fold. The proposed method by micellar reversed sweeping and CE separation with QDs ECL detection realized the simultaneous and sensitive determination of ractopamine and clenbuterol in meat samples. The linear range were (0.8~2960) and (3.0~5520) μg/L and the limit of detection (LOD) were 96.8 and 192.5 ng/L for ractopamine and clenbuterol, respectively. CE based QDs ECL that combines the high separation efficiency of CE and the high sensitivity of QDs ECL has been proven to be a promising technique for amines compound assays.
The strategy for electrochemiluminescence (ECL) sensor based on the CdSe quantum dots (QDs) to detect amines is proposed. We investigated the QDs ECL toward different amines, and found that amines could lead to the enhancement of ECL intensity. A novel amines detection platform based on micellar reversed sweeping, capillary electrophoresis (CE) separation, and quantum dots electrochemiluminescence detection was proposed for simultaneous detection of ractopamine and clenbuterol in meat samples. Firstly, the capillary was filled with running buffer containing SDS micelles. The electrophoretic velocity of SDS micelle was reverse to that of electroosmotic velocity. By controlling electroosmotic flow, the SDS-sample conjugates were at an immobile state in capillary. This immobile state was maintained for an extended period of time so that essentially unlimited volume of sample solution could be injected into the capillary. Then the sample was electrokinetically introduced into the separation capillary at 20 kV for 50 min. The negative charged SDS micelles in the buffer attracted the sample ions at the boundary of sample and buffer solution. The micellar reversed sweeping process allows introducing large amount of analytes into capillary to accumulate at the capillary inlet. After CE separation, the preconcentrated analytes sequentially enter into detection cell and lead to the enhancement of ECL intensity of QDs. The micellar reversed sweeping allows a large number of analytes trapped by SDS micelles, which could significantly amplify the QD's ECL signal for 6000-fold. The proposed method by micellar reversed sweeping and CE separation with QDs ECL detection realized the simultaneous and sensitive determination of ractopamine and clenbuterol in meat samples. The linear range were (0.8~2960) and (3.0~5520) μg/L and the limit of detection (LOD) were 96.8 and 192.5 ng/L for ractopamine and clenbuterol, respectively. CE based QDs ECL that combines the high separation efficiency of CE and the high sensitivity of QDs ECL has been proven to be a promising technique for amines compound assays.
2019, 77(2): 184-188
doi: 10.6023/A18090393
Abstract:
Surface-enhanced Raman spectroscopy (SERS) technology, based on noble metal nanostructures as substrate, is a highly sensitive method for the detected substance. When the surface of noble metal with special nanostructure is irradiated by laser, the free electrons on the metal surface will be greatly oscillated. While the frequency of the incident light is close to that of the oscillation, the surface plasmon resonance (SPR) will occur around the noble metal nanostructures material, greatly enhancing the local electric field intensity of the metal surface. The intensity of incident light and the scattering light will be also multiplied. As a result, the Raman scattering signals of molecules adsorbed on the surface of noble metal nanostructures will be effectively enhanced. In this paper, the octahedral Au/Ag composite nanocages were prepared by using NaBH4 reduction-acid etching template method. The prepared octahedral Au/Ag composite nanocages are uniform in shape, with the size of about 600 nm, and there is no residual cuprous oxide template. The Au element is uniformly distributed on the Ag nanocages with the mass fraction about 16.8%. Compared with that of Ag nanocages, the UV-vis absorption peak of the Au/Ag composite nanocages is red-shifted. More importantly, the synergistical action of Au and Ag element endow the Au/Ag composite nanocages with ultra-high SERS sensitivity and reproducibility. The trace detection of R6G at an ultralow concentration of 5×10-14 mol/L can be attributed to the high electromagnetic field intensity generated by the surface plasmon resonance, which was certificated by the finite difference time domain (FDTD) simulation method. Besides, the addition of the Au element provided the Au/Ag composite nanocages with excellent oxidation resistance and chemical stability. The excellent SERS performance can be kept even after soaking in 1% H2O2 solution for 3 h. The octahedral Au/Ag composite nanocages are a promising SERS substrate with high sensitivity and stability.
Surface-enhanced Raman spectroscopy (SERS) technology, based on noble metal nanostructures as substrate, is a highly sensitive method for the detected substance. When the surface of noble metal with special nanostructure is irradiated by laser, the free electrons on the metal surface will be greatly oscillated. While the frequency of the incident light is close to that of the oscillation, the surface plasmon resonance (SPR) will occur around the noble metal nanostructures material, greatly enhancing the local electric field intensity of the metal surface. The intensity of incident light and the scattering light will be also multiplied. As a result, the Raman scattering signals of molecules adsorbed on the surface of noble metal nanostructures will be effectively enhanced. In this paper, the octahedral Au/Ag composite nanocages were prepared by using NaBH4 reduction-acid etching template method. The prepared octahedral Au/Ag composite nanocages are uniform in shape, with the size of about 600 nm, and there is no residual cuprous oxide template. The Au element is uniformly distributed on the Ag nanocages with the mass fraction about 16.8%. Compared with that of Ag nanocages, the UV-vis absorption peak of the Au/Ag composite nanocages is red-shifted. More importantly, the synergistical action of Au and Ag element endow the Au/Ag composite nanocages with ultra-high SERS sensitivity and reproducibility. The trace detection of R6G at an ultralow concentration of 5×10-14 mol/L can be attributed to the high electromagnetic field intensity generated by the surface plasmon resonance, which was certificated by the finite difference time domain (FDTD) simulation method. Besides, the addition of the Au element provided the Au/Ag composite nanocages with excellent oxidation resistance and chemical stability. The excellent SERS performance can be kept even after soaking in 1% H2O2 solution for 3 h. The octahedral Au/Ag composite nanocages are a promising SERS substrate with high sensitivity and stability.
2019, 77(2): 189-194
doi: 10.6023/A18090400
Abstract:
The elasticity of a single polymer chain has been widely investigated in last decades. However, the direct measurement of the single polymer elasticity in an unperturbed state (i.e. inherent elasticity) remains a challenge. The main obstacle in this regard is that most force measurements are carried out in a liquid environment. The single polymer elasticity may be strongly affected by the complex interactions between solvent molecules and polymer such as van der Waals (vdW) forces, hydrogen bonds and/or thermal motions. For instance, the single-chain elasticity of poly(ethylene glycol) (PEG) in water is different from that in nonpolar organic solvents, since hydrogen bonds can be formed between PEG and water molecules. In this study, the single-chain elasticity of PEG is investigated in high vacuum by means of atomic force microscopy (AFM)-based single-molecule force spectroscopy (SMFS). Solvent molecules and surface adsorbed water are removed thoroughly under high vacuum so that the situation is greatly simplified. PEG is dissolved in DI water to a concentration of 50 μg/mL, which is used for the polymer physisorption on a quartz substrate. Then, the sample is rinsed with abundant DI water to remove the loosely adsorbed polymer and dried by air flow. After that, the AFM chamber is pumped down to ca. 7.0×10-4 Pa to achieve high vacuum, where almost all adsorbed water molecules can be removed from the environment. The results show that PEG maintains its inherent elasticity in high vacuum, which can be well described by an elastic model of a single polymer chain (QM-FRC model) when F>100 pN. In a nonpolar organic solvent (nonane), since there are only vdW forces between solvent molecules and PEG, PEG presents an elasticity virtually identical to that in high vacuum. However, a slight difference can be observed in the low force region (F < 100 pN) in different environments. The long plateau (ca. 45 pN) observed in high vacuum can be attributed to the adsorption/desorption force (mainly vdW forces) of PEG on the substrate. It is greatly anticipated that the method used in the current study can be applied to investigate the inherent elasticity of other polymers in the future.
The elasticity of a single polymer chain has been widely investigated in last decades. However, the direct measurement of the single polymer elasticity in an unperturbed state (i.e. inherent elasticity) remains a challenge. The main obstacle in this regard is that most force measurements are carried out in a liquid environment. The single polymer elasticity may be strongly affected by the complex interactions between solvent molecules and polymer such as van der Waals (vdW) forces, hydrogen bonds and/or thermal motions. For instance, the single-chain elasticity of poly(ethylene glycol) (PEG) in water is different from that in nonpolar organic solvents, since hydrogen bonds can be formed between PEG and water molecules. In this study, the single-chain elasticity of PEG is investigated in high vacuum by means of atomic force microscopy (AFM)-based single-molecule force spectroscopy (SMFS). Solvent molecules and surface adsorbed water are removed thoroughly under high vacuum so that the situation is greatly simplified. PEG is dissolved in DI water to a concentration of 50 μg/mL, which is used for the polymer physisorption on a quartz substrate. Then, the sample is rinsed with abundant DI water to remove the loosely adsorbed polymer and dried by air flow. After that, the AFM chamber is pumped down to ca. 7.0×10-4 Pa to achieve high vacuum, where almost all adsorbed water molecules can be removed from the environment. The results show that PEG maintains its inherent elasticity in high vacuum, which can be well described by an elastic model of a single polymer chain (QM-FRC model) when F>100 pN. In a nonpolar organic solvent (nonane), since there are only vdW forces between solvent molecules and PEG, PEG presents an elasticity virtually identical to that in high vacuum. However, a slight difference can be observed in the low force region (F < 100 pN) in different environments. The long plateau (ca. 45 pN) observed in high vacuum can be attributed to the adsorption/desorption force (mainly vdW forces) of PEG on the substrate. It is greatly anticipated that the method used in the current study can be applied to investigate the inherent elasticity of other polymers in the future.
