吡啶在Au电极上吸附的紫外可见反射光谱法研究

电化学调制紫外可见反射光谱技术可用来测定金属电极上吸附物种的取向和吸附物种与金属表面间的相互作用,金属Au与已研究过的Pb、In和Pt^[1～]具有不同形式的能带结构,吸附物种与电极表面间相互作用的电位依赖性可能不同。本文测定了吡啶分子吸附时Au电极的反射差谱,并试图从能带模型角度探讨吡啶分子与Au电极表面原子间的相互作用。     

用固体核磁共振研究HZSM-35分子筛的酸性

分别采用氘代吡啶和三甲基膦为探针分子,利用高分辨固体核磁共振技术研究了HZSM-35分子筛与探针分子之间的相互作用以及分子筛的酸性. 结果表明,探针分子氘代吡啶能够进入分子筛的十元环孔道和八元环孔道,但需在300 ℃下长时间吸附才能扩散到八元环开口的孔穴中. 吸附氘代吡啶后的 1H MAS NMR谱和吸附三甲基膦后的 31P MAS NMR谱表明,这两种孔道中均具有两种酸强度不同的B酸位,并且B酸的数量多于L酸的数量.     

各种孔结构活性炭吸附苯、环己烷、正戊烷和正己烷的~1H和~(13)C NMR研究

~1H和~(13)C NMR研究证明被吸附在不同孔结构活性炭中的烃类以毛细管凝聚和吸附在固体表面两种状态存在。链状烷烃平铺地吸附在固体表面。被吸附烃与活性炭表面酸性基团的质子交换在弛豫过程中起着重要作用。     

含吡啶环的N-(1,3,4-噻二唑-2-基)苯甲酰胺类化合物的合成及其抑菌活性

以3-吡啶乙酸盐酸盐与氨基硫脲为原料经环化反应制备中间体2-氨基-5-(3-吡啶亚甲基)-1,3,4-噻二唑,后者与取代苯甲酰氯反应合成了一系列含吡啶环的N-(1,3,4-噻二唑-2-基)取代苯甲酰胺(3a~3k),其结构通过IR、~1H NMR、~(13)C NMR、MS和元素分析确证。用菌丝生长速率法测定了目标化合物对灰霉菌的离体抑菌活性,结果表明,部分化合物对病原菌有一定的抑制活性。     

基于吡啶甲酮衍生物的蓝色磷光主体材料的合成及性质

以4-苯甲酰吡啶、吩噁嗪和9,9-二甲基吖啶为原料,合成了两种蓝色磷光主体材料:[(2-溴-5-吩噁嗪-10-基)苯基](吡啶-4-基)甲酮(BPPPM),[2-溴-5-(9,9-二甲基-9H-吖啶-10-基)苯基](吡啶-4-基)甲酮(BDPPM)。并用~1H NMR、~(13)C NMR和元素分析对其结构进行了表征,研究了它们的光电性质和热性质。结果表明,BPPPM和BDPPM的光学带隙(Eg)分别为3.31和2.64 e V;它们的发射峰分别位于405和435 nm,发深蓝和蓝色荧光;它们均具有较高的三线态能级(2.70,2.65e V),可与蓝色磷光客体材料FIrpic(2.65e V)的三线态能级相匹配;它们均具有匹配的HOMO(-5.45、-5.35e V)与LUMO能级(-2.14、-2.82e V),且其HOMO、LUMO轨道的电子云分离突出,具有良好的双极性质;此外它们均具有较好的热稳定性和成膜性。     

Au@SiO2膜/Ti电极吸附吡啶的表面增强拉曼光谱研究

基于壳层隔绝纳米粒子增强拉曼光谱技术,合成了Au@SiO₂纳米粒子,并对其进行了相关表征. 结果表明,包裹的二氧化硅层连续、致密,Au@SiO₂膜/Ti电极上可获得金属钛电极上吸附吡啶分子的高质量表面增强拉曼光谱（SERS）信号. 通过Pt、Ni电极的测试,证实该信号源于吸附在基底表面的吡啶分子. 此外,Au@SiO₂膜/Ti电极上吸附吡啶分子的现场SERS光谱研究表明,在-0.1 V ~ -0.6 V电位区间,吡啶分子平躺吸附,从-0.6 V起吸附的吡啶分子由平躺逐转变为垂直,而当电位为-1.2 V时,电极表面析氢,吡啶脱附.     

含吡啶端基9,10-双芳基蒽共轭分子的合成、聚集诱导荧光增强及双光子诱导荧光

通过Heck反应合成了2个以吡啶为端基的9,10-双芳基蒽共轭分子9,10-二{4-{4-[N,N-二(4-吡啶乙烯基)苯基]氨基}苯乙烯基}蒽(4Py-PAA)和9,10-二{4-{4-[N,N-二(2-吡啶乙烯基)苯基]氨基}苯乙烯基}蒽(2Py-PAA),化合物结构经过1H NMR,13C NMR,HRMS-MALDI-TOF确证.测定了化合物在不同极性溶剂中的紫外吸收光谱、荧光光谱、荧光寿命及量子产率,测算了4Py-PAA和2Py-PAA的偶极矩.通过循环伏安法研究了它们的前线轨道能级.测定了4Py-PAA和2Py-PAA的固体荧光光谱、固体荧光量子产率及在不同含水量的水/THF混合溶液中的荧光光谱.实验发现4Py-PAA在THF溶液中发出蓝绿色荧光,固体时发出红色荧光,在含水量为70%的水/THF混合溶剂中发出黄色荧光,荧光强度是纯四氢呋喃(THF)的3倍,呈现聚集荧光增强性质.在800 nm飞秒激光下采用双光子诱导荧光参比法测定了4Py-PAA和2Py-PAA在THF溶液中的双光子吸收截面分别为193和101 GM.实验结果表明含有2位和4位吡啶端基9,10-双芳基蒽共轭分子具有良好的荧光发射性能及双光子吸收性质.     

新型双卤代吡啶酰腙的合成及生物活性研究

以2-氯吡啶-4-甲酸甲酯(1)和水合肼缩合生成2-氯吡啶-4-甲酰肼(2),2与卤代(F,Cl,Br)对苯甲醛反应得到3种新型双卤代吡啶酰腙[C13H9N3OFCl(3a),C13H9N3OCl2(3b)和C13H9N3OClBr(3c)],其结构经1H NMR,13C NMR,IR和元素分析表征。紫外光谱证实,3a^3c与小牛胸腺DNA(ct-DNA)均产生了插入作用。荧光光谱显示,3a^3c均与牛血清蛋白BSA通过静态猝灭形成了复合物。3a^3c与ct-DNA,BSA的结合常数Kb及KA的关系均为3b>3c>3a。抑菌测试结果表明:3种酰腙化合物对大肠杆菌、金黄色葡萄球菌、枯草芽孢杆菌及铜绿假单胞菌等4种细菌的抑菌圈均超过8 mm。其中,3a对4种细菌的最大抑菌圈达10.97 mm。     

新型吡啶衍生物的合成

以2-甲基吡啶为原料,经氧化、硝化、还原反应合成了重要中间体4-氨基-2-甲基吡啶(3); 3分别经1,4-加成反应、Heck反应及取代反应合成了11个吡啶类化合物(4~14),其中5, 6和8~14为新化合物,其结构经¹H NMR, ¹³C NMR, MS和HR-MS进行表征。     

新型含取代哌嗪的5-(吡啶-3-基)-1,2,4-三唑Mannich碱和双Mannich碱的合成及生物活性

根据药物分子设计的活性基团组合原理,通过在1,2,4-三唑环的5位引入吡啶基,同时在4位芳基亚甲氨基的苯环上引入氟或三氟甲基,设计合成了一系列含氟、吡啶和哌嗪基团的1,2,4-三唑Mannich碱和双Mannich碱类化合物.通过核磁共振氢谱(~1H NMR)、碳谱(~(13)C NMR)和元素分析确证了目标化合物的结构.生物活性测试结果表明,部分化合物对油菜具有一定的除草活性;化合物2a,2d和2f(50 mg/L)对苹果轮纹病菌表现出较好的抑制活性,与对照药三唑酮活性相当;化合物2a,2b,2d和2i(180 mg/L)对酮醇酸还原异构酶(KARI酶)表现出了显著的离体抑制活性(抑制率51.7%~88.7%).     

A Theoretical Study of the Interaction of Hydrogen and Oxygen with Palladium or Gold Adsorbed on Pyridine‐Like Nitrogen‐Doped Graphene

The interaction of H₂ and O₂ molecules in the presence of nitrogen‐doped graphene decorated with either a palladium or gold atom was investigated by using density functional theory. It was found that two hydrogen molecules were adsorbed on the palladium atom. The interaction of these adsorbed hydrogen molecules with two oxygen molecules generates two hydrogen peroxide molecules first through a Eley–Rideal mechanism and then through a Langmuir–Hinshelwood mechanism. The barrier energies for this reaction were small; therefore, we expect that this process may occur spontaneously at room temperature. In the case of gold, a single hydrogen molecule is adsorbed and dissociated on the metal atom. The interaction of the dissociated hydrogen molecule on the surface with one oxygen molecule generates a water molecule. The competitive adsorption between oxygen and hydrogen molecules slightly favors oxygen adsorption.     

C70分子吸附于铜表面的增强拉曼光谱研究

报道了C70分子吸附于铜表面的增强拉曼光谱.通过与正常拉曼光谱以及银表面SERS谱的比较发现,C70分子与铜表面之间的吸附属于物理吸附,增强机制主要是电磁增强.C70分子在银表面上的吸附状态与铜表面上的不同,这导致了两者特征峰谱线强度分布存在差异.以C60的振动模式为参考,推断出C70分子在2种金属表面上的吸附状态可能分别处于使碳笼的挤压振动模接近于“平躺”和“竖直”的2种状态.     

Methanol adsorption on the beta-Ga2O3 surface with oxygen vacancies: theoretical and experimental approach

Methanol adsorption on beta-Ga2O3 surface has been studied by Fourier transform infrared spectroscopy (FTIR) and by means of density functional theory (DFT) cluster model calculations. Adsorption sites of tetrahedral and octahedral gallium ions with different numbers of oxygen vacancies have been compared. The electronic properties of the adsorbed molecules have been monitored by computing adsorption energies, optimized geometry parameters, overlap populations, atomic charges, and vibrational frequencies. The gallia-methanol interaction has different behaviors according to the local surface chemical composition. The calculations show that methanol can react in three different ways with the gallia surface giving rise to a nondissociative adsorption, a dissociative adsorption, and an oxidative decomposition. The surface without oxygen vacancies is very reactive and produces the methanol molecule decomposition. The molecule is nondissociatively adsorbed by means of a hydrogen bond between the alcoholic hydrogen atom and a surface oxygen atom and a bond between the alcoholic oxygen atom and a surface gallium atom. Two neighbor oxygen vacancies on tetrahedral gallium sites produce the dissociation of the methanol molecule and the formation of a bridge bond between two surface gallium atoms and the methoxy group.     

Theoretical Study of Retinol,Niacinamide and Glycolic Acid with Halloysite Clay Mineral as Active Ingredients for Topical Skin Care Formulations

The adsorption of retinol, niacinamide and glycolic acid active ingredients on the internal surface of halloysite in an aqueous environment was explored at the molecular level by means of calculations based on quantum mechanics and force fields from empirical interatomic potentials. These active ingredients are stably adsorbed on the internal surface of halloysite forming hydrogen bonds between the hydrogen, oxygen and nitrogen atoms with the hydroxyl groups of the inner surface of the halloysite. In addition, electrostatic interaction between these active ingredients with the water molecules was observed. Therefore, the theoretical results indicate that the adsorption of these active principles is favourable in the halloysite nanotube, which allows directing future experimental investigations for the development and design of retinol, niacinamide and glycolic acid with halloysite nanotubes systems, which may be topical formulations for skincare.     

Adsorption of benzethonium chloride from aqueous solutions on dispersed adsorbents

The adsorption of benzethonium chloride from aqueous solutions on the surface of finely dispersed particles of aluminum oxide, titanium dioxide, and zirconium dioxide is investigated. The ratio of the amount of adsorbed benzethonium chloride molecules to the amount of surface hydroxyl groups as potential adsorption sites is proposed to be used for characterizing the structure of adsorption layers. It is shown that the formation of supramolecular structures of benzethonium chloride molecules on solid surfaces begins when its concentrations in suspensions is significantly lower than the critical micellization concentration. It is established that benzethonium chloride is adsorbed via simultaneous interaction of the surfactant molecules with the surface hydroxyl groups and hydrophobic interaction of their hydrocarbon tails; the amounts of molecules adsorbed as a result of these interactions depend on both benzethonium chloride concentration in a solution and the density of the hydroxyl groups on an oxide surface.     

MP2 study on adsorption of hydrated Na+ and Au+ cations on the Au(111) surface

The interactions of Na+ and Au+ cations with an Au(111) surface in the presence and absence of water molecules were investigated using Au18 and Au22 cluster models and the MP2 method with a triple-zeta valence basis set. The interactions between Na+ ions and the Au(111) surface were found to be primarily electrostatic, contrary to the much stronger Au+-Au(111) interactions that were dominated by orbital contributions. The largest CP-corrected MP2 adsorption energies were -156.9 kJ/mol for Na+ and -478.7 kJ/mol for Au+. When hydrated, Na+ prefers to be completely surrounded by water molecules rather than adsorbed to the surface, whereas Au+ remains adsorbed to the surface as water molecules bond with each other and with the Au surface. CP correction did not change the relative adsorption energy trends of Na+ or Au+ ions, but it had an effect on the interaction energy trends of the hydrated cations because of the weak water-surface and water-water interactions.     

Adsorption of a cationic surfactant, miramistin, from aqueous solutions on the surface of highly dispersed silica

The adsorption of a universal antiseptic agent, the cationic surfactant miramistin, on the surface of highly dispersed silica has been studied. It has been shown that, when miramistin is adsorbed from acidic premicellar solutions, the main contribution to miramistin binding with the surface is made by hydrogen bonding between amide groups of surfactant molecules and silanol groups of silica, which is, at higher pH values, accompanied by ionic interaction between positively charged quaternary nitrogen atoms of miramistin and negatively charged dissociated silanol groups. In the case of adsorption from a micellar solution, an increase in the surface concentration of miramistin is almost independent of solution pH, because the second layer is predominantly formed due to hydrophobic interactions.     

Eluotropic strength in non-aqueous liquid chromatography with porous graphitic carbon

Protein adsorption can be either endothermic or exothermic depending upon the protein, the sorbent and process conditions. In the case of protein adsorption onto ion-exchange surfaces exothermic adsorption heats are usually characterized as representing the electrostatic interaction between two oppositely charged surfaces. Endothermic adsorption heats are typically characterized as representing protein reconfiguration and/or repulsive interactions between adsorbed molecules. In certain segments of the literature surface dehydration and solution non-idealities have been suggested as possible sources of endothermic heats of adsorption. Each of these phenomena was investigated during studies concerning the adsorption of bovine serum albumin and ovalbumin onto an anion-exchange sorbent. The results demonstrated that electrostatic repulsive interactions between adsorbed molecules appears to be a larger contributor to endothermic heats of adsorption than surface dehydration or solution non-idealities. The presence of mobile phase cations can reduce the magnitude of endothermic adsorption heats by screening repulsive interactions between adsorbed molecules. Although water release was not found to be a major contributor to endothermic adsorption heats, it is likely to be a contributor to the entropic driving force associated with the adsorption of bovine serum albumin.     

Comparative simulation study of nitrogen and ammonia adsorption on graphitized and nongraphitized carbon blacks

Grand canonical Monte Carlo simulation is used to study the adsorption of nitrogen at 77 K and ammonia at 240 K to represent weakly polar and polar molecules, respectively, on infinite and finite graphite surfaces. These graphite surfaces were modeled with different percentages of carbons removed (defects) from the top graphite layer. Increasing the number of defects increases the adsorption and the isosteric heat of nitrogen at low pressure. At moderate pressures the amount adsorbed is less due to the disruption in the packing of the nitrogen in the first layer. In contrast, the adsorption of ammonia at all pressures is reduced as the percentage of defects is increased. This is due to the disruption in ammonia bonding caused by the defects. The condensation-like step change in the ammonia isotherm on the perfect graphite surface is not observed for any of these surfaces with defects even for the case of only 10% defects. At high percentage of defects the adsorption isotherm is close to Henry law behavior for much of the pressure range. The adsorption on finite surfaces shows that the amount adsorbed for both molecules decreases compared with that of the infinite surfaces, resulting from interaction potentials with the surface and other fluid molecules at the edge. The decrease is much greater for the ammonia adsorption because the bonding between ammonia molecules is disrupted, meaning that the adsorption cannot follow the mechanism of condensation seen for the infinite surface.     

H2分子在LaFeO3表面吸附的第一性原理研究

基于密度泛函理论的第一性原理方法,通过计算表面能确定LaFeO₃(010)表面为最稳定的吸附表面,研究了H₂分子在LaFeO₃(010)表面的吸附性质。LaFeO₃(010)表面存在LaO和FeO₂两种终止表面,但吸附主要发生在FeO₂终止表面,由于LaFeO₃(010)表面弛豫的影响,使得凹凸不平的表面层增加了表面原子与H原子的接触面积,表面晶胞的纵向体积增加约2.5%,有利于H原子向晶体内扩散。研究发现,H₂分子在LaFeO₃(010)表面主要存在3种化学吸附方式:第一种吸附发生在O-O桥位,2个H原子分别吸附在2个O原子上,形成2个-OH基,这是最佳吸附位置,此时H原子与表面O原子的作用主要是H1s与O2p轨道杂化作用的结果,H-O之间为典型的共价键。H₂分子的解离能垒为1.542 eV,说明表面需要一定的热条件,H₂分子才会发生解离吸附;第二种吸附发生在Fe-O桥位,1个H原子吸附在O原子上形成1个-OH基,另一个H原子吸附在Fe原子上形成金属键;第三种吸附发生在O顶位,2个H原子吸附在同一个O原子上,形成H₂O分子,此时H₂O分子与表面形成物理吸附,H₂O分子逃离表面后容易形成氧空位。此外,H₂分子在LaFeO₃(010)表面还可以发生物理吸附。