高效液相色谱荧光检测法快速测定天然生育酚中痕量苯并[a]芘

建立了一种快速、新颖的高效液相色谱荧光检测法测定天然生育酚中痕量苯并[a]芘.天然生育酚样品经中性氧化铝柱色谱富集和净化后在 XDB-C,18反相柱上,采用水-乙腈(体积比20比80)为流动相进行分离,采用荧光检测器进行检测,其激发波长为 260 nm,发射波长为 408 nm.苯并[a]芘的定量下限为 0.50 ng·g-1.加标回收率大于 77.9%.分析了 3 个不同试样,测定结果的相对标准偏差在 3.0%～10.6%之间.     

基于Ru(bpy)32+-SiO2纳米颗粒的核酸适配体传感器对凝血酶的电致化学发光检测

本文应用核酸适配体构建了一种新型的电致化学发光检测蛋白体系。两个核酸适配体结合凝血酶的两个不同位点,利用这两核酸适配体与凝血酶的高亲和力构建三明治传感体系检测凝血酶。一个核酸适配体固定在金电极上用来捕获凝血酶,另一个标记有包裹电致化学发光活性物Ru(bpy)₃²⁺的二氧化硅纳米颗粒,用来检测电致化学发光信号。此核酸适配体传感器对凝血酶具有特异识别性,电致化学发光信号与凝血酶的浓度直接相关,非特异性识别的牛血红蛋白、牛血清白蛋白不干扰测定。由于在检测的核酸适配体上标记的纳米颗粒包裹有多个发光活性物,因此大大提高了发光效率和灵敏度,此法对凝血酶的线性响应范围为2.0 fmol•L^-1～2.0 pmol•L^-1,检测限可达1.0 fmol•L^-1。     

Synthesis and Mesomorphic Behavior of 3‐Alkyl‐2,5‐ bis[p‐(hexa‐2,4‐dienoyloxy)phenyl]‐Thiophene Derivatives

3‐Alkyl‐2,5‐bis[p‐(hexa‐2,4‐dienoyloxy)phenyl]‐thiophene derivatives were synthesized by using Kumada coupling and Suzuki coupling reactions as key steps. The thermotropic liquid crystalline behavior of these compounds was investigated by optical polarized microscopy, monotropic nematic mesophases were observed in such compounds.     

Amidyl Radical Directed γ-C(sp3)−H Functionalization with Silyl Enol Ethers via Photoredox Catalysis

Herein we reported an efficient photoredox-catalyzed reaction for site-selective C(sp³)−H functionalization of carboxamides with silyl enol ethers as radical acceptors. The reaction proceeded through amidyl radical-directed 1,5-hydrogen atom transfer (1,5-HAT) and C(sp³)−C(sp³) bond formation via radical addition of silyl enol ethers. The process features mild conditions and high functional-group tolerance, allowing the preparation of a series of carboxamides with pendant carbonyl moieties.     

取代基对木质素三聚体模型化合物醚键均裂反应影响的密度泛函理论研究

利用密度泛函理论M062X/6-31++G(d,p)方法,对27种具有不同取代基(甲基、羟甲基和甲氧基)的木质素三聚体模型化合物的Cα-O和Cβ-O键均裂解离能进行了理论计算,探究了不同位置取代基对醚键解离能的影响规律。结果表明,当R2或R3位氢原子仅有一个被甲氧基取代时,Cβ-O键解离能变化很小;当R2、R3位氢原子均被甲氧基取代时,Cβ-O键解离能明显降低;且R4、R5位甲氧基能强化R2、R3位甲氧基对Cβ-O键解离能的降低程度,而不受R1位取代基的影响。当R4、R5位氢原子相继被甲氧基取代时,Cα-O键解离能逐渐降低,且R2、R3位甲氧基也能强化R4、R5位甲氧基对Cα-O键解离能的降低程度。当R1位氢原子相继被甲基、羟甲基取代时,Cα-O键解离能逐渐升高,然而R2、R3位甲氧基会弱化R1位甲基、羟甲基对Cα-O键解离能的升高程度;R1位甲基不会影响Cβ-O键解离能,羟甲基却能明显提高Cβ-O键解离能。     

Luminescent Properties of a Polymer Photoluminescent Composite Containing the Binuclear (EU,TB) Complex as an Emitter

Uninuclear europium (Eu), as well as binuclear Eu and terbium (Tb), complexes were synthesized using acrylic acid (AA) as the first ligand and 1,10-phenanthroline (Phen) as the second ligand. The relative weight ratio of the europium (III) (Eu³⁺) to terbium (III) (Tb³⁺) ions of the binuclear complex was 1:1 as determined via energy dispersive X-ray analysis. The structures of the Eu(AA)₃Phen and Eu_0.5Tb_0.5(AA)₃Phen complexes were characterized by Fourier transform infrared spectroscopy. A series of tri-cellulose acetate (TCA)/ the Eu(AA)₃Phen and TCA/Eu_0.5Tb_0.5(AA)₃Phen composites were prepared by solution blending, and their luminescent properties were investigated by fluorescence spectrophotometry. The excitation spectra of all composites indicated that the TCA matrix probably affected the energy absorption and transfer of organic ligands. In TCA/Eu_0.5Tb_0.5(AA)₃Phen composites the introduced Tb³⁺ ions had some influence on energy absorption and transfer of organic ligands; the energy transfer process of the complex is suggested to be as follows: Phen→AA→Tb³⁺ion→Eu³⁺ion. The emission spectra indicated that the luminescent intensity of the TCA/Eu_0.5Tb_0.5(AA)₃Phen composites was noticeably stronger than that of the TCA/Eu(AA)₃Phen composites, suggesting that the comparatively stable and high-efficiency energy transfer process was only slightly influenced by the TCA matrix. In summary, the TCA/Eu_0.5Tb_0.5(AA)₃Phen (90/10) composite possesses fine luminescent properties for potential usage as red fluorescent materials.     

Singly versus Doubly Reduced Nickel Porphyrins for Proton Reduction: Experimental and Theoretical Evidence for a Homolytic Hydrogen‐Evolution Reaction

A nickel(II) porphyrin Ni‐P (P=porphyrin) bearing four meso‐C₆F₅ groups to improve solubility and activity was used to explore different hydrogen‐evolution‐reaction (HER) mechanisms. Doubly reduced Ni‐P ([ Ni‐P ]^2?) was involved in H₂ production from acetic acid, whereas a singly reduced species ([ Ni‐P ]^?) initiated HER with stronger trifluoroacetic acid (TFA). High activity and stability of Ni‐P were observed in catalysis, with a remarkable i_c/i_p value of 77 with TFA at a scan rate of 100 mV s^?1 and 20 °C. Electrochemical, stopped‐flow, and theoretical studies indicated that a hydride species [H‐ Ni‐P ] is formed by oxidative protonation of [ Ni‐P ]^?. Subsequent rapid bimetallic homolysis to give H₂ and Ni‐P is probably involved in the catalytic cycle. HER cycling through this one‐electron‐reduction and homolysis mechanism has been proposed previously but rarely validated. The present results could thus have broad implications for the design of new exquisite cycles for H₂ generation.     

Laminar-turbulent reactive flows in porous media

We state some recent results concerning liquid-vapor phase transitions for a fluid flow through a porousmedium. The focus is on the friction exerted by the porous medium, which is modeled in such a way to include both laminar and turbulent flows. In this way we obtain a hyperbolic system of three balance laws with a forcing term that is discontinuous in the state variables. Existence, uniqueness and qualitative behavior of traveling waves is proved by a novel regularization technique.     

Traveling Waves for the Mass in Mass Model of Granular Chains

In the present work, we consider the mass in mass (or mass with mass) system of granular chains, namely, a granular chain involving additionally an internal (or, respectively, external) resonator. For these chains, we rigorously establish that under suitable “anti-resonance” conditions connecting the mass of the resonator and the speed of the wave, bell-shaped traveling-wave solutions continue to exist in the system, in a way reminiscent of the results proven for the standard granular chain of elastic Hertzian contacts. We also numerically touch upon settings, where the conditions do not hold, illustrating, in line also with recent experimental work, that non-monotonic waves bearing non-vanishing tails may exist in the latter case.     

Y型分子筛结构破坏的动力学分析(英文)

Y型分子筛是催化裂化(FCC)的速率控制组分.FCC过程中,催化剂在反应器和再生器中往往面临高温水蒸气存在的苛刻环境.因此,分子筛的热稳定性和水热稳定性是催化剂最为关注的性能之一.由于FCC原料中通常含有V、Ni、Na、Fe等不同数量的金属污染物,会对催化剂造成污染及钝化.进料中存在的卟啉类有机复合物持续不断的沉积在催化剂表面,由于含钒的有机金属卟啉化合物在反应中转化形成V_2O_5,V_2O_5在水热条件下形成H_3VO_4组分,在高温水热气氛下加速分子筛骨架结构水解,破坏了Y型分子筛的晶体结构,从而降低了催化剂活性,影响产品选择性.稀土Y型分子筛在FCC中扮演重要的角色,稀土交换分子筛可以提高催化酸性、裂化活性和热与水热稳定性.此外,Na在高温水蒸气条件下也会对分子筛结构造成破坏.一方面,钠能够中和Y型分子筛B酸中心,降低催化裂化活性;另一方面,水热条件下钠的存在会加速破坏Y型分子筛的结构.有关Y型分子筛结构破坏的机理解释较多,然而该过程的动力学研究鲜有报道.反应动力学不能提供一个直接的反应机理,但是任何反应机理的提出必须符合反应动力学的数据.本文采用离子交换法分别制备了一系列不同Na含量USY,不同稀土含量USY,以及含钠和稀土的USY分子筛,通过固相动力学模型考察了上述Y型分子筛水热结构破坏活化能的变化及钒对其活化能的影响.结果表明,Y型分子筛的结构破坏存在三种路径,分别是脱铝、脱硅和La-O键的断裂.钒加速了分子筛骨架水解速率;钒钠具有协同作用,同时存在时对分子筛破坏作用更加显著;NaOH的形成是速率控制步骤;稀土稳定了分子筛的结构,降低了分子筛的水热脱铝速率;钒与定位于分子筛小笼里稀土作用,破坏分子筛的[RE-OH-RE]~(5+)的RE-O键夺取分子筛的骨架氧,导致骨架结构崩塌.由于稀土本身稳定了分子筛的结构,同时钒稀土作用时形成稳定的REVO_4固定了钒的流动性,因此钒对REY结构的影响是几种因素相互叠加和抵消的结果.