Charge-Assisted Hydrogen-Bonded Organic Frameworks with Inorganic Ammonium Regulated Switchable Open Polar Sites

Surface open polar sites within the voids of porous molecular crystals define the localized physicochemical environment for critical functions such as gas separation and molecular recognition. This study presents a new charge-assisted hydrogen bonding (H-bonding) motif, by exploiting inorganic ammonium (NH₄⁺) cations as H-bond donors, to regulate the assembly of C₂-symmetric carboxylic tectons for building robust H-bonded frameworks with permanent ultra-micropores and open oxygen sites. Diverse building blocks are bridged by tetrahedral NH₄⁺ to expand distinctive H-bonded networks with varied pore architectures. Particularly, the open polar oxygen sites can be switched by altering NH₄⁺ sources to tune the deprotonation of carboxyl-containing tectons. The activated porous PTBA·NH₄·DMF preserves the pore architecture and open polar oxygen sites, exhibiting remarkably selective sorption of CO₂ (107.8 cm³ g⁻¹,195 K) over N₂ (11.2 cm³ g⁻¹, 77 K) and H₂ (1.4 cm³ g⁻¹, 77 K).     

Phase equilibria in the HfO2-ZrO2-CeO2 system at 1250°C

The 1250°C phase equilibria in the HfO₂-ZrO₂-CeO₂ system have been studied for the first time over the entire composition triangle, and the 1250°C section of the HfO₂-ZrO₂-CeO₂ phase diagram has been constructed using x-ray diffraction, optical microscopy, and scanning electron microscopy. No new phases have been identified in the system. We have located three regions of solid solutions based on the constituent oxides (M-HfO₂, T-ZrO₂, and F-CeO₂), three two-phase (T + F, T + M, and F + M) regions, and one three-phase (T + F + M) region.     

Switchable Cavitation in Silicone Coatings for Energy-Saving Cooling and Heating

Space cooling and heating currently result in huge amounts of energy consumption and various environmental problems. Herein, a switching strategy is described for efficient energy-saving cooling and heating based on the dynamic cavitation of silicone coatings that can be reversibly and continuously tuned from a highly porous state to a transparent solid. In the porous state, the coatings can achieve efficient solar reflection (93%) and long-wave infrared emission (94%) to induce a subambient temperature drop of about 5 °C in hot weather (≈35 °C). In the transparent solid state, the coatings allow active sunlight permeation (95%) to induce solar heating to raise the ambient temperature from 10 to 28 °C in cold weather. The coatings are made from commercially available, cheap materials via a facile, environmentally friendly method, and are durable, reversible, and patternable. They can be applied immediately to various existed objects including rigid substrates.     

Molecular Approach to Electrochemically Switchable Monolayer MoS2 Transistors

As Moore's law is running to its physical limit, tomorrow's electronic systems can be leveraged to a higher value by integrating “More than Moore” technologies into CMOS digital circuits. The hybrid heterostructure composed of two-dimensional (2D) semiconductors and molecular materials represents a powerful strategy to confer new properties to the former components, realize stimuli-responsive functional devices, and enable diversification in “More than Moore” technologies. Here, an ionic liquid (IL) gated 2D MoS₂ field-effect transistor (FET) with molecular functionalization is fabricated. The suitably designed ferrocene-substituted alkanethiol molecules not only improve the FET performance, but also show reversible electrochemical switching on the surface of MoS₂. Field-effect mobility of monolayer MoS₂ reaches values as high as ≈116 cm² V⁻¹ s⁻¹ with I_on/I_off ratio exceeding 10⁵. Molecules in their neutral or charged state impose distinct doping effect, efficiently tuning the electron density in monolayer MoS₂. It is noteworthy that the joint doping effect from IL and switchable molecules results in the steep subthreshold swing of MoS₂ FET in the backward sweep. These results demonstrate that the device architecture represents an unprecedented and powerful strategy to fabricate switchable 2D FET with a chemically programmed electrochemical signal as a remote control, paving the road toward novel functional devices.     

极性环烯烃共聚物的研究进展

评述了具有殷实应用前景的极性环烯烃共聚物最新研究进展。主要对比了后处理法、前处理法及直接共聚法三种不同的制备途径。后处理法因极性基团通过后处理产生,故不会影响聚合活性,且极性基团含量较高,但步骤繁琐。前处理法使极性基团的保护与聚合过程相耦合,操作较后处理法简便。直接共聚法工艺最为简单,但其催化剂活性还有待进一步提高。同时,在基于制备过程特征的基础上,围绕提高环烯烃及极性基团的有效插入率进行了重点阐述。     

Nanoscale Ultrasound‐Switchable FRET‐Based Liposomes for Near‐Infrared Fluorescence Imaging in Optically Turbid Media

A new approach for fluorescence imaging in optically turbid media centered on the use of nanoscale ultrasound‐switchable FRET‐based liposome contrast agents is reported. Liposomes containing lipophilic carbocyanine dyes as FRET pairs with emission wavelengths located in the near‐infrared window are prepared. The efficacy of FRET and self‐quenching for liposomes with a range of fluorophore concentrations is first calculated from measurement of the liposome emission spectra. Exposure of the liposomes to ultrasound results in changes in the detected fluorescent signal, the nature of which depends on the fluorophores used, detection wavelength, and the fluorophore concentration. Line scanning of a tube containing the contrast agents with 1 mm inner diameter buried at a depth of 1 cm in a heavily scattering tissue phantom demonstrates an improvement in image spatial resolution by a factor of 6.3 as compared with images obtained in the absence of ultrasound. Improvements are also seen in image contrast with the highest obtained being 9% for a liposome system containing FRET pairs. Overall the results obtained provide evidence of the potential the nanoscale ultrasound‐switchable FRET‐based liposomes studied here have for in vivo fluorescence imaging.     

Doping and Switchable Photovoltaic Effect in Lead‐Free Perovskites Enabled by Metal Cation Transmutation

Creating defect tolerant lead‐free halide perovskites is the major challenge for development of high‐performance photovoltaics with nontoxic absorbers. Few compounds of Sn, Sb, or Bi possess ns² electronic configuration similar to lead, but their poor photovoltaic performances inspire us to evaluate other factors influencing defect tolerance properties. The effect of heavy metal cation (Bi) transmutation and ionic migration on the defects and carrier properties in a 2D layered perovskite (NH₄)₃(Sb_(1?x)Bi_x)₂I₉ system is investigated. It is shown, for the first time, the possibility of engineering the carriers in halide perovskites via metal cation transmutation to successfully form intrinsic p‐ and n‐type materials. It is also shown that this material possesses a direct–indirect bandgap enabling high absorption coefficient, extended carrier lifetimes >100 ns, and low trap densities similar to lead halide perovskites. This study also demonstrates the possibility of electrical poling to induce switchable photovoltaic effect without additional electron and hole transport layers.     

中国的极轨气象卫星

气象卫星是具有巨大经济和社会效益的应用卫星，中国的极轨气象卫星经历了从试验阶段到业务应用阶段的发展历程。文章简要介绍了“风云一号”（FY-1）极轨气象卫星的发展概况和技术性能，星载十通道扫描辐射计和长寿命、高可靠极轨卫星平台取得的成功；重点介绍了中国新一代的极轨气象卫星“风云三号”（FY-3）的总体概况，归纳了卫星的技术特点。     

Quantitative High‐Dynamic‐Range Electron Diffraction of Polar Nanodomains in Pb2ScTaO6

Highly B‐site ordered Pb₂ScTaO₆ crystals are studied as a function of temperature via dielectric spectroscopy and in situ high‐dynamic‐range electron diffraction. The degree of ordering is examined on the local and macroscopic scale and is determined to be 76%. Novel analysis of the electron diffraction patterns provides structural information with two types of antiferroelectric displacements determined to be present in the polar structure. It is then found that a low‐temperature transition occurs on cooling at ≈210 K that is not present on heating. This phenomenon is discussed in terms of the freezing of dynamic polar nanodomains where a high density of domain walls creates a metastable state.     

d维平稳Gauss过程极集的性质

研究了d维平稳Gauss过程极集的性质，得到了其极性的必要条件。     

氧化锌压敏陶瓷中氧化锌晶粒极性生长现象的研究

发现了ZnO压敏陶瓷中的锥状或柱状“突起物”现象.通过能谱发现“突起物”的物质构成是ZnO,而且是ZnO晶粒生长形成的实体,并非气体在ZnO中形成的气泡.进一步论证了这种现象是ZnO极性生长造成的,并从内因和外因两个方面进行了分析.内因是ZnO的极性晶格结构和结晶形态,外因是ZnO压敏陶瓷中Bi₂O₃液相提供了极性生长得以显现的物化环境,并且通过单独添加Bi₂O₃的97mol%ZnO+3mol%Bi₂O₃配方和100mol%纯ZnO配方制备样品进行对比实验,验证了Bi₂O₃的作用.     

极坐标扶钎器在凿岩工作中的应用

目前常用的凿岩设备,在开孔时固定孔位的方法仍多用人工手扶钎杆的办法。本文详细介绍了极坐标扶钎器的构造,工作原理,使用方法及应用范围。     

填料诱导聚偏氟乙烯极性晶型及其性能研究进展

聚偏氟乙烯(PVDF)是一种极性较强的结晶高分子材料,其中极性的β和γ晶在压电和热电方面具有较广阔的应用前景。然而通用的加工方法只能得到非极性的α晶,为此,简要介绍了一种简便有效的形成极性PVDF晶的方法——填料诱导法。综述了各种不同填料及表面改性剂对PVDF中α、β和γ晶型的诱导规律和诱导机理,并简单分析了填料填充PVDF复合材料的物理和力学性能,指出研究高含量β晶的制备方法及其转变机理是今后PVDF改性的主要发展方向。     

低合金高强钢极地环境加速腐蚀试验谱编制与研究

针对低合金高强钢在极地低温环境下的腐蚀演化行为与寿命预测需求,开展极地环境加速试验环境谱及加速腐蚀试验方法研究,为探究低合金钢在低温、冻-融循环服役环境下的耐蚀性及腐蚀机理提供技术手段。根据中山站大气环境数据建立极地自然环境谱,将南极环境分为潮湿空气、冻融循环、低温冰冻3个阶段。利用大气腐蚀传感器,采用电化学工作站监测电偶电流变化,计算当量折算系数。通过盐雾-冻融-冰冻耦合加速腐蚀试验完成对南极腐蚀环境的仿真过程,为低温环境谱的编制提供方法及依据,编制的极地环境加速腐蚀试验环境谱与室外环境腐蚀具有较好的相关性。