碳纳米管添加剂对质子交换膜燃料电池低铂载量膜电极性能的影响研究

以碳纳米管（CNT）作为低铂载量膜电极（CCM）催化层（0.1 mg_Pt·cm^-2）添加剂，研究了CNT的添加方式对催化层微观结构以及膜电极性能的影响.结果表明，与常规低铂载量催化层相比，在其表面喷涂一层CNT或将CNT均匀分散到Pt/C催化层中均有利于提升低铂载量膜电极的输出性能，在70℃和100%相对湿度条件下最高输出功率比常规低铂载量膜电极的0.522 W·cm^-2分别提升了22.4%和60.0%，并且均匀分散添加方式优于分层添加方式.其原因在于分层添加CNT后改善了低铂催化层和气体扩散层之间的接触界面，降低了催化层与扩散层间的接触电阻，而均匀分散添加方式除了可降低界面接触电阻外，还显著改善了低铂催化层中的气体传输，大幅提升了Pt催化剂的利用效率，使得膜电极电化学反应电阻明显降低.进一步对均匀分散添加方式中CNT的载量进行优化，表明CNT添加量为37.5 μg·cm^-2时电池输出性能最佳，70℃和100%相对湿度条件下的最大输出功率达到0.91 W·cm^-2.本研究工作表明，将CNT均匀分散添加到催化层中是一种有效提升低铂载量膜电极性能的方法.     

Anthracene derivatives bearing thiourea group as fluoride selective fluorescent and colorimetric chemosensors

New anthracene derivatives bearing thiourea group have been synthesized and characterized including X-ray crystallography. These chemosensors display selective ratiometric changes in their fluorescence spectra upon the addition of fluoride ion.     

Determination of drug-protein interactions by microdialysis coupled with liquid chromatography and electrochemical detection based on a nickel hexacyanoferrate modified electrode

Microdialysis sampling coupled with liquid chromatography-electrochemical detection (LC-ED) was developed and applied to determine the interaction of thiopurine (TP) with bovine serum albumin (BSA). A nickel hexacyanoferrate (NiHCNFe) modified electrode was fabricated and used as the working electrode in LC-ED for the determination of TP. Cyclic voltammetric experiments demonstrate that this chemically modified electrode (CME) can effectively catalyze the electrooxidation of TP. The mechanism of the catalytic oxidation of TP at the CME involves an 'EC' process. In the LC-ED, the CME also shows good stability and reproducibility for the determination of TP. The limit of detection is 5.0 x 10(-7) mol l(-1) for 6-TP with a signal-to-noise ratio of 3. The utility of microdialysis as a quantitative sampling technique for in vitro studies of drug-protein interactions was studied. The microdialysis experiments were performed in phosphate buffer solution (pH 7.4) containing different molar ratios of the drug and protein at 37 degrees C. The collected microdialysis sample with unbound TP was analyzed at the NiHCNFe CME in the LC-ED. The relative recovery of TP determined in vitro is 18.3% at a perfusion rate of 1.0 microl min(-1) and the RSD is about 2.1%. The association constant and the number of binding sites on a BSA molecule calculated with the Scatchard equation are 3.72 x 10(-3) (1 mol(-1)) and 1.51, respectively. This method provides a fast, sensitive and simple technique for the study of drug-protein interactions.     

O2在MgO(001)完整和缺陷表面上的吸附

在密度泛函理论的框架下， 采用嵌入点电荷簇模型研究了O2在MgO(001)完整和缺陷表面上的吸附.用电荷自洽的方法确定了点电荷的值.计算结果表明， O2倾向吸附在低配位的角Mg2＋端.并且发现， 当O2为平躺吸附时，键长有较大的拉伸，将有利于O2的解离.同时，分别计算了使用裸簇和嵌入表观±2.0 e点电荷簇模型时的吸附能，并与采用电荷自洽方法的计算值进行了比较.结果表明，电荷自洽方法更能有效反映簇周围的环境，得到的计算结果能够较好地与实验值吻合.最后，分别计算了不同吸附情况下O2的振动频率.     

Time-resolved ultraviolet laser-induced breakdown spectroscopy for organic material analysis

Ultraviolet pulses (266 nm) delivered by a quadrupled Nd:YAG laser were used to analyze organic samples with laser-induced breakdown spectroscopy (LIBS). We present characteristics of the spectra obtained from organic samples with special attentions on the emissions of organic elements, O and N, and molecular bonds CN. The choice of these atomic or molecular species is justified on one hand, by the importance of these species to specify organic or biological materials; and on the other hand by the possible interferences with ambient air when laser ablation takes place in the atmosphere. Time-resolved LIBS was used to determine the time-evolution of line intensity emitted from these species. We demonstrate different kinetic behaviors corresponding to different origins of emitters: native atomic or molecular species directly vaporized from the sample or those generated through dissociation or recombination due to interaction between laser-induced plasma and air molecules. Our results show the ability of time-resolved UV-LIBS for detection and identification of native atomic or molecular species from an organic sample.     

catena‐Poly[[diiodo­zinc(II)]‐μ‐4,4′‐bipyridine‐κ2N:N′]

The title compound, [ZnI₂(bipy)]_n (bipy is 4,4′‐bipyridine, C₁₀H₈N₂), has been prepared by the hydro­thermal reaction of ZnI₂ and bipy at 433 K. Each Zn atom is coordinated by two N atoms from two different bipy ligands and by two I atoms in a distorted tetra­hedral geometry, with Zn—N distances ranging from 2.068 (7) to 2.101 (8) Å and Zn—I distances ranging from 2.5471 (13) to 2.5673 (13) Å. The mol­ecular structure features a zigzag polymeric chain. Face‐to‐face π–π stacking inter­actions between adjacent bipy ligands stabilize the structure.     

A new diarylheptanoid and a new diarylheptanoid glycoside isolated from the roots of Juglans mandshurica and their anti-inflammatory activities

A new diarylheptanoid, (2S,3S,5S)-2,3,5-trihydroxy-1,7-bis(4-hydroxy- 3-methoxyphenyl)heptane (1), and a new diarylheptanoid glycoside, (2S,3S,5S)-2,3-dihydroxy-5-O-β-d-xylopyranosyl-7-(4-hydroxy-3-methoxyphenyl)-1-(4-hydroxyphenyl)heptane (2), together with three known compounds, rhoiptelol C (3), rhoiptelol B (4) and 3′,4″-epoxy-2-O-β-d-glucopyanosyl-1-(4-hydroxyphenyl)- 7-(3-methoxyphenyl)heptan-3-one (5) were isolated from the roots of Juglans mandshurica (Juglandaceae). The structures of compounds 1 and 2 were identified based on HR-ESI-MS, 1D and 2D NMR spectroscopic methods. Compounds 1–5 were assayed for their inhibitory effects on the production of NO, TNF-α and IL-6 in LPS-stimulated RAW264.7 cells.     

Regulation of redox balance using a biocompatible nanoplatform enhances phototherapy efficacy and suppresses tumor metastasis

Many cancer treatments including photodynamic therapy (PDT) utilize reactive oxygen species (ROS) to kill tumor cells. However, elevated antioxidant defense systems in cancer cells result in resistance to the therapy involving ROS. Here we describe a highly effective phototherapy through regulation of redox homeostasis with a biocompatible and versatile nanotherapeutic to inhibit tumor growth and metastasis. We systematically explore and exploit methylene blue adsorbed polydopamine nanoparticles as a targeted and precise nanocarrier, oxidative stress amplifier, photodynamic/photothermal agent, and multimodal probe for fluorescence, photothermal and photoacoustic imaging to enhance anti-tumor efficacy. Remarkably, following the glutathione-stimulated photosensitizer release to generate exogenous ROS, polydopamine eliminates the endogenous ROS scavenging system through depleting the primary antioxidant, thus amplifying the phototherapy and effectively suppressing tumor growth in vitro and in vivo. Furthermore, this approach enables a robust inhibition against breast cancer metastasis, as oxidative stress is a vital impediment to distant metastasis in tumor cells. Innovative, safe and effective nanotherapeutics via regulation of redox balance may provide a clinically relevant approach for cancer treatment.

Amplified oxidative stress achieved by modulating redox homeostasis with PDA–MB for highly effective synergistic phototherapy to inhibit primary tumors and metastases.     

Stereodivergent and regioselective synthesis of 3,4-cis- and 3,4-trans-pyrrolidinediols from alpha-amino acids

[reaction: see text] Highly stereodivergent Woodward-Prevost reaction applied to iodoacetates derived from homochiral alpha-amino acids afforded enantiopure 3,4-cis- and 3,4-trans-pyrrolidinediol derivatives, with control over the protecting group, allowing for differential protection.     

用EXAFS研究NiO在γ-Al2O3表面上的分散

本文使用EXAFS方法研究NiO在γ-Al_2O_3的表面上的分散情况。文章讨论了Ni含量为7%、13%、18%、26%、35%的NiO/γ-Al_2O_3体系的径向结构函数图以及Ni含量为13%、26%的NiO/α-Al_2O_3样品的径向结构函数图,认为NiO能在γ-Al_2O_3表面上成单层分散。分散后的Ni-O距离接近NiO晶体的Ni-O距离,表明Ni离子和γ-Al_2O_3表面上的氧有很强的相互作用。