Synthesis strategies of hard carbon anodes for sodium-ion batteries

Sodium-ion battery(SIB)is an ideal candidate for large-scale energy storage due to high abundant sodium sources,relatively high energy density,and potentially low costs.Hard carbons,as one of the most promising anodes,could deliver high plateau capacities at low potentials,which boosts the energy densities of SIBs.Their slope capacities have been demonstrated from the defect adsorption of sodium ions,while the plateau capacity depends highly on intercalation and pore filling.Nevertheless,the specific structures of sodium ions stored in hard carbons have not been clarified,namely active sites of adsorption,intercalation,and pore-filling mechanisms.Therefore,delicate synthesis methods are required to prepare hard carbons with controllable specific structures,along with elucidating the precise active sites for enhancing the Na-ion storage performance.To offer databases for future designs,we summarized the synthesis strategies of hard carbon anodes for constructing active sites of plateau capacities.Synthesis methods were highlighted with corresponding influences on the meticulous structures of hard carbons and Na-ion storage behaviors.Last but not least,perspectives were proposed for developing hard carbon anodes from the points of research and practical applications.

Crystal Structure of 8β-Hydroxyeremophil-7(11)-ene-12,8α(4β,6α)-diolide

8β-hydroxyeremophil-7（11）-ene-12,8α（4β,6α）-diolide was isolated from the Ligularia intermedia and characterized by MS, multi NMR and X-ray single crystal diffraction. Its crystal structure was determined as in a orthorhombic type, with space group P212121 with a=6.8519（5）, b=10.7191（8）, c=18.5942（14） A, V=1365.67（18） A,^3 Z=4, and the calculated density is 1.354 mg/m^3. F（000）=592, μ=0.101 mm^-1.

Microstructure and mechanical properties of Ti−Nb−Fe−Zr alloys with high strength and low elastic modulus

Zr was added to Ti−Nb−Fe alloys to develop low elastic modulus and high strengthβ-Ti alloys for biomedical applications.Ingots of Ti−12Nb−2Fe−(2,4,6,8,10)Zr(at.%)were prepared by arc melting and then subjected to homogenization,cold rolling,and solution treatments.The phases and microstructures of the alloys were analyzed by optical microscopy,X-ray diffraction,and transmission electron microscopy.The mechanical properties were measured by tensile tests.The results indicate that Zr and Fe cause a remarkable solid-solution strengthening effect on the alloys;thus,all the alloys show yield and ultimate tensile strengths higher than 510 MPa and 730 MPa,respectively.Zr plays a weak role in the deformation mechanism.Further,twinning occurs in all the deformed alloys and is beneficial to both strength and plasticity.Ti−12Nb−2Fe−(8,10)Zr alloys with metastableβphases show low elastic modulus,high tensile strength,and good plasticity and are suitable candidate materials for biomedical implants.

Preparation and properties of GAGG:Ce/glass composite scintillation material

The translucent GGAG:Ce/glass composites are prepared successfully by ball-milling,tableting,and pressureless sintering.The thickness of composites is about 400μm.The x-ray diffraction(XRD),differential scanning calorimetry(DSC),density of composite materials are measured and discussed systematically.The scanning electron microscopy(SEM)and energy dispersive spectrometer(EDS)elemental mapping are employed to analyze the particle size,the shape of powders,and the distribution of GGAG:Ce particles in the glass matrix,respectively.The decay time,ultraviolet,(UV),x-ray excitation luminescence spectra,and temperature spectra are studied.The results show that the composite materials have high light output,good thermostability,and short decay time.The method adopted in this work is an effective method to reduce the preparation time and cost of the sample.The ultralow afterglow indicates that the composite materials have an opportunity to be used for x-ray detection and imaging.

Oxidation of petroleum-based byproducts diformyltricyclodecanes(DFTD)with O2 under catalyst-free and ultra-low temperature

Oxidation of petroleum-based byproduct dicyclopentadiene derived diformyltricyclodecanes(DFTD) to dicarboxyltriclodecanesacids(DCTDA) was conducted under catalyst-free and ultra-low temperature conditions with O2 as oxidant. In the perspective of industry process, oxygen pressure and contents, solvent and raw material initial concentrations were screened to evaluate their influence on DCTDA generation. Results indicate that DFTD oxidation can occur rather easily under no-catalyst and ultra-low temperature conditions with O2 as oxidant. Oxygen content and pressure had positive effect on DCTDA production, γ-valerolactone(GVL) behaved best on DFTD generation in dynamics, while methanol could be used as a protective solvent to preserve DFTD.Besides, the existence of water in solvent was not beneficial to DCTDA production because of poor DFTD compatibility with water. The mechanisms of O2 and solvent influence on DCTDA generation were discussed. Meanwhile,the oxidation route of DFTD–Intermediate–DCTDA was proposed. The present work exhibits the valued potential of DFTD, which will have a positive effect on high added value of petroleum based by-products.

Low-Dose 1 MeV Electron Irradiation-Induced Enhancement in the Photoluminescence Emission of Ga-Rich InGaN Multiple Quantum Wells

We investigate the photoluminescence(PL)emission from InGaN/GaN multiple quantum-well structures before and after 1 MeV electron irradiation.The PL peak intensity exhibits a slight enhancement after low-dose electron irradiation(2×10^(13) e/cm^(2)),and then decreases with the cumulative electron dose.Meanwhile,the full width at half maximum of the PL spectrum narrows after low-dose electron irradiation and widens when the irradiation dose is relatively high.With respect to the yellow photoluminescence,there is no significant change until the electron fluence has accumulated up to 10^(14) e/cm^(2).

δ-Calculus:A New Approach to Quantifying Location Privacy

With the rapid development of mobile wireless Internet and high-precision localization devices,location-based services(LBS)bring more convenience for people over recent years.In LBS,if the original location data are directly provided,serious privacy problems raise.As a response to these problems,a large number of location-privacy protection mechanisms(LPPMs)(including formal LPPMs,FLPPMs,etc.)and their evaluation metrics have been proposed to prevent personal location information from being leakage and quantify privacy leakage.However,existing schemes independently consider FLPPMs and evaluation metrics,without synergizing them into a unifying framework.In this paper,a unified model is proposed to synergize FLPPMs and evaluation metrics.In detail,the probabilistic process calculus(calledδ-calculus)is proposed to characterize obfuscation schemes(which is a LPPM)and integrateα-entropy toδ-calculus to evaluate its privacy leakage.Further,we use two calculus moving and probabilistic choice to model nodes’mobility and compute its probability distribution of nodes’locations,and a renaming function to model privacy leakage.By formally defining the attacker’s ability and extending relative entropy,an evaluation algorithm is proposed to quantify the leakage of location privacy.Finally,a series of examples are designed to demonstrate the efficiency of our proposed approach.

Clamping effect driven design and fabrication of new infrared birefringent materials with large optical anisotropy

Infrared(IR)birefringent materials with large optical anisotropy and wide transparency range are important for efficient light manipulation in various IR optical devices.Herein,two new IR birefringent materials AMgGeSe_(3)(A=Li,Na)with large optical anisotropy were rationally designed by a rigid octahedron and flexible dimer combined strategy and fabricated in experiment.The introduction of rigid[LiSe_(6)]/[NaSe_(6)]and[MgSe_(6)]octahedra effectively regulates the geometry and arrangement of the flexible[Ge2Se6]dimers,resulting in the birefringence as large as 0.334@1,064 nm in LiMgGeSe_(3) and 0.445@1,064 nm(the largest one in the reported[Ge_(2)Se_(6)]dimer-contained selenides)in NaMgGeSe_(3).Density functional theory(DFT)calculations and statistical analyses highlight the influence of polarizability anisotropy,density,arrangement of units,as well as layer distance on birefringence.The results indicate that AMgGeSe_(3)(A=Li,Na)crystals are the promising IR birefringent materials and it gives an insight into the exploration of new IR birefringent materials with large birefringence based on the clamping effect from rigid groups.

Fluorooxoborates:A precious treasure of deep-ultraviolet nonlinear optical materials

As the key components of all-solid-state deep-ultraviolet(DUV,λ<200 nm)laser sources,exploring DUV nonlinear optical(NLO)materials has been a research hotspot for a long time.However,as the only material that has been practically used to generate DUV coherent light through the direct second harmonic generation(SHG)process,KBe_(2)BO_(3)F_(2)(KBBF)still meets bottlenecks,namely,severe layered crystal growth tendency,for extensive application.In the search for the next generation of DUV NLO materials,fluorooxoborates are highly expected due to their excellent NLO performances,flexible structures,and rich structural chemistry.So far,a large number of materials with prominent properties have emerged in the fluorooxoborate system.By investigating the differences in structures and properties among fluorooxoborates and borates and borate fluorides,the excellent NLO per-formances of fluorooxoborates are attributed to functionalized B-O/F chromophores.In this review,by analyzing the published fluorooxoborates,the fluorooxoborate system is a precious treasure for exploring DUV NLO ma-terials.The synthesis,structures,and properties of some representative fluorooxoborates in the research history are introduced and summarized.Finally,we put forward the opportunities and challenges of future research in fluorooxoborate DUV NLO crystals.

A family of oligo(p-phenylenevinylene)derivative aggregation-induced emission probes:Ultrasensitive,rapid,and anti-interfering fluorescent sensing of perchlorate via precise alkyl chain length modulation

The precise regulation of interactions provided by aggregation-induced emission(AIE)probes is of considerable significance for improving the sensing performance in the field of on-site detection.Here,a highly sensitive perchlorate detection probe was designed by precisely modulating the van der Waals interactions by adjusting the length of the alkyl chain.The optimized AIE probe demonstrated superior perchlorate detection performance owing to its strong van der Waals interactions with perchlorate,including a low detection limit(53.81 nM),rapid response(<5 s),and excellent specificity even in the presence of 16 interfering anions.In addition,a hydrogel-based device loaded with the probe was constructed to achieve ultrasensitive recognition of perchlorate particles with a detection limit as low as 15 fg under a fluorescence microscope.Moreover,the practicality of the probe was further verified by employing a sensing chip in a portable detector,and thus the probe has been proven to be highly promising for trace perchlorate monitoring in real scenarios.We expect the present study to be of great value for the efficient design of high-performance fluorescent probes.

Intermolecular through-space charge transfer enabled by bicomponent assembly for ultrasensitive detection of synthetic cannabinoid JWH-018

Launching the intermolecular through-space charge transfer(TSCT)from a bicomponent assembly for photophysical property manipulation is of great significance in fluorescence probe design.Here,we demonstrate the elaborate control of droplet evaporation dynamics for intermolecular TSCT can facilitate the ultrasensitive detection of JWH-018,a representative synthetic cannabinoid.Driven by diverse intermolecular interactions,the probe,and JWH-018 assemble in a closely stacked manner to emit strong fluorescence at 477 nm,ascribing to the intermolecular TSCT at the S2 state.The strategy realizes an ultra-low limit of detection of 11 nmol/mL and great selectivity towards JWH-018.The practicability is further verified by constructing a sensing chip for JWH-018 aerosol detection,which facilitates the on-site drug abuser screening with the naked eye.Moreover,the proposed assembly-enabled TSCT is expected to find a variety of applications for optoelectronic materials design and photophysical mechanism-dominated molecular recognition.

Review on birefringence in borates based on birefringence-active functional groups and arrangements

As a fundamental parameter of the optical crystals,birefringence plays a vital role in many optical applications,such as phase modulation,light splitting,and polarization,especially the phase matching process of the nonlinear optical crystals.The big birefringence not only benefits to the miniaturization of related devices,but also broadens the phase-matching wavelength range of nonlinear optical crystals.The design and synthesis of crystals with large birefringence becomes a hot research topic due to its more and more important applications in the optical modulation and laser technology fields.Herein,crystals with birefringence greater than 0.05 in the borate system are reviewed and classified according to different birefringent active groups,and the relationship between structure and properties is thoroughly explored.It is hoped that this review will provide a clear understanding of what kinds of building units and arrangements would have more opportunity to get adequate birefringence in borate systems and provide the statistical references to encourage the emergence of better crystal materials with large birefringence.

Crystal structure graph neural networks for high-performance superconducting critical temperature prediction

The utilization of machine learning methods to predict the superconducting critical temperature(T_(c))traditionally necessitates manually constructing elemental features,which challenges both the provision of meaningful chemical insights and the accuracy of predictions.In this work,we introduced crystal structure graph neural networks to extract structure-based features for T_(c)prediction.Our results indicated that these structure-based models outperformed all previously reported models,achieving an impressive coefficient of determination(R^(2))of 0.962 and a root mean square error(RMSE)of 6.192 K.From the existing Inorganic Crystal Structure Database(ICSD),our model successfully identified 76 potential high-temperature superconducting compounds with T_(c)≥77 K.Among these,Tl_(5)Ba_(6)Ca_(6)Cu_(9)O_(29)and TlYBa_(2)Cu_(2)O_(7)exhibit remarkably high T_(c)values of 108.4 and 101.8 K,respectively.This work provides a perspective on the structure-property relationship for reliable T_(c)prediction.

Enhanced nonlinear optical functionality in birefringence and refractive index dispersion of the deep-ultraviolet fluorooxoborates

As a promising candidate,the fluorooxoborate has enkindled new explorations of nonlinear optical materials to meet the deep-ultraviolet criteria.However,big challenges and open questions still remain facing this exciting new field,especially the birefringence and dispersion of refractive index which are fundamental parameters for determining the phasematching second harmonic generation wavelength.Here we designed possible anionic groups in fluorooxoborates,and analyzed the optical anisotropy to check its influence on birefringence,which was proved further by the response electronic distribution anisotropy approximation.The functional modules modulating birefringence in fluorooxoborates were explored systematically.We developed an approach for evaluating the behavior of the refractive index dispersions and found that the fluorooxoborates had small refractive index dispersions owing to the introduction of fluorooxoborate modules.Our results demonstrate that fluorooxoborates can be utilized to realize short phase-matching wavelength markedly and offer a path toward novel performance-driven materials design.

Designing excellent mid-infrared nonlinear optical materials with fluorooxo-functional group of d^0 transition metal oxyfluorides

Exploration of new infrared(IR) nonlinear optical(NLO) materials is still in urgency owing to the indispensable roles in optoelectronic devices, resource exploration, and long-distance laser communication. The formidable challenge is to balance the contradiction between wide band gaps and large second harmonic generation(SHG) effects in IR NLO materials. In the present work, we proposed new kinds of NLO active units, d^0 transition metal fluorooxofunctional groups for designing mid-IR NLO materials. By studying a series of d^0 transition metal oxyfluorides(TMOFs),the influences of fluorooxo-functional groups with different d^0 configuration cations on the band gap and SHG responses were explored. The results reveal that the fluorooxo-functional groups with different d^0 configuration cations can enlarge band gaps in mid-IR NLO materials. The first-principles calculations demonstrate that the nine alkali/alkaline earth metals d^0 TMOFs exhibit wide band gaps(all the band gaps >3.0 e V), large birefringence Δn(> 0.07), and two W/Mo TMOFs also exhibit large SHG responses. Moreover, by comparing with other fluorooxo-functional groups, it is found that introducing fluorine into building units is an effective way to enhance optical performance. These d^0 TMOFs with superior fluorooxo-functional groups represent a new exploration family of the mid-IR region, which sheds light on the design of mid-IR NLO materials possessing large band gap.

Degradation of the front and back channels in a deep submicron partially depleted SOI NMOSFET under off-state stress

The hot-carrier effect charactenstic in a deep submicron partially depleted SOI NMOSFET is investigated. Obvious hot-carrier degradation is observed under off-state stress.The hot-carrier damage is supposed to be induced by the parasitic bipolar effects of a float SOI device.The back channel also suffers degradation from the hot carrier in the drain depletion region as well as the front channel.At low gate voltage,there is a hump in the sub-threshold curve of the back gate transistor,and it does not shift in the same way as the main transistor under stress.While under the same condition,there is a more severe hot-carrier effect with a shorter channel transistor. The reasons for those phenomena are discussed in detail.

Total dose irradiation and hot-carrier effects of sub-micro NMOSFETs

Total dose irradiation and the hot-carrier effects of sub-micro NMOSFETs are studied. The results show that the manifestations of damage caused by these two effects are quite different, though the principles of damage formation are somewhat similar. For the total dose irradiation effect, the most notable damage lies in the great increase of the off-state leakage current. As to the hot-carrier effect, most changes come from the decrease of the output characteristics curves as well as the decrease of trans-conductance. It is considered that the oxide-trapped and interface-trapped charges related to STI increase the current during irradiation, while the negative charges generated in the gate oxide, as well as the interface-trapped charges at the gate interface, cause the degradation of the hot-carrier effect. Different aspects should be considered when the device is generally hardened against these two effects.

Syntheses, characterization, and theoretical calculation of Rb2Mg3（P2O7）2 polymorphs with deep-ultraviolet cutoff edges

By the combination of the isolated P2O7 dimers and Mg O4 tetrahedra,α-andβ-Rb2Mg3(P2O7)2 polymorphs were synthesized by a high-temperature solution method.α-Rb2Mg3(P2O7)2 crystallizes in non-centrosymmetric space group P212121,whileβ-Rb2Mg3(P2O7)2 crystallizes in centrosymmetric P21/c.Both structures contain a three dimensional[Mg3P4O14]^2- anionic framework,while Rb^+ cations are in the space.Structure analyses show that the isolated P2O7 dimers can easily adjust their variable configurations and orientations to fit the different coordination environments of the cations,which is conducive to the formation of polymorphs.The phase transformation process fromα-toβ-Rb2Mg3(P2O7)2 was further investigated by powder X-ray diffraction and thermal gravimetric/differential scanning calorimetry measurements.In addition,UV-vis-NIR diffusion spectra indicate both materials have deep-ultraviolet cut-off edges(below 190 nm).α-Rb2Mg3(P2O7)2 is second-harmonic generation(SHG)-active and the origin of SHG response was investigated by the SHG density calculations.The first-principle calculations were also carried out to illuminate their structure-property relationships.

Tunable electronic band structure,luminescence properties and thermostability of(Gd_(1-x)La_(x))_(2)Si_(2)O_(7):Ce scintillator by adjusting La/Gd ratio

Mixed crystal strategy is an effective approach of improving the luminescence properties of optical materials and has been adopted widely in many systems.In this paper,the La-mixed Gd_(2)Si_(2)O_(7):Ce polycrystalline samples were successfully synthesized by a sol-gel method.The crystal structure and luminescence properties were confirmed and discussed by XRD,UV-Vis luminescence spectra,and XEL,respectively.The vacuum ultraviolet excitation spectra and thermoluminescence glow curves were also systematically investigated and discussed at varied temperature.A combination of the first-principles calculations and optical characterization experiments was employed to study the electronic band structure of host material,revealing that the band gap is narrowed and the 5d_(1) level of Ce^(3+) shifts to higher energy as the La content increases.The luminescence the rmo-stability and activation energy were also measured and calculated.It indicates that thermo-stability is strongly dependent on the La concentration.An effective approach is developed to tune the electronic band structure,luminescence properties and thermostability of(Gd_(1-x)La_(x))_(2)Si_(2)O_(7):Ce scintillator by adjusting La/Gd ratio.

Toward the Enhancement of Critical Performance for Deep-Ultraviolet Frequency-Doubling Crystals Utilizing Covalent Tetrahedra

Deep-ultraviolet(deep-UV,λ<200 nm)coherent light is emerging as an indispensable driving force behind the innovation of optics and materials science.The deep-UV-driven applications range from laser interference photolithography to precise micromachining to futuristic ideas such as space propulsion using remotely controlled positioning lasers.Unlike conventional approaches to obtaining deep-UV light,for instance,synchrotron radiation,direct laser excitation,and gas discharge,nonlinear frequency conversion can be regarded as a more attractive way to endow such resource with high photon energy,high photon flux,and high spectral resolution.Actually,the nonlinear frequency conversion can be efficient only with the use of highperforming frequency-doubling crystals,which should be well-suited to the physics of nonlinear optical process.However,the necessary prerequisites for a practical frequency-doubling crystal are extremely strict,and thus very few crystals can be used to generate the deep-UV light.Faced with this,sustained effort has been expended by chemists and materials scientists toward discovering novel deep-UV frequency-doubling crystals.Studies have so far indicated that the main difficulty in finding a perfect candidate comes from the combination of three critical properties(absorption edge,nonlinear optical coefficients,and birefringence)into one crystal because they share the mutual relation of restriction and influence.In this Account,we present recent progress in discovering emergent deep-UV frequency-doubling crystals with the discussion of our efforts to balance the three critical properties by introducing the covalent tetrahedra[MO4−nXn](n=1−3),in which M refers to central atoms such as B,P,Si,S,Al,Zn,and Be and X can be apical atoms such as F,Cl,Br,and N.By analyzing the influence of the covalent tetrahedra on optical properties,we came to the conclusion of how to use the oxidized tetrahedra to achieve the improvement of the absorption edge,nonlinear optical coefficients,and birefringence for deep-UV frequency-doubling crystals.The followings are the key points in achieving the above goals:(i)elimination of dangling bonds with covalent tetrahedra to push the absorption edge of crystals into the deep-UV spectral region;(ii)orbital hybridization enhancement,charge-transfer energy reduction,and symmetry breaking of original tetrahedra with the introduction of X atoms and thereby the achievement of the enhancement of nonlinear optical coefficients;and(iii)uniform alignment of tetrahedral distorted units and the introduction of polarized X atoms containing[MO_(4−n)X_(n)]tetrahedra with high polarizability anisotropy to cause the large enhancement of birefringence.These findings allow us to understand the microcosmic behaviors of covalent tetrahedra on pushing the current limitations and provide an optional functional group toward the maximum thresholds of three critical parameters for deep-UV frequency-doubling crystals.Finally,we conclude this Account with a better understanding of the positive roles of covalent tetrahedra in enhancing the optical performance and how they can facilitate the construction of high-performing deep-UV crystals.