锂离子电池用多孔硅/石墨/碳复合负极材料的研究

在两步高能球磨和酸蚀条件下制得了多孔硅/石墨复合材料，并对其进行碳包覆制成多孔硅/石墨/碳复合材料。通过TEM，SEM等测试手段研究了多孔硅材料的结构。作为锂离子电池负极材料，电化学测试结果表明多孔硅/石墨/碳复合材料相比纳米硅/石墨/碳复合材料有更好的循环稳定性。同时，改变复合体配比、热解碳前驱物、粘结剂种类和用量也会对材料的电化学性能产生较大的影响。其中使用质量分数为10％的LA132粘结剂的电极200次循环以后充电容量保持在649.9 mAh·g^-1，几乎没有衰减。良好的电化学性能主要归因于主活性体-多孔硅颗粒中的纳米孔隙很好地抑制了嵌锂过程中自身的体积膨胀，而且亚微米石墨颗粒和碳的复合也减轻了电极材料的体积效应并改善了其导电性。     

Si-O-C骨架支撑型高循环性能锂离子电池硅基负极材料

通过经济有效的方法制备得到一种具有长循环寿命的高效稳定性硅/硅氧碳/无定形碳的复合负极材料结构. 在这种结构中,以具有稳定化学性能的硅氧碳结构作为骨架,来支撑和隔离硅纳米颗粒结构. 材料中包含的无定形碳组分可提高硅/硅氧碳结构的电导性能. 这种复合负极结构在0.3C电流充放电情况下,不仅能发挥出637.3 mAh·g^-1的比容量,而且在经过100 周的充放电循环后,其容量保持率也达到86%. 这种新型硅基负极材料的设计为其他功能材料的设计提供了一种潜在可能的方法.     

硅镍纳米颗粒的氢电弧等离子体制备及电化学性能研究

采用氢电弧等离子体方法成功地合成了硅镍合金纳米颗粒， 分别用透射电子显微镜(TEM)、X射线衍射(XRD)和能谱分析(EDS)的方法对其形貌、晶体结构和元素化学成分进行了表征，结果显示得到的纳米颗粒由Si和Si₂Ni两相组成。电化学测量的结果表明，在锂嵌入硅镍纳米颗粒的过程中，硅充当活性中心，形成了非晶态的Li_xSi合金，并且在以后的循环中一直保持非晶状态，而其中的Si₂Ni作为惰性成分，不与Li反应，而是充当缓冲基体及导电剂的作用。硅镍合金纳米颗粒的可逆容量达1 304 mAh·g^-1，并且循环性能明显优于纯硅材料。硅镍合金纳米颗粒与石墨组成的复合材料，不但具有较高的可逆比容量，而且有较好的循环稳定性，20次循环后比容量仍为518 mAh·g^-1，容量保持率为86％,是有希望的锂离子电池负极材料。     

纳米银修饰的超疏水界面用于农药的超灵敏检测

采用化学还原法,在具有不同微观结构的规整的不锈钢网和聚纤维素酯薄膜表面合成了银纳米颗粒.利用氟化试剂对复合界面进行处理,形成超疏水性能的界面,能有效地浓缩目标分子.以罗丹明6G(R 6G)为分析物,纳米银修饰聚纤维素酯薄膜为基底,采用表面增强拉曼散射(SERS)分析了氟化处理前后基底对目标分子的检测能力.实验结果表明,具有超疏水性能的复合基底对R 6G分子的检出限为1 ×10-16 mol/L.以纳米银修饰的不锈钢网和聚纤维素酯两种复合材料为基底,对常用杀虫剂敌百虫的检出限分别为1×10-15 mol/L和1×10-16 mol/L.     

纳米银颗粒在模拟体液中的表面吸附特性

为了了解纳米银颗粒在体内是以Ag⁺还是以纳米银颗粒的形式存在,本研究设计了体外模拟试验,考察纳米银颗粒在模拟体液中所发生的表面化学反应。将纳米银颗粒放在模拟体液中反应5 min, 30 min, 1 h和4 h,反应结束后利用ICP-MS测定溶解到模拟体液中的银离子浓度,利用TEM观察纳米银颗粒在模拟体液中的分散状态,利用XPS分析与模拟体液反应后纳米银颗粒表面化学元素组成。结果显示,纳米银颗粒与体液接触后,体液中的蛋白质会吸附到纳米银颗粒表面,绝大部分纳米银颗粒转化成覆蛋白膜的颗粒,这些覆膜颗粒可以均匀的分散在模拟体液中。只有极小一部分(小于0.01%)的纳米银颗粒会在初始阶段溶解为Ag⁺。这一结果说明纳米银颗粒在模拟体液中主要是以覆蛋白膜的纳米银颗粒形式存在,预示着在体内纳米银颗粒能够以颗粒形态在全身分布。这一特性可能会导致一些生物负效应的发生。     

电化学沉积含纳米银羟基磷灰石涂层及抗菌性能研究

应用柠檬酸钠还原法制得纳米银胶体溶液,并在钛基表面电泳沉积纳米银颗粒,再由电化学沉积法沉积羟基磷灰石涂层.X射线电子能谱(XPS)、X射线衍射(XRD)和高分辨透射电子显微镜(HRTEM/SEM)证实该涂层含羟基磷灰石(HAp)和Ag,其纳米银颗粒尺度为5~20 nm.抗菌试验表明,涂层中含银量随电泳沉积液纳米银粒子浓度升高而增加,抗菌性也相应增强.但如沉积液中银粒子超过一定浓度时,则其在钛表面会发生明显团聚,导致抗菌性能的降低.据此,初步优化了抗菌效果最佳的复合涂层制备技术.     

纳米银在细菌纤维素凝胶膜中的原位合成及性能表征

在细菌纤维素纳米纤维网络结构中采用吐伦试剂与含醛基化合物原位反应生成纳米银颗粒, 制备了纳米银/细菌纤维素(n-Ag/BC)复合凝胶膜, 研究了不同反应条件对复合材料的银含量、 化学结构和晶体结构的影响以及n-Ag/BC的微观结构和纳米银在纤维素网络中的存在形态; 探讨了纳米银颗粒在纤维素网络中的形成机理; 采用伤口常见细菌之一金黄色葡萄球菌测试了n-Ag/BC的抑菌性能; 将n-Ag/BC与胎鼠表皮细胞共培养考察了材料的生物相容性. 研究结果表明, 在细菌纤维素纳米网络结构中可生成直径约为几十纳米的单质纳米银粒子; n-Ag/BC的银含量随着吐伦试剂浓度的增加而增加, 同时银含量还取决于含醛基化合物的用量; 原位反应生成纳米银粒子后细菌纤维素的晶型和结晶度没有发生变化; 纳米银颗粒在细菌纤维素纳米网络结构的交叉处生成, 复合材料n-Ag/BC对金黄色葡萄球菌的抑菌率达到99%以上, 不影响细胞的增殖和分化过程, 具有良好的生物相容性, 是一种有广阔应用前景的创伤修复抗感染材料.     

氮掺杂碳层包覆金属钴颗粒与氮掺杂石墨烯纳米复合材料作为高容量锂离子电池负极材料

合成了一种石墨烯基纳米复合材料即：由氮掺杂碳层包覆的金属钴纳米颗粒,充分分散于氮掺杂的石墨烯表面。这种纳米复合材料进一步提高了石墨烯的导电性,增加了石墨烯的储锂容量。该材料被用作锂离子电池负极材料,在性能测试中展现了良好的循环性能,在以100 mA·g^-1的电流密度循环200圈后,放电容量高达950.1 mAh·g^-1,库伦效率约为98%。     

氮掺杂碳层包覆金属钴颗粒与氮掺杂石墨烯纳米复合材料作为高容量锂离子电池负极材料

合成了一种石墨烯基纳米复合材料即：由氮掺杂碳层包覆的金属钴纳米颗粒,充分分散于氮掺杂的石墨烯表面。这种纳米复合材料进一步提高了石墨烯的导电性,增加了石墨烯的储锂容量。该材料被用作锂离子电池负极材料,在性能测试中展现了良好的循环性能,在以100 mA·g^-1的电流密度循环200圈后,放电容量高达950.1 mAh·g^-1,库伦效率约为98%。     

碳在锂离子电池硅碳复合材料中的作用

随着低比容量硅碳复合材料(<500 mAh/g)在锂离子电池中的商业化应用,硅基负极材料也从实验室研究走向了产业化发展。近年来的研究工作中,许多方法被用来解决硅在循环过程中体积变化(>300%)所带来的一系列问题。在材料结构方面,从最初的硅材料纳米化、硅与其他材料复合等技术手段转变到了硅碳复合材料二次颗粒的结构设计、表面包覆层设计等方法;在应用性能方面,除了早期文献报道的材料比容量、循环性能等参数外,还增加了材料比表面积、振实密度、首次及循环库仑效率等更符合电池实际应用要求的性能参数研究,从而极大地推动了硅基负极材料的商业化应用进程。本文首先综述了近年来硅碳复合材料组成、结构设计的发展脉络,进一步分析了由石墨、软碳、硬碳、碳纤维和石墨烯等碳源合成的硅碳复合材料的结构特点,并对其电化学性能进行分析对比,总结了碳在硅碳复合材料结构及其性能上发挥的作用。最后,对硅碳复合材料制备过程中的结构设计要求和碳材料的选择进行了分析和展望。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.