We report a colloidal process to coat a layer of TiO2onto SiO2composite nanofibers containing embedded CdS and upconversion nanoparticles(UCNPs).The SiO2composite nanofibers were fabricated by electrospinning.To impro...We report a colloidal process to coat a layer of TiO2onto SiO2composite nanofibers containing embedded CdS and upconversion nanoparticles(UCNPs).The SiO2composite nanofibers were fabricated by electrospinning.To improve the energy transfer efficiency,UCNPs and CdS nanoparticles were bound in close proximity to each other within the SiO2matrix.β‐NaYF4:Yb(30%),Tm(0.5%)@NaYF4:Yb(20%),Er(2%)core–shell nanoparticles were used as nanotransducers for near infrared light.These nanoparticles exhibited enhanced upconversion fluorescence compared withβ‐NaYF4:Yb(30%),Tm(0.5%)orβ–NaYF4:Yb(30%),Tm(0.5%)@NaYF4nanoparticles.The morphologies,size and chemical compositions have been extensively investigated using field emission scanning electron microscopy(FESEM),transmission electron microscopy(TEM),X‐ray diffraction(XRD)and X‐ray photoelectron spectra(XPS),respectively.The TEM images showed that the TiO2composite nanotubes were embedded with a large amount of UCNPs and CdS nanoparticles.The composite TiO2nanotubes degraded more than90%of rhodamine B(RhB)dye during20min of irradiation by simulated solar light.In particular,more than50%of RhB was decomposed in70min,under irradiation of near infrared light(NIR).This high degradation was attributed to the full spectrum absorption of solar light,and the enhanced transfer efficiency for near infrared light.The as‐prepared nanostructures can harness solar energy,and provide an alternative to overcome energy shortages and environmental protection.展开更多
A DNA fluorescence probe system based on fluorescence resonance energy transfer (FRET) from CdTe quantum dot (QD) donors to Au nanoparticle (AuNP) acceptors is presented. CdTe QDs, 2.5nm in diameter, as energy d...A DNA fluorescence probe system based on fluorescence resonance energy transfer (FRET) from CdTe quantum dot (QD) donors to Au nanoparticle (AuNP) acceptors is presented. CdTe QDs, 2.5nm in diameter, as energy donors, were prepared in water. Au nanoparticles, 16nm in diameter, as energy acceptors, were prepared from gold chloride by reduction. CdTe QDs were linked to 5'-NH2-DNA through 1-ethyl-3-(dimethylaminopropyl)car- bodiimide hydrochloride (EDC) as a linker, and the 3'-SH-DNA was self-assembled onto the surface of AuNPs. The hybridization of complementary double stranded DNA (dsDNA) bound to the QDs and AuNPs (CdTe-dsDNA-Au) determined the FRET distance of CdTe QDs and Au nanoparticles. Compared to the fluorescence of CdTe-DNA, the fluorescence of CdTe-DNA-Au conjugates decreased extremely, which indicated that the FRET occurred between CdTe QDs and Au nanoparticles. The fluorescence change of this conjugate depended on the ratio of Au-DNA to CdTe-DNA. When the AuNPs-DNA to QD-DNA ratio was 10:1, the FRET efficiency reached a maximum. The probe system would have a certain degree of fluorescence recovery when a complementary single stranded DNA was introduced into this system, which showed that the distance between CdTe QDs and Au nanoparticles was increased.展开更多
Carbon deposition is sensitive to the metal particle sizes of supported Ni catalysts in CH_4/CO_2 reforming.To explore the reason of this phenomenon,Ni4,Ni8,and Ni12 which re flect the different cluster thicknesses su...Carbon deposition is sensitive to the metal particle sizes of supported Ni catalysts in CH_4/CO_2 reforming.To explore the reason of this phenomenon,Ni4,Ni8,and Ni12 which re flect the different cluster thicknesses supported on the MgO(100) slabs,have been employed to simulate Ni/MgO catalysts,and the reaction pathways of CH_4/CO_2 reforming on Nix/MgO(100) models are investigated by density functional theory.The reforming mechanisms of CH_4/CO_2 on different Nix/MgO(100) indicate the energy barriers of CH_4 dissociated adsorption,CH dissociation,and C oxidation three factors are all declining with the decrease of the Ni cluster sizes.The Hirshfeld charges analyses of three steps as described above show only Ni atoms in bottom two layers can obtain electrons from the MgO supporters,and the main electron transfer occurs between adsorbed species and their directly contacted Ni atoms.Due to more electron-rich Ni atoms in contact with the MgO supporters,the Ni/MgO catalysts with small Ni particles have a strong metal particle size effect and lead to its better catalytic activity.展开更多
Photocatalytic reduction of CO2 into various types of fuels has attracted great interest,and serves as a potential solution to addressing current global warming and energy challenges.In this work,Ag-Cu nanoparticles a...Photocatalytic reduction of CO2 into various types of fuels has attracted great interest,and serves as a potential solution to addressing current global warming and energy challenges.In this work,Ag-Cu nanoparticles are densely supported on N-doped TiO2 nanowire through a straightforward nanofabrication approach.The range of light absorption by N-doped TiO2 can be tuned to match the plasmonic band of Ag nanoparticles,which allows synergizing a resonant energy transfer process with the Schottky junction.Meanwhile,Cu nanoparticles can provide active sites for the reduction of CO2 molecules.Remarkably,the performance of photocatalytic CO2 reduction is improved to produce CH4 at a rate of 720μmol·g-1·h-1 under full-spectrum irradiation.展开更多
A fully grouted bolt provides greater shear load capacity for transmitting the load from the rock to the bolt, and vice versa. When grout fills irregularities between the bolt and the rock, a keying effect is created ...A fully grouted bolt provides greater shear load capacity for transmitting the load from the rock to the bolt, and vice versa. When grout fills irregularities between the bolt and the rock, a keying effect is created to transfer the load to the bolt via shear resistance at the interface and within the grout. Previous research has revealed that the mechanical properties of the grout had a great impact on the load transfer capacity of the rock bolting system. This paper presents a method to enhance the rock bolting strength by introducing metal granules into the grouting material. Experimental results suggest that both the average peak load of pullout tests and the total energy absorption of the system will increase if some metal granules are mixed into the resin.展开更多
Metal nanoparticle catalysts, especially gold and its bimetallic nanoparticle catalysts, have been widely used in organic transformations as powerful and green catalysts. The concept of employing two distinct catalyst...Metal nanoparticle catalysts, especially gold and its bimetallic nanoparticle catalysts, have been widely used in organic transformations as powerful and green catalysts. The concept of employing two distinct catalysts in one reaction system, such as in cooperative and synergistic catalysis, is a powerful strategy in homogeneous catalysis. However, the adaption of such a strategy to metal nanoparticle catalysis is still under development. Recently, we have found that cooperative catalytic systems of gold/palladium bimetallic nanoparticles and Lewis acid can be used for the N‐alkylation of primary amides through hydrogen autotransfer reaction between amide and alcohol. Herein, the results of a detailed investigation into the effects of Lewis acids on this hydrogen autotransfer reac‐tion are reported. It was found that the choice of Lewis acid affected not only the reaction pathway leading to the desired product, but also other reaction pathways that produced several intermedi‐ates and by‐products. Weak Lewis acids, such as alkaline‐earth metal triflates, were found to be optimal for the desired N‐alkylation of amides.展开更多
A high-speed digital camera is used to record the saltation of three sand samples(diameter range:300–500,200–300 and100–125μm).This is followed by an overlapping particle tracking algorithm to reconstruct the salt...A high-speed digital camera is used to record the saltation of three sand samples(diameter range:300–500,200–300 and100–125μm).This is followed by an overlapping particle tracking algorithm to reconstruct the saltating trajectory and the differential scheme to abstract the kinetic parameters of saltating grains.The velocity results confirm the propagating feature of saltation in maintaining near-face aeolian sand transport.Moreover,the acceleration of saltating sand grains was obtained directly from the reconstructed trajectory,and the results reveal that the climbing stage of the saltating trajectory represents an critical process of energy transfer while the sand grains travel through air.展开更多
A general stepwise strategy for the preparation of new humidity-responsive plasmonic nanosensor was described for the first time, based on Ag film functionalization by polyacrylamide(PAAM) brushes via surface-initia...A general stepwise strategy for the preparation of new humidity-responsive plasmonic nanosensor was described for the first time, based on Ag film functionalization by polyacrylamide(PAAM) brushes via surface-initiated atom transfer radical polymerization(SI-ATRP) method and then assembled with gold nanoparticles(Au NPs). We designed by this way a new plasmonic device made of Au NPs embedded in a humid vapor responsive polymer layer on Ag film and extensively characterized by surface-enhanced Raman scattering(SERS). When the relative humidity(RH) is above 50%, the number of plasmonic hotspots decreases, causing SERS signal reduced noticeably, for the volume expansion of PAAM brushes varied the nano-gap between closely spaced Au NPs, and between Au NPs and Ag film. The reversible optical properties of the prepared nanocomposite tuned by RH were probed through SERS using 4-mercaptopyridine(4-Mpy) as a molecular probe, and the decrease of the RH reversibly induces a significant enhancement of the 4-Mpy SERS signal. By means of the high reversibility, the RH responsive nanocomposite developed in this paper provides a dynamic SERS platform and can be applied as plasmonic nanosensor which is proved to be stable for at least two months.展开更多
Semiconductor-based photocatalysis for efficient solar energy conversion is an ideal strategy to tackle the growing global energy and environmental crisis.However,the development of photocatalysis is still limited by ...Semiconductor-based photocatalysis for efficient solar energy conversion is an ideal strategy to tackle the growing global energy and environmental crisis.However,the development of photocatalysis is still limited by problems such as low utilization of visible light,low efficiency of charge transfer and separation,and insufficient reactive sites.Herein,Au nanoparticles(NPs)were deposited on the surface of Bi_(2)WO_(6)by a one-step reduction method,which simultaneously induced the formation of oxygen vacancies(OVs)on the surface of Bi_(2)WO_(6).The OVs concentration is found to be increased with the increase of Au loading.Au NPs and OVs improve the light absorption and facilitate the separation and transport of the photogenerated carriers.In addition,OVs act synergistically with the nearby metal active sites to optimize the adsorption energy of reactants on the catalyst surface,changing the adsorption form of CO_(2)molecules on the catalyst surface.The as-synthesized photocatalyst achieved a photocatalytic performance of up to 34.8μmol g^(−1)h^(−1)of CO_(2)reduction to CO without sacrificial agent in a gas-solid system,which is 9.4 times higher than that of the pristine Bi_(2)WO_(6).This work may further deepen our understanding on the relationship between metal NPs and OVs,and their combined role in photocatalysis.展开更多
基金supported in part by the National Natural Science Foundation of China(21471043,21304028,51403195,31501576)~~
文摘We report a colloidal process to coat a layer of TiO2onto SiO2composite nanofibers containing embedded CdS and upconversion nanoparticles(UCNPs).The SiO2composite nanofibers were fabricated by electrospinning.To improve the energy transfer efficiency,UCNPs and CdS nanoparticles were bound in close proximity to each other within the SiO2matrix.β‐NaYF4:Yb(30%),Tm(0.5%)@NaYF4:Yb(20%),Er(2%)core–shell nanoparticles were used as nanotransducers for near infrared light.These nanoparticles exhibited enhanced upconversion fluorescence compared withβ‐NaYF4:Yb(30%),Tm(0.5%)orβ–NaYF4:Yb(30%),Tm(0.5%)@NaYF4nanoparticles.The morphologies,size and chemical compositions have been extensively investigated using field emission scanning electron microscopy(FESEM),transmission electron microscopy(TEM),X‐ray diffraction(XRD)and X‐ray photoelectron spectra(XPS),respectively.The TEM images showed that the TiO2composite nanotubes were embedded with a large amount of UCNPs and CdS nanoparticles.The composite TiO2nanotubes degraded more than90%of rhodamine B(RhB)dye during20min of irradiation by simulated solar light.In particular,more than50%of RhB was decomposed in70min,under irradiation of near infrared light(NIR).This high degradation was attributed to the full spectrum absorption of solar light,and the enhanced transfer efficiency for near infrared light.The as‐prepared nanostructures can harness solar energy,and provide an alternative to overcome energy shortages and environmental protection.
基金Supported by the Natural Science Foundation of Tianjin(Nos.06TXTJJC14400, 07JCYBJC15900) and Young Teacher Foun-dation of Tianjin Polytechnic University (No.029624).
文摘A DNA fluorescence probe system based on fluorescence resonance energy transfer (FRET) from CdTe quantum dot (QD) donors to Au nanoparticle (AuNP) acceptors is presented. CdTe QDs, 2.5nm in diameter, as energy donors, were prepared in water. Au nanoparticles, 16nm in diameter, as energy acceptors, were prepared from gold chloride by reduction. CdTe QDs were linked to 5'-NH2-DNA through 1-ethyl-3-(dimethylaminopropyl)car- bodiimide hydrochloride (EDC) as a linker, and the 3'-SH-DNA was self-assembled onto the surface of AuNPs. The hybridization of complementary double stranded DNA (dsDNA) bound to the QDs and AuNPs (CdTe-dsDNA-Au) determined the FRET distance of CdTe QDs and Au nanoparticles. Compared to the fluorescence of CdTe-DNA, the fluorescence of CdTe-DNA-Au conjugates decreased extremely, which indicated that the FRET occurred between CdTe QDs and Au nanoparticles. The fluorescence change of this conjugate depended on the ratio of Au-DNA to CdTe-DNA. When the AuNPs-DNA to QD-DNA ratio was 10:1, the FRET efficiency reached a maximum. The probe system would have a certain degree of fluorescence recovery when a complementary single stranded DNA was introduced into this system, which showed that the distance between CdTe QDs and Au nanoparticles was increased.
基金Supported by the National Natural Science Foundation of China(U1361202,51276120)
文摘Carbon deposition is sensitive to the metal particle sizes of supported Ni catalysts in CH_4/CO_2 reforming.To explore the reason of this phenomenon,Ni4,Ni8,and Ni12 which re flect the different cluster thicknesses supported on the MgO(100) slabs,have been employed to simulate Ni/MgO catalysts,and the reaction pathways of CH_4/CO_2 reforming on Nix/MgO(100) models are investigated by density functional theory.The reforming mechanisms of CH_4/CO_2 on different Nix/MgO(100) indicate the energy barriers of CH_4 dissociated adsorption,CH dissociation,and C oxidation three factors are all declining with the decrease of the Ni cluster sizes.The Hirshfeld charges analyses of three steps as described above show only Ni atoms in bottom two layers can obtain electrons from the MgO supporters,and the main electron transfer occurs between adsorbed species and their directly contacted Ni atoms.Due to more electron-rich Ni atoms in contact with the MgO supporters,the Ni/MgO catalysts with small Ni particles have a strong metal particle size effect and lead to its better catalytic activity.
基金supported by the National Key R&D Program of China (2017YFA0207301)National Natural Science Foundation of China (No.21725102, No.21471141,No.21601173)+3 种基金CAS Key Research Program of Frontier Sciences(QYZDB-SSWSLH018)CAS Interdisciplinary Innovation Team,Innovative Program of Development Foundation of Hefei Center for Physical Science and Technology (No.2016FXCX003)Anhui Provincial Natural Science Foundation (No.1608085QB24)Chinese Universities Scientific Fund (WK2310000067)
文摘Photocatalytic reduction of CO2 into various types of fuels has attracted great interest,and serves as a potential solution to addressing current global warming and energy challenges.In this work,Ag-Cu nanoparticles are densely supported on N-doped TiO2 nanowire through a straightforward nanofabrication approach.The range of light absorption by N-doped TiO2 can be tuned to match the plasmonic band of Ag nanoparticles,which allows synergizing a resonant energy transfer process with the Schottky junction.Meanwhile,Cu nanoparticles can provide active sites for the reduction of CO2 molecules.Remarkably,the performance of photocatalytic CO2 reduction is improved to produce CH4 at a rate of 720μmol·g-1·h-1 under full-spectrum irradiation.
文摘A fully grouted bolt provides greater shear load capacity for transmitting the load from the rock to the bolt, and vice versa. When grout fills irregularities between the bolt and the rock, a keying effect is created to transfer the load to the bolt via shear resistance at the interface and within the grout. Previous research has revealed that the mechanical properties of the grout had a great impact on the load transfer capacity of the rock bolting system. This paper presents a method to enhance the rock bolting strength by introducing metal granules into the grouting material. Experimental results suggest that both the average peak load of pullout tests and the total energy absorption of the system will increase if some metal granules are mixed into the resin.
基金partially supported by a Grant-in-Aid for Science Research from the Japan Society for the Promotion of Science(JSPS)the Global COE Program,the University of Tokyo,the Japan Science and Technology Agency(JST)the Ministry of Education,Culture,Sports,Science and Tech-nology(MEXT,Japan)
文摘Metal nanoparticle catalysts, especially gold and its bimetallic nanoparticle catalysts, have been widely used in organic transformations as powerful and green catalysts. The concept of employing two distinct catalysts in one reaction system, such as in cooperative and synergistic catalysis, is a powerful strategy in homogeneous catalysis. However, the adaption of such a strategy to metal nanoparticle catalysis is still under development. Recently, we have found that cooperative catalytic systems of gold/palladium bimetallic nanoparticles and Lewis acid can be used for the N‐alkylation of primary amides through hydrogen autotransfer reaction between amide and alcohol. Herein, the results of a detailed investigation into the effects of Lewis acids on this hydrogen autotransfer reac‐tion are reported. It was found that the choice of Lewis acid affected not only the reaction pathway leading to the desired product, but also other reaction pathways that produced several intermedi‐ates and by‐products. Weak Lewis acids, such as alkaline‐earth metal triflates, were found to be optimal for the desired N‐alkylation of amides.
基金supported by the National Natural Science Foundation of China(Grant No.11272252)
文摘A high-speed digital camera is used to record the saltation of three sand samples(diameter range:300–500,200–300 and100–125μm).This is followed by an overlapping particle tracking algorithm to reconstruct the saltating trajectory and the differential scheme to abstract the kinetic parameters of saltating grains.The velocity results confirm the propagating feature of saltation in maintaining near-face aeolian sand transport.Moreover,the acceleration of saltating sand grains was obtained directly from the reconstructed trajectory,and the results reveal that the climbing stage of the saltating trajectory represents an critical process of energy transfer while the sand grains travel through air.
基金supported by the National Natural Science Foundation of China (51572009)
文摘A general stepwise strategy for the preparation of new humidity-responsive plasmonic nanosensor was described for the first time, based on Ag film functionalization by polyacrylamide(PAAM) brushes via surface-initiated atom transfer radical polymerization(SI-ATRP) method and then assembled with gold nanoparticles(Au NPs). We designed by this way a new plasmonic device made of Au NPs embedded in a humid vapor responsive polymer layer on Ag film and extensively characterized by surface-enhanced Raman scattering(SERS). When the relative humidity(RH) is above 50%, the number of plasmonic hotspots decreases, causing SERS signal reduced noticeably, for the volume expansion of PAAM brushes varied the nano-gap between closely spaced Au NPs, and between Au NPs and Ag film. The reversible optical properties of the prepared nanocomposite tuned by RH were probed through SERS using 4-mercaptopyridine(4-Mpy) as a molecular probe, and the decrease of the RH reversibly induces a significant enhancement of the 4-Mpy SERS signal. By means of the high reversibility, the RH responsive nanocomposite developed in this paper provides a dynamic SERS platform and can be applied as plasmonic nanosensor which is proved to be stable for at least two months.
基金the National Natural Science Foundations of China(51972288 and 51672258)the Fundamental Research Funds for the Central Universities(2652018287)the 2021 Graduate Innovation Fund Project of China University of Geosciences,Beijing(ZY2021YC006).
文摘Semiconductor-based photocatalysis for efficient solar energy conversion is an ideal strategy to tackle the growing global energy and environmental crisis.However,the development of photocatalysis is still limited by problems such as low utilization of visible light,low efficiency of charge transfer and separation,and insufficient reactive sites.Herein,Au nanoparticles(NPs)were deposited on the surface of Bi_(2)WO_(6)by a one-step reduction method,which simultaneously induced the formation of oxygen vacancies(OVs)on the surface of Bi_(2)WO_(6).The OVs concentration is found to be increased with the increase of Au loading.Au NPs and OVs improve the light absorption and facilitate the separation and transport of the photogenerated carriers.In addition,OVs act synergistically with the nearby metal active sites to optimize the adsorption energy of reactants on the catalyst surface,changing the adsorption form of CO_(2)molecules on the catalyst surface.The as-synthesized photocatalyst achieved a photocatalytic performance of up to 34.8μmol g^(−1)h^(−1)of CO_(2)reduction to CO without sacrificial agent in a gas-solid system,which is 9.4 times higher than that of the pristine Bi_(2)WO_(6).This work may further deepen our understanding on the relationship between metal NPs and OVs,and their combined role in photocatalysis.