Pyrolysis Process of Plant Fibers北大核心CSCD

The natural plant fiber has a large molecular weight and complex structure and composition,and its thermal cracking products and the composition distribution are also more complex. The fast pyrolysiscomprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry（Py-GC×GC-TOF/MS）,thermogravimetry-Fourier transform infrared spectroscopy（TG-FT-IR）,and in situ Fourier transform infrared spectroscopy（in situ FT-IR）methods were used to study the thermal pyrolysis process of six different natural fibers. The distribution of thermal pyrolysis products of different fibers under different pyrolysis temperatures was investigated and the product form was fully discussed. The research results show that the products of fiber pyrolysis mainly include alcohols,aldehydes,ketones,acids,esters,hydrocarbons, dehydrated sugars and CO2,etc. The types of pyrolysis products of different natural plant fibers are obviously different,and the main product types obtained are all different. At the same time,the results of in situ infrared spectroscopy and mass spectrometry show that pyrolysis products are closely related to the pyrolysis temperature. The results of in situ infrared experiments show that when the pyrolysis temperature is lower than 100 °C,the adsorbed water on the surface of the fiber structure is desorbed,but the fiber structure does not change significantly. When the pyrolysis temperature range is 100~200 °C,the temperature has little effect toward the pyrolysis process. When the temperature exceeds 300 °C,the fiber pyrolysis reaction intensifies and the surface structure changes significantly,and the main products are aldehydes and ketones. © 2022, Science Press (China). All rights reserved.     

Unleashing non-conjugated polymers as charge relay mediators

The core factors affecting the efficiency of photocatalysis are predominantly centered on controllable modulation of anisotropic spatial charge separation/transfer and regulating vectorial charge transport pathways in photoredox catalysis, yet it still meets with limited success. Herein, we first conceptually demonstrate the rational design of unidirectional cascade charge transfer channels over transition metal chalcogenide nanosheets (TMC NSs: ZnIn₂S₄, CdS, CdIn₂S₄, and In₂S₃), which is synergistically enabled by a solid-state non-conjugated polymer, i.e., poly(diallyldimethyl ammonium chloride) (PDDA), and MXene quantum dots (MQDs). In such elaborately designed photosystems, an ultrathin PDDA layer functions as an intermediate charge transport mediator to relay the directional electron transfer from TMC NSs to MQDs that serve as the ultimate electron traps, resulting in a considerably boosted charge separation/migration efficiency. The suitable energy level alignment between TMC NSs and MQDs, concurrent electron-withdrawing capabilities of the ultrathin PDDA interim layer and MQDs, and the charge transport cascade endow the self-assembled TMC/PDDA/MQD heterostructured photosystems with conspicuously improved photoactivities toward anaerobic selective reduction of nitroaromatics to amino derivatives and photocatalytic hydrogen evolution under visible light irradiation. Furthermore, we ascertain that this concept of constructing a charge transfer cascade in such TMC-insulating polymer-MQD photosystems is universal. Our work would afford novel insights into smart design of spatial vectorial charge transport pathways by precise interface modulation via non-conjugated polymers for solar energy conversion.

Electron relay of interim polymer layer boosts photocatalytic organic transformation.     

氢化物发生-原子荧光光谱法测定化探样品中砷、锑、铋和汞的注意事项

针对氢化物发生-原子荧光光谱法测定化探样品中砷、锑、铋和汞的空白、试样制备和分离、干扰、污染、设备和配件故障等同题,分析并总结出应注意的事项和解决方法.     

溅射-置换法制备染料敏化太阳能电池对电极Pt/FTO

采用溅射-置换(SD)法在导电玻璃(FTO)基底上制备了染料敏化太阳能电池(DSSC)对电极SD-Pt/FTO.形貌表征显示,和热解法(PY)所获得的对电极(PY-Pt/FTO)相比,SD法获得的对电极SD-Pt/FTO上Pt颗粒分散性显著改善.光电流-光电压特性曲线测试表明,以SD-Pt/FTO为DSSC对电极的光电转化效率比以PY-Pt/FTO为DSSC对电极的提高了16.5%.DSSC电池性能改善与SD-Pt/FTO对电极具有较低的电阻和由Pt颗粒分散性改善引起催化性能改善密切相关.     

形貌可控纳米SrFe_(12)O_(19)的制备及其磁性能

以FeCl3为原料,NaOH作为沉淀剂,通过化学沉淀法,制备出球状的Fe(OH)3中间体,同时以FeCl2为原料,采用化学沉淀法,分别使用NH3·H2O、Na2CO3和NaOH作为沉淀剂制得了不同形貌的中间体,利用柠檬酸法在中间体表面包裹锶的柠檬酸络合物,煅烧后分别制得了球形、纺锤体及棒状的纳米SrFe12O19.利用X射线衍射(XRD)和透射电镜(TEM)等测试手段对不同形貌的纳米SrFe12O19进行表征,并利用振动样品磁强计(VSM)对磁性能进行研究.结果表明:在用化学沉淀-柠檬酸法制备SrFe12O19的过程中,铁盐的种类以及沉淀剂的碱性对中间体的物相和SrFe12O19的形貌有着至关重要的影响.当原料为Fe3+时,制得了球形的纳米SrFe12O19;当原料为Fe2+时,利用碱性不同的沉淀剂可制得不同形貌的纳米SrFe12O19.随着沉淀剂碱性的增加,所得SrFe12O19的长径比增加,形貌各向异性增加.SrFe12O19的矫顽力(Hc)主要取决于粒子的各向异性,各向异性越大,矫顽力越大,饱和磁化强度(Ms)随着样品的各向异性的增加也有所增加,以FeCl2为原料,NaOH作为沉淀剂时制得的棒状SrFe12O19的矫顽力和饱和磁化强度最大分别为458.2kA·m-1和64.2A·m2·kg-1.     

掺杂对棒状纳米SrFe_(12)O_(19)形貌和性能的影响

以FeCl2为原料,利用化学沉淀法制备了针状纳米α-FeOOH中间体,并通过柠檬酸法在针状纳米α-FeOOH表面包裹锶的柠檬酸配合物,煅烧后形成的棒状纳米SrFe12O19并分别在共沉淀和溶胶-凝胶2个不同过程中对纳米SrFe12O19进行镧掺杂。采用XRD,TEM和振动样品磁强计(VSM)对SrFe12O19及掺杂锶铁氧体的结构、形貌及磁性能进行了表征。结果表明:沉淀法和柠檬酸法相结合后制得的针状前驱体于900℃煅烧后可制得平均直径为40nm,长径比为15～20的棒状纳米SrFe12O19。在沉淀过程中对前驱体进行掺杂后制得的SrLaxFe12-xO19较同温度时在溶胶-凝胶过程中进行掺杂制得样品的长径比有所增加,进而使得SrLaxFe12-xO19的各向异性变大,磁性能增加,且在沉淀过程中掺杂镧后,样品的矫顽力和饱和磁化强度达到最大值时,x值明显大于溶胶-凝胶过程中进行掺杂制得的棒状SrLaxFe12-xO19。利用共沉淀法掺杂后,当x=0.15时制备的样品的矫顽力最大为6179.1Oe,此时样品的饱和磁化强度和剩余磁化强度分别65.7和38.4emu·g-1。当x=0.2时制备的样品的饱和磁化强度达到最大值为67.3emu·g-1,样品的矫顽力为5852.7Oe。     

Synthesis of monoclinic WO3 nanosphere hydrogen gasochromic film via a sol–gel approach using PS-b-PAA diblock copolymer as template

A monoclinic tungsten trioxide (WO₃) nanosphere film was synthesized via a sol–gel approach using an amphiphilic diblock copolymer polystyrene-b-polyacrylic acid (PS-b-PAA) as template in toluene. The morphology, surface area and crystal structure of as-synthesized WO₃ were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET (N₂) and powder X-ray diffraction (XRD). The XRD pattern of WO₃ nanosphere film can be identified as a pure monoclinic WO₃ phase. The WO₃ precursor nanospheres had diameters ranging from 20 to 150 nm and surface area of 78.8 m² g^?1. The hydrogen gasochromic experiments revealed that such WO₃ nanosphere film with high surface area had a rapid response (5 ～ 10 s) to pure hydrogen at room temperature.     

三唑农药的手性拆分及对映体的转化

利用Chiralcel OJ-H和Chiralcel OD-H手性柱对烯唑醇、三唑酮和三唑醇的手性拆分进行了研究,进一步测定了烯唑醇和三唑酮对映体的旋光性质,据此确定了两种农药对映体的绝对构型,在此基础上结合三唑酮转化为三唑醇的还原实验确定了三唑醇4个对映异构体的绝对构型。考察了几种三唑农药在有机溶剂和缓冲溶液中的手性稳定性,其中三唑酮在甲醇、乙醇和水中存在明显的对映体转化行为,而烯唑醇和三唑醇则是手性稳定的,升高温度及碱性环境会加快三唑酮的对映体转化。     

基于分子识别的外泌体纳米界面原位DNA组装

<正>细胞膜是一类间隔细胞内外环境的具有生物活性的界面,膜表面的受体通过外界物质刺激调控胞内的生化反应,从而影响细胞乃至整个生命体的进程。对细胞膜表面进行改造和功能化,从而实现原位识别、组装并调控细胞膜表面结构在癌症检测和治疗等方面具有重要的作用~1。外泌体是细胞向胞外分泌的纳米级囊泡样膜包被小体,在细胞间的通讯、肿瘤早期诊断、心肌损伤保护和药物运输等研究领域展现重要的应用价值~(2-4)。虽然利用DNA纳米技术在构筑功能化细胞膜等     

纳米CuFe_2O_4-rGO复合材料的制备及电化学性能

采用溶剂热法成功制备了纳米CuFe_2O_4-rGO复合材料。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和电化学工作站对样品的结构、形貌及电容特性进行表征。结果表明,CuFe_2O_4纳米粒子均匀地分散在石墨烯片层间,其中CuFe_2O_4-20%rGO复合材料具有最优的电化学性能,当电流密度1 A·g~(-1)时,其比电容为1 952.5 F·g~(-1),当电流密度为1 A·g~(-1)时,CuFe_2O_4-20%rGO复合材料经1 000次充放电后的比电容保持率为86.17%。