联苯二甲酸构筑的镍配合物的合成、晶体结构及对罗丹明B的光催化性能

通过水热方法获得了2个镍配合物:[Ni(3,3′-dpdc)(dpp)]n(1),[Ni(2,2′-dpdc)(phen)(H2O)2]n(2)(3,3′-H2dpdc=3,3′-联苯二甲酸,2,2′-H2dpdc=2,2′-联苯二甲酸、phen=菲咯啉,dpp=1,3-二(4-吡啶基)丙烷),通过X射线单晶衍射的方法测定了其晶体结构。配合物1为二维网格型结构,中心金属离子为扭曲的[NiO4N2]八面体构型,3,3′-dpdc配体的2个羧基采取双齿螯合的配位模式与Ni髤离子配位形成Ni-(3,3′-dpdc)一维链结构,dpp配体采取单氮原子桥连的配位模式连接2个Ni髤离子形成Ni-dpp一维链,两种链相互贯穿形成二维网格型结构,二维网格结构之间通过氢键C15D-H15…O2、C21-H21A…O1形成三维超分子结构。配合物2为一维之字链结构,中心金属离子为扭曲的[NiO_4N_2]八面体构型,2,2′-dpdc的2个羧基均采取单齿桥连配位模式连接2个Ni髤离子形成一维之字型链结构,一维链之间通过O-H…O和C-H…π弱作用力连接形成三维超分子结构。探究了2种配合物对有机染料罗丹明B的光催化降解性能,结果表明配合物可以高效地降解罗丹明B。     

Elastic properties of chemically modified baker's yeast cells studied by AFM

Chemical pretreatment is widely used to facilitate transformation of living cells when foreign components are introduced into a cell through the cell wall. The influence of appropriate chemicals on the wall properties and mechanism of transformation is still a matter of intensive studies. Saccharomyces cerevisiae cells (also known as baker's yeast) were investigated by atomic force microscopy (AFM). The cell walls were modified by lithium acetate and dithiothreitol. The AFM imaging was performed in liquid water‐based environment. The living cells were fixed by trapping into the holes of a polycarbonate membrane. Mechanical and morphological properties of initial intact cells and treated cells were investigated. The increased stiffness of the chemically treated cells was observed. As deduced from the applied theoretical Hertz‐Sneddon model, the treated cells show completely different response mechanism to applied mechanical pressure in comparison with the intact cells. Also, the increased roughness of the cell wall of the treated yeasts was observed. Copyright © 2011 John Wiley & Sons, Ltd.     

表面Cu2O纳米颗粒修饰高效促进γ-Bi2MoO6的可见光催化活性

采用水热法在γ-Bi₂MoO₆光催化剂表面修饰了纳米级Cu₂O, 得到了具有高效可见光响应的复合光催化材料, 并利用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、选区电子衍射(SAED)、X射线光电子能谱(XPS)和紫外-可见漫反射光谱(UV-Vis-DRS)等技术对其相结构、微观形貌和光吸收性能进行了表征. 在可见光条件下(λ>400 nm)考察了Cu₂O表面修饰对γ-Bi₂MoO₆光催化降解亚甲基蓝(MB)性能的促进作用. 结果表明, 纳米级Cu₂O(~10 nm)颗粒均匀地修饰于γ-Bi₂MoO₆的表面, 使γ-Bi₂MoO₆的可见光吸收带发生明显红移, 且吸收强度大幅提高, 增强了复合材料光生电子-空穴对的分离效率, 从而使复合材料表现出较高的光催化活性. 当Cu₂O的表面修饰量为1.5%(w)时, 复合光催化剂降解MB的活性与纯γ-Bi₂MoO₆相比提高了6.4倍.     

Reactivity and mechanistic insight into visible-light-induced aerobic cross-dehydrogenative coupling reaction by organophotocatalysts

With visible-light irradiation, a mild, simple, and efficient metal-free photocatalytic system for the facile construction of sp(3)-sp(3) C-C bonds between tertiary amines and activated C-H bonds has been achieved. Spectroscopic study and product analysis demonstrate for the first time that photoinduced electron transfer from N-aryl tetrahydroisoquinolines to eosin Y bis(tetrabutylammonium salt) (TBA-eosin Y) takes place to generate TBA-eosin Y radical anion, which can subsequently react with nucleophiles and molecular oxygen. More strikingly, electron spin resonance (ESR) measurements provide direct evidence for the formation of superoxide radical anions (O(2)(-.)) rather than singlet oxygen ((1)O(2)) during visible-light irradiation. This active species is therefore believed to be responsible for the large rate of acceleration of the aerobic photocatalytic reactions.     

静电纺丝法制备的钴酸镍微米带的磁性以及电化学性能

通过直接退火静电纺丝前驱样品以及调节升温速率最终得到了钴酸镍(NiCo₂O₄)微米带. 通过X射线衍射、扫描电镜、振动样品磁强计以及电化学工作站等分析手段对钴酸镍微米带的晶体结构、形貌、磁学性能以及电化学性能进行了研究. 结果显示, 以1℃·min^-1的升温速率得到的NiCo₂O₄微米带属于立方尖晶石结构, 高温处理后仍能保持一维结构. 室温磁化结果显示制备的NiCo₂O₄微米带具有超顺磁性, 在10 kOe时磁化强度为6.35 emu·g^-1. 此外, 电化学测试结果显示, NiCo₂O₄微米带的电容特性是典型的赝电容, 并且比电容随着放电电流密度的增加而减小.     

Amination of benzylic C-H bonds by arylazides catalyzed by CoII-porphyrin complexes: a synthetic and mechanistic study

Co(II)-porphyrin complexes catalyze the reaction of aromatic azides (ArN(3)) with hydrocarbons that contain a benzylic group (ArR(1)R(2)CH) to give the corresponding amines (ArR(1)R(2)C-NHAr). When at least one of the R substituents is hydrogen, the catalytic reaction proceeds further to give the imine ArRC=NAr in good yields. The reaction mechanism has been investigated. The reaction proceeds through a reversible coordination of the arylazide to the Co(II)-porphyrin complex. This unstable adduct can either react with the hydrocarbon in the rate-determining step or decompose by a unimolecular mechanism to afford a putative "nitrene" complex, which reacts with more azide, but not with the hydrocarbon, to afford the byproduct diaryldiazene. The kinetics of the catalytic reaction have been investigated for a range of azides and substituted toluenes. Arylazides with electron-withdrawing substituents react at a faster rate and a good correlation is found between the log(k) and the Taft parameters. On the other hand, an excellent correlation between the logarithm of the rate for substituted toluenes relative to that of toluene and a radical parameter (sigma*JJ) alone was found, with no significant contribution by polar parameters. An explanation has been proposed for this anomalous effect and for the very high isotopic effect (k(H)/k(D)=14) found.     

对氯硝基苯吸附在银纳米粒子上的偶联反应

表面增强拉曼光谱(SERS)具有极高的检测灵敏度, 通过检测吸附分子的SERS信号, 可以获得表面吸附分子的结构以及可能发生的反应. 在拉曼激发光源的辐射下, 在碱性溶液中, 银纳米粒子表面吸附的对氯硝基苯(PCNB)的SERS光谱与其固体的常规拉曼光谱相比, 出现异常SERS谱. 通过采用密度泛函理论(DFT)计算, 对PCNB以及可能的偶联产物p,p''-二氯偶氮苯(DCAB)进行理论分析以及谱峰归属, 发现这些异常峰来自其偶联产物DCAB的偶氮C－N＝N－C基团的基频振动.     

Inhibition of cell proliferation by a resveratrol analog in human pancreatic and breast cancer cells

Resveratrol has been reported to possess cancer preventive properties. In this study, we analyzed anti-tumor activity of a newly synthesized resveratrol analog, cis-3,4'',5-trimethoxy-3''-hydroxystilbene (hereafter called 11b) towards breast and pancreatic cancer cell lines. 11b treatments reduced the proliferation of human pancreatic and breast cancer cells, arrested cells in the G2/M phase, and increased the percentage of cells in the subG1/G0 fraction. The 11b treatments also increased the total levels of mitotic checkpoint proteins such as BubR1, Aurora B, Cyclin B, and phosphorylated histone H3. Mechanistically, 11b blocks microtubule polymerization in vitro and it disturbed microtubule networks in both pancreatic and breast cancer cell lines. Computational modeling of the 11b-tubulin interaction indicates that the dimethoxyphenyl group of 11b can bind to the colchicine binding site of tubulin. Our studies show that the 11b treatment effects occur at lower concentrations than similar effects associated with resveratrol treatments and that microtubules may be the primary target for the observed effects of 11b. These studies suggest that 11b should be further examined as a potentially potent clinical chemotherapeutic agent for treating pancreatic and breast cancer patients.