“Self-Lockable” Liquid Crystalline Diels–Alder Dynamic Network Actuators with Room Temperature Programmability and Solution Reprocessability

Novel main-chain liquid crystalline Diels—Alder dynamic networks (LCDANs) were prepared that exhibit unprecedented ease for actuator programming and reprocessing compared to existing liquid crystalline network (LCN) systems. Following cooling from 125 °C, LCDANs are deformed with aligned mesogens self-locked at room temperature by slowly formed Diels–Alder (DA) bonds, which allows for the formation of solid 3D actuators capable of reversible shape change, and strip walker and wheel-capable light-driven locomotion upon either thermally or optically induced order–disorder phase transition. Any actuator can readily be erased at 125 °C and reprogrammed into a new one under ambient conditions. Moreover, LCDANs can be processed directly from melt (for example, fiber drawing) and from solution (for example, casting tubular actuators), which cannot be achieved with LCNs using exchangeable covalent bonds. The combined attributes of LCDANs offer significant progress toward developing easily programmable/processable LCN actuators.     

单层类水滑石纳米片的可控合成及规模生产展望

水滑石(LDHs)是一种阴离子黏土材料,由于其主体层板厚度的可调性,使其在光/电催化、电池、超级电容器、传感器以及生物医药等领域都具有广泛应用。降低层厚至单层可使材料的物理化学性质发生根本改变,从而优化催化性能。近期研究表明,利用自上而下,自下而上的方法,可以实现单层LDHs类材料的合成,但是受限于产量(g级)以及成本设备等问题,目前规模化制备高质量单层LDHs类材料还没有工业案例。成核晶化隔离法是目前唯一规模化合成纳米LDHs的工业化方法,具有成本低,产量可吨级放大等优点。本综述从合成方法、表征手段、应用三个角度讨论了单层及超薄LDHs的精准调控,详细论述了近期关于单层及超薄LDHs合成突破以及LDHs的规模化生产进展,并对其性能进行了总结,为后续设计高性能单层LDHs提供思路。     

两种形貌纳米Fe2O3对TKX-50热分解的催化性能研究

Energy components used in solid rocket propellants are beneficial for improving the energy performance, and their thermal decomposition characteristics significantly affect the combustion properties of the propellants. As a kind of energetic material with both high energy and low sensitivity (impact and friction), 5, 5'-bistetrazole-1, 1'-diolate (TKX-50) can effectively improve the energy and safety characteristics of solid propellants. Burning catalyst is another important component of solid propellants, which can significantly improve the burning rate of the propellant and reduce the pressure exponent. Among various burning catalysts, nanoscale transition metal oxides can promote the thermal decomposition of the energetic component, thus enhancing the combustion properties of the solid propellant. However, the catalytic effects of nanoscale transition metal oxides with different morphologies on the thermal decomposition of TKX-50 have rarely been studied. Based on the excellent catalytic activity of Fe₂O₃ for TKX-50 thermal decomposition, nano-Fe₂O₃ particles with spherical and tubular microstructures were used for TKX-50 thermal decomposition. The Fe₂O₃ nanoparticles were successfully fabricated via the solvothermal method and characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) analyses. The XRD, FT-IR, and XPS results confirmed the successful fabrication of spherical and tubular Fe₂O₃ samples. The SEM and TEM images showed that the spherical Fe₂O₃ samples are composed of agglomerated Fe₂O₃ nanoparticles with an average particle size of 110 nm. In addition, the average diameter and length of hollow tubular Fe₂O₃ nanoparticles are 120 nm and 200 nm, respectively. The catalytic activities of spherical and tubular Fe₂O₃ for TKX-50 decomposition were studied by thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) methods. The DSC and TG-DTG curves showed that both tubular and spherical Fe₂O₃ could effectively promote TKX-50 thermal decomposition. The first thermal decomposition peak temperature (T_FDP) of TKX-50 was reduced by 36.5 K and 26.3 K in the presence of tubular and spherical Fe₂O₃, respectively, at 10 K·min⁻¹. The activation energy (E_a) of TKX-50, determined by the iso-conversional method, was significantly reduced in the presence of both tubular and spherical Fe₂O₃. The results indicated that the microstructure of the catalyst has a significant effect on its catalytic performance for TKX-50 thermal decomposition, and that tubular Fe₂O₃ with hollow microstructure possesses better catalytic activity than spherical Fe₂O₃. The excellent catalytic activity of tubular Fe₂O₃ can be attributed to the hollow microstructure, which has more active sites for TKX-50 thermal decomposition.     

四卤化锰(Ⅱ)配合物的结构调控及力致发光性能

力致发光是一种力刺激诱导的发光现象。由于其独特的发光方式,使得力致发光材料在结构损伤检测、压力传感、显示和安全标记等方面展现出了巨大的应用价值。目前已报道的力致发光材料大多基于无机材料体系,而有机力致发光材料体系相对较少,并且人们对其发光机理的认识仍不清晰。在本文中,我们发现锰(Ⅱ)配合物[BPP]2[Mn Br4]具有力致发光特性,并在此基础上设计合成了一系列具有力致发光性质的四卤化锰(Ⅱ)配合物。改变有机阳离子配体或者卤素阴离子可对其光物理性质进行有效调控。固态下,这些锰(Ⅱ)配合物均显示出了较强的光致发光现象,同时表现出了明显的力致发光特性。晶体结构分析表明,分子内/分子间强的C―H…X (X=Br或Cl)相互作用对锰(Ⅱ)配合物的力致发光起到了至关重要的作用,它可在较大程度上降低由分子振动和旋转造成的能量损失。本工作将为力刺激响应型材料体系的拓展提供一定的参考价值。     

新型丁烯内酯衍生物的设计合成及诱导胃癌细胞凋亡研究

开发了一条合成天然产物Uncinine的新方法,基于此设计合成了一系列新型的丁烯内酯衍生物.通过噻唑蓝(MTT)法评价了目标化合物对胃癌细胞的增殖抑制活性,分析了其构效关系.其中,3-吗啉甲基-4-(4-叔丁基苯基)亚基丁烯内酯(9l)对MGC803的IC50为2.9μmol/L,对胃癌细胞MGC803、HGC27以及SGC7901具有明显的选择性增殖抑制作用,而对正常的胃粘膜上皮细胞GES1具有较小的毒性.初步的作用机制研究表明,化合物9l诱导胃癌细胞MGC803凋亡依赖Caspase 9/3激活.     

通过赝反伽伐尼反应实现金纳米粒子模块替换

通过可控的方式精确调控纳米粒子的结构仍是一个富有挑战性和鼓舞人心的课题.尽管单原子或两、三个金属原子的精细调控已经在金纳米粒子中实现,涉及三个以上金属原子的取代（模块取代）还没有报道.本工作报道了环己硫醇配体保护的Au₄₈（CHT）₂₆的合成及其通过赝反伽伐尼过程的模块取代.单晶结构揭示模块取代的产物与母体团簇共用一个相似的Au₃₁（CHT）₁₂主体,但剩余部分不同（Au₆（CHT）₁₁ vs.Au₁₆（CHT）₁₄）.一个有趣的发现是模块取代抑制了Au₄₈（CHT）₂₆的光热过程,却增强了它的发射,赋予了所合成团簇更好的双（多）功能应用潜力.光热效应的减弱和发射的增强也暗示了这两种作用能够彼此至少部分转化,对于研究这两种效应之间的相互影响也具有重要的启示.     

Conjugated polymer nanoparticles as fluorescence switch for selective cell imaging

Fluorescence switch plays a vital role in bioelectronics and bioimaging.Herein,we presented a new kind of facile electrostatic complex nanoparticles(ECNs)for fluorescence switching in cells and marking of individual cell.The ECNs were prepared by mixing positively charged poly(6-(2-(thiophen-3-yl)ethoxy)hexyl trimethylammonium bromide)(PT)and negatively charged diarylethene sodium salt(DAECOONa).DAE-COONa is a photoswitchable molecule which can be transformed between the ring-closed fo rm and ring-open form under the irradiation of UV or visible light.The closed-form of DAE-COONa can efficie ntly quench the fluorescence of PT through intermolecular energy transfer,while the open form of DAE-COONa does not influence the emission of PT.Thus,the fluorescence of ECNs can be modulated by light irradiation,and the ECNs with good fluorescence switching performance have been employed for fluorescence imaging and individual cell lighting up process successfully.We demonstrate that the electrostatic complex strategy provides a facile method to construct fluorescence switch fo r selective cell marking and imaging applications.     

自支撑硫镍基电极材料制备及其赝电容性能

硫镍基赝电容超级电容器具有较高的比电容和功率密度等优点,是下一代理想的储能装置之一,但其实际应用受到其活性材料的制约,如导电性低和循环性能差等。研究者围绕增强硫镍基赝电容电极材料导电性和提升循环稳定性进行了大量的研究工作。其中,构建自支撑的电极材料被认为是一种降低活性材料和集流体之间界面电阻的有效方法。本文综述了制备自支撑硫镍基赝电容电极的常见方法,并就活性材料的形貌与性能关系进行了总结,主要着眼于集流体改性、离子掺杂、复合材料构建及形貌调控优化等。最后对自支撑硫镍基赝电容电极材料的研究方向进行了展望。     

Stabilities,Electronic Structures,and Bonding Properties of Iron Complexes (E1E2)Fe(CO)2(CNArTripp2)2 (E1E2=BF,CO, N2, CN−, or NO+)**

The coordination of 10-electron diatomic ligands (BF, CO N₂) to iron complexes Fe(CO)₂(CNAr^Tripp2)₂ [Ar^Tripp2=2,6-(2,4,6-(iso-propyl)₃C₆H₂)₂C₆H₃] have been realized in experiments very recently (Science, 2019 , 363, 1203–1205). Herein, the stability, electronic structures, and bonding properties of (E₁E₂)Fe-(CO)₂(CNAr^Tripp2)₂ (E₁E₂=BF, CO, N₂, CN⁻, NO⁺) were studied using density functional (DFT) calculations. The ground state of all those molecules is singlet and the calculated geometries are in excellent agreement with the experimental values. The natural bond orbital analysis revealed that Fe is negatively charged while E₁ possesses positive charges. By employing the energy decomposition analysis, the bonding nature of the E₂E₁–Fe(CO)₂(CNAr^Tripp2)₂ bond was disclosed to be the classic dative bond E₂E₁→Fe(CO)₂(CNAr^Tripp2)₂ rather than the electron-sharing double bond. More interestingly, the bonding strength between BF and Fe(CO)₂(CNAr^Tripp2)₂ is much stronger than that between CO (or N₂) and Fe(CO)₂(CNAr^Tripp2)₂, which is ascribed to the better σ-donation and π back-donations. However, the orbital interactions in CN⁻→Fe(CO)₂(CNAr^Tripp2)₂ and NO⁺→Fe(CO)₂(CNAr^Tripp2)₂ mainly come from σ-donation and π back-donation, respectively. The different contributions from σ donation and π donation for different ligands can be well explained by using the energy levels of E₁E₂ and Fe(CO)₂(CNAr^Tripp2)₂ fragments.