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2016 Volume 74 Issue 5
2016, 74(5): 385-391
doi: 10.6023/A16020105
Abstract:
New particle formation (NPF) and its subsequent growth plays a key role in air quality and climate change at regional and global scales. Especially under complex air pollution in China, nucleation and growth can be highly efficient, claimed to be a main source of cloud condensation nuclei (CCN) and an important cause of secondary aerosol pollution. Currently, the mechanism of particle formation and growth as well as its environmental effects are still poorly understood. Thereby, fully understanding of the atmospheric nucleation and subsequent growth still presents a big challenge to atmospheric chemistry researches. This study reviews the current results from studies on mechanisms and environmental effects of atmospheric nucleation and growth. We summarize that traditional nucleation theories such as binary nucleation of H2SO4-H2O, ternary nucleation of H2SO4-NH3-H2O, ion-induced nucleation are not capable in explaining new particle formation under complex air pollution, while newly proposed mechanisms such as organic acids and amine induced nucleation were not verified because of technique limitation. We propose that the future researches should focus on identifying the key chemical precursor response for driving nucleation and initial and subsequent growth, and understand the physical and chemical processing of new particle formation and growth. In particularly, application and development of novel techniques, such as APi-TOF-CIMS, PSM, Nano-HTDMA in new particle formation study is very important. Also, future researches should establish whole process tracking on new particle formation, from precursor, nucleation, growth till the environmental effects, by integrating field observation, chamber simulation, and modelling. Currently, the mechanism of highly efficient nucleation and rapid growth taking place under complex air pollution in China is urgently needed to be in-depth studied in order to improve our understanding of regional haze formation. This could be helpful to understand the similarity and difference in the nucleation mechanism between clean and polluted atmospheric environments.
New particle formation (NPF) and its subsequent growth plays a key role in air quality and climate change at regional and global scales. Especially under complex air pollution in China, nucleation and growth can be highly efficient, claimed to be a main source of cloud condensation nuclei (CCN) and an important cause of secondary aerosol pollution. Currently, the mechanism of particle formation and growth as well as its environmental effects are still poorly understood. Thereby, fully understanding of the atmospheric nucleation and subsequent growth still presents a big challenge to atmospheric chemistry researches. This study reviews the current results from studies on mechanisms and environmental effects of atmospheric nucleation and growth. We summarize that traditional nucleation theories such as binary nucleation of H2SO4-H2O, ternary nucleation of H2SO4-NH3-H2O, ion-induced nucleation are not capable in explaining new particle formation under complex air pollution, while newly proposed mechanisms such as organic acids and amine induced nucleation were not verified because of technique limitation. We propose that the future researches should focus on identifying the key chemical precursor response for driving nucleation and initial and subsequent growth, and understand the physical and chemical processing of new particle formation and growth. In particularly, application and development of novel techniques, such as APi-TOF-CIMS, PSM, Nano-HTDMA in new particle formation study is very important. Also, future researches should establish whole process tracking on new particle formation, from precursor, nucleation, growth till the environmental effects, by integrating field observation, chamber simulation, and modelling. Currently, the mechanism of highly efficient nucleation and rapid growth taking place under complex air pollution in China is urgently needed to be in-depth studied in order to improve our understanding of regional haze formation. This could be helpful to understand the similarity and difference in the nucleation mechanism between clean and polluted atmospheric environments.
2016, 74(5): 392-400
doi: 10.6023/A15110712
Abstract:
In recent years, molybdenum disulfide (MoS2), as a material that shows analogous structure to graphene, has attracted more and more attentions of scientists. Due to its layered structure, special electronic and electrochemical properties, large specific surface area and the potential of surface modification, nano-sized MoS2 is widely used in many fields. In this review, the authors introduce several preparation methods of nano-sized MoS2, mainly including micromechanical cleavage, liquid exfoliation, lithium intercalation, hydrothermal reaction, vapor deposition and thermal decomposition. All these methods possess their own advantages, but at present, there is no good ways to achieve the large-scale production of large-area MoS2 nanosheets with controllable layer number or MoS2 nano-architectures with controllable shape. Apart from the preparation methods, the authors mainly introduce the research progress on the application of nano-sized MoS2 in the fields of optoelectronic devices, catalysis, sensing, energy storage and conversion, and stress the research status of the application in the aspects of electrochemistry and biosensing analysis. In addition, the development direction of nano-sized MoS2 in the future is also been pointed out. According to the present researches, nano-sized MoS2 possesses enormous potential in the fields of energy storage and conversion, sensing analysis, and devices, etc., and it may become a kind of multi-functional material with excellent performance in the wake of graphene.
In recent years, molybdenum disulfide (MoS2), as a material that shows analogous structure to graphene, has attracted more and more attentions of scientists. Due to its layered structure, special electronic and electrochemical properties, large specific surface area and the potential of surface modification, nano-sized MoS2 is widely used in many fields. In this review, the authors introduce several preparation methods of nano-sized MoS2, mainly including micromechanical cleavage, liquid exfoliation, lithium intercalation, hydrothermal reaction, vapor deposition and thermal decomposition. All these methods possess their own advantages, but at present, there is no good ways to achieve the large-scale production of large-area MoS2 nanosheets with controllable layer number or MoS2 nano-architectures with controllable shape. Apart from the preparation methods, the authors mainly introduce the research progress on the application of nano-sized MoS2 in the fields of optoelectronic devices, catalysis, sensing, energy storage and conversion, and stress the research status of the application in the aspects of electrochemistry and biosensing analysis. In addition, the development direction of nano-sized MoS2 in the future is also been pointed out. According to the present researches, nano-sized MoS2 possesses enormous potential in the fields of energy storage and conversion, sensing analysis, and devices, etc., and it may become a kind of multi-functional material with excellent performance in the wake of graphene.
2016, 74(5): 401-409
doi: 10.6023/A16020096
Abstract:
Dendrimers are a novel polymer material, which have received more and more attention due to the functional groups on their surface, hydrophobic cavity and adjustable sizes. Thus, dendrimers have been widely used in many fields. Peptide dendrimer is a sort of dendritic polymer, which contains peptide bonds in the structure. Owing to the globular structure similar to the protein, excellent water solubility, biocompatibility, biodegradability and low toxicity, peptide dendrimer could be used as drug delivery carrier. In addition, hydrophobic cavity can be used to solubilize hydrophobic drugs, in which the drugs can be released slowly. The present review highlights the current status of synthesis of peptide dendrimers, and it also summarizes and forecasts the interaction mechanism between drug molecules and peptide dendrimers, and the application of peptide dendrimers in drug delivery system.
Dendrimers are a novel polymer material, which have received more and more attention due to the functional groups on their surface, hydrophobic cavity and adjustable sizes. Thus, dendrimers have been widely used in many fields. Peptide dendrimer is a sort of dendritic polymer, which contains peptide bonds in the structure. Owing to the globular structure similar to the protein, excellent water solubility, biocompatibility, biodegradability and low toxicity, peptide dendrimer could be used as drug delivery carrier. In addition, hydrophobic cavity can be used to solubilize hydrophobic drugs, in which the drugs can be released slowly. The present review highlights the current status of synthesis of peptide dendrimers, and it also summarizes and forecasts the interaction mechanism between drug molecules and peptide dendrimers, and the application of peptide dendrimers in drug delivery system.
2016, 74(5): 410-414
doi: 10.6023/A16020102
Abstract:
The first asymmetric total synthesis of (+)-alsmaphorazine D has been achieved through a traceless chirality transfer strategy, which also enabled absolute configuration reassignment of the natural product. Key steps of this efficient approach entail a catalytic oxidative cyclization [To a solution of indoline ester 8 (5.82 g, 10 mmol) in AcOH (100 mL) were added CAN (550 mg, 1 mmol) and NaOAc (1.64 g, 20 mmol). The reaction vessel was exposed to air through a CaCl2 tube. The resulting mixture was stirred at 110 ℃ for 12 h before it was concentrated in vacuo. The residue was diluted with H2O, neutralized with NaHCO3 (sat. aq.) and extracted with EtOAc. The combined organic layers were washed with brine, dried (Na2SO4) and concentrated in vacuo. Flash column chromatography (silica gel, hexanes/EtOAc, V:V=4:1) afforded δ-lactamindole 7 (4.34 g, 75%) as a white amorphous solid], a diastereoselective oxidative cyclic aminal formation [To a stirred solution of mono-ester 13 (5.20 g, 10 mmol, dr=1:1) in acetone (100 mL) at 0 ℃ was added NaHCO3 (100 mL, sat. aq.). The resulting mixture was stirred for 0.5 h before it was added oxone (12.28 g, 20 mmol) slowly. The reaction mixture was stirred at 0 ℃ for an additional 2 h before it was diluted with H2O. The aqueous layer was extracted with CH2Cl2. The combined organic layers were washed with brine, dried (Na2SO4) and concentrated in vacuo. Flash column chromatography (silica gel, hexanes/EtOAc, V:V=3:1) afforded pyrroloindole 6' (1.61 g, 71%) as a white amorphous solid] and an intramolecular radical cyclization [To a stirred solution of ent-5 (250 mg, 0.47 mmol) in benzene (5 mL) at 80 ℃ were added n-Bu3SnH (152 μL, 0.56 mmol) and AIBN (5 μL, 0.047 mmol). The resulting mixture was stirred for 0.5 h before it was concentrated in vacuo. Flash column chromatography (silica gel, hexanes/EtOAc, V:V=１:1) afforded C(16)-epi-ent-4 (213 mg, 72%) as a colorless oil.].
The first asymmetric total synthesis of (+)-alsmaphorazine D has been achieved through a traceless chirality transfer strategy, which also enabled absolute configuration reassignment of the natural product. Key steps of this efficient approach entail a catalytic oxidative cyclization [To a solution of indoline ester 8 (5.82 g, 10 mmol) in AcOH (100 mL) were added CAN (550 mg, 1 mmol) and NaOAc (1.64 g, 20 mmol). The reaction vessel was exposed to air through a CaCl2 tube. The resulting mixture was stirred at 110 ℃ for 12 h before it was concentrated in vacuo. The residue was diluted with H2O, neutralized with NaHCO3 (sat. aq.) and extracted with EtOAc. The combined organic layers were washed with brine, dried (Na2SO4) and concentrated in vacuo. Flash column chromatography (silica gel, hexanes/EtOAc, V:V=4:1) afforded δ-lactamindole 7 (4.34 g, 75%) as a white amorphous solid], a diastereoselective oxidative cyclic aminal formation [To a stirred solution of mono-ester 13 (5.20 g, 10 mmol, dr=1:1) in acetone (100 mL) at 0 ℃ was added NaHCO3 (100 mL, sat. aq.). The resulting mixture was stirred for 0.5 h before it was added oxone (12.28 g, 20 mmol) slowly. The reaction mixture was stirred at 0 ℃ for an additional 2 h before it was diluted with H2O. The aqueous layer was extracted with CH2Cl2. The combined organic layers were washed with brine, dried (Na2SO4) and concentrated in vacuo. Flash column chromatography (silica gel, hexanes/EtOAc, V:V=3:1) afforded pyrroloindole 6' (1.61 g, 71%) as a white amorphous solid] and an intramolecular radical cyclization [To a stirred solution of ent-5 (250 mg, 0.47 mmol) in benzene (5 mL) at 80 ℃ were added n-Bu3SnH (152 μL, 0.56 mmol) and AIBN (5 μL, 0.047 mmol). The resulting mixture was stirred for 0.5 h before it was concentrated in vacuo. Flash column chromatography (silica gel, hexanes/EtOAc, V:V=１:1) afforded C(16)-epi-ent-4 (213 mg, 72%) as a colorless oil.].
2016, 74(5): 415-421
doi: 10.6023/A16020076
Abstract:
Herein we reported the synthesis, self-assembly and light-responsive disassembly of a "linear-hyperbranched" supramolecular polymer. Firstly, a hyperbranched polymer CD-g-HPG composed of hyperbranched polyglycerol with a β-cyclodextrin group in the center was synthesized by ring-opening multibranching polymerization (ROMBP). Secondly, a linear polymer AZO-PS composed of polystyrene with an azobenzene group at the end was synthesized via atom transfer radical polymerization (ATRP). Then, the linear AZO-PS and hyperbranched CD-g-HPG were conjugated together through the specific CD/AZO host-guest interactions, leading to the formation of the "linear-hyperbranched" supramolecular polymer PS-b-HPG. This supramolecular polymer was amphiphilic and could self-assemble into vesicles in water. The host-guest complexation ability was characterized by UV-Vis titration. In the case of keeping the concentration of AZO-PSs unchanged, the absorption peak at 330 nm increased gradually with the addition of CD-g-HPGs, which supported the occurrence of complexation between β-CD groups in CD-g-HPGs and AZO groups in AZO-PSs. The host-guest CD/AZO complexation constant of 4.14×104 M-1 was calculated by the Benesi-Hildebrand plot. A Job plot was generated, from which it was determined that the binding stoichiometry between AZO-PS and CD-g-HPG is 1:1. The self-assemblies of the amphiphlic linear-hyperbranched supramolecular polymers were characterized by SEM and TEM. The SEM images showed that the self-assemblies were spherical particles, and the holes directly be seen in some particles indicated that they were vesicles or hollow spheres with a very thin wall thickness. The TEM images of self-assemblies stained with ruthenium tetroxide (RuO4) indicated that the spherical particles were vesicles according to a clear contrast difference between the inner pool and the outer thin wall. At last, we showed that the vesicles could disassemble under UV light due to the trans-to-cis isomerisation of the AZO groups. With the continuous UV irradiation on vesicles, the absorption peak of trans-AZO diminished gradually and almost completely disappeared after 900 seconds. Meanwhile, the solution was transformed from turbid to transparent followed with the appearance of yellow precipitates in the bottom of the bottle.
Herein we reported the synthesis, self-assembly and light-responsive disassembly of a "linear-hyperbranched" supramolecular polymer. Firstly, a hyperbranched polymer CD-g-HPG composed of hyperbranched polyglycerol with a β-cyclodextrin group in the center was synthesized by ring-opening multibranching polymerization (ROMBP). Secondly, a linear polymer AZO-PS composed of polystyrene with an azobenzene group at the end was synthesized via atom transfer radical polymerization (ATRP). Then, the linear AZO-PS and hyperbranched CD-g-HPG were conjugated together through the specific CD/AZO host-guest interactions, leading to the formation of the "linear-hyperbranched" supramolecular polymer PS-b-HPG. This supramolecular polymer was amphiphilic and could self-assemble into vesicles in water. The host-guest complexation ability was characterized by UV-Vis titration. In the case of keeping the concentration of AZO-PSs unchanged, the absorption peak at 330 nm increased gradually with the addition of CD-g-HPGs, which supported the occurrence of complexation between β-CD groups in CD-g-HPGs and AZO groups in AZO-PSs. The host-guest CD/AZO complexation constant of 4.14×104 M-1 was calculated by the Benesi-Hildebrand plot. A Job plot was generated, from which it was determined that the binding stoichiometry between AZO-PS and CD-g-HPG is 1:1. The self-assemblies of the amphiphlic linear-hyperbranched supramolecular polymers were characterized by SEM and TEM. The SEM images showed that the self-assemblies were spherical particles, and the holes directly be seen in some particles indicated that they were vesicles or hollow spheres with a very thin wall thickness. The TEM images of self-assemblies stained with ruthenium tetroxide (RuO4) indicated that the spherical particles were vesicles according to a clear contrast difference between the inner pool and the outer thin wall. At last, we showed that the vesicles could disassemble under UV light due to the trans-to-cis isomerisation of the AZO groups. With the continuous UV irradiation on vesicles, the absorption peak of trans-AZO diminished gradually and almost completely disappeared after 900 seconds. Meanwhile, the solution was transformed from turbid to transparent followed with the appearance of yellow precipitates in the bottom of the bottle.
2016, 74(5): 422-428
doi: 10.6023/A15110736
Abstract:
With the development and widespread use of transition metal catalysts, C—H activation has become a hot topic in organic synthesis, especially in the construction of C—C bond of organic compounds. As an important and cheap catalyst, manganese complex has shown great potential for catalyzing C—H activation both in academic and industrial applications. In this paper, the mechanism of manganese-catalyzed dehydrogenative [4+2] annulation by C—H/N—H activation was investigated systematically with the aid of density functional theory (DFT) calculations in 1, 4-dioxane solvent. In detail, we use M06-L/[SDD:6-311+G(d, p)(SMD)]//M06-L/[LANL2DZ:6-31G(d)] to examine the Gibbs free energy, structure and other properties of possible intermediates and transition states in this catalytic cycle. By comprehensive comparison and discussion, we obtained a favorable pathway consisting of five steps: (1) catalyst initiation occurred with the assistance of bromine anion rather than imide to form active catalyst; (2) alkyne inserted into the active catalyst to generate a seven-membered manganacycle after dissociation of a carbon monoxide; (3) double bond migration happened in this seven-membered manganacycle to form a product precursor; (4) the product precursor would dissociate by β-H elimination and generated product isoquinoline and active Mn—H complex; (5) the active Mn—H complex was subsequently combined with an imine followed by dehydrogenative C—H activation to complete the whole catalytic cycle. In this context, the reason for the highly atom-economical C—H activation by direct dehydrogenation (eliminates the necessity for oxidants or additives) has been clarified by this mechanism. The present study was aimed at further understanding of Mn(I)-catalyzed dehydrogenative C—H activation, and provided more theoretical basis for future more Mn-catalyzed C—H activation.
With the development and widespread use of transition metal catalysts, C—H activation has become a hot topic in organic synthesis, especially in the construction of C—C bond of organic compounds. As an important and cheap catalyst, manganese complex has shown great potential for catalyzing C—H activation both in academic and industrial applications. In this paper, the mechanism of manganese-catalyzed dehydrogenative [4+2] annulation by C—H/N—H activation was investigated systematically with the aid of density functional theory (DFT) calculations in 1, 4-dioxane solvent. In detail, we use M06-L/[SDD:6-311+G(d, p)(SMD)]//M06-L/[LANL2DZ:6-31G(d)] to examine the Gibbs free energy, structure and other properties of possible intermediates and transition states in this catalytic cycle. By comprehensive comparison and discussion, we obtained a favorable pathway consisting of five steps: (1) catalyst initiation occurred with the assistance of bromine anion rather than imide to form active catalyst; (2) alkyne inserted into the active catalyst to generate a seven-membered manganacycle after dissociation of a carbon monoxide; (3) double bond migration happened in this seven-membered manganacycle to form a product precursor; (4) the product precursor would dissociate by β-H elimination and generated product isoquinoline and active Mn—H complex; (5) the active Mn—H complex was subsequently combined with an imine followed by dehydrogenative C—H activation to complete the whole catalytic cycle. In this context, the reason for the highly atom-economical C—H activation by direct dehydrogenation (eliminates the necessity for oxidants or additives) has been clarified by this mechanism. The present study was aimed at further understanding of Mn(I)-catalyzed dehydrogenative C—H activation, and provided more theoretical basis for future more Mn-catalyzed C—H activation.
2016, 74(5): 429-434
doi: 10.6023/A15120789
Abstract:
In order to enhance the field effect mobility of poly(3-dodecylthiophene), Si nanowires were added to the poly(3-dodecylthiophene) solution prior to film formation. The Si nanowires were produced by the electroless metal deposition method which involved the etching of silicon wafers in aqueous hydrofluoric acid and silver nitrate solution. The observation of scanning electron microscopy proved the uniform Si nanowires were obtained. The blend film was treated with thermal annealing to form ordered microcrystalline structure by self-organization. The annealing effect was measured by X-ray diffraction and atomic force microscopy which showed the enhancing diffraction peak and ordered atomic force microscopy images after annealing films. In the bottom gated field effect transistors, the blend film of Si nanowires and poly(3-dodecylthiophene) were formed on the SiO2/Si substrate by spin coating. The surface of the SiO2/Si substrate was coated with hexamethyldisilazane to produce a hydrophobic surface. The thickness of the Au source/drain electrodes was 100 nm. The annealing blend films worked as the semiconducting layer, 300 nm SiO2 worked as the gate dielectric and Si worked as the gate electrode. The charge carrier mobility of poly(3-dodecylthiophene) thin films was 0.015 cm2·V-1·s-1 and the charge carrier mobility of blend films was up to 0.68 cm2·V-1·s-1. The remarkable increase in the field effect mobility over that of pristine poly(3-dodecylthiophene) film is due to the high conductivity of Si nanowires which act as fast conducting channel between the crystalline regions of the poly(3-dodecylthiophene) film. To confirm and enhance the field effect transistors properties, we used the electric-double-layer transistor based on the blend films in which ion gel worked as the gate dielectric instead of SiO2. Here, Au foil worked as the gate electrode to form a top-gated field effect transistors. The charge carrier mobility of blend films was found to be relatively higher (6.2 cm2·V-1·s-1) when using ion gel as the dielectric layer.
In order to enhance the field effect mobility of poly(3-dodecylthiophene), Si nanowires were added to the poly(3-dodecylthiophene) solution prior to film formation. The Si nanowires were produced by the electroless metal deposition method which involved the etching of silicon wafers in aqueous hydrofluoric acid and silver nitrate solution. The observation of scanning electron microscopy proved the uniform Si nanowires were obtained. The blend film was treated with thermal annealing to form ordered microcrystalline structure by self-organization. The annealing effect was measured by X-ray diffraction and atomic force microscopy which showed the enhancing diffraction peak and ordered atomic force microscopy images after annealing films. In the bottom gated field effect transistors, the blend film of Si nanowires and poly(3-dodecylthiophene) were formed on the SiO2/Si substrate by spin coating. The surface of the SiO2/Si substrate was coated with hexamethyldisilazane to produce a hydrophobic surface. The thickness of the Au source/drain electrodes was 100 nm. The annealing blend films worked as the semiconducting layer, 300 nm SiO2 worked as the gate dielectric and Si worked as the gate electrode. The charge carrier mobility of poly(3-dodecylthiophene) thin films was 0.015 cm2·V-1·s-1 and the charge carrier mobility of blend films was up to 0.68 cm2·V-1·s-1. The remarkable increase in the field effect mobility over that of pristine poly(3-dodecylthiophene) film is due to the high conductivity of Si nanowires which act as fast conducting channel between the crystalline regions of the poly(3-dodecylthiophene) film. To confirm and enhance the field effect transistors properties, we used the electric-double-layer transistor based on the blend films in which ion gel worked as the gate dielectric instead of SiO2. Here, Au foil worked as the gate electrode to form a top-gated field effect transistors. The charge carrier mobility of blend films was found to be relatively higher (6.2 cm2·V-1·s-1) when using ion gel as the dielectric layer.
2016, 74(5): 435-440
doi: 10.6023/A16010073
Abstract:
In the present study, based on spectral overlap between 1, 8-naphthalimide and N-acrylyl-N'-rhodamine B acylhydrazine thiourea (RhBHA), reversible "on-off" ring reaction of RhBHA at various pH values, and thermosensitive property of poly(N-isopropyl acrylamide) (PNIPAM), a novel linear polymer P(NIPAM-co-RhBHA)-NP was prepared via a series of chemical reactions. Firstly, 4-(2-aminoethyl)amino-N-aminopropane-1, 8-naphthalimide (NP-NH2) and RhBHA were prepared respectively, and they were used as the donor and acceptor to construct a fluorescence resonance energy transfer (FRET) system. Secondly, incorporating RhBHA into PNIPAM by reversible addition-fragmentation chain transfer polymerization (RAFT), P(NIPAM-co-RhBHA) was synthesized. Finally, P(NIPAM-co-RhBHA)-NP was fabricated by amide condensation between NP-NH2 and the as-prepared P(NIPAM-co-RhBHA). The structure of P(NIPAM-co-RhBHA)-NP was characterized via 1H NMR, FTIR, UV-vis and GPC. The fluorescence responsive behavior of the polymer to environmental temperature and pH value was investigated by photoluminescence (PL) in buffer solutions, and the mechanism was discussed in detail. The results indicate that, in an acidic solution, energy can be transferred from NP-NH2 moieties to RhBHA moieties via FRET mechanism, either pH values or environmental temperatures play important roles to affect the fluorescence emission of P(NIPAM-co-RhBHA)-NP.
In the present study, based on spectral overlap between 1, 8-naphthalimide and N-acrylyl-N'-rhodamine B acylhydrazine thiourea (RhBHA), reversible "on-off" ring reaction of RhBHA at various pH values, and thermosensitive property of poly(N-isopropyl acrylamide) (PNIPAM), a novel linear polymer P(NIPAM-co-RhBHA)-NP was prepared via a series of chemical reactions. Firstly, 4-(2-aminoethyl)amino-N-aminopropane-1, 8-naphthalimide (NP-NH2) and RhBHA were prepared respectively, and they were used as the donor and acceptor to construct a fluorescence resonance energy transfer (FRET) system. Secondly, incorporating RhBHA into PNIPAM by reversible addition-fragmentation chain transfer polymerization (RAFT), P(NIPAM-co-RhBHA) was synthesized. Finally, P(NIPAM-co-RhBHA)-NP was fabricated by amide condensation between NP-NH2 and the as-prepared P(NIPAM-co-RhBHA). The structure of P(NIPAM-co-RhBHA)-NP was characterized via 1H NMR, FTIR, UV-vis and GPC. The fluorescence responsive behavior of the polymer to environmental temperature and pH value was investigated by photoluminescence (PL) in buffer solutions, and the mechanism was discussed in detail. The results indicate that, in an acidic solution, energy can be transferred from NP-NH2 moieties to RhBHA moieties via FRET mechanism, either pH values or environmental temperatures play important roles to affect the fluorescence emission of P(NIPAM-co-RhBHA)-NP.
2016, 74(5): 441-449
doi: 10.6023/A16010036
Abstract:
Molybdenum oxide (MoO3)/dodecylamine (DDA) intercalated materials were synthesized via direct thermal treatment followed by calcination to give MoO3/C-N hybrid materials. These prepared intercalated materials were characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy to investigate the influences of the calcination conditions, such as calcination temperature, calcination heating rate and calcination time, on the structure and composition of these materials. The results exhibited the order-disorder-order changes of the crystal structure during the calcination temperature from 400 ℃ to 800 ℃. Meanwhile, the valence of some Mo was reduced from +6 to +4 or +2. XRD patterns showed that calcination heating rate had almost no effect on the composite structure. Crystal MoO2 was produced with the increase of calcination time at 600 ℃ in N2 atmosphere. Crystal Mo2C was formed and the crystalline became regular with the increase of calcination temperature when the calcination temperature was higher than 600 ℃. SEM and TEM images clearly showed that molybdenum oxide layers were kept with the reducing of interlayer spacing as the calcination temperature below 600 ℃. With the calcination temperature rising up to 800 ℃, the carbonization effect of carbonaceous molecules and the enormous loss of gas molecules made the layer structure collapsed. In addition, the carbon and nitrogen elements were detected on the surface of molybdenum oxide. MoO3/C-N hybrid materials were used as catalyst for the oxidation of benzyl alcohol. The results showed that the structure and composition of the materials have a certain effect on the catalytic yield and the selectivity. The MoO3/C-N hybrid materials formed at calcination of 600 ℃ in 2 h was found to catalyze benzyl alcohol to benzaldehyde efficiently with high selectivity and relative stability. The yield of oxidation of benzyl alcohol to benzaldehyde in 3 h was up to 30% with a high selectivity retention, which was nearly 4 times compared with that of the pristine MoO3. The MoO3/C-N hybrid materials used as catalyst can be recycled several times with high selectivity.
Molybdenum oxide (MoO3)/dodecylamine (DDA) intercalated materials were synthesized via direct thermal treatment followed by calcination to give MoO3/C-N hybrid materials. These prepared intercalated materials were characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy to investigate the influences of the calcination conditions, such as calcination temperature, calcination heating rate and calcination time, on the structure and composition of these materials. The results exhibited the order-disorder-order changes of the crystal structure during the calcination temperature from 400 ℃ to 800 ℃. Meanwhile, the valence of some Mo was reduced from +6 to +4 or +2. XRD patterns showed that calcination heating rate had almost no effect on the composite structure. Crystal MoO2 was produced with the increase of calcination time at 600 ℃ in N2 atmosphere. Crystal Mo2C was formed and the crystalline became regular with the increase of calcination temperature when the calcination temperature was higher than 600 ℃. SEM and TEM images clearly showed that molybdenum oxide layers were kept with the reducing of interlayer spacing as the calcination temperature below 600 ℃. With the calcination temperature rising up to 800 ℃, the carbonization effect of carbonaceous molecules and the enormous loss of gas molecules made the layer structure collapsed. In addition, the carbon and nitrogen elements were detected on the surface of molybdenum oxide. MoO3/C-N hybrid materials were used as catalyst for the oxidation of benzyl alcohol. The results showed that the structure and composition of the materials have a certain effect on the catalytic yield and the selectivity. The MoO3/C-N hybrid materials formed at calcination of 600 ℃ in 2 h was found to catalyze benzyl alcohol to benzaldehyde efficiently with high selectivity and relative stability. The yield of oxidation of benzyl alcohol to benzaldehyde in 3 h was up to 30% with a high selectivity retention, which was nearly 4 times compared with that of the pristine MoO3. The MoO3/C-N hybrid materials used as catalyst can be recycled several times with high selectivity.
