The reduction of CO_(2)toward CO and CH_(4)over Ni-loaded MoS_(2)-like layered nanomaterials is investigated.The mild hydrothermal synthesis induced the formation of a molybdenum oxysulfide(MoO_(x)S_(y))phase,enriched...The reduction of CO_(2)toward CO and CH_(4)over Ni-loaded MoS_(2)-like layered nanomaterials is investigated.The mild hydrothermal synthesis induced the formation of a molybdenum oxysulfide(MoO_(x)S_(y))phase,enriched with sulfur defects and multiple Mo oxidation states that favor the insertion of Ni^(2+)cations via photo-assisted precipitation.The photocatalytic tests under LED irradiation at different wavelengths from 365 to 940 nm at 250℃rendered 1%CO_(2)conversion and continuous CO production up to 0.6 mmol/(gcat h).The incorporation of Ni into the MoO_(x)S_(y)structure boosted the continuous production of CO up to 5.1 mmol/(gcat h)with a CO_(2)conversion of 3.5%.In situ spectroscopic techniques and DFT simulations showed the O-incorporated MoS_(2)structure,in addition to Ni clusters as a supported metal catalyst.The mechanistic study of the CO_(2)reduction reaction over the catalysts revealed that the reverse water-gas shift reaction is favored due to the preferential formation of carboxylic species.展开更多
The electron spin dynamics is investigated by the time-resolved Kerr rotation technique in a pair of special GaAs/AlGaAs asymmetric quantum well samples grown on(111)-oriented substrates,whose structures are the same ...The electron spin dynamics is investigated by the time-resolved Kerr rotation technique in a pair of special GaAs/AlGaAs asymmetric quantum well samples grown on(111)-oriented substrates,whose structures are the same except for their opposite directions of potential asymmetry.A large difference of spin lifetimes between the two samples is observed at low temperature.This difference is interpreted in terms of a cancellation effect between the Dresselhaus spin-splitting term in the conduction band and another term induced by interface inversion asymmetry.The deviation decreases with the increasing temperature,and almost disappears when T>100 K because the cubic Dresselhaus term becomes more important.展开更多
Quantum sensing has emerged as a powerful technique to detect and measure physical and chemical parameters with exceptional precision.One of the methods is to use optically active spin defects within solid-state mater...Quantum sensing has emerged as a powerful technique to detect and measure physical and chemical parameters with exceptional precision.One of the methods is to use optically active spin defects within solid-state materials.These defects act as sensors and have made significant progress in recent years,particularly in the realm of two-dimensional(2D)spin defects.In this article,we focus on the latest trends in quantum sensing that use spin defects in van der Waals(vdW)materials.We discuss the benefits of combining optically addressable spin defects with 2D vdW materials while highlighting the challenges and opportunities to use these defects.To make quantum sensing practical and applicable,the article identifies some areas worth further exploration.These include identifying spin defects with properties suitable for quantum sensing,generating quantum defects on demand with control of their spatial localization,understanding the impact of layer thickness and interface on quantum sensing,and integrating spin defects with photonic structures for new functionalities and higher emission rates.The article explores the potential applications of quantum sensing in several fields,such as superconductivity,ferromagnetism,2D nanoelectronics,and biology.For instance,combining nanoscale microfluidic technology with nanopore and quantum sensing may lead to a new platform for DNA sequencing.As materials technology continues to evolve,and with the advancement of defect engineering techniques,2D spin defects are expected to play a vital role in quantum sensing.展开更多
A CMOS compatible process is prese nted in order to grow self-catalyzed InAs nano wires on silic on by molecular beam epitaxy. The crucial step of this process is a new in-situ surface preparation under hydrogen (gas ...A CMOS compatible process is prese nted in order to grow self-catalyzed InAs nano wires on silic on by molecular beam epitaxy. The crucial step of this process is a new in-situ surface preparation under hydrogen (gas or plasma) during the substrate degassing combined with an in-situ arsenic ann eali ng prior to growth. Morphological and structural characterizati ons of the InAs nano wires are prese nted and growth mecha nisms are discussed in detail. The major in flue nee of surface termi nation is exposed both experime ntally and theoretically using statistics on ensemble of nanowires and density functional theory (DFT) calculations. The differences observed between Molecular Beam Epitaxy (MBE) and Metal Organic Vapor Phase Epitaxy (MOVPE) growth of I nAs nano wires can be explai ned by these differe nt surfaces termi nations. The transition between a vapor solid (VS) and a vapor liquid solid (VLS) growth mechanism is presented. Optimized growth conditions lead to very high aspect ratio nano wires (up to 50 nm in diameter and 3 micron in len gth) without passi ng the 410℃ thermal limit, which makes the whole process CMOS compatible. Overall, our results suggest a new method for surface preparation and a possible tuning of the growth mechanism using different surface termi nations.展开更多
We investigate the charge transport in close-packed ultra-narrow （1.5 nm diameter） gold nanowires stabilized by oleylamine ligands. We give evidence of charging effects in the weakly coupled one-dimensional （1D） n...We investigate the charge transport in close-packed ultra-narrow （1.5 nm diameter） gold nanowires stabilized by oleylamine ligands. We give evidence of charging effects in the weakly coupled one-dimensional （1D） nanowires, monitored by the temperature and the bias voltage. At low temperature, in the Coulomb blockade regime, the current flow reveals an original cooperative multi-hopping process between 1D-segments of Au-NWs, minimising the charging energy cost. Above the Coulomb blockade threshold voltage and at high temperature, the charge transport evolves into a sequential tunneling regime between the nearest- nanowires. Our analysis shows that the effective length of the Au-NWs inside the bundle is similar to the 1D localisation length of the electronic wave function （of the order of 120 nm _＋ 20 nm）, but almost two orders of magnitude larger than the diameter of the nanowire. This result confirms the high structural quality of the Au-NW segments.展开更多
The peculiar electronic structure of scandium phosphinoalkylidene complex [LSc{C（SiMe3）PPh2}THF] （L=[MeC（NDIPP）CHC（NDIPP）Me]-）, DIPP= 2,6-（Pr）2C6H3） leads to an interesting versatile reactivity, which is de...The peculiar electronic structure of scandium phosphinoalkylidene complex [LSc{C（SiMe3）PPh2}THF] （L=[MeC（NDIPP）CHC（NDIPP）Me]-）, DIPP= 2,6-（Pr）2C6H3） leads to an interesting versatile reactivity, which is demonstrated both experimentally and computationally. The complex undergoes [2＋2] cycloaddition reactions with alkynes, and easily activates various X-O bonds such as C-O of propylene oxide, N-O of 3,5-dimethylisoxazole, B-O of pinacolborane and Si-O of triethoxysilane. These reactions occur on the Sc-C bond of the phosphinoalkylidene complex. Interestingly, the Sc-P bond can also be activated as the presence of a Sc-C-P three center π interaction in the complex allows performing C-F activation of 2,6-difluoro- pyridine and 1,2 addition with imine or ketone. The complex also reacts with metal complexes, [（COD）RhCl]2 and （Ph3P）AuCl, to form structural intriguing heterobimetallic complexes.展开更多
We present results of the synthesis of cobalt nanorods using the polyol process and the mechanism of magnetization reversal. We show that the nucleation step is significantly dependent on the nature of the ruthenium c...We present results of the synthesis of cobalt nanorods using the polyol process and the mechanism of magnetization reversal. We show that the nucleation step is significantly dependent on the nature of the ruthenium chloride used as the nucleating agent. This allows varying the diameter and aspect ratio of the cobalt nanorods independently. Co nanorods with aspect ratio, mean diameter, and mean length in the ranges ARm =3-16, Din= 7-25 nm, and Lm=30-300 nm, respectively, were produced using this method. X-ray diffraction and electron microscopy showed that a strong discrepancy between the structural coherence and morphological aspect ratio can exist because of stacking faults. The coercivity of assemblies of different nanorods was systematically measured, and the highest values were obtained for the smallest diameter and the largest structural coherence length. Micromagnetic simulations were performed to account for the dependence of the coercive field on the diameter. An important observation is that simple coherent magnetization rotation models do not apply to these magnetic nano-objects. Even for very small diameters （Dm = 5-10 nm） well below the theoretical coherent diameter Dcoh（CO）= 24 nm, we observed inhomogeneous reversal modes dominated by nucleation at the rod edges or at structural defects such as stacking faults. We conclude that, in order to produce high-coercivity materials based on nanowires, moderate aspect ratios of 5-10 are sufficient for providing a structural coherence similar to the morphological aspect ratio. Thus, the first priority should be to avoid the formation of stacking faults within the Co nanowires.展开更多
The study of small-molecule activation by f-block elements still lags far behind that of transition metals.Although a few uranium complexes have been reported to activate dinitrogen,reports on the activation of heavie...The study of small-molecule activation by f-block elements still lags far behind that of transition metals.Although a few uranium complexes have been reported to activate dinitrogen,reports on the activation of heavier congeners,such as white phosphorus(P_(4)),by uranium species are extremely rare,and no example of uranium-mediated activation of elemental arsenic has appeared.展开更多
Ligands play a key role in controlling activity of organometallic complexes so that development of new ligands to overcome the challenge is the main topic of modern chemistry.The first example of 1,1-hydride migratory...Ligands play a key role in controlling activity of organometallic complexes so that development of new ligands to overcome the challenge is the main topic of modern chemistry.The first example of 1,1-hydride migratory insertion and intramolecular redox reaction has been realized in this work by applying a new ligand in rare-earth metal chemistry.The novel rare-earth metal complexes L^(Mes)RECH2TMS(THF)(RE=Y(1a),Dy(1b),Er(1c),Yb(1d),L^(Mes)=1-(3-(2,6-iPr_(2)C_(6)H_(3)N=CH)C8H4N)-CH_(2)CH_(2)-3-(2-CH2–4,6-Me_(2)C_(6)H_(2))-(N(CH)_(2)NC),THF=tetrahydrofuran)bearing a ligand with imino,indolyl,NHC(N-heterocyclic carbene)multiple functionalities were synthesized and characterized.Treatment of complexes 1 with silanes(PhSiH3or PhSiH2Me or PhSiD3)selectively produced the unprecedented 1,1-hydride(or deuterated H)migratory insertion of the indolyl moiety of the novel unsymmetrical dinuclear rare-earth metal complexes 2.The complex 2a reacts with Ph_(2)C=O to give the selective C=O double bond insertion to the RE–Co-methylene-Mesbond product 3a which further reacts with another Ph_(2)C=O(or DMAP,4-N,N-dimethylaminopyridine)affording the novelμ-η^(2):η^(3)-dianionic 3-iminoindolyl dinuclear rare-earth metal complex 4a.The latter is formed through an unusual intramolecular redox reaction(through electron migration from the 2-carbanion of the indolyl ring to the imino motif)resulting in the re-aromatization of the indolyl ring.展开更多
The metal-substituted silylenes are of high interest,as the theoretical studies indicated that the silylenes with electropositive substituents have a smallΔE_(S-T)(singlet-triplet energy gap)or even the ground-state ...The metal-substituted silylenes are of high interest,as the theoretical studies indicated that the silylenes with electropositive substituents have a smallΔE_(S-T)(singlet-triplet energy gap)or even the ground-state triplets.However,such compounds are highly unstable,and only two transient alkali metal-substituted silylenes M(^(t)Bu_(3)Si)Si:(M=Li,K)were generated by photoextrusion of the alkali metal-substituted silacyclopropenes and merely studied by spectroscopic method(EPR)at low temperature(14 to 50 K).Herein,we report the generation of transient zinc-substituted silylenes from zinc silacyclopropanyl complexes under very mild and convenient conditions.The generated transient zinc-substituted silylenes are highly reactive and undergo intermolecular cycloaddition with alkenes for the synthesis of zinc-substituted Si-heterocyclic compounds.If there is no substrate,the zinc-substituted silylenes attack the C-C bonds of theβ-diketiminato ligands and break the C-C bonds.DFT studies further highlight the silylene nature of the zinc-substituted silylene and a very smallΔE_(S-T)(4.4 kcal/mol).展开更多
基金Financial support from the Spanish Ministry of Science and Universities through CEX2023-001286-S,PID2020-114926RB-I00,and CTQ2016-77144-Rthe MICINN Scholarship.
文摘The reduction of CO_(2)toward CO and CH_(4)over Ni-loaded MoS_(2)-like layered nanomaterials is investigated.The mild hydrothermal synthesis induced the formation of a molybdenum oxysulfide(MoO_(x)S_(y))phase,enriched with sulfur defects and multiple Mo oxidation states that favor the insertion of Ni^(2+)cations via photo-assisted precipitation.The photocatalytic tests under LED irradiation at different wavelengths from 365 to 940 nm at 250℃rendered 1%CO_(2)conversion and continuous CO production up to 0.6 mmol/(gcat h).The incorporation of Ni into the MoO_(x)S_(y)structure boosted the continuous production of CO up to 5.1 mmol/(gcat h)with a CO_(2)conversion of 3.5%.In situ spectroscopic techniques and DFT simulations showed the O-incorporated MoS_(2)structure,in addition to Ni clusters as a supported metal catalyst.The mechanistic study of the CO_(2)reduction reaction over the catalysts revealed that the reverse water-gas shift reaction is favored due to the preferential formation of carboxylic species.
基金Supported by the China-France NSFC-ANR Research Project under Grant No 10911130356Chinese Academy of Sciences under Grant No 2011T1J37+1 种基金the National Basic Research Program of China(2009CB930500)National Science Foundation of China under Grant Nos 10774183 and 10874212.
文摘The electron spin dynamics is investigated by the time-resolved Kerr rotation technique in a pair of special GaAs/AlGaAs asymmetric quantum well samples grown on(111)-oriented substrates,whose structures are the same except for their opposite directions of potential asymmetry.A large difference of spin lifetimes between the two samples is observed at low temperature.This difference is interpreted in terms of a cancellation effect between the Dresselhaus spin-splitting term in the conduction band and another term induced by interface inversion asymmetry.The deviation decreases with the increasing temperature,and almost disappears when T>100 K because the cubic Dresselhaus term becomes more important.
基金the National Key R&D Program of China(No.2022YFB4600400)the National Natural Science Foundation of China(No.62075115 and 62335013)for their financial support。
文摘Quantum sensing has emerged as a powerful technique to detect and measure physical and chemical parameters with exceptional precision.One of the methods is to use optically active spin defects within solid-state materials.These defects act as sensors and have made significant progress in recent years,particularly in the realm of two-dimensional(2D)spin defects.In this article,we focus on the latest trends in quantum sensing that use spin defects in van der Waals(vdW)materials.We discuss the benefits of combining optically addressable spin defects with 2D vdW materials while highlighting the challenges and opportunities to use these defects.To make quantum sensing practical and applicable,the article identifies some areas worth further exploration.These include identifying spin defects with properties suitable for quantum sensing,generating quantum defects on demand with control of their spatial localization,understanding the impact of layer thickness and interface on quantum sensing,and integrating spin defects with photonic structures for new functionalities and higher emission rates.The article explores the potential applications of quantum sensing in several fields,such as superconductivity,ferromagnetism,2D nanoelectronics,and biology.For instance,combining nanoscale microfluidic technology with nanopore and quantum sensing may lead to a new platform for DNA sequencing.As materials technology continues to evolve,and with the advancement of defect engineering techniques,2D spin defects are expected to play a vital role in quantum sensing.
文摘A CMOS compatible process is prese nted in order to grow self-catalyzed InAs nano wires on silic on by molecular beam epitaxy. The crucial step of this process is a new in-situ surface preparation under hydrogen (gas or plasma) during the substrate degassing combined with an in-situ arsenic ann eali ng prior to growth. Morphological and structural characterizati ons of the InAs nano wires are prese nted and growth mecha nisms are discussed in detail. The major in flue nee of surface termi nation is exposed both experime ntally and theoretically using statistics on ensemble of nanowires and density functional theory (DFT) calculations. The differences observed between Molecular Beam Epitaxy (MBE) and Metal Organic Vapor Phase Epitaxy (MOVPE) growth of I nAs nano wires can be explai ned by these differe nt surfaces termi nations. The transition between a vapor solid (VS) and a vapor liquid solid (VLS) growth mechanism is presented. Optimized growth conditions lead to very high aspect ratio nano wires (up to 50 nm in diameter and 3 micron in len gth) without passi ng the 410℃ thermal limit, which makes the whole process CMOS compatible. Overall, our results suggest a new method for surface preparation and a possible tuning of the growth mechanism using different surface termi nations.
文摘We investigate the charge transport in close-packed ultra-narrow （1.5 nm diameter） gold nanowires stabilized by oleylamine ligands. We give evidence of charging effects in the weakly coupled one-dimensional （1D） nanowires, monitored by the temperature and the bias voltage. At low temperature, in the Coulomb blockade regime, the current flow reveals an original cooperative multi-hopping process between 1D-segments of Au-NWs, minimising the charging energy cost. Above the Coulomb blockade threshold voltage and at high temperature, the charge transport evolves into a sequential tunneling regime between the nearest- nanowires. Our analysis shows that the effective length of the Au-NWs inside the bundle is similar to the 1D localisation length of the electronic wave function （of the order of 120 nm _＋ 20 nm）, but almost two orders of magnitude larger than the diameter of the nanowire. This result confirms the high structural quality of the Au-NW segments.
基金This work was supported by the National Natural Science Foundation of China （Nos. 21732007 and 21325210）, the Strategic Priority Research Program of the Chinese Academy of Sciences {Grant No. XDB20000000）, and the Program of Shanghai Academ- ic Research Leader. LM is a member of the Institut Universitaire de France. LM acknowledges Humboldt foundation and the Chinese Scholarship Council.
文摘The peculiar electronic structure of scandium phosphinoalkylidene complex [LSc{C（SiMe3）PPh2}THF] （L=[MeC（NDIPP）CHC（NDIPP）Me]-）, DIPP= 2,6-（Pr）2C6H3） leads to an interesting versatile reactivity, which is demonstrated both experimentally and computationally. The complex undergoes [2＋2] cycloaddition reactions with alkynes, and easily activates various X-O bonds such as C-O of propylene oxide, N-O of 3,5-dimethylisoxazole, B-O of pinacolborane and Si-O of triethoxysilane. These reactions occur on the Sc-C bond of the phosphinoalkylidene complex. Interestingly, the Sc-P bond can also be activated as the presence of a Sc-C-P three center π interaction in the complex allows performing C-F activation of 2,6-difluoro- pyridine and 1,2 addition with imine or ketone. The complex also reacts with metal complexes, [（COD）RhCl]2 and （Ph3P）AuCl, to form structural intriguing heterobimetallic complexes.
文摘We present results of the synthesis of cobalt nanorods using the polyol process and the mechanism of magnetization reversal. We show that the nucleation step is significantly dependent on the nature of the ruthenium chloride used as the nucleating agent. This allows varying the diameter and aspect ratio of the cobalt nanorods independently. Co nanorods with aspect ratio, mean diameter, and mean length in the ranges ARm =3-16, Din= 7-25 nm, and Lm=30-300 nm, respectively, were produced using this method. X-ray diffraction and electron microscopy showed that a strong discrepancy between the structural coherence and morphological aspect ratio can exist because of stacking faults. The coercivity of assemblies of different nanorods was systematically measured, and the highest values were obtained for the smallest diameter and the largest structural coherence length. Micromagnetic simulations were performed to account for the dependence of the coercive field on the diameter. An important observation is that simple coherent magnetization rotation models do not apply to these magnetic nano-objects. Even for very small diameters （Dm = 5-10 nm） well below the theoretical coherent diameter Dcoh（CO）= 24 nm, we observed inhomogeneous reversal modes dominated by nucleation at the rod edges or at structural defects such as stacking faults. We conclude that, in order to produce high-coercivity materials based on nanowires, moderate aspect ratios of 5-10 are sufficient for providing a structural coherence similar to the morphological aspect ratio. Thus, the first priority should be to avoid the formation of stacking faults within the Co nanowires.
基金supported by the National Natural Science Foundation of China(grant nos.21772088 and 91961116)the Fundamental Research Funds for the Central Universities(nos.14380216 and 14380262)Programs for high-level entrepreneurial and innovative talents introduction of Jiangsu Province(individual and group programs).L.M.is a senior member of the Institut Universitaire de France.The Humboldt Foundation and Chinese Academy of Science are acknowledged for financial support。
文摘The study of small-molecule activation by f-block elements still lags far behind that of transition metals.Although a few uranium complexes have been reported to activate dinitrogen,reports on the activation of heavier congeners,such as white phosphorus(P_(4)),by uranium species are extremely rare,and no example of uranium-mediated activation of elemental arsenic has appeared.
基金supported by the National Natural Science Foundation of China(22031001,21871004,21861162009,22171004)the grants from the Education Department of Anhui Province(GXXT-2021-052)。
文摘Ligands play a key role in controlling activity of organometallic complexes so that development of new ligands to overcome the challenge is the main topic of modern chemistry.The first example of 1,1-hydride migratory insertion and intramolecular redox reaction has been realized in this work by applying a new ligand in rare-earth metal chemistry.The novel rare-earth metal complexes L^(Mes)RECH2TMS(THF)(RE=Y(1a),Dy(1b),Er(1c),Yb(1d),L^(Mes)=1-(3-(2,6-iPr_(2)C_(6)H_(3)N=CH)C8H4N)-CH_(2)CH_(2)-3-(2-CH2–4,6-Me_(2)C_(6)H_(2))-(N(CH)_(2)NC),THF=tetrahydrofuran)bearing a ligand with imino,indolyl,NHC(N-heterocyclic carbene)multiple functionalities were synthesized and characterized.Treatment of complexes 1 with silanes(PhSiH3or PhSiH2Me or PhSiD3)selectively produced the unprecedented 1,1-hydride(or deuterated H)migratory insertion of the indolyl moiety of the novel unsymmetrical dinuclear rare-earth metal complexes 2.The complex 2a reacts with Ph_(2)C=O to give the selective C=O double bond insertion to the RE–Co-methylene-Mesbond product 3a which further reacts with another Ph_(2)C=O(or DMAP,4-N,N-dimethylaminopyridine)affording the novelμ-η^(2):η^(3)-dianionic 3-iminoindolyl dinuclear rare-earth metal complex 4a.The latter is formed through an unusual intramolecular redox reaction(through electron migration from the 2-carbanion of the indolyl ring to the imino motif)resulting in the re-aromatization of the indolyl ring.
基金supported by the National Natural Science Foundation of China(21890721,21732007)the Shanghai Municipal Committee of Science and Technologythe Chinese Academy of Sciences President’s International Fellowship Initiative。
文摘The metal-substituted silylenes are of high interest,as the theoretical studies indicated that the silylenes with electropositive substituents have a smallΔE_(S-T)(singlet-triplet energy gap)or even the ground-state triplets.However,such compounds are highly unstable,and only two transient alkali metal-substituted silylenes M(^(t)Bu_(3)Si)Si:(M=Li,K)were generated by photoextrusion of the alkali metal-substituted silacyclopropenes and merely studied by spectroscopic method(EPR)at low temperature(14 to 50 K).Herein,we report the generation of transient zinc-substituted silylenes from zinc silacyclopropanyl complexes under very mild and convenient conditions.The generated transient zinc-substituted silylenes are highly reactive and undergo intermolecular cycloaddition with alkenes for the synthesis of zinc-substituted Si-heterocyclic compounds.If there is no substrate,the zinc-substituted silylenes attack the C-C bonds of theβ-diketiminato ligands and break the C-C bonds.DFT studies further highlight the silylene nature of the zinc-substituted silylene and a very smallΔE_(S-T)(4.4 kcal/mol).
