An Efficient Boron Source Activation Strategy for the Low‑Temperature Synthesis of Boron Nitride Nanotubes

Lowering the synthesis temperature of boron nitride nanotubes(BNNTs)is crucial for their development.The primary reason for adopting a high temperature is to enable the effective activation of highmelting-point solid boron.In this study,we developed a novel approach for efficiently activating boron by introducing alkali metal compounds into the conventional MgO–B system.This approach can be adopted to form various low-melting-point AM–Mg–B–O growth systems.These growth systems have improved catalytic capability and reactivity even under low-temperature conditions,facilitating the synthesis of BNNTs at temperatures as low as 850℃.In addition,molecular dynamics simulations based on density functional theory theoretically demonstrate that the systems maintain a liquid state at low temperatures and interact with N atoms to form BN chains.These findings offer novel insights into the design of boron activation and are expected to facilitate research on the low-temperature synthesis of BNNTs.

Design of a Control Device for Synthetic Making Test Based on Pre-Arcing Current Detection and Phase Control

The synthetic making test has been widely used in evaluating the break ability of high-voltage circuit breaker. However, the test research and application are still inadequate, especially in the condition of rated voltage. According to the realistic conditions of test stations in China, a control device based on pre-arcing current detection and phase control is proposed in this paper. A sample of the control device made up of DSP TMS320LF2407A is fabricated, in which the CPLD MAX7064 is used to transmit signals for EMC design. It can be applied in full voltage synthetic making test at a level of 126kV/63kA. The test results show that, it is accurate to control the making phase of the applied voltage, whether the closing is demanded at voltage peak or zero.

The compatibly large nonlinear optical effect and high laser-induced damage threshold in a thiophosphate CsInP_(2)S_(7)constructed with[P_(2)S_(7)]^(4-)and[InS_(6)]^(9-)

It is challenging to cooperatively improve the nonlinear optical(NLO)efficiency and the laser-induced damage threshold(LIDT).This work reports a novel IR NLO materials CsInP_(2)S_(7)(CIPS)designed by combination the strategies of alkali metals substitution and microscopic NLO units PS4 introduction based on AgGaS_(2).CIPS was composed of strongly distorted[InS_(6)]^(9-)octahedra and[P_(2)S_(7)]4-dimers constructed by corner-sharing[PS_(4)]^(3-),which increase the NLO efficiency and decrease thermal expansion anisotropy simultaneously.Compared with AgGaS_(2),CIPS exhibited strong phase matchable NLO response ca.1.1×AGS@2.1μm,high LIDT ca.20.8×AgGaS_(2),and IR transparency up to 15.3μm.Structural analysis and theoretical investigation confirmed that large SHG effect and ultrahigh LIDT of CIPS originated from the synergistic contribution of[InS_(6)]^(9-)octahedra and[P_(2)S_(7)]4-dimers.These results indicate that CIPS is a promising NLO candidate in the mid-IR region,and this study provides a new approach for developing potential NLO-LIDT compatible materials.

Non-layered InSe nanocrystalline bulk materials with ultra-low thermal conductivity

Exploring new prototypes for a given chemical composition is of great importance and interest to several disciplines.As a famous semiconducting binary compound,InSe usually exhibits a two-dimensional layered structure with decent physical and mechanical properties.However,it is less noticed that InSe can also adopt a monoclinic structure,denoted as mcl-InSe.The synthesis of such a phase usually re-quires high-pressure conditions,and the knowledge is quite scarce on its chemical bonding,lattice dynamics,and thermal transport.Here in this work,by developing a facile method combining me-chanical alloying and spark plasma sintering,we successfully synthesize mcl-InSe bulks with well-crystallized nanograins.The chemical bonding of mcl-InSe is understood as compared with layered InSe via charge analysis.Low cut-off frequencies of acoustic phonons and several low-lying optical modes are demonstrated.Noticeably,mcl-InSe exhibits a low room-temperature thermal conductivity of 0.6 W·m^(-1)·K^(-1),which is smaller than that of other materials in the IneSe system and many other selenides.Low-temperature thermal analyses corroborate the role of nanograin boundaries and low-frequency optical phonons in scattering acoustic phonons.This work provides new insights into the non-common prototype of the InSe binary compound with potential applications in thermoelectrics or thermal insulation.

Deciphering urban traffic impacts on air quality by deep learning and emission inventory

Air pollution is a major obstacle to future sustainability,and traffic pollution has become a large drag on the sustainable developments of future metropolises.Here,combined with the large volume of real-time monitoring data,we propose a deep learning model,iDeepAir,to predict surface-level PM2.5 concentration in Shanghai megacity and link with MEIC emission inventory creatively to decipher urban traffic impacts on air quality.Our model exhibits high-fidelity in reproducing pollutant concentrations and reduces the MAE from 25.355μg/m^(3) to 12.283μg/m^(3) compared with other models.And identifies the ranking of major factors,local meteorological conditions have become a nonnegligible factor.Layer-wise relevance propagation(LRP)is used here to enhance the interpretability of the model and we visualize and analyze the reasons for the different correlation between traffic density and PM_(2.5) concentration in various regions of Shanghai.Meanwhile,As the strict and effective industrial emission reduction measurements implementing in China,the contribution of urban traffic to PM_(2.5) formation calculated by combining MEIC emission inventory and LRP is gradually increasing from 18.03%in 2011 to 24.37% in 2017 in Shanghai,and the impact of traffic emissions would be ever-prominent in 2030 according to our prediction.We also infer that the promotion of vehicular electrification would achieve further alleviation of PM_(2.5) about 8.45% by 2030 gradually.These insights are of great significance to provide the decision-making basis for accurate and high-efficient traffic management and urban pollution control,and eventually benefit people’s lives and high-quality sustainable developments of cities.

Temperature-driven reversible structural transformation and conductivity switching in ultrathin Cu_(9)S_(5)crystals

Two-dimensional(2D)materials with reversible phase transformation are appealing for their rich physics and potential applications in information storage.However,up to now,reversible phase transitions in 2D materials that can be driven by facile nondestructive methods,such as temperature,are still rare.Here,we introduce ultrathin Cu_(9)S_(5)crystals grown by chemical vapor deposition(CVD)as an exemplary case.For the first time,their basic electrical properties were investigated based on Hall measurements,showing a record high hole carrier density of~1022 cm^(-3) among 2D semiconductors.Besides,an unusual and repeatable conductivity switching behavior at~250 K were readily observed in a wide thickness range of CVD-grown Cu_(9)S_(5)(down to 2 unit-cells).Confirmed by in-situ selected area electron diffraction,this unusual behavior can be ascribed to the reversible structural phase transition between the room-temperature hexagonalβphase and low-temperatureβ’phase with a superstructure.Our work provides new insights to understand the physical properties of ultrathin Cu_(9)S_(5)crystals,and brings new blood to the 2D materials family with reversible phase transitions.

Growth of boron nitride nanotubes from magnesium-based catalysts

This study reports an efficient method for growing high-quality boron nitride nanotubes(BNNTs)via chemical vapor deposition of low-melting-point precursors—magnesium diboride(MgB_(2)),magnesium nitride(Mg_(3)N_(2)),and diboron trioxide(B_(2)O)at a growth temperature of 1000–1300℃.The strong oxygen-capturing ability of Mg_(3)N_(2)inhibits the formation of high-melting-point Mg_(3)B_(2)O_(6),which helps MgB_(2)to maintain an efficient and stable catalytic capacity,thereby enhancing its growth efficiency and utilization of the boron source.Moreover,polydimethylsiloxane(PDMS)composites formed from these BNNTs demonstrated much greater thermal conductivities than pure PDMS.Thus,this novel strategy for preparing BNNTs is efficient,and they have great potential for application as thermal interface materials.

利用电子衍射解析晶体结构的研究进展

电子衍射技术是解析晶体结构的基本手段之一,随着透射电子显微镜硬件设施的不断改善以及结构解析方法的发展,电子衍射在探究材料构效关系领域发挥着越来越重要的作用.本文主要介绍了本课题组在利用电子衍射解析结构方面的工作,以及国内外关于电子衍射技术发展的最新进展和展望.本课题组利用选区电子衍射及三维电子衍射技术,结合粉末X射线衍射、单晶X射线衍射、高分辨电子显微镜等表征手段,解析了许多复杂的晶体结构,包括无机功能材料、分子筛、共价有机框架材料等.

Degradable Hybrid CuS Nanoparticles for Imaging-Guided Synergistic Cancer Therapy via Low-Power NIR-II Light Excitation

Near-infrared(NIR)-II light-excitable photonic agents capable of generating tumor hyperthermia and cytotoxic free radicals are promising for synergistic phototherapy of tumors.However,the lack of NIR-II excitable agents makes it challenging to achieve combinational tumor phototherapy.Here,the authors have reported on a tumor-targeting and degradable hybrid copper sulfide(CuS)nanoparticle(AIBA@CuS-FA)via loading a hydrophilic Azo initiator(AIBA)into an amphiphilic lipid-encapsulating CuS nanoparticle.AIBA@CuS-FA shows high photothermal conversion efficiency(PCE≈47.5%)at 1064 nm,enabling heat production to trigger tumor hyperthermia and thermal decomposition of AIBA into cytotoxic free alkyl radicals upon irradiation with a 1064-nm laser under low-power density(0.5 W/cm2).Moreover,alkyl radicals can drive degradation of AIBA@CuS-FA and embedded CuS nanodisks,releasing Cu^(2+)ions that can catalyze a Fenton-like reaction for hydroxyl radical(•OH)production to promote tumor therapy.Findings demonstrate promise for combinational photothermal therapy(PTT),oxygen-independent alkyl radical therapy,and chemodynamic therapy(CDT)of tumors.

Accurate structure determination of nanocrystals by continuous precession electron diffraction tomography

Structures are the cornerstones of structure-function relationship research of materials.After more than a hundred years of development,single crystal X-ray diffraction(SC-XRD)becomes the most common method to determine structures of materials.Nevertheless,the weak interaction between X-ray and matter requires crystals to be larger than 5μm ×5μm × 5μm for normal SC-XRD diffractometer.Recent appearances of X-ray free electron lasers(XFEL)and micro-focused synchrotron beamlines allow SC-XRD data collection from micron-sized crystals,but access to these facilities is limited.The development of three-dimensional(3D)electron diffraction(ED)has provided a powerful tool for scientists to explore the microcosmos,extending the limit of the SC-XRD method[1].

Pressure-driven symmetry breaking and electron disproportionation of the trigonal Nb_(3)cluster in Nb_(3)Cl_(8)

Symmetry breaking of metal cluster-based strongly correlated systems can give rise to collective phenomena.Here,the twodimensional Nb_(3) cluster compound Nb_(3)Cl_(8) is shown to suffer dramatic symmetry breaking and electron disproportionation under compression.A structural phase transition from trigonal P–3m1 to monoclinic C2/m is observed near 8 GPa with the three-fold symmetry breaking.Electron disproportionation occurs on Nb_(3) clusters from delocalized Nb^(8/3+)Nb^(8/3+)Nb^(8/3+)to localized Nb^(3+)Nb^(3+)Nb^(2+),which results in a subtle bandgap discontinuity,as evidenced by electrical transport and UV-Vis absorption measurements.

Exciton-harvesting enabled efficient charged particle detection in zero-dimensional halides

Materials for radiation detection are critically important and urgently demanded in diverse fields,starting from fundamental scientific research to medical diagnostics,homeland security,and environmental monitoring.Lowdimensional halides(LDHs)exhibiting efficient self-trapped exciton(STE)emission with high photoluminescence quantum yield(PLQY)have recently shown a great potential as scintillators.However,an overlooked issue of excitonexciton interaction in LDHs under ionizing radiation hinders the broadening of its radiation detection applications.Here,we demonstrate an exceptional enhancement of exciton-harvesting efficiency in zero-dimensional(0D)Cs_(3)Cu_(2)I_(5):Tl halide single crystals by forming strongly localized Tl-bound excitons.Because of the suppression of nonradiative exciton-exciton interaction,an excellentα/βpulse-shape-discrimination(PSD)figure-of-merit(FoM)factor of 2.64,a superior rejection ratio of 10^(−9),and a high scintillation yield of 26000 photons MeV−1 under 5.49 MeVα-ray are achieved in Cs_(3)Cu_(2)I_(5):Tl single crystals,outperforming the commercial ZnS:Ag/PVT composites for charged particle detection applications.Furthermore,a radiation detector prototype based on Cs_(3)Cu_(2)I_(5):Tl single crystal demonstrates the capability of identifying radioactive 220Rn gas for environmental radiation monitoring applications.We believe that the exciton-harvesting strategy proposed here can greatly boost the applications of LDHs materials.