Insight into the thermal decomposition of kaolinite intercalated with potassium acetate: an evolved gas analysis

The thermal decomposition process of kaolinite–potassium acetate intercalation complex has been studied using simultaneous thermogravimetry coupled with Fourier-transform infrared spectroscopy and mass spectrometry (TG-FTIR-MS). The results showed that the thermal decomposition of the complex took place in four temperature ranges, namely 50–100, 260–320, 320–550, and 650–780 °C. The maximal mass losses rate for the thermal decomposition of the kaolinite–potassium acetate intercalation complex was observed at 81, 296, 378, 411, 486, and 733 °C, which was attributed to (a) loss of the adsorbed water, (b) thermal decomposition of surface-adsorbed potassium acetate (KAc), (c) the loss of the water coordinated to potassium acetate in the intercalated kaolinite, (d) the thermal decomposition of intercalated KAc in the interlayer of kaolinite and the removal of inner surface hydroxyls, (e) the loss of the inner hydroxyls, and (f) the thermal decomposition of carbonate derived from the decomposition of KAc. The thermal decomposition of intercalated potassium acetate started in the range 320–550 °C accompanied by the release of water, acetone, carbon dioxide, and acetic acid. The identification of pyrolysis fragment ions provided insight into the thermal decomposition mechanism. The results showed that the main decomposition fragment ions of the kaolinite–KAc intercalation complex were water, acetone, carbon dioxide, and acetic acid. TG-FTIR-MS was demonstrated to be a powerful tool for the investigation of kaolinite intercalation complexes. It delivers a detailed insight into the thermal decomposition processes of the kaolinite intercalation complexes characterized by mass loss and the evolved gases.     

Facile Synthesis of Chiral Spirooxindole‐Based Isotetronic Acids and 5‐1H‐Pyrrol‐2‐ones through Cascade Reactions with Bifunctional Organocatalysts

Unprecedented organocatalyzed asymmetric cascade reactions have been developed for the facile synthesis of chiral spirooxindole‐based isotetronic acids and 5‐1H‐pyrrol‐2‐ones.The asymmetric 1,2‐addition reactions of α‐ketoesters to isatins and imines by using an acid–base bifunctional 6′‐OH cinchona alkaloid catalyst, followed by cyclization and enolization of the resulting adducts, gave chiral spiroisotetronic acids and 5‐1H‐pyrrol‐2‐ones, respectively, in excellent optical purities (up to 98 % ee). FT‐IR analysis supported the existence of hydrogen‐bonding interaction between the 6′‐OH group of the cinchona catalyst and an isatin carbonyl group, an interaction that might be crucial for catalyst activity and stereocontrol.     

Modulating Aβ33–42 Peptide Assembly by Graphene Oxide

Graphene oxide (GO) is utilized as the modulator to tune the formation and development of amyloid fibrils (Aβ_33–42). Atomic force microscopy temporal evolution measurements reveal that the initial binding between the peptide monomer and the large available surface of the GO sheets can redirect the assembly pathway of amyloid beta. The results support the possibility to develop graphene‐based materials to inhibit amyloidosis.     

Synthesis of Polycyclic Indole Skeletons by a Gold(I)‐Catalyzed Cascade Reaction

The conversion of simple, easily available urea‐substituted 3‐phenylpropargyl alcohols catalyzed by a simple IPr–gold(I) catalyst in a gold(I)‐catalyzed cascade reaction composing of a gold‐catalyzed nucleophilic addition and a subsequent gold‐catalyzed substitution reaction delivers 1H‐imidazo[1, 5?a]indol‐3(2 H)‐ones. Other gold(I) catalysts or silver catalysts gave lower yields and often gave other side products. Gold(III) and copper(II) catalysts decomposed the starting material. Twelve examples, including donor and acceptor substituents on the distal nitrogen of the urea substructure, are provided. An X‐ray crystal structure analysis confirmed the structural assignment. The mechanistic investigation including isolation and further conversion of intermediates and reactions with enantiopure starting materials indicated that after the nucleophilic‐addition step, the substrate undergoes an S_N1‐type benzylic substitution reaction at the indolyl alcohol intermediate or an intramolecular hydroamination reaction of the 2‐vinylindole intermediate.     

侧链为端羧基聚乙二醇的梳形聚氨酯的合成与表征

以L-赖氨酸、乙二胺和端羧基聚乙二醇(PEG)为原料合成一种带聚乙二醇侧链的二元胺扩链剂(Lys-NH-PEG),然后以4,4'-二苯基甲烷二异氰酸酯(MDI)和Lys-NH-PEG为硬段,聚碳酸酯二醇(PCD)为软段,制备一种含端羧基聚乙二醇侧链的梳形聚氨酯.对所合成聚氨酯材料进行傅立叶变换红外光谱(FTIR)、氢核磁共振谱(1H-NMR)、凝胶渗透色谱(GPC)测试,测试结果表明得到了目标聚合物.该聚合物能在水中形成胶体,并能化学接枝白蛋白,表明所合成的聚氨酯的PEG侧链端羧基具有反应活性.这种具有可反应性的聚氨酯为进一步接枝生物分子以提高生物相容性提供了广阔的空间.     

氨蒸发诱导法制备纳米结构LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2及其作为高功率型锂离子电池正极材料的性能

采用氨蒸发诱导法成功制备出纳米结构LiNi1/3Co1/3Mn1/3O2正极材料,借助X射线衍射(XRD)分析、扫描电镜(SEM)、透射电镜(TEM)、高分辨率透射电镜(HRTEM)、能量分散谱(EDS)和比表面测试等表征手段及恒电流充放电测试研究了其晶体结构、微观形貌和电化学性能.研究表明该方法制备出的材料具有良好的α-NaFeO2层状结构,阳离子混排程度低.纳米片交错堆积而成核桃仁状形貌,片与片之间形成许多纳米孔,而且纳米片的侧面属于{010}活性面,能够提供较多的锂离子的脱嵌通道.在室温下及3.0-4.6 V充放电范围内,该材料在电流密度为0.5C、1C、3C、5C和10C时放电比容量分别为172.90、153.95、147.09、142.16和131.23mAh?g-1.说明其具有优异的电化学性能,非常有潜力用于动力汽车等高功率密度锂离子电池中.     

凝胶渗透色谱净化-柱后光化学衍生-高效液相色谱法同时测定食用植物油中9种真菌毒素

提出了用凝胶渗透色谱净化和柱后光化学衍生-高效液相色谱法(HPLC)测定食用油中9种真菌毒素。样品用乙腈均质提取,用凝胶色谱柱进行净化。为解决黄曲霉素B1和G1在水溶液中的荧光猝灭问题,在二极管阵列检测器(DAD)和荧光检测器(FLD)之间连接了光化学衍生器,使B1和G1衍生成荧光强度高的物质。HPLC分析中用SunFireTMC18色谱柱和以不同体积比的(A)水和(B)甲醇-乙腈(1+1)溶液的混合液为流动相进行梯度洗脱。9种真菌毒素分别在一定浓度范围内呈线性,检出限(3S/N)在0.01~0.20mg·kg-1之间。以空白样品作基体进行加标回收试验,回收率在83.0%~97.4%之间,相对标准偏差(n=6)在1.2%~4.8%之间。     

PW_(11)O_(39)Co(Ⅱ)(H_2O)~(5-)的均相及异相体系可见光催化性能研究

以模型污染物罗丹明B(RhB)的光降解为探针,评估了Keggin型钴取代杂多阴离子PW11O39Co髤(H2O)5-(PW11Co)及其异相体系PW11Co/D301R的可见光催化活性,提出了光催化反应的机理,同时考察了催化剂用量、溶液酸度以及溶液中PW11Co和RhB的相互作用对RhB可见光催化降解速率的影响。实验结果表明,PW11Co均相体系及其异相体系PW11Co/D301R对RhB的可见光降解均有较高的光催化活性,但PW11Co/D301R的光催化活性更高。导致RhB降解的主要是羟基自由基。与PW11Co均相体系相比,在PW11Co/D301R异相体系中由于PW11Co与RhB的配位作用大为减弱,同时D301R对RhB具有富集作用,因而大大提高了RhB的光催化降解速率。     

基于三唑配体的金属锰(Ⅱ)、锌(Ⅱ)配合物的合成、晶体结构与性质研究(英文)

在不同反应条件下,采用三唑衍生物作为配体与乙酸锰和硝酸锌反应,合成了2个具有三维结构的配位化合物{Mn(pytyba)(H2O)3]·2H2O}n(1)和{[Zn(pytyba)(H2O)3]·4H2O}n(2),并通过元素分析、热重分析、荧光性、X射线单晶衍射对化合物进行分析。结构分析表明1和2有许多共同特征:两个聚合物的晶体均属于单斜晶系,C2/c空间群,Mn2+和Zn2+均为六配位畸变八面体配位结构,具有相似的热稳定性、荧光性以及相近的孔隙率。配体中的氧原子与金属离子配位形成一维链状结构,然后又通过O-H…N、O-H…O氢键作用和π…π芳香堆积形成超分子结构。此外,通过测定化合物抗氧化活性(SOD)的经典方法-Marklund法对配合物1和2的抗氧化活性进行了研究。