Single negatively charged nitrogen vacancy(NV-)centers in diamond have emerged as promising platforms for quantum information science,where long coherence times are essential for advancing quantum technologies.However...Single negatively charged nitrogen vacancy(NV-)centers in diamond have emerged as promising platforms for quantum information science,where long coherence times are essential for advancing quantum technologies.However,traditional fabrication methods often introduce lattice damage during the irradiation process used to create vacancies,significantly impairing the spin coherence properties of NV-centers.展开更多
As a substitute for synthetic ammonia under mild condition, electrocatalytic nitrogen reduction reaction(NRR) provides a hopeful approach for the development of ammonia. Nevertheless, the current development of NRR el...As a substitute for synthetic ammonia under mild condition, electrocatalytic nitrogen reduction reaction(NRR) provides a hopeful approach for the development of ammonia. Nevertheless, the current development of NRR electrocatalysts is far from enough and a systematic research is needed to gain a better improvement. This article presents that 2 D C_(3)N_(4)-NV with a large specific surface area and abundant nitrogen vacancies is prepared by a simple and feasible method, and used as a metal-free catalyst for electrocatalytic NRR. Experiment result and density functional theory(DFT) calculation reveal that nitrogen vacancies in 2 D C_(3)N_(4)-NV can act as an efficient active site for catalytic NRR, which is conducive to capturing and activating N_(2), lowering Gibbs free energy(DG) in reaction and inhibiting hydrogen evolution reaction(HER) at the same time. In addition, the larger specific surface area also makes more active site exposed, which is good for the contact between the electrolyte and the active site, thus enhancing its NRR activity. The electrocatalyst shows an excellent catalytic activity for NRR in 0.1 M HCl, including Faradaic efficiency of 10.96%, NH_(3) yields of 17.85 lg h^(-1) mg_(cat)^(-1)., and good stability(over 20 h).展开更多
To study the influence of the nitrogen vacancy （VN） on mechanical and electrical properties of zirconium nitride deeply, ZrNx films with different VN concentrations were synthesized on the Si （111） substrates by e...To study the influence of the nitrogen vacancy （VN） on mechanical and electrical properties of zirconium nitride deeply, ZrNx films with different VN concentrations were synthesized on the Si （111） substrates by enhanced magnetic filtering arc ion plating. The morphologies, microstructures, residual stresses, compositions, chemical states, mechanical and electrical properties of the as-deposited films were characterized by field-emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectrometry, Nanoindenter and Hall effect measurements. The results showed that ZrNx films exhibited rocksalt single-phase structure within a VN concentration ranging from 26 to 5%. The preferred orientation, thickness, grain size and residual stress of the ZrNx films kept constant at different VN concentrations. Both the nanohardness and elastic modulus first increased and then decreased with the decrease in VN concentration, reaching the peaks around 16%. And the electric conductivity of the ZrNx films showed a similar tendency with nanohardness. The underlying atomic-scale mechanisms of VN concentration-dependent hardness and electric conductivity enhancements were discussed and attributed to the different electronic band structures, rather than conventional meso-scale factors, such as preferred orientation, grain size and residual stress.展开更多
A central goal in quantum information science is to efficiently interface photons with single optical modes for quantum networking and distributed quantum computing.Here,we introduce and experimentally demonstrate a c...A central goal in quantum information science is to efficiently interface photons with single optical modes for quantum networking and distributed quantum computing.Here,we introduce and experimentally demonstrate a compact and efficient method for the low-loss coupling of a solid-state qubit,the nitrogen vacancy(NV)center in diamond,with a single-mode optical fiber.In this approach,single-mode tapered diamond waveguides containing exactly one high quality NV memory are selected and integrated on tapered silica fibers.Numerical optimization of an adiabatic coupler indicates that near-unity-efficiency photon transfer is possible between the two modes.Experimentally,we find an overall collection efficiency between 16%and 37%and estimate a single photon count rate at saturation above 700 kHz.This integrated system enables robust,alignment-free,and efficient interfacing of single-mode optical fibers with single photon emitters and quantum memories in solids.展开更多
Hybrid quantum system of negatively charged nitrogen–vacancy（NV^-） centers in diamond and superconducting qubits provide the possibility to extend the performances of both systems. In this work, we numerically simu...Hybrid quantum system of negatively charged nitrogen–vacancy（NV^-） centers in diamond and superconducting qubits provide the possibility to extend the performances of both systems. In this work, we numerically simulate the coupling strength between NV^-ensembles and superconducting flux qubits and obtain a lower bound of 1016cm^（-3） for NV^-concentration to achieve a sufficiently strong coupling of 10 MHz when the gap between NV^-ensemble and flux qubit is 0. Moreover, we create NV^-ensembles in different types of diamonds by14^（N＋）and12（C＋）ion implantation, electron irradiation, and high temperature annealing. We obtain an NV^-concentration of 1.05 × 1016cm^（-3） in the diamond with1-ppm nitrogen impurity, which is expected to have a long coherence time for the low nitrogen impurity concentration. This shows a step toward performance improvement of flux qubit-NV^-hybrid system.展开更多
While lithium-sulfur(Li-S)battery has attracted remarkable attention owing to the high theoretical capacity,its practical application is still hindered by the shuttle and sluggish conversion kinetics of intermediate l...While lithium-sulfur(Li-S)battery has attracted remarkable attention owing to the high theoretical capacity,its practical application is still hindered by the shuttle and sluggish conversion kinetics of intermediate lithium polysulfides(Li PSs).Defect engineering,which can regulate the electronic structure and in turn influence the surface adsorption and catalytic capability,has been regarded as a feasible strategy to deal with the above challenges.However,few studies on nitrogen vacancies and their mechanisms are reported.Herein,cobalt nitride with nitrogen vacancies grown on multi-walled carbon nanotube(CNTCo N-VN)is designed and applied as the separator modification material to investigate the enhancing mechanism of nitrogen vacancies on Li-S batteries.The experimental evidence and theoretical calculation indicate that the introduction of nitrogen vacancies into cobalt nitride can enhance the chemical affinity to Li PSs and effectively hamper the shuttle effect.Meanwhile the reduced band gap of the d-band center of Co and p-band center of N for CNT-Co N-VNand the promoted diffusion of Li^(+) can expedite the solid-liquid and liquid-liquid conversions of sulfur species.Due to these superiorities,the cell with CNT-Co NVNmodified separator delivers a favorable initial capacity of 901 m Ah g^(-1)and a capacity of 660 m Ah g^(-1)can be achieved after 250 cycles at 2 C.This work explores the application of metal nitride with nitrogen vacancies and sheds light on the development of functional separators for high-efficient Li-S batteries.展开更多
Electrochemical nitrate reduction reaction (NITRR) is regarded as a “two birds-one stone” method for the treatment of nitrate contaminant in polluted water and the synthesis of valuable ammonia, which is retarded by...Electrochemical nitrate reduction reaction (NITRR) is regarded as a “two birds-one stone” method for the treatment of nitrate contaminant in polluted water and the synthesis of valuable ammonia, which is retarded by the lack of highly reactive and selective electrocatalysts .Herein, for the first time, nickel foam supported Co_(4) N was designed as a high-performance NITRR catalyst by an in-situ nonmetal leaching-induced strategy.At the optimal potential, the Co_(4) N/NF catalyst achieves ultra-high Faraday efficiency and NH_(3) selectivity of 95.4% and 99.4%, respectively.Ex situ X-ray absorption spectroscopy (XAS), together with other experiments powerfully reveal that the nitrogen vacancies produced by nitrogen leaching are stable and play a key role in boosting nitrate reduction to ammonia.Theoretical calculations confirm that Co_(4) N with abundant nitrogen vacancies can optimize the adsorption energies of NO_(3)^(-) and intermediates, lower the free energy (Δ G ) of the potential-determining step (*NH_(3) to NH_(3) ) and inhibit the formation of N-containing byproducts.In addition, we also conclude that the nitrogen vacancies can stabilize the adsorbed hydrogen, making H_(2) quite difficult to produce, and lowering ΔG from *NO to *NOH, which facilitates the selective reduction of nitrate.This study reveals significant insights about the in-situ nonmetal leaching to enhance the NITRR activity.展开更多
Urea oxidation reaction (UOR),which has favorable thermodynamic energy barriers compared with oxygen evolution reaction (OER),can provide more cost-effective electrons for the renewable energy systems,but is trapped b...Urea oxidation reaction (UOR),which has favorable thermodynamic energy barriers compared with oxygen evolution reaction (OER),can provide more cost-effective electrons for the renewable energy systems,but is trapped by its sluggish UOR kinetics and intricate reaction intermediates formation/desorption process.Herein,we report a novel and effective electrocatalyst consisting of carbon cloth supported nitrogen vacancies-enriched Ce-doped Ni_(3)N hierarchical nanosheets (Ce-Ni_(3)N @CC) to optimize the flat-footed UOR kinetics,especially the stiff rate-determine CO_(2)desorption step of UOR.Upon the introduction of valance state variable Ce,the resultant nitrogen vacancies enriched Ce-Ni_(3)N @CC exhibits an enhanced UOR performance where the operation voltage requires only 1.31 V to deliver the current density of 10 mA cm^(-2),which is superior to that of Ni_(3)N @CC catalyst (1.36 V) and other counterparts.Density functional theory (DFT) results demonstrate that the incorporation of Ce in Ni_(3)N lowers the formation energy of nitrogen vacancies,resulting in rich nitrogen vacancies in Ce-Ni_(3)N @CC.Moreover,the nitrogen vacancies together with Ce doping optimize the local charge distribution around Ni sites,and balance the adsorption energy of CO_(2)in the rate-determining step (RDS),as well as affect the initial adsorption structure of urea,leading to the superior UOR catalytic performance of Ce-Ni_(3)N @CC.When integrating the Ce-Ni_(3)N catalyst in UOR//HER and UOR//CO_(2)R flow electrolyzer,both of them perform well with low operation voltage and robust long-term stability,proofing that the thermodynamically favorable UOR can act as a suitable substitute anodic reaction compared with that of OER.Our findings here not only provide a novel UOR catalyst but also offer a promising design strategy for the future development of energy-related devices.展开更多
The nitrogen-vacancy(NV)color center in diamond is a promising solid-state quantum system at room temperature.However,its sensitivity is limited by its low fluorescence collection efficiency,and its coherence time is ...The nitrogen-vacancy(NV)color center in diamond is a promising solid-state quantum system at room temperature.However,its sensitivity is limited by its low fluorescence collection efficiency,and its coherence time is limited by spin interference of impurity electrons around the NV color center.Here,we innovatively fabricated a one-dimensional photonic crystal on the surface of diamond,which greatly improved the fluorescence intensity of the NV color centers and increased the sensitivity of NV ensembles by a factor of 2.92.In addition,the laser reflected by the photonic crystal excites impurity electrons around the NV color centers,improving the electric field environment around the NV color centers,which exponentially prolongs the dephasing time(from 209 to841 ns),opening avenues for NV color-center ensemble sensors.展开更多
Optically detected magnetic resonance(ODMR)has emerged as a powerful technique for quantum sensing,enabling high-sensitivity detection of physical quantities even at room temperature.Solid-state defects,such as nitrog...Optically detected magnetic resonance(ODMR)has emerged as a powerful technique for quantum sensing,enabling high-sensitivity detection of physical quantities even at room temperature.Solid-state defects,such as nitrogen-vacancy(NV)centers in diamond,have demonstrated remarkable capabilities in this domain[1–4].However,these systems are limited by their rigid lattice structures and lack tunability.展开更多
Microwave chips are widely utilized in modern communication,national defense,and various technological domains.However,effective signal identification remains challenging due to complex multi-frequency microwave inter...Microwave chips are widely utilized in modern communication,national defense,and various technological domains.However,effective signal identification remains challenging due to complex multi-frequency microwave interference.To address this issue,we propose an advanced optical imaging framework based on nitrogen-vacancy(NV)center near-field microscopy.This framework enables the separation and imaging characterization of mixed multi-frequency microwave signals across a wide field of view(2000μm×1600μm,spatial resolution of 5μm)on chip surfaces.By leveraging the NV color center as a mixer,combined with a multi-frequency hybrid model and fast Fourier transform(FFT)analysis,we convert the invisible electromagnetic waves into visible optical information.Using a wide-field microscopy system equipped with a high-speed optical camera,our approach effectively enables the separation and imaging of mixed microwave signals across two complex scenarios.Comparative analysis with finite element simulation validates the accuracy of this approach.Experimental results reveal m Hz frequency resolution for GHz microwaves andμT-level signal intensity resolution,showcasing its superior capability for imaging mixed signals with multi-frequency.These findings provide critical technical support for microwave chip characterization,interference signal identification,and diagnostic testing,highlighting the broad applicability of this technique.展开更多
The negatively charged nitrogen vacancy(NV^(−))center ensemble in as-grown chemical vapor deposition(CVD)diamond is a promising candidate for quantum sensing due to its long coherence time and excellent optical proper...The negatively charged nitrogen vacancy(NV^(−))center ensemble in as-grown chemical vapor deposition(CVD)diamond is a promising candidate for quantum sensing due to its long coherence time and excellent optical properties.However,achieving a high concentration of NV^(−)centers in as-grown CVD diamond remains a critical challenge,which constrains the performance of NV^(−)based sensors.In this study,we observe that NV^(−)center formation efficiency is significantly enhanced during the initial growth phase,with a coherence time T_(2)^(*)of 1.1μs.These findings demonstrate that high-concentration NV^(−)centers can be achieved in as-grown diamonds,greatly enhancing their utility in high-performance magnetometers and quantum sensing.展开更多
Sodium-ion storage devices are highly desirable for large-scale energy storage applications owing to the wide availability of sodium resources and low cost.Transition metal nitrides(TMNs)are promising anode materials ...Sodium-ion storage devices are highly desirable for large-scale energy storage applications owing to the wide availability of sodium resources and low cost.Transition metal nitrides(TMNs)are promising anode materials for sodium-ion storage,while their detailed reaction mechanism remains unexplored.Herein,we synthesize the mesoporous Mo3N2 nanowires(Meso-Mo_(3)N_(2)-NWs).The sodium-ion storage mechanism of Mo3N2 is systematically investigated through in-situ XRD,ex-situ experimental characterizations and detailed kinetics analysis.Briefly,the Mo_(3)N_(2) undergoes a surface pseudocapacitive redox charge storage process.Benefiting from the rapid surface redox reaction,the Meso-Mo_(3)N_(2)-NWs anode delivers high specific capacity(282 m Ah g^(-1) at 0.1 A g^(-1)),excellent rate capability(87 m Ah g^(-1) at 16 A g^(-1))and long cycling stability(a capacity retention of 78.6%after 800 cycles at 1 A g^(-1)).The present work highlights that the surface pseudocapacitive sodium-ion storage mechanism enables to overcome the sluggish sodium-ion diffusion process,which opens a new direction to design and synthesize high-rate sodiumion storage materials.展开更多
The density functional theory(DFT)calculations have been performed to investigate the catalytic properties of monolayer MoSi_(2)N_(4) for hydrogen evolution reaction(HER).The DFT results show that similar to the major...The density functional theory(DFT)calculations have been performed to investigate the catalytic properties of monolayer MoSi_(2)N_(4) for hydrogen evolution reaction(HER).The DFT results show that similar to the majority of other two-dimensional(2D)materials,the pristine MoSi_(2)N_(4) is inert for HER due to its weak affinity toward hydrogen,while monolayer MoSi_(2)N_(4-x)(x=0–0.25)exhibits the highly desirable HER catalytic activities by introducing surface nitrogen vacancy(NV).The predicted HER overpotential(0–60 mV)of monolayer MoSi_(2)N_(4-x) is lower than that(90 mV)of noble metal Pt,when the concentration of surface NV is lower than 5.6%.Electronic structure calculations show that the spin-polarized states appear around the Fermi level after introducing surface NV,thus making the surface NV on 2D MoSi_(2)N_(4) a quite suitable site for HER.Moreover,the HER activity of MoSi_(2)N_(4-x) is highly dependent on the surface NV concentration,which can be further related to the center of Si-3p band.Our results demonstrate that the newly discovered 2D MoSi_(2)N_(4) can be served as a promising electrocatalyst for HER via appropriate defect engineering.展开更多
In view of the low resolution and accuracy of traditional magnetometer,a method of microwave frequency modulation technology based on nitrogen-vacancy(NV)center in diamond for magnetic detection was proposed.The magne...In view of the low resolution and accuracy of traditional magnetometer,a method of microwave frequency modulation technology based on nitrogen-vacancy(NV)center in diamond for magnetic detection was proposed.The magnetometer studied can reduce the frequency noise of system and improve the magnetic sensitivity by microwave frequency modulation.Firstly,ESR spectra by sweeping the microwave frequency was obtained.Further,the microwave frequency modulated was gained through the mixed high-frequency sinusoidal modulation signal generated by signal generator.In addition,the frequency through the lock-in amplifier was locked,and the signal which was proportional to the first derivative of the spectrum was obtained.The experimental results show that the sensitivity of magnetic field detection can reach 17.628 nT/Hz based on microwave frequency modulation technology.The method realizes high resolution and sensitivity for magnetic field detection.展开更多
We investigate the mechanism for the improvement of p-type doping efficiency in Mg-Al0.14Ga0.86N/GaN super- lattices （SLs）. It is shown that the hole concentration of SLs increases by nearly an order of magnitude, f...We investigate the mechanism for the improvement of p-type doping efficiency in Mg-Al0.14Ga0.86N/GaN super- lattices （SLs）. It is shown that the hole concentration of SLs increases by nearly an order of magnitude, from 1.1 × 1017 to 9.3×1017 cm-3, when an AlN interlayer is inserted to modulate the strains. SchrSdinger-Poisson self-consistent calculations suggest that such an increase could be attributed to the reduction of donor-like defects caused by the strain modulation induced by the AlN interlayer. Additionally, the donor-acceptor pair emission exhibits a remarkable decrease in intensity of the cathodoluminescence spectrumlfor SLs with an A1N interlayer. This supports the theoretical calculations and indicates that the strain modulation of SLs could be beneficial to the donor-like defect suppression as well as the p-type doping efficiency improvement.展开更多
As the dominated composition of Si_(3)N_(4)ceramics,α-silicon nitride(α-Si_(3)N_(4))can satisfy the strength and fracture toughness demand in the applications.However,α-Si_(3)N_(4)is oxygen-sensitive at high temper...As the dominated composition of Si_(3)N_(4)ceramics,α-silicon nitride(α-Si_(3)N_(4))can satisfy the strength and fracture toughness demand in the applications.However,α-Si_(3)N_(4)is oxygen-sensitive at high temperatures,which limits its high-temperature performance.To improve the oxidation resistance ofα-Si_(3)N_(4)ceramics,it is necessary to shed light on the oxidation mechanism.Herein,the initial oxidation ofα-Si_(3)N_(4)was systematically studied at the atomic and molecular levels.The density functional theory(DFT)calculation denotes that the(001)surface ofα-Si_(3)N_(4)has the best stability at both room temperature and high temperature.Besides,the oxidation process of theα-Si_(3)N_(4)(001)surface consists of O adsorption and N desorption,and the consequent formation of nitrogen-vacancy(VN)is the key step for further oxidation.Moreover,the molecular dynamics(MD)simulation indicates that the oxidation rate ofα-Si_(3)N_(4)(100)surface is slower than that ofα-Si_(3)N_(4)(001)surface due to the lower N concentration at the outermost layer.Therefore,the oxidation resistance ofα-Si_(3)N_(4)can be improved by regulating the(100)surface as the dominant exposure surface.In addition,reducing the concentration of N on the final exposed surface ofα-Si_(3)N_(4)by mean of constructing the homojunction of the Si-terminal(100)surface and other N-containing surfaces(such as(001)surface)should be also a feasible approach.展开更多
Adsorption and activation of dinitrogen(N_(2)) is an indispensable process in nitrogen fixation.Metal nitride species continue to attract attention as a promsing catalyst for ammonia synthesis.However,the detailed mec...Adsorption and activation of dinitrogen(N_(2)) is an indispensable process in nitrogen fixation.Metal nitride species continue to attract attention as a promsing catalyst for ammonia synthesis.However,the detailed mechanisms at a molecular level between reactive nitride species and N_(2) remain unclear at elevated temperature,which is important to understand the temperature effect and narrow the gap between the gas phase system and condensed phase system.Herein,the ^(15)N/^(14)N isotopic exchange in the reaction between tantalum nitride cluster anions Ta_(3)^(14)N_(3)^(-) and ^(15)N_(2) leading to the regeneration of ^(14)N_(2)/^(14)N^(15)N was observed at elevated temperature(393-593 K)using mass spectrometry.With the aid of theoretical calculations,the exchange mechanism and the effect of temperature to promote the dissociation of N_(2) on Ta_(3)N_(3)^(-) were elucidated.A comparison experiment for Ta_(3)^(14)N_(4)^(-)/^(15)N_(2) couple indicated that only desorption of ^(15)N_(2) from Ta_(3)^(14)N_(4)^(15)N_(2)^(-) took place at elevated temperature.The different exchange behavior can be well understood by the fact that nitrogen vacancy is a requisite for the dinitrogen activation over metal nitride species.This study may shed light on understanding the role of nitrogen vacancy in nitride species for ammonia synthesis and provide clues in designing effective catalysts for nitrogen fixation.展开更多
A tightly linked dual ring antenna is designed,and it is specifically tailored for uniformly coupling the microwave magnetic field to the nitrogen-vacancy(NV)center.The designed antenna operates at a center frequency ...A tightly linked dual ring antenna is designed,and it is specifically tailored for uniformly coupling the microwave magnetic field to the nitrogen-vacancy(NV)center.The designed antenna operates at a center frequency of about 2.87 GHz,with a bandwidth of around 200 MHz,allowing it to address multiple resonance peaks in the optically detected magnetic resonance(ODMR)spectrum in an external magnetic field.Moreover,the antenna generates a fairly uniform magnetic field in a range with a radius of 0.75 mm.High resolution imaging of the magnetic field distribution on the surface of the antenna is conducted by using a fiber diamond probe.We also investigate the effect of magnetic field uniformity on the linewidth of ODMR,so as to provide insights into reducing the inhomogeneous broadening of ODMR.展开更多
Nanozyme antibacterial agents with high enzyme-like catalytic activity and strong bacteria-binding ability have provided an alternative method to efficiently disinfect drug-resistance microorganism.Herein,the carbon n...Nanozyme antibacterial agents with high enzyme-like catalytic activity and strong bacteria-binding ability have provided an alternative method to efficiently disinfect drug-resistance microorganism.Herein,the carbon nitride quantum dots(CNQDs)nanozymes with high nitrogen vacancies(NVs)were mass-productively prepared by a simple ultrasonic-crushing method assisted by propylene glycol.It was found that the NVs of CNQDs were stemmed from the selective breaking of surface N-(C)_(2)sites,accounting for 6.2%.Experiments and density functional theory(DFT)simulations have demonstrated that the presence of NVs can alter the local electron distribution and extend theπ-electron delocalization to enhance the peroxidase-like activity.Biocompatible CNQDs could enter inside microorganisms by diffusion and elevate the bacteria-binding ability,which enhanced the accurate and rapid attack of·OH to the microorganisms.The sterilization rate of CNQDs against Gram-negative bacteria(E.coli),Gram-positive bacteria(S.aureus,B.subtilis),fungi(R.solani)reaches more than 99%.Thus,this work showed great potential for engineered nanozymes for broad-spectrum antibacterial in biomedicine and environmental protection.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.112374012 and 11974208)Shandong Provincial Natural Science Foundation(Grant Nos.ZR2023JQ001 and tsqn202211128)。
文摘Single negatively charged nitrogen vacancy(NV-)centers in diamond have emerged as promising platforms for quantum information science,where long coherence times are essential for advancing quantum technologies.However,traditional fabrication methods often introduce lattice damage during the irradiation process used to create vacancies,significantly impairing the spin coherence properties of NV-centers.
基金funded by the National Natural Science Foundation of China (21802058 and 21872066)the Fundamental Research Funds for the Central Universities (China, lzujbky-2020-42)the Natural Science Foundation of Gansu Province (20JR5RA225)。
文摘As a substitute for synthetic ammonia under mild condition, electrocatalytic nitrogen reduction reaction(NRR) provides a hopeful approach for the development of ammonia. Nevertheless, the current development of NRR electrocatalysts is far from enough and a systematic research is needed to gain a better improvement. This article presents that 2 D C_(3)N_(4)-NV with a large specific surface area and abundant nitrogen vacancies is prepared by a simple and feasible method, and used as a metal-free catalyst for electrocatalytic NRR. Experiment result and density functional theory(DFT) calculation reveal that nitrogen vacancies in 2 D C_(3)N_(4)-NV can act as an efficient active site for catalytic NRR, which is conducive to capturing and activating N_(2), lowering Gibbs free energy(DG) in reaction and inhibiting hydrogen evolution reaction(HER) at the same time. In addition, the larger specific surface area also makes more active site exposed, which is good for the contact between the electrolyte and the active site, thus enhancing its NRR activity. The electrocatalyst shows an excellent catalytic activity for NRR in 0.1 M HCl, including Faradaic efficiency of 10.96%, NH_(3) yields of 17.85 lg h^(-1) mg_(cat)^(-1)., and good stability(over 20 h).
基金supported financially by the National Natural Science Foundation of China(No.51271047)
文摘To study the influence of the nitrogen vacancy （VN） on mechanical and electrical properties of zirconium nitride deeply, ZrNx films with different VN concentrations were synthesized on the Si （111） substrates by enhanced magnetic filtering arc ion plating. The morphologies, microstructures, residual stresses, compositions, chemical states, mechanical and electrical properties of the as-deposited films were characterized by field-emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectrometry, Nanoindenter and Hall effect measurements. The results showed that ZrNx films exhibited rocksalt single-phase structure within a VN concentration ranging from 26 to 5%. The preferred orientation, thickness, grain size and residual stress of the ZrNx films kept constant at different VN concentrations. Both the nanohardness and elastic modulus first increased and then decreased with the decrease in VN concentration, reaching the peaks around 16%. And the electric conductivity of the ZrNx films showed a similar tendency with nanohardness. The underlying atomic-scale mechanisms of VN concentration-dependent hardness and electric conductivity enhancements were discussed and attributed to the different electronic band structures, rather than conventional meso-scale factors, such as preferred orientation, grain size and residual stress.
基金supported in part by the MIT SuperUROP(Undergraduate Research Opportunities Program)supported by the Alexander von Humboldt-Foundation+3 种基金supported by the NASA Office of the Chief Technologist’s Space Technology Research Fellowshipsupport from the Air Force Office of Scientific Research PECASE(supervised by G.Pomrenke)supported in part by the AFOSR Quantum Memories MURI and by a fellowship from the NSF iQuISE program,award number 0801525supported by the US Department of Energy,Office of Basic Energy Sciences,under Contract No.DE-AC02-98CH10886.
文摘A central goal in quantum information science is to efficiently interface photons with single optical modes for quantum networking and distributed quantum computing.Here,we introduce and experimentally demonstrate a compact and efficient method for the low-loss coupling of a solid-state qubit,the nitrogen vacancy(NV)center in diamond,with a single-mode optical fiber.In this approach,single-mode tapered diamond waveguides containing exactly one high quality NV memory are selected and integrated on tapered silica fibers.Numerical optimization of an adiabatic coupler indicates that near-unity-efficiency photon transfer is possible between the two modes.Experimentally,we find an overall collection efficiency between 16%and 37%and estimate a single photon count rate at saturation above 700 kHz.This integrated system enables robust,alignment-free,and efficient interfacing of single-mode optical fibers with single photon emitters and quantum memories in solids.
基金Project supported in part by the National Natural Science Foundation of China(Grant Nos.91321208,11574386,11374344,and 11574380)the National Basic Research Program of China(Grant Nos.2014CB921401 and 2016YFA0300601)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB07010300)
文摘Hybrid quantum system of negatively charged nitrogen–vacancy（NV^-） centers in diamond and superconducting qubits provide the possibility to extend the performances of both systems. In this work, we numerically simulate the coupling strength between NV^-ensembles and superconducting flux qubits and obtain a lower bound of 1016cm^（-3） for NV^-concentration to achieve a sufficiently strong coupling of 10 MHz when the gap between NV^-ensemble and flux qubit is 0. Moreover, we create NV^-ensembles in different types of diamonds by14^（N＋）and12（C＋）ion implantation, electron irradiation, and high temperature annealing. We obtain an NV^-concentration of 1.05 × 1016cm^（-3） in the diamond with1-ppm nitrogen impurity, which is expected to have a long coherence time for the low nitrogen impurity concentration. This shows a step toward performance improvement of flux qubit-NV^-hybrid system.
基金supported by the Beijing Institute of Technology Research Fund Program for Young Scholars and the Analysis&Testing Center(Beijing Institute of Technology)the National Natural Science Foundation of China(22179007)。
文摘While lithium-sulfur(Li-S)battery has attracted remarkable attention owing to the high theoretical capacity,its practical application is still hindered by the shuttle and sluggish conversion kinetics of intermediate lithium polysulfides(Li PSs).Defect engineering,which can regulate the electronic structure and in turn influence the surface adsorption and catalytic capability,has been regarded as a feasible strategy to deal with the above challenges.However,few studies on nitrogen vacancies and their mechanisms are reported.Herein,cobalt nitride with nitrogen vacancies grown on multi-walled carbon nanotube(CNTCo N-VN)is designed and applied as the separator modification material to investigate the enhancing mechanism of nitrogen vacancies on Li-S batteries.The experimental evidence and theoretical calculation indicate that the introduction of nitrogen vacancies into cobalt nitride can enhance the chemical affinity to Li PSs and effectively hamper the shuttle effect.Meanwhile the reduced band gap of the d-band center of Co and p-band center of N for CNT-Co N-VNand the promoted diffusion of Li^(+) can expedite the solid-liquid and liquid-liquid conversions of sulfur species.Due to these superiorities,the cell with CNT-Co NVNmodified separator delivers a favorable initial capacity of 901 m Ah g^(-1)and a capacity of 660 m Ah g^(-1)can be achieved after 250 cycles at 2 C.This work explores the application of metal nitride with nitrogen vacancies and sheds light on the development of functional separators for high-efficient Li-S batteries.
基金financial supports from National Natural Science Foundation of China(Nos.91741105,22006120)Program for Innovation Team Building at Institutions of Higher Education in Chongqing(No.CXTDX201601011)Chongqing Municipal Natural Science Foundation(No.cstc2018jcyjAX0625).
文摘Electrochemical nitrate reduction reaction (NITRR) is regarded as a “two birds-one stone” method for the treatment of nitrate contaminant in polluted water and the synthesis of valuable ammonia, which is retarded by the lack of highly reactive and selective electrocatalysts .Herein, for the first time, nickel foam supported Co_(4) N was designed as a high-performance NITRR catalyst by an in-situ nonmetal leaching-induced strategy.At the optimal potential, the Co_(4) N/NF catalyst achieves ultra-high Faraday efficiency and NH_(3) selectivity of 95.4% and 99.4%, respectively.Ex situ X-ray absorption spectroscopy (XAS), together with other experiments powerfully reveal that the nitrogen vacancies produced by nitrogen leaching are stable and play a key role in boosting nitrate reduction to ammonia.Theoretical calculations confirm that Co_(4) N with abundant nitrogen vacancies can optimize the adsorption energies of NO_(3)^(-) and intermediates, lower the free energy (Δ G ) of the potential-determining step (*NH_(3) to NH_(3) ) and inhibit the formation of N-containing byproducts.In addition, we also conclude that the nitrogen vacancies can stabilize the adsorbed hydrogen, making H_(2) quite difficult to produce, and lowering ΔG from *NO to *NOH, which facilitates the selective reduction of nitrate.This study reveals significant insights about the in-situ nonmetal leaching to enhance the NITRR activity.
基金financially supported by the National Natural Science Foundation of China (22109073, 22072067 and 21875112)the supports from National and Local Joint Engineering Research Center of Biomedical Functional Materialsa project sponsored by the Priority Academic Program Development of Jiangsu Higher Education Institutions。
文摘Urea oxidation reaction (UOR),which has favorable thermodynamic energy barriers compared with oxygen evolution reaction (OER),can provide more cost-effective electrons for the renewable energy systems,but is trapped by its sluggish UOR kinetics and intricate reaction intermediates formation/desorption process.Herein,we report a novel and effective electrocatalyst consisting of carbon cloth supported nitrogen vacancies-enriched Ce-doped Ni_(3)N hierarchical nanosheets (Ce-Ni_(3)N @CC) to optimize the flat-footed UOR kinetics,especially the stiff rate-determine CO_(2)desorption step of UOR.Upon the introduction of valance state variable Ce,the resultant nitrogen vacancies enriched Ce-Ni_(3)N @CC exhibits an enhanced UOR performance where the operation voltage requires only 1.31 V to deliver the current density of 10 mA cm^(-2),which is superior to that of Ni_(3)N @CC catalyst (1.36 V) and other counterparts.Density functional theory (DFT) results demonstrate that the incorporation of Ce in Ni_(3)N lowers the formation energy of nitrogen vacancies,resulting in rich nitrogen vacancies in Ce-Ni_(3)N @CC.Moreover,the nitrogen vacancies together with Ce doping optimize the local charge distribution around Ni sites,and balance the adsorption energy of CO_(2)in the rate-determining step (RDS),as well as affect the initial adsorption structure of urea,leading to the superior UOR catalytic performance of Ce-Ni_(3)N @CC.When integrating the Ce-Ni_(3)N catalyst in UOR//HER and UOR//CO_(2)R flow electrolyzer,both of them perform well with low operation voltage and robust long-term stability,proofing that the thermodynamically favorable UOR can act as a suitable substitute anodic reaction compared with that of OER.Our findings here not only provide a novel UOR catalyst but also offer a promising design strategy for the future development of energy-related devices.
基金National Key Research and Development Program of China(2023YFB3811700,2022YFF0503600)Fundamental Research Funds for the Central Universities(HIT.OCEF.2022048,HIT.DZJJ.2023041)+3 种基金National Natural Science Foundation of China(52072087)Henan Provincial Science and Technology Research Project(231100230300)Natural Science Foundation of Heilongjiang Province(YQ2021E018)National Key Laboratory of Science,Technology on Advanced Composites in Special Environments,HIT。
文摘The nitrogen-vacancy(NV)color center in diamond is a promising solid-state quantum system at room temperature.However,its sensitivity is limited by its low fluorescence collection efficiency,and its coherence time is limited by spin interference of impurity electrons around the NV color center.Here,we innovatively fabricated a one-dimensional photonic crystal on the surface of diamond,which greatly improved the fluorescence intensity of the NV color centers and increased the sensitivity of NV ensembles by a factor of 2.92.In addition,the laser reflected by the photonic crystal excites impurity electrons around the NV color centers,improving the electric field environment around the NV color centers,which exponentially prolongs the dephasing time(from 209 to841 ns),opening avenues for NV color-center ensemble sensors.
文摘Optically detected magnetic resonance(ODMR)has emerged as a powerful technique for quantum sensing,enabling high-sensitivity detection of physical quantities even at room temperature.Solid-state defects,such as nitrogen-vacancy(NV)centers in diamond,have demonstrated remarkable capabilities in this domain[1–4].However,these systems are limited by their rigid lattice structures and lack tunability.
基金National Natural Science Foundation of China(52435011,51821003,62175219,62103385)。
文摘Microwave chips are widely utilized in modern communication,national defense,and various technological domains.However,effective signal identification remains challenging due to complex multi-frequency microwave interference.To address this issue,we propose an advanced optical imaging framework based on nitrogen-vacancy(NV)center near-field microscopy.This framework enables the separation and imaging characterization of mixed multi-frequency microwave signals across a wide field of view(2000μm×1600μm,spatial resolution of 5μm)on chip surfaces.By leveraging the NV color center as a mixer,combined with a multi-frequency hybrid model and fast Fourier transform(FFT)analysis,we convert the invisible electromagnetic waves into visible optical information.Using a wide-field microscopy system equipped with a high-speed optical camera,our approach effectively enables the separation and imaging of mixed microwave signals across two complex scenarios.Comparative analysis with finite element simulation validates the accuracy of this approach.Experimental results reveal m Hz frequency resolution for GHz microwaves andμT-level signal intensity resolution,showcasing its superior capability for imaging mixed signals with multi-frequency.These findings provide critical technical support for microwave chip characterization,interference signal identification,and diagnostic testing,highlighting the broad applicability of this technique.
基金supported by the National Natural Science Foundation of China(Grant Nos.11374280 and 50772110).
文摘The negatively charged nitrogen vacancy(NV^(−))center ensemble in as-grown chemical vapor deposition(CVD)diamond is a promising candidate for quantum sensing due to its long coherence time and excellent optical properties.However,achieving a high concentration of NV^(−)centers in as-grown CVD diamond remains a critical challenge,which constrains the performance of NV^(−)based sensors.In this study,we observe that NV^(−)center formation efficiency is significantly enhanced during the initial growth phase,with a coherence time T_(2)^(*)of 1.1μs.These findings demonstrate that high-concentration NV^(−)centers can be achieved in as-grown diamonds,greatly enhancing their utility in high-performance magnetometers and quantum sensing.
基金supported by the National Natural Science Foundation of China(51832004,51521001)the National Key Research and Development Program of China(2016YFA0202603)+2 种基金the Program of Introducing Talents of Discipline to Universities(B17034)the Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory(XHT2020-003)the “Double-First Class”Foundation of Materials and Intelligent Manufacturing Discipline of Xiamen University。
文摘Sodium-ion storage devices are highly desirable for large-scale energy storage applications owing to the wide availability of sodium resources and low cost.Transition metal nitrides(TMNs)are promising anode materials for sodium-ion storage,while their detailed reaction mechanism remains unexplored.Herein,we synthesize the mesoporous Mo3N2 nanowires(Meso-Mo_(3)N_(2)-NWs).The sodium-ion storage mechanism of Mo3N2 is systematically investigated through in-situ XRD,ex-situ experimental characterizations and detailed kinetics analysis.Briefly,the Mo_(3)N_(2) undergoes a surface pseudocapacitive redox charge storage process.Benefiting from the rapid surface redox reaction,the Meso-Mo_(3)N_(2)-NWs anode delivers high specific capacity(282 m Ah g^(-1) at 0.1 A g^(-1)),excellent rate capability(87 m Ah g^(-1) at 16 A g^(-1))and long cycling stability(a capacity retention of 78.6%after 800 cycles at 1 A g^(-1)).The present work highlights that the surface pseudocapacitive sodium-ion storage mechanism enables to overcome the sluggish sodium-ion diffusion process,which opens a new direction to design and synthesize high-rate sodiumion storage materials.
基金supported by the National Natural Science Foundation of China(Nos.51972312 and 51472249)
文摘The density functional theory(DFT)calculations have been performed to investigate the catalytic properties of monolayer MoSi_(2)N_(4) for hydrogen evolution reaction(HER).The DFT results show that similar to the majority of other two-dimensional(2D)materials,the pristine MoSi_(2)N_(4) is inert for HER due to its weak affinity toward hydrogen,while monolayer MoSi_(2)N_(4-x)(x=0–0.25)exhibits the highly desirable HER catalytic activities by introducing surface nitrogen vacancy(NV).The predicted HER overpotential(0–60 mV)of monolayer MoSi_(2)N_(4-x) is lower than that(90 mV)of noble metal Pt,when the concentration of surface NV is lower than 5.6%.Electronic structure calculations show that the spin-polarized states appear around the Fermi level after introducing surface NV,thus making the surface NV on 2D MoSi_(2)N_(4) a quite suitable site for HER.Moreover,the HER activity of MoSi_(2)N_(4-x) is highly dependent on the surface NV concentration,which can be further related to the center of Si-3p band.Our results demonstrate that the newly discovered 2D MoSi_(2)N_(4) can be served as a promising electrocatalyst for HER via appropriate defect engineering.
基金National Natural Science Foundation of China(Nos.51635011,61503346,51727808)National Science Foundation of Shanxi Province(No.201701D121080)
文摘In view of the low resolution and accuracy of traditional magnetometer,a method of microwave frequency modulation technology based on nitrogen-vacancy(NV)center in diamond for magnetic detection was proposed.The magnetometer studied can reduce the frequency noise of system and improve the magnetic sensitivity by microwave frequency modulation.Firstly,ESR spectra by sweeping the microwave frequency was obtained.Further,the microwave frequency modulated was gained through the mixed high-frequency sinusoidal modulation signal generated by signal generator.In addition,the frequency through the lock-in amplifier was locked,and the signal which was proportional to the first derivative of the spectrum was obtained.The experimental results show that the sensitivity of magnetic field detection can reach 17.628 nT/Hz based on microwave frequency modulation technology.The method realizes high resolution and sensitivity for magnetic field detection.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61076012,61076013,and 51102003)the National High Technology Research and Development Program of China (Grant No. 2007AA03Z403)+1 种基金the Specialized Research Fund for the Doctoral Program of Higher Education,China (Grant No. 20100001120014)the National Basic Research Program of China (Grant No. 2012CB619304)
文摘We investigate the mechanism for the improvement of p-type doping efficiency in Mg-Al0.14Ga0.86N/GaN super- lattices （SLs）. It is shown that the hole concentration of SLs increases by nearly an order of magnitude, from 1.1 × 1017 to 9.3×1017 cm-3, when an AlN interlayer is inserted to modulate the strains. SchrSdinger-Poisson self-consistent calculations suggest that such an increase could be attributed to the reduction of donor-like defects caused by the strain modulation induced by the AlN interlayer. Additionally, the donor-acceptor pair emission exhibits a remarkable decrease in intensity of the cathodoluminescence spectrumlfor SLs with an A1N interlayer. This supports the theoretical calculations and indicates that the strain modulation of SLs could be beneficial to the donor-like defect suppression as well as the p-type doping efficiency improvement.
基金financially supported by the National Science Fund for Distinguished Young Scholars(No.52025041)the National Natural Science Foundation of China(Nos.51904021,51974021,51902020)+1 种基金the Fundamental Research Funds for the Central Universities(No.FRF-TP-19-008A1)the State Key Laboratory of Refractories and Metallurgy,Wuhan University of Science and Technology(No.G202003)。
文摘As the dominated composition of Si_(3)N_(4)ceramics,α-silicon nitride(α-Si_(3)N_(4))can satisfy the strength and fracture toughness demand in the applications.However,α-Si_(3)N_(4)is oxygen-sensitive at high temperatures,which limits its high-temperature performance.To improve the oxidation resistance ofα-Si_(3)N_(4)ceramics,it is necessary to shed light on the oxidation mechanism.Herein,the initial oxidation ofα-Si_(3)N_(4)was systematically studied at the atomic and molecular levels.The density functional theory(DFT)calculation denotes that the(001)surface ofα-Si_(3)N_(4)has the best stability at both room temperature and high temperature.Besides,the oxidation process of theα-Si_(3)N_(4)(001)surface consists of O adsorption and N desorption,and the consequent formation of nitrogen-vacancy(VN)is the key step for further oxidation.Moreover,the molecular dynamics(MD)simulation indicates that the oxidation rate ofα-Si_(3)N_(4)(100)surface is slower than that ofα-Si_(3)N_(4)(001)surface due to the lower N concentration at the outermost layer.Therefore,the oxidation resistance ofα-Si_(3)N_(4)can be improved by regulating the(100)surface as the dominant exposure surface.In addition,reducing the concentration of N on the final exposed surface ofα-Si_(3)N_(4)by mean of constructing the homojunction of the Si-terminal(100)surface and other N-containing surfaces(such as(001)surface)should be also a feasible approach.
基金supported by the National Natural Science Foundation of China(No.21973101 and No.21833011)the Youth Innovation Promotion Association CAS(No.2020034)the K.C.Wong Education Foundation。
文摘Adsorption and activation of dinitrogen(N_(2)) is an indispensable process in nitrogen fixation.Metal nitride species continue to attract attention as a promsing catalyst for ammonia synthesis.However,the detailed mechanisms at a molecular level between reactive nitride species and N_(2) remain unclear at elevated temperature,which is important to understand the temperature effect and narrow the gap between the gas phase system and condensed phase system.Herein,the ^(15)N/^(14)N isotopic exchange in the reaction between tantalum nitride cluster anions Ta_(3)^(14)N_(3)^(-) and ^(15)N_(2) leading to the regeneration of ^(14)N_(2)/^(14)N^(15)N was observed at elevated temperature(393-593 K)using mass spectrometry.With the aid of theoretical calculations,the exchange mechanism and the effect of temperature to promote the dissociation of N_(2) on Ta_(3)N_(3)^(-) were elucidated.A comparison experiment for Ta_(3)^(14)N_(4)^(-)/^(15)N_(2) couple indicated that only desorption of ^(15)N_(2) from Ta_(3)^(14)N_(4)^(15)N_(2)^(-) took place at elevated temperature.The different exchange behavior can be well understood by the fact that nitrogen vacancy is a requisite for the dinitrogen activation over metal nitride species.This study may shed light on understanding the role of nitrogen vacancy in nitride species for ammonia synthesis and provide clues in designing effective catalysts for nitrogen fixation.
基金Project supported by the National Key Research and Development Program of China(Grant No.2021YFB2012600)the Shanghai Aerospace Science and Technology Innovation Fund(Grant No.SAST-2022-102).
文摘A tightly linked dual ring antenna is designed,and it is specifically tailored for uniformly coupling the microwave magnetic field to the nitrogen-vacancy(NV)center.The designed antenna operates at a center frequency of about 2.87 GHz,with a bandwidth of around 200 MHz,allowing it to address multiple resonance peaks in the optically detected magnetic resonance(ODMR)spectrum in an external magnetic field.Moreover,the antenna generates a fairly uniform magnetic field in a range with a radius of 0.75 mm.High resolution imaging of the magnetic field distribution on the surface of the antenna is conducted by using a fiber diamond probe.We also investigate the effect of magnetic field uniformity on the linewidth of ODMR,so as to provide insights into reducing the inhomogeneous broadening of ODMR.
基金the National Natural Science Foundation of China(Nos.21876099,22106088,and 22276110)Key Research&Developmental Program of Shandong Province(No.2021CXGC011202)Fundamental Research Funds of Shandong University(No.zy202102).
文摘Nanozyme antibacterial agents with high enzyme-like catalytic activity and strong bacteria-binding ability have provided an alternative method to efficiently disinfect drug-resistance microorganism.Herein,the carbon nitride quantum dots(CNQDs)nanozymes with high nitrogen vacancies(NVs)were mass-productively prepared by a simple ultrasonic-crushing method assisted by propylene glycol.It was found that the NVs of CNQDs were stemmed from the selective breaking of surface N-(C)_(2)sites,accounting for 6.2%.Experiments and density functional theory(DFT)simulations have demonstrated that the presence of NVs can alter the local electron distribution and extend theπ-electron delocalization to enhance the peroxidase-like activity.Biocompatible CNQDs could enter inside microorganisms by diffusion and elevate the bacteria-binding ability,which enhanced the accurate and rapid attack of·OH to the microorganisms.The sterilization rate of CNQDs against Gram-negative bacteria(E.coli),Gram-positive bacteria(S.aureus,B.subtilis),fungi(R.solani)reaches more than 99%.Thus,this work showed great potential for engineered nanozymes for broad-spectrum antibacterial in biomedicine and environmental protection.
