Intramolecular Hydrogen Bond Improved Durability and Kinetics for Zinc‑Organic Batteries

Organic compounds have the advantages of green sustainability and high designability,but their high solubility leads to poor durability of zinc-organic batteries.Herein,a high-performance quinone-based polymer(H-PNADBQ)material is designed by introducing an intramolecular hydrogen bonding(HB)strategy.The intramolecular HB(C=O⋯N-H)is formed in the reaction of 1,4-benzoquinone and 1,5-naphthalene diamine,which efficiently reduces the H-PNADBQ solubility and enhances its charge transfer in theory.In situ ultraviolet-visible analysis further reveals the insolubility of H-PNADBQ during the electrochemical cycles,enabling high durability at different current densities.Specifically,the H-PNADBQ electrode with high loading(10 mg cm^(-2))performs a long cycling life at 125 mA g^(-1)(>290 cycles).The H-PNADBQ also shows high rate capability(137.1 mAh g^(−1)at 25 A g^(−1))due to significantly improved kinetics inducted by intramolecular HB.This work provides an efficient approach toward insoluble organic electrode materials.

First-principles study of lattice dynamics and thermodynamics of osmium under pressure

We have performed the first-principles linear response calculations of the lattice dynamics, thermal equation of state and thermodynamical properties of hcp Os metal by using the plane-wave pseudopotential method. The ther-modynamical properties are deduced from the calculated Helmholtz free energy by taking into account the electronic contribution and lattice vibrational contribution. The phonon frequencies at Gamma point are consistent with ex- perimental values and the dispersion curves at various pressures have been determined. The calculated volume, bulk modulus and their pressure derivatives as a function of temperature are in excellent agreement with the experimental results. The calculated specific heat indicates that the electronic contribution is important not only at very low tem-peratures but also at high temperatures due to the electronic thermal excitation. The calculated Debye temperature at a very low temperature is in good agreement with experimental values and drops to a constant until 100 K.

Analysis of Cr atom focusing deposition properties in the double half Gaussian standing wave field

The use of the dipole force on atoms is a new technology that is used to build nanostructures.In this way,a high quality standard nano-grating can be obtained.Based on the semi-classical model,the motion equation is investigated and the trajectories of atoms in double half Gaussian standing wave field are simulated.Compared with the Gaussian standing wave field,the double half Gaussian standing wave can well focus the Cr atoms.In order to obtain this kind of beam,a prism is designed and the experimental result shows that the beam is well generated.

Impact of counter-rotating-wave term on quantum heat transfer and phonon statistics in nonequilibrium qubit–phonon hybrid system

Counter-rotating-wave terms(CRWTs)are traditionally viewed to be crucial in open small quantum systems with strong system–bath dissipation.Here by exemplifying in a nonequilibrium qubit–phonon hybrid model,we show that CRWTs can play the significant role in quantum heat transfer even with weak system–bath dissipation.By using extended coherent phonon states,we obtain the quantum master equation with heat exchange rates contributed by rotating-waveterms(RWTs)and CRWTs,respectively.We find that including only RWTs,the steady state heat current and current fluctuations will be significantly suppressed at large temperature bias,whereas they are strongly enhanced by considering CRWTs in addition.Furthermore,for the phonon statistics,the average phonon number and two-phonon correlation are nearly insensitive to strong qubit–phonon hybridization with only RWTs,whereas they will be dramatically cooled down via the cooperative transitions based on CRWTs in addition.Therefore,CRWTs in quantum heat transfer system should be treated carefully.

Experimental Study of Tunneling modes in Photonic Crystal Heterostructure Consisting of Single-Negative Materials

The pair structure and the photonic crystal heterostructure consisting of ε-negative and μ-negative materials are successfully fabricated by using the transmission line approach.We experimentally investigate the tunneling mode properties by simulating and measuring the scattering parameters and phase shifts.It is shown that the pair structure and the photonic crystal heterostructures possess tunneling modes when the general zero average permittivity and zero average permeability condition are satisfied.At the tunneling frequency,the field (voltage)mainly concentrates in the center of the constructed structures based on the amplification of the evanescent wave.Moreover,the tunneling mode of the photonic crystal heterostructure has zero phase delay.The characteristics have potential applications in design of zero phase delay filters.

Directional Design of Materials Based on Multi-Objective Optimization:A Case Study of Two-Dimensional Thermoelectric SnSe

The directional design of functional materials with multi-objective constraints is a big challenge,in which performance and stability are determined by a complicated interconnection of different physical factors.We apply multi-objective optimization,based on the Pareto Efficiency and Particle-Swarm Optimization methods,to design new functional materials directionally.As a demonstration,we achieve the thermoelectric design of 2D SnSe materials via the above methods.We identify several novel metastable 2D SnSe structures with simultaneously lower free energy and better thermoelectric performance in their experimentally reported monolayer structures.We hope that the results of our work on the multi-objective Pareto Optimization method will represent a step forward in the integrative design of future multi-objective and multi-functional materials.

Designing radiative cooling metamaterials for passive thermal management by particle swarm optimization

The passive radiative cooling technology shows a great potential application on reducing the enormous global energy consumption.The multilayer metamaterials could enhance the radiative cooling performance.However,it is a challenge to design the radiative cooler.In this work,based on the particle swarm optimization(PSO)evolutionary algorithm,we develop an intelligent workflow in designing photonic radiative cooling metamaterials.Specifically,we design two 10-layer SiO_(2) radiative coolers doped by cylindrical MgF_(2) or air impurities,possessing high emissivity within the selective(8–13μm)and broadband(8–25μm)atmospheric transparency windows,respectively.Our two kinds of coolers demonstrate power density as high as 119 W/m^(2) and 132 W/m^(2) at the room temperature(300 K).Our scheme does not rely on the usage of special materials,forming high-performing metamaterials with conventional poor-performing components.This significant improvement of the emission spectra proves the effectiveness of our inverse design algorithm in boosting the discovery of high-performing functional metamaterials.

Geometric Thermoelectric Pump:Energy Harvesting beyond Seebeck and Pyroelectric Effects

Thermal-electric conversion is crucial for smart energy control and harvesting,such as thermal sensing and waste heat recovering.So far,researchers are aware of two main ways of direct thermal-electric conversion,Seebeck and pyroelectric effects,each with different working mechanisms,conditions and limitations.Here,we report the concept of Geometric Thermoelectric Pump(GTEP),as the third way of thermal-electric conversion beyond Seebeck and pyroelectric effects.In contrast to Seebeck effect that requires spatial temperature difference,GTEP converts the time-dependent ambient temperature fluctuation into electricity.Moreover,GTEP does not require polar materials but applies to general conducting systems,and thus is also distinct from pyroelectric effect.We demonstrate that GTEP results from the temperature-fluctuation-induced charge redistribution,which has a deep connection to the topological geometric phase in non-Hermitian dynamics,as a consequence of the fundamental nonequilibrium thermodynamic geometry.The findings advance our understanding of geometric phase induced multiple-physics-coupled pump effect and provide new means of thermal-electric energy harvesting.

Electric Field Analysis of Space Charge Injection from a Conductive Nano-Filler Electrode

电极附近的电场分发上的模拟被建议为使用与乙烯乙烯基醋酸盐混合的 nanosized 碳黑色解释原因，当电极能比使用一个扔的金属电极导致更多的费用注射进聚合物。电极与固定尺寸和经常的电的潜力被简化到传导性的半范围的层。由使用有限元素方法，两个都，在邻近的半范围之间的半范围和距离的尺寸能戏剧性地在范围的表面附近影响电场，这被发现；这些被认为是为在各种各样的材料的电极注射率的费用的二个明确的因素。[从作者抽象]

Disappearance of the Dirac cone in silicene due to the presence of an electric field

Using the two-dimensional ionic Hubbard model as a simple basis for describing the electronic structure of silicene in the presence of an electric field induced by the substrate, we use the coherent-potential approximation to calculate the zero-temperature phase diagram and the associated spectral function at half filling. We find that any degree of symmetrybreaking induced by the electric field causes the silicene structure to lose its Dirac fermion characteristics, thus providing a simple mechanism for the disappearance of the Dirac cone.

Structured mirror array for two-dimensional collimation of a chromium beam in atom lithography

Direct-write atom lithography,one of the potential nanofabrication techniques,is restricted by some difficulties in producing optical masks for the deposition of complex structures.In order to make further progress,a structured mirror array is developed to transversely collimate the chromium atomic beam in two dimensions.The best collimation is obtained when the laser red detunes by natural line-width of transition 7S3 → 7P40 of the chromium atom.The collimation ratio is 0.45 vertically(in x axis),and it is 0.55 horizontally(in y axis).The theoretical model is also simulated,and success of our structured mirror array is achieved.

Nonadiabatic spin-torque and damping effects on vortex core switching triggered by a single current pulse

Switching the orientation of a vortex core by spin-polarised pulse current introduces a promising concept for the reliable addressing of a single nanodisc element inside dense arrays.In this paper,micromagnetic simulations are employed to study the vortex core switching behaviour excited by a short in-plane Gaussian current pulse.We find that both the switching mechanism and the switching time are not sensitive to changes in the phenomenological parameters of spin-torque nonadiabaticity and Gilbert damping.The switching time,however,strongly depends on the current strength.In addition,we have theoretically predicted the parameter range of current pulses to achieve a single switching event.

Adsorption of cationic dyes from aqueous solution using hydrophilic silica aerogel via ambient pressure drying

In order to remove the organic dyes of textile waste water,the silica aerogel was successfully prepared by using E-40 as a novel precursor and then dried in ambient pressure.The synthesized sample was verified by Scanning Electron Microscopy(SEM)and Fourier Transform Infrared Spectroscopy(FTIR).After calcining,the hydrophilic silica aerogel(HSA)was used as adsorbent to remove Methylene Blue(MB),Malachite Green(MG),and Gentian Violet(GV)from aqueous solution.The effects of initial concentration of dyes and adsorbent dosage on the adsorption process were examined.It was found that HSA showed excellent adsorption capacities,the maximum percentage of removal dyes could reach 98%.Herein,the Langmuir,Freundlich and de Boer-Zwikker isotherm modes were employed to discuss the adsorption behavior.The results indicated that the de Boer–Zwikker model can effectively describe the adsorption behavior.Besides,the HSA could be utilized as the recyclable adsorbent in degradation experiment,after five cycles,no obvious loss of adsorption capacity was found.As an efficient,low-cost,environmental friendly and recyclable adsorbent,silica aerogel is expected to be used for dyes removal.

SnS_2 nanosheets arrays sandwiched by N-doped carbon and TiO_2 for high-performance Na-ion storage

In this paper, SnS_2 nanosheets arrays sandwiched by porous N-doped carbon and TiO_2(TiO_2@SnS_2@N-C) on flexible carbon cloth are prepared and tested as a free-standing anode for high-performance sodium ion batteries. The as-obtained TiO_2@SnS_2@N-C composite delivers a remarkable capacity performance(840 mA h g^(-1) at a current density of 200 mA g^(-1)), excellent rate capability and long-cycling life stability(293 mA h g^(-1) at 1 A g^(-1) after 600 cycles). The excellent electrochemical performance can be attributed to the synergistic effect of each component of the unique hybrid structure, in which the SnS_2 nanosheets with open framworks offer high capacity, while the porous N-doped carbon nanoplates arrays on flexible carbon cloth are able to improve the conductivity and the TiO_2 passivation layer can keep the structure integrity of SnS_2 nanosheets.

Thermal conductivity of nanowires

Thermal conductivity of nanowires(NWs) is a crucial criterion to assess the operating performance of NWs-based device applications, such as in the field of heat dissipation, thermal management, and thermoelectrics. Therefore, numerous research interests have been focused on controlling and manipulating thermal conductivity of one-dimensional materials in the past decade. In this review, we summarize the state-of-the-art research status on thermal conductivity of NWs from both experimental and theoretical studies. Various NWs are included, such as Si, Ge, Bi, Ti, Cu, Ag, Bi_2Te_3, ZnO, AgTe,and their hybrids. First, several important size effects on thermal conductivity of NWs are discussed, such as the length,diameter, orientation, and cross-section. Then, we introduce diverse nanostructuring pathways to control the phonons and thermal transport in NWs, such as alloy, superlattices, core–shell structure, porous structure, resonant structure, and kinked structure. Distinct thermal transport behaviors and the associated underlying physical mechanisms are presented.Finally, we outline the important potential applications of NWs in the fields of thermoelectrics and thermal management,and provide an outlook.

From Elastic Spin to Phonon Spin:Symmetry and Fundamental Relations

This work is mainly based on postgraduate lectures at Tongji University since 2020 spring.We firstly revisit the elastic spin and orbital angular momentum[Proc.Natl.Acad.Sci.USA 115,9951(2018)]but more general for anisotropic systems by applying Noether’s theorem to the elastic Lagrangian and by applying the symmetry argument in the field theory.Then,fundamental relations between elastic energy flux and elastic spin are uncovered.In particular cases,the wave spin is closely related to the vorticity of energy flux and momentum.Secondly,we move forward from the elastic spin to revisit the phonon spin[Fizika Tverdogo Tela 3,2160(1961)]by applying the second quantization to elastic fields.We show that the uncovered phonon spin,a polarized elastic-vibration quanta,is generally not restricted to transverse phonon modes,but applying to general phonon modes,such as the longitudinal phonon modes,surface phonon modes,and hybridized phonon modes,regarded as a consequence of mode interferences.The elastic spin and phonon spin originate from the local rotating of the field polarization in time domain,not the local circulation(vorticity)of displacement or velocity in space domain.It is hopeful that the present results could advance the fundamental understanding of phonon spin and elastic spin,and promote the spin phononics for hybrid quantum sensing and technology with multiple degrees of freedom.

Erratum to“Designing thermal demultiplexer:Splitting phonons by negative mass and genetic algorithm optimization”

Equations(8)and(9)in the original paper[Chin.Phys.B 30036301(2021)]are corrected.

The Luminescence of a CuI Film Scintillator Controlled by a Distributed Bragg Reflector

We investigate the emission properties of CuI film scintillators and the effect of distributed Bragg reflectors.The free-exciton emission and the donor-acceptor pair emission from the CuI thin film with the peak wavelengths of 410 nm and 420 nm are observed.However,for the two emission bands,the distributed Bragg reflector reflection results in different enhancements,which is interpreted by the varying transmittance with wavelength.Angle-dependence of emission profile is decided by the transmittance and DBR reflection,which may be useful in scintillation detection applications.

Designing thermal demultiplexer: Splitting phonons by negative mass and genetic algorithm optimization

We propose the concept of thermal demultiplexer, which can split the heat flux in different frequency ranges intodifferent directions. We demonstrate this device concept in a honeycomb lattice with dangling atoms. From the view ofeffective negative mass, we give a qualitative explanation of how the dangling atoms change the original transport property.We first design a two-mass configuration thermal demultiplexer, and find that the heat flux can flow into different ports incorresponding frequency ranges roughly. Then, to improve the performance, we choose the suitable masses of danglingatoms and optimize the four-mass configuration with genetic algorithm. Finally, we give out the optimal configuration witha remarkable effect. Our study finds a way to selectively split spectrum-resolved heat to different ports as phonon splitter,which would provide a new means to manipulate phonons and heat, and to guide the design of phononic thermal devices inthe future.

Excess Diffusion of a Driven Colloidal Particle in a Convection Array

We numerically investigate the transport of a passive colloidal particle in a periodic array of planar counterrotating convection rolls,at high Peclet numbers.It is shown that an external bias,oriented parallel to the array,produces a huge excess diffusion peak,in cases where bias and advection drag become comparable.This effect is not restricted to one-dimensional convection geometries,and occurs independently of the array’s boundary conditions.