基于Fe3O4@SiO2@Ag/GCE传感器检测土霉素

合成了具有核壳结构的Fe₃O₄@SiO₂纳米复合材料,在Fe₃O₄@SiO₂表面负载银纳米离子,制备了一种新型的Fe₃O₄@SiO₂@Ag复合材料,并采用玻碳电极(GCE)构建Fe₃O₄@SiO₂@Ag/GCE传感器,对土霉素(OTC)进行定量检测。优化了电解质溶液的种类和pH,Fe₃O₄@SiO₂@Ag用量以及富集时间和富集电位等实验条件。在最佳条件下,OTC浓度(c)与峰电流(I_p)在0.01～120μmol/L范围内呈线性关系,线性方程为I_p=0.9307c-0.0033,线性相关系数R²=0.9986,检出限为8.2 nmol/L。该传感器对牛奶中OTC的检测结果与国标法结果一致。     

多功能Fe3O4@SiO2 Janus颗粒

采用溶剂热法和溶胶-凝胶法制备了顺磁性Fe₃O₄@SiO₂颗粒,以Pickering乳液界面保护法实现颗粒表面分区获得Fe₃O₄@SiO₂ Janus颗粒,进一步选区复合生长Pt或Ag纳米颗粒制备Fe₃O₄@SiO₂-Pt和Fe₃O₄@SiO₂-Ag Janus颗粒.Fe₃O₄@SiO₂-Pt Janus颗粒的Pt一侧进行催化过氧化氢的反应,具有自驱动功能.因其顺磁性和两亲性,Fe₃O₄@SiO₂-Ag Janus颗粒能够作为磁响应颗粒乳化剂稳定油水乳液,并将Ag的催化功能引入界面.     

磁性介孔纳米粒子的制备及对抗癌药紫杉醇的传输

以十六烷基溴化铵(CTAB)为结构导向剂, 正硅酸乙酯(TEOS)为硅源, 在碱性环境下经过自组装过程对单分散性磁性Fe₃O₄纳米粒子进行包覆, 制备出磁性硅基介孔纳米粒子Fe₃O₄@SiO₂. 结合X射线衍射、 傅里叶变换红外光谱(FTIR)、 透射电子显微镜(TEM)以及氮气吸附-脱附等技术对Fe₃O₄@SiO₂粒子进行表征. 结果表明Fe₃O₄@SiO₂纳米粒子具有球形形貌, 平均直径约为150 nm, 蠕虫状介孔结构, 比表面积为932 m²/g, 孔径为2.5 nm且分布较均匀, 包覆后Fe₃O₄的结构得以保持, 同时材料具有很好的磁响应能力. 以抗癌药紫杉醇(Paelitaxel, TXL)为模型药物进行负载, 实验结果表明, Fe₃O₄@SiO₂对TXL的负载能力为80 mg/g, TXL-Fe₃O₄@SiO₂对TXL的缓释时间持续120 h以上, 累积释放量达到30 mg/g. 通过噻唑蓝比色(MTT)法测量了TXL-Fe₃O₄@SiO₂粒子对体外培养的HeLa细胞的细胞毒性, 与相同浓度的TXL相比, TXL-Fe₃O₄@SiO₂对HeLa细胞的抑制率明显增高.     

磁光Fe3O4@SiO2@CdS复合材料的制备及表征

采用水解三氯化铁得到Fe₃O₄磁核,然后水解四乙氧基硅烷(TEOS)得到Fe₃O₄@SiO₂,再在其表面包覆半导体CdS即可得到良好的磁性光电信标Fe₃O₄@SiO₂@CdS。材料形貌、组成分析及光电化学测试表明成功地合成了具有超顺磁性的Fe₃O₄@SiO₂@CdS纳米复合材料。该材料分散均匀、具有良好的光学性能、在光电化学传感及光电催化等领域具有良好的应用前景。     

梯度液相色谱保留时间公式在梯形梯度洗脱研究中的应用

根据前期得到的梯度液相色谱保留时间计算公式,在不指定溶剂强度模型形式的前提下,探讨了梯形梯度洗脱的一些特点。对于溶质在梯形梯度坡度上流出时的情形,推导得到溶质流出色谱柱所对应的流动相组成(φ_R)随梯度斜率(B)变化的表达式。该公式表明,在该情形中φ_R将会随着B值的增加而增加。对于溶质在梯形梯度最后一个等度区间流出时的情形,如果初始和终止流动相组成保持不变而仅有梯度的斜率发生变化时,从理论上证明了溶质保留时间(t_R)与梯度斜率的倒数(1/B)之间呈线性关系。实验中以C18色谱柱为固定相,甲醇-水为流动相,联苯为样品,测定了不同流动相组成以及梯形梯度条件下的保留时间,所得到的实验值与理论值吻合,从而验证了理论方法的正确性。     

反相高效液相色谱中流动相线性梯度洗脱条件下溶质保留时间预测的新方法

 在计算溶质的梯度保留时间时 ,根据流动相在色谱柱内的分布规律 ,对溶质在色谱柱内的迁移距离和流动相梯度同时进行校正 ,从而建立了一种预测溶质线性梯度洗脱条件下保留时间的新方法。该方法在不同的仪器系统中 ,对于弱保留和强保留溶质在不同线性梯度洗脱条件下保留时间的预测 ,都具有良好的准确度。以 15种氨基酸和 8种苯的同系物为例 ,该方法对于弱保留溶质保留时间的预测 ,相对平均误差分别为 3 70 %和 4 90 % ,远小于文献方法得到的结果 (2 3 6 1%和 31 16 % ) ;对于强保留溶质保留时间的预测 ,相对平均误差分别为 0 2 1%和6 0 1% ,略小于文献 。     

Encapsulation of superparamagnetic Fe3O4@SiO2 core/shell nanoparticles in MnO2 microflowers with high surface areas

Microflowers made of interconnected MnO₂ nanosheets have been successfully synthesized in a microwave reactor through a hydrothermal reduction of KMnO₄ with aqueous HCI at elevated temperatures in the presence of superparamagnetic Fe₃O₄SiO₂ core-shell nanoparticles.Due to the chemical compatibility between SiO₂ and MnO₂,the heterogeneous reaction leads to the spontaneous encapsulation of the Fe₃O₄@SiO₂ core-shell nanoparticles in the MnO₂ microflowers.The resulting hybrid particles exhibit multiple properties including high surface area associated with the MnO₂nanosheets and superparamagnetism originated from the Fe₃O₄@SiO₂ core-shell nanoparticles.which are beneficial for applications requiring both high surface area and magnetic separation.     

磁性印迹纳米粒子固定血红蛋白修饰磁性电极构建过氧化氢传感器

采用表面印迹技术,以磁性二氧化硅纳米粒子（Fe₃O₄@SiO₂ NPs）作为载体、血红蛋白（Hb）为模板分子、正硅酸乙酯（TEOS）为印迹聚合物单体,制备了Hb印迹Fe₃O₄@SiO₂的磁性印迹纳米粒子（MMIPs NPs）. MMIPs NPs具有磁性内核和血红蛋白印迹壳层的核壳结构,可以富集并固定Hb. 使用壳聚糖将MMIPs NPs固定于磁性电极表面,构建血红蛋白类酶生物传感器,研究了Hb对过氧化氢（H₂O₂）的催化活性. MMIPS NPS相比于磁性非印迹纳米粒子（MNIPS NPS）,催化电流增加了14.3%. 采用磁性电极,MMIPS NPS、Hb和O₂的顺磁性使得该类酶生物传感器对H₂O₂的催化电流增加了60.0%. 血红蛋白类酶生物传感器电流响应与H₂O₂浓度在25 ~ 200 μmol·L^-1间呈线性关系,检出限为3 μmol·L^-1（S/N=3）,表明该类酶传感器对H₂O₂具有良好的催化性能.     

磁性反相限进材料的制备及其应用

以磁性二氧化硅（Fe₂O₃@SiO₂）为基质,利用表面原子转移自由基聚合技术（SI-ATRP）,在改性后的Fe₂O₃@SiO₂内表面接枝甲基丙烯酸十八烷基酯（SMA）、外表面接枝甲基丙烯酸缩甘油酯（GMA）,酸解后得到磁性反相限进材料Fe₂O₃@SiO₂-SMA-GMMA,并通过扫描电镜（SEM）、X射线衍射（XRD）、透射电镜（TEM）、振动样品磁强计（VSM）和元素分析对其进行表征。研究表明,Fe₂O₃@SiO₂-SMA-GMMA对牛血清白蛋白（BSA）的排阻能力为90.4%;对磺胺异恶唑（SIZ）、磺胺二甲氧基嘧啶（SDM）、甲氧苄啶（TMP）和磺胺甲基嘧啶（SMR）的最大吸附量分别为2.76、2.24、1.51和1.34 mg/g。Fe₂O₃@SiO₂-SMA-GMMA应用于牛奶和牛血清样品中SIZ、SMR和SDM的分离富集,SIZ、SMR和SDM的加标回收率为88.7%~90.8%,相对标准偏差为3.3%~5.3%。磁性反相限进材料可简化生物基质样品的前处理过程,对血液样品或食品样品等领域的分析检测具有重要价值。     

蛋黄-壳结构Fe3O4@SiO2@PMO磁性微球的制备及对漆酶的固定化

以蛋黄-壳结构的Fe₃O₄@SiO₂@PMO磁性微球作为载体, 采用交联法对漆酶进行固定, 考察了戊二醛浓度等对固定效果的影响, 并对固定后漆酶的活性进行了研究. 结果表明, 蛋黄-壳结构的磁性微球负载漆酶仅需6 h, 磁性微球对漆酶的固载量高达475 mg/g. 固定后漆酶的稳定性显著提高, 在pH=2.5~4.5的强酸性条件下, 固定后漆酶酶活仍可保持70%以上, 即使温度升高至60 ℃, 固定后漆酶的相对酶活仍保持65%以上. 这说明漆酶经所合成的材料固定后, 其耐酸和耐热能力都明显优于游离漆酶. 包覆的Fe₃O₄粒子使得材料很容易经磁铁分离法回收, 固定后漆酶经磁分离循环使用10次后仍然能保留85%的酶活, 具有良好的可操作性和稳定性, 有效降低了漆酶的使用成本.     

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%.     

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.     

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.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

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.