Sensitizing molecular triplets by colloidal nanocrystals via triplet energy transfer is important for applications such as upconversion or organic synthesis.Typically two step triplet energy transfer(TET)are included ...Sensitizing molecular triplets by colloidal nanocrystals via triplet energy transfer is important for applications such as upconversion or organic synthesis.Typically two step triplet energy transfer(TET)are included in these applications:firstly the triplet energy stored in nanocrystals are extracted into surface ligands,and then the ligands further transfer triplet energy into molecules in bulk solution.Here we report one-step TET application from CsPbBr_(3)perovskite nanocrystals(NCs)to surface-anchored metalloporphyrin derivative molecules(MP).Compared to conventional two-step TET,the one-step TET mechanism possess lower energy loss and higher TET efficiency which is more generally implementable.In this scheme,photoexcitation of CsPbBr_(3)NCs leads to the sensitization of MP ligands triplets which efficiently emit phosphorescence.The enhanced light absorption of MP ligands and down-shifted photon emission can be useful in devices such as luminescent solar concentrators.展开更多
Pt nanoparticles entrapped in ordered mesoporous CMK-3 carbons with p6mm symmetry were prepared using a facile impregnation method, and the resulting materials were characterized using X-ray diffraction spectroscopy, ...Pt nanoparticles entrapped in ordered mesoporous CMK-3 carbons with p6mm symmetry were prepared using a facile impregnation method, and the resulting materials were characterized using X-ray diffraction spectroscopy, N2 adsorption-desorption, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The Pt nanoparticles were highly dispersed in the CMK-3 with 43.7% dispersion. The Pt/CMK-3 catalyst was an effective catalyst for the liquid-phase hydrogenation of nitrobenzene and its derivatives under the experimental conditions studied here. The Pt/CMK-3 catalyst was more active than commercial Pt/C catalyst in most cases. A highest turnover frequency of 43.8 s-1 was measured when the Pt/CMK-3 catalyst was applied for the hydrogenation of 2-methyl-nitrobenzene in ethanol under optimal conditions. It is worthy of note that the Pt/CMK-3 catalyst could be recycled easily, and could be reused at least fourteen times without any loss in activity or selectivity for the hydrogenation of nitrobenzene in ethanol.展开更多
Catalytic hydrodeoxygenation(HDO)is one of the most promising strategies to transform oxygen-rich biomass derivatives into high value-added chemicals and fuels,but highly challenging due to the lack of highly efficien...Catalytic hydrodeoxygenation(HDO)is one of the most promising strategies to transform oxygen-rich biomass derivatives into high value-added chemicals and fuels,but highly challenging due to the lack of highly efficient nonprecious metal catalysts.Herein,we report for the first time of a facile synthetic approach to controllably fabricate well-defined Ni-Co alloy NPs confined on the tip of N-CNTs as HDO catalyst.The resultant Ni-Co alloy catalyst possesses outstanding HDO performance towards biomass-derived vanillin into 2-methoxy-4-methylphenol in water with 100%conversion efficiency and selectivity under mild reaction conditions,surpassing the reported high performance nonprecious HDO catalysts.Impressively,our experimental results also unveil that the Ni-Co alloy catalyst can be generically applied to catalyze HDO of vanillin derivatives and other aromatic aldehydes in water with 100%conversion efficiency and over 90%selectivity.Importantly,our DFT calculations and experimental results confirm that the achieved outstanding HDO catalytic performance is due to the greatly promoted selective adsorption and activation of C=O,and desorption of the activated hydrogen species by the synergism of the alloyed Ni-Co NPs.The findings of this work affords a new strategy to design and develop efficient transition metal-based catalysts for HDO reactions in water.展开更多
An intermediate compound 2, 4-bis（laurylamino）-6-（1-（2-aminoethyl）-piperazine）-1, 3, 5-triazine was prepared by stepwise nucleophilic substitution on triazine ring by lauryl amine and subsequently 1-（2-aminoet...An intermediate compound 2, 4-bis（laurylamino）-6-（1-（2-aminoethyl）-piperazine）-1, 3, 5-triazine was prepared by stepwise nucleophilic substitution on triazine ring by lauryl amine and subsequently 1-（2-aminoethyl）-piperazine. Then imidization of perylene-3, 4, 9, 10-tetracarboxylic acid dianhydride with 2,4-bis（laurylamino）-6-（1-（2-aminoethyl）-piperazine）-1, 3, 5-triazine was carried out to afford a novel perylene derivative bearing two melamine blocks （S2） and 1, 6, 7, 12-tetra（4-tert-butyl phenoxy）-perylene-3, 4, 9, 10-tetracarboxylic acid bisimide （S1. The hydrogen-bonding interactions between S1 and S2 were investigated by IH NMR spectrum, UV/Vis spectrum and fluorescence spectrum. The influences on the morphologies of S1·S2 aggregates were investigated. The results show that well-defined nanofibers with a diameter of about 100 nm can be obtained by self-assembly between S1 and S2 only in CH2Cl2 solution. Based on these results, guidelines for the molecular design and self-assembly of supramolecular polymer materials are presented.展开更多
High-efficiency photocatalysts are of great importance to satisfy the requirements of green chemistry nowadays.Here we reported a novel solar-driven photocatalyst fabricated by a facile surface modification method,wit...High-efficiency photocatalysts are of great importance to satisfy the requirements of green chemistry nowadays.Here we reported a novel solar-driven photocatalyst fabricated by a facile surface modification method,with the two-dimensional carboxylated zinc phthalocyanine-carboxylated C60-titanium dioxide(Zn Pc-C3-Ti O2)nanosheets,in which the surface modifications of Zn Pc and C60derivative were designed to extend the absorption range and promote charge separation,respectively.Benefiting from the unique structure and positive synergetic effect,the Zn Pc-C3-Ti O2 nanocomposite shows promising applications in selective reduction of nitroarenes for high-value-added aromatic amines under solar light.Especially,for the photocatalytic reduction of nitrobenzene to aniline,the Zn Pc-C3-Ti O2 nanocomposite possesses both high efficiency and selectivity(up to 99%).展开更多
We demonstrate that the near-infrared （NIR） absorptivity of semiconducfing single-walled carbon nanotubes （s-SWCNTs） can be harnessed in blended heterojunctions with the fullerene derivative [6,6]-phenyl-C61-butyr...We demonstrate that the near-infrared （NIR） absorptivity of semiconducfing single-walled carbon nanotubes （s-SWCNTs） can be harnessed in blended heterojunctions with the fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester （PCBM）. Photogenerated charge separation is efficiently driven by the ultrahigh interracial area of the blends and the favorable energy offsets between the two materials. NIR-sensitive photovoltaic and photodetector devices utilizing the stack （indium tin oxide/ca. 10 nm s-SWCNT：PCBM/100 nm CJ10 nm 2,9- dimethyl-4,7-diphenyl-],10-phenanthroline （BCP）/Ag） were fabricated with NIR power conversion efficiencies 〉1.3% and peak, zero bias external quantum efficiency of 18% at λ = 1205 nm.展开更多
Understanding the mechanisms underlying the assembly of nucleobases is a great challenge. The ability to deeply understand how nucleobases interact with themselves as well as with other molecules will allow us to gain...Understanding the mechanisms underlying the assembly of nucleobases is a great challenge. The ability to deeply understand how nucleobases interact with themselves as well as with other molecules will allow us to gain valuable insights into how we might be able to harness these interesting biological molecules to construct complex nanostructures and materials. Uracil and thymine derivatives have been reported for use in biological applications and in self-assembling triple hydrogen bonded systems. Either uracil or thymine possesses three binding sites （Site 1, Site 2, and Site 3） that can induce strong directional N-H...O=C hydrogen bonding interaction. In this paper, theoretical calculations are carded out on the structural features and binding energies of hydrogen-bonded dimers and trimers formed by uracil and thymine bases. We find that the hydrogen bonds formed through Site 1 are the strongest, those formed through Site 3 are next, while those formed through Site 2 are the weakest. The atoms in molecules analysis show that the electron densities at the bond critical points and the corresponding Laplacians have greater values for those hydrogen bonds formed through Site 1 than through Site 2. All these results indicate that a uracil （or thymine） would interact with another uracil or thymine most likely through Site 1 and least likely through Site 2. We also find that a simple summation rule roughly exists for the binding energies in these dimers and trimers.展开更多
The magnetic transitions in graphene oxide （GO） have been investigated experimentally. Micron-sized GO flakes exhibit dominant diamagnetism accompanied by weak ferromagnetism at room temperature. However, when the l...The magnetic transitions in graphene oxide （GO） have been investigated experimentally. Micron-sized GO flakes exhibit dominant diamagnetism accompanied by weak ferromagnetism at room temperature. However, when the lateral dimensions of GO flakes are reduced from micron-size to nano-size, a clear transition from dominant diamagnetism to ferromagnetism is observed. After reducing the GO chemically or thermally, the dominant magnetic properties are not altered markedly except for the gradual enhancement of ferromagnetic components. In contrast, at 2 K, significant paramagnetism is present in both the micron-sized and nano-sized GO sheets. The effects of different functional groups on magnetic transitions in graphene derivatives have been further investigated using on hydroxyl-, carboxyl-, amino- and thiol- functionalized graphene. The results reveal that significant diamagnetism with weak ferromagnetism is present at room temperature in all of these functionalized graphene derivatives and the ability of different functional groups to introduce magnetic moments follows the order -SH 〉 --OH 〉 -COOH, -NH2. Notably, at 5 K, diamagnetism, paramagnetism and ferromagnetism coexist in thiol-, hydroxyl- and carboxyl-functionalized graphene, while amino-graphene exhibits dominant paramagnetism, analogous to the low-temperature magnetism in GO. These results indicate that diamagnetism, paramagnetism and ferromagnetism can coexist in graphene derivatives and magnetic transitions among the three states can be achieved which depend on edge states, vacancies, chemical doping and the attached functional groups. The results obtained may help settle the current controversy about the magnetism of graphene-related materials.展开更多
基金This work is supported by the National Natural Science Foundation of China(No.21803070).
文摘Sensitizing molecular triplets by colloidal nanocrystals via triplet energy transfer is important for applications such as upconversion or organic synthesis.Typically two step triplet energy transfer(TET)are included in these applications:firstly the triplet energy stored in nanocrystals are extracted into surface ligands,and then the ligands further transfer triplet energy into molecules in bulk solution.Here we report one-step TET application from CsPbBr_(3)perovskite nanocrystals(NCs)to surface-anchored metalloporphyrin derivative molecules(MP).Compared to conventional two-step TET,the one-step TET mechanism possess lower energy loss and higher TET efficiency which is more generally implementable.In this scheme,photoexcitation of CsPbBr_(3)NCs leads to the sensitization of MP ligands triplets which efficiently emit phosphorescence.The enhanced light absorption of MP ligands and down-shifted photon emission can be useful in devices such as luminescent solar concentrators.
基金supported by the National Natural Science Foundation of China(21273076 and 21373089)the Open Research Fund of Top Key Discipline of Chemistry in Zhejiang Provincial Colleges and Key Laboratory of the Ministry of Education for Catalysis Materials(Zhejiang Normal University,ZJHX2013)Shanghai Leading Academic Discipline Project (B409)~~
文摘Pt nanoparticles entrapped in ordered mesoporous CMK-3 carbons with p6mm symmetry were prepared using a facile impregnation method, and the resulting materials were characterized using X-ray diffraction spectroscopy, N2 adsorption-desorption, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The Pt nanoparticles were highly dispersed in the CMK-3 with 43.7% dispersion. The Pt/CMK-3 catalyst was an effective catalyst for the liquid-phase hydrogenation of nitrobenzene and its derivatives under the experimental conditions studied here. The Pt/CMK-3 catalyst was more active than commercial Pt/C catalyst in most cases. A highest turnover frequency of 43.8 s-1 was measured when the Pt/CMK-3 catalyst was applied for the hydrogenation of 2-methyl-nitrobenzene in ethanol under optimal conditions. It is worthy of note that the Pt/CMK-3 catalyst could be recycled easily, and could be reused at least fourteen times without any loss in activity or selectivity for the hydrogenation of nitrobenzene in ethanol.
文摘Catalytic hydrodeoxygenation(HDO)is one of the most promising strategies to transform oxygen-rich biomass derivatives into high value-added chemicals and fuels,but highly challenging due to the lack of highly efficient nonprecious metal catalysts.Herein,we report for the first time of a facile synthetic approach to controllably fabricate well-defined Ni-Co alloy NPs confined on the tip of N-CNTs as HDO catalyst.The resultant Ni-Co alloy catalyst possesses outstanding HDO performance towards biomass-derived vanillin into 2-methoxy-4-methylphenol in water with 100%conversion efficiency and selectivity under mild reaction conditions,surpassing the reported high performance nonprecious HDO catalysts.Impressively,our experimental results also unveil that the Ni-Co alloy catalyst can be generically applied to catalyze HDO of vanillin derivatives and other aromatic aldehydes in water with 100%conversion efficiency and over 90%selectivity.Importantly,our DFT calculations and experimental results confirm that the achieved outstanding HDO catalytic performance is due to the greatly promoted selective adsorption and activation of C=O,and desorption of the activated hydrogen species by the synergism of the alloyed Ni-Co NPs.The findings of this work affords a new strategy to design and develop efficient transition metal-based catalysts for HDO reactions in water.
基金Project(50573019)support by the National Natural Science Foundation of China
文摘An intermediate compound 2, 4-bis（laurylamino）-6-（1-（2-aminoethyl）-piperazine）-1, 3, 5-triazine was prepared by stepwise nucleophilic substitution on triazine ring by lauryl amine and subsequently 1-（2-aminoethyl）-piperazine. Then imidization of perylene-3, 4, 9, 10-tetracarboxylic acid dianhydride with 2,4-bis（laurylamino）-6-（1-（2-aminoethyl）-piperazine）-1, 3, 5-triazine was carried out to afford a novel perylene derivative bearing two melamine blocks （S2） and 1, 6, 7, 12-tetra（4-tert-butyl phenoxy）-perylene-3, 4, 9, 10-tetracarboxylic acid bisimide （S1. The hydrogen-bonding interactions between S1 and S2 were investigated by IH NMR spectrum, UV/Vis spectrum and fluorescence spectrum. The influences on the morphologies of S1·S2 aggregates were investigated. The results show that well-defined nanofibers with a diameter of about 100 nm can be obtained by self-assembly between S1 and S2 only in CH2Cl2 solution. Based on these results, guidelines for the molecular design and self-assembly of supramolecular polymer materials are presented.
基金supported by Beijing Natural Science Foundation(2182094)the National Natural Science Foundation of China(51772300 and 51832008)the Youth Innovation Promotion Association of CAS(2018039)。
文摘High-efficiency photocatalysts are of great importance to satisfy the requirements of green chemistry nowadays.Here we reported a novel solar-driven photocatalyst fabricated by a facile surface modification method,with the two-dimensional carboxylated zinc phthalocyanine-carboxylated C60-titanium dioxide(Zn Pc-C3-Ti O2)nanosheets,in which the surface modifications of Zn Pc and C60derivative were designed to extend the absorption range and promote charge separation,respectively.Benefiting from the unique structure and positive synergetic effect,the Zn Pc-C3-Ti O2 nanocomposite shows promising applications in selective reduction of nitroarenes for high-value-added aromatic amines under solar light.Especially,for the photocatalytic reduction of nitrobenzene to aniline,the Zn Pc-C3-Ti O2 nanocomposite possesses both high efficiency and selectivity(up to 99%).
基金Acknowledgements The authors acknowledge the assistance of Frederick C. Prehn in sample preparation. This work was supported by the National Science Foundation （Grant No. DMR- 0905861）.
文摘We demonstrate that the near-infrared （NIR） absorptivity of semiconducfing single-walled carbon nanotubes （s-SWCNTs） can be harnessed in blended heterojunctions with the fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester （PCBM）. Photogenerated charge separation is efficiently driven by the ultrahigh interracial area of the blends and the favorable energy offsets between the two materials. NIR-sensitive photovoltaic and photodetector devices utilizing the stack （indium tin oxide/ca. 10 nm s-SWCNT：PCBM/100 nm CJ10 nm 2,9- dimethyl-4,7-diphenyl-],10-phenanthroline （BCP）/Ag） were fabricated with NIR power conversion efficiencies 〉1.3% and peak, zero bias external quantum efficiency of 18% at λ = 1205 nm.
基金supported by the National Natural Science Foundation of China (20973088)the Educational Department of Liaoning Province (2007T091, 2008T106)
文摘Understanding the mechanisms underlying the assembly of nucleobases is a great challenge. The ability to deeply understand how nucleobases interact with themselves as well as with other molecules will allow us to gain valuable insights into how we might be able to harness these interesting biological molecules to construct complex nanostructures and materials. Uracil and thymine derivatives have been reported for use in biological applications and in self-assembling triple hydrogen bonded systems. Either uracil or thymine possesses three binding sites （Site 1, Site 2, and Site 3） that can induce strong directional N-H...O=C hydrogen bonding interaction. In this paper, theoretical calculations are carded out on the structural features and binding energies of hydrogen-bonded dimers and trimers formed by uracil and thymine bases. We find that the hydrogen bonds formed through Site 1 are the strongest, those formed through Site 3 are next, while those formed through Site 2 are the weakest. The atoms in molecules analysis show that the electron densities at the bond critical points and the corresponding Laplacians have greater values for those hydrogen bonds formed through Site 1 than through Site 2. All these results indicate that a uracil （or thymine） would interact with another uracil or thymine most likely through Site 1 and least likely through Site 2. We also find that a simple summation rule roughly exists for the binding energies in these dimers and trimers.
基金This work is supported by the National Natural Science Foundation of China （No. 51372133）, the Beijing Science and Technology Program （No. D141100000514001）, the National Program on Key Basic Research Projects （Nos. 2013CB934201, 2011CB013000）, and the Tsinghua University Initiative Scientific Research Program （No. 2012Z02102）.
文摘The magnetic transitions in graphene oxide （GO） have been investigated experimentally. Micron-sized GO flakes exhibit dominant diamagnetism accompanied by weak ferromagnetism at room temperature. However, when the lateral dimensions of GO flakes are reduced from micron-size to nano-size, a clear transition from dominant diamagnetism to ferromagnetism is observed. After reducing the GO chemically or thermally, the dominant magnetic properties are not altered markedly except for the gradual enhancement of ferromagnetic components. In contrast, at 2 K, significant paramagnetism is present in both the micron-sized and nano-sized GO sheets. The effects of different functional groups on magnetic transitions in graphene derivatives have been further investigated using on hydroxyl-, carboxyl-, amino- and thiol- functionalized graphene. The results reveal that significant diamagnetism with weak ferromagnetism is present at room temperature in all of these functionalized graphene derivatives and the ability of different functional groups to introduce magnetic moments follows the order -SH 〉 --OH 〉 -COOH, -NH2. Notably, at 5 K, diamagnetism, paramagnetism and ferromagnetism coexist in thiol-, hydroxyl- and carboxyl-functionalized graphene, while amino-graphene exhibits dominant paramagnetism, analogous to the low-temperature magnetism in GO. These results indicate that diamagnetism, paramagnetism and ferromagnetism can coexist in graphene derivatives and magnetic transitions among the three states can be achieved which depend on edge states, vacancies, chemical doping and the attached functional groups. The results obtained may help settle the current controversy about the magnetism of graphene-related materials.
