牛血红蛋白与银纳米粒子相互作用的光谱研究

运用紫外-可见吸收光谱(UV-Vis)、荧光光谱、同步荧光光谱、圆二色光谱(CD)及傅立叶变换红外光谱(FTIR)等手段, 研究牛血红蛋白(Bovine Hemoglobin, 简称BHb)与银纳米粒子的相互作用. 结果表明, BHb能吸附在银纳米粒子的表面, 使其415 nm处的特征等离子体共振吸收峰强度下降, 峰位红移. 随银纳米粒子的浓度增大, BHb分子中Soret带的吸收持续降低, 说明银纳米粒子可能使部分血红素辅基从它们的键腔中脱离出来. Stern-Volmer方程分析表明, 银纳米粒子静态猝灭BHb的内源荧光. 由UV-Vis和荧光光谱的变化, 计算BHb与银纳米粒子的结合常数, 其数量级达到10⁹～10¹⁰. 同步荧光光谱的蓝移说明, 银纳米粒子扰动BHb分子内部的酪氨酸、色氨酸残基所处的微环境, 使之包埋于疏水腔中. 拟合计算远紫外CD数据发现, 银纳米粒子诱导BHb产生轻微的二级结构改变, α-螺旋含量降低. FTIR光谱结果提示, BHb中半胱氨酸残基的硫、羧基氧、酰胺及氨基酸残基中的氮原子与银纳米粒子可能有表面键合作用.     

银电极表面异亮氨酸单分子膜结构和表面性质的表面增强拉曼光谱研究

利用表面增强拉曼光谱(SERS)技术研究了在粗糙化银电极表面吸附的异亮氨酸自组装单层膜结构及其表面性质随溶液酸碱性和电极电位改变的特征.研究结果表明溶液pH值的变化并没有显著改变异亮氨酸分子在银电极表面以去质子化羧基吸附为主的特征.借助于高氯酸根离子这一SERS光谱探针,对异亮氨酸单分子膜的表面酸碱性质进行了表征和分析.而就电位改变对该单分子膜结构的影响而言,在所研究的电位范围内,单分子膜中的异亮氨酸分子是通过去质子化羧基与氨基两个位点而吸附的,且吸附作用随电位负移而呈现有规律的变化.     

气液界面磷脂单分子膜的表面增强拉曼光谱

采用纳米银胶作为成膜亚相, 原位获得了十八胺单分子膜、十八胺/卵磷脂复合膜的表面增强拉曼信号.研究表明,增强主要来源于亚相中的银粒子与成膜分子之间较强的作用.通过在磷脂膜内添加十八胺分子辅助增强而获取了卵磷脂的分子振动信息.     

银纳米粒子自组装结构的光谱性质研究

采用自组装方法在玻璃基底表面上构筑了银纳米粒子二维亚单层结构, 进而以对巯基苯胺为耦联分子进行银粒子的二次组装, 构成具有分子尺寸间隙的银粒子簇. 银粒子表面等离子体共振依赖于粒子间距、表面吸附分子和粒子组装方式. 同层内的银粒子相互间电磁偶合可导致银粒子偶极子等离子体共振蓝移; 对巯基苯胺的吸附则使得表面等离子体共振红移. 表面增强拉曼光谱结果表明, 具有分子尺寸间隙的银粒子簇对耦联于粒子间的对巯基苯胺分子的拉曼散射具有极大的增强效应, 同时也使耦联的对巯基苯胺与银粒子间产生更大程度的电荷转移.     

银纳米粒子有序自组装体中偶联分子的表面增强拉曼光谱研究

采用自组装方法,分别以1,4-二巯基苯和对巯基苯胺为偶联分子,在光滑银基底表面上构筑了银纳米粒子的单层和双层有序结构.表面增强拉曼光谱研究表明,在有序银纳米粒子组装体中偶联分子的拉曼散射得到很大增强,其中1,4-对巯基苯的拉曼散射增强效应主要来自光滑银基底表面与单层银纳米粒子间的电磁耦合,而对巯基苯胺的拉曼散射增强效应则主要由两层银纳米粒子之间耦合作用所致.两种不同的耦合作用所产生的增强效应大致相近.     

金与银电极表面甘氨酸分子吸附作用的SERS光谱研究

本文利用表面增强拉曼光谱(SERS)技术研究了甘氨酸在金与银基底表面的吸附作用特征。研究表明甘氨酸分子以COO-的不对称形式吸附于金电极表面,且NH2也是其可能的吸附位点;而在银电极表面,则主要是通过COO-的对称形式而吸附。在此基础上,进一步研究了电极电位与溶液酸碱性对吸附于粗糙化银电极表面甘氨酸分子吸附作用的影响。研究结果表明,甘氨酸分子中去质子化羧基的吸附作用受电位影响较小,而电位对-NH3+吸附作用的影响程度较大。另一方面,溶液pH值对银电极表面的甘氨酸分子吸附行为的影响也较为显著。随着溶液酸性减小羧基倾向于相对于电极表面平行吸附。这是由于随着溶液碱性增大氨基质子化程度的减小,有利于氨基在银电极表面吸附。这将改变分子的吸附构型使其更接近于电极表面。这些变化主要出现在pH值大于10的条件下。     

基于银镜的高灵敏表面增强拉曼光谱基底制备及其用于呋喃唑酮检测

采用化学沉积法制备了表面增强拉曼散射光谱(SERS)银镜基底,用NaCl溶液与HCl溶液除去银镜表面杂质后,通过扫描电子显微镜对基底进行了表征,表明该基底表面的银纳米粒子平均粒径约为200 nm,以对巯基苯胺为探针分子测得其增强因子为4.6×105.利用表面增强拉曼光谱及表面吸附选择定律研究了广谱抗菌药呋喃唑酮在该基底表面的吸附状态,证明呋喃唑酮分子主要是通过CN吸附于银纳米粒子表面的.     

溶剂对香兰素分子印迹聚合物制备的影响

本文考察了5种溶剂对分子印迹聚合物制备过程的影响.在不同的溶剂体系中,模板分子、功能单体、交联剂间的摩尔比均在1:5:20时达到最好,但最佳反应温度随溶剂的不同而不同.所制备的印迹聚合物的吸附等温线、选择性吸附实验表明:极性溶剂有利于聚合反应的进行,尤以二甲亚砜溶剂为佳,所制备的聚合物对香兰素的选择性吸附高达91%.     

维生素PP的表面增强拉曼散射光谱研究

报道了维生素PP分子的常规拉曼光谱(NRS)及该分子在活性衬底银胶上的表面增强拉曼散射(SERS),并对它的拉曼特征峰进行了初步的指认和归属.维生素PP的常规拉曼光谱和SERS谱的对比表明,该分子吸附在银表面时,它的C‖O键与银粒子发生电荷转移,碳氧双键打开形成C-O 单键.通过分析可以推断维生素PP通过羰基和氨基垂直或斜立吸附在银表面上.     

Cu2O/Ag纳米复合物的表面增强拉曼光谱

用一种简单的化学还原方法制备了银纳米粒子包覆的氧化亚铜（Cu2O）纳米复合物。扫描电子显微镜显示Cu2O 为八面体型的纳米粒子,表面光滑,结构对称。包覆的Ag部分占据Cu2O粒子表面。通过比较Ag/Cu2O纳米复合物、Ag溶胶及Cu纳米粒子表面吸附的4-巯基吡啶（4-Mpy）分子表面增强拉曼光谱（SERS）发现,利用此方法得到了Cu2O粒子表面吸附分子的拉曼光谱。银纳米粒子所产生的电磁场增强又增强了吸附在Cu2O上的4-Mpy拉曼信号。这种方法为初步研究Cu2O表面吸附分子性质提供了依据,扩宽了SERS的使用范围,使SERS应用在纳米半导体材料上成为可能。     

高效相转移法制备金属有机溶胶

Organosols of silver and gold nanoparticles stabilized by sodium oleate were prepared with high efficiency by simple phase transfer of their hydrosols to isooctane. Concentrations of sodium oleate and magnesium chloride have crucial effects on the phase transfer efficiency. UV-visible absorption spectroscopy and transmission electron microscopy have been used to characterize the nanoparticles. A possible phase transfer mechanism was proposed based on the anchoring positions of oleate deduced by molecular modeling calculations.     

Thermodynamic properties of some concentrated polymer solutions

Solubilities of several solvents were measured in four molten polymers by using an isobaric vapor-pressure apparatus. Solvent concentration ranged from 0.5 to 15 wt-%. The systems polyisoprene–benzene and polyisobutylene–benzene were studied at 80.0°C; polyisobutylene–cyclohexane was studied at 100.0°C; ethylene–vinyl acetate copolymer (EVA)–cyclohexane, EVA–isooctane, and poly(vinyl acetate)–isooctane were studied at 110.0°C. Of six polymer–solvent systems studied, all except poly(vinyl acetate)–isooctane appear to exhibit hysteresis in a single sorption–desorption cycle starting with dry polymer. The desorption curves of solvent activity plotted versus solvent weight fraction show an inflection point, suggesting localized adsorption of solvent molecules. Experimental data were analyzed with a theory which takes into account adsorption of solvent by polymer in addition to differences in free volumes and intermolecular forces. The theory gives a semiquantitative representation of the experimental data.     

Computational investigation of the strategy of DNA/RNA stabilization through the study of the conjugation of an oligonucleotide with silver and gold nanoparticles

This research deals with the potential of metallic nanoparticles in DNA/RNA stabilization. In this regard, the interaction of adenosine monophosphate (AMP) as a representative of the nucleotide family was theoretically investigated through density functional theory. AMP is a short form of DNA or RNA macromolecules that can interact with gold (Au) and silver (Ag) nanoparticles. The literature represents the thiolation of oligonucleotides as a suitable way for DNA/RNA adsorption on the stated nanoparticles. In this study, the role of different solvents on the thiolation of AMP is scrutinized. The results showed that acetonitrile is the best solvent for the thiolation of AMP with reaction enthalpy (ΔH) of −66.3 kJ/mol. The adsorption of thiolated adenosine monophosphate (TAMP) on the surface of Ag/Au nanoparticles (Ag/AuNP) was studied in different solvents, and in the gas phase. Our results revealed the interaction of TAMP with adsorption energies of −65.3 and −74.1 kJ/mol (gas phase), −54.8 and −62.5 kJ/mol (acetonitrile), and −59.2 and −70.6 kJ/mol (water) on AgNPs and AuNPs, respectively. AuNPs have a shorter bond distance in adsorption of TAMP compared to AgNPs (2.61 vs. 2.78 Å). For all systems, the frontier molecular orbital, the electronic charge passed through the nanoparticles, the density of states, and the molecular electrostatic potential were investigated. The results confirm the suitability of these nanoparticles as carriers for nucleotides that may be useful in gen delivery applications.     

Heat of adsorption of surfactants and its role on nanoparticle stabilization

In this work, the binding between sodium oleate (SO), sodium laurate (SL), sodium dodecyl sulfate (SDS), and sodium dodecylphosphonate (SDP) and iron oxide nanoparticles was systematically investigated using isothermal titration calorimetry (ITC). Comparing the heat exchanged during the isothermal titration with the corresponding surfactant adsorption isotherm, in the cases of SO and SDP, a strong binding takes place at low surfactant concentrations. The binding enthalpy at this low surfactant concentrations depends on the type of surfactant anionic head group. For C12 surfactants, the phosphonate group produced the strongest endothermic binding, followed by the exothermic binding with the carboxylate group, followed by weak exothermic interaction with the sulfate group. For carboxylate surfactants, longer surfactant tails result in larger exothermic binding. Surfactants that exhibited large binding enthalpies also produced more stable suspensions. The Langmuir (L), Freundlich (F), and Langmuir–Freundlich (L–F) adsorption models were used to interpret the adsorption isotherms during the titration with sodium oleate. The L–F adsorption isotherm model was selected to calculate the heat of the formation of the SO monolayer and bilayer on the iron oxide nanoparticles. The L–F model reflects the finite or limited adsorption of the Langmuir model, but accounts for non-homogeneous adsorption of the Freundlich model that help account for surfactant self-assembly before and after adsorption. Coupling the adsorption model with the titration data is possible to calculate the real heat of adsorption of the surfactants on the metal oxide.     

Electronic properties and ultraviolet absorption and fluorescence spectra of 2-pyridinamine

The u.v. absorption and fluorescence spectra of 2-pyridinamine, its methyl derivatives and its carboxylate salts were measured in various solvents (isooctane, methylcyclohexane and isopentane mixed solvent, ethanol and isooctane mixed solvent, acetic acid and isooctane mixed solvent, and pH adjusted solvent) at room temperature and 77 K. These spectral data were interpretated by the molecular orbital method. From these results it was found that the formation of 2(1H)-pyridinimine with the accompanying 2-pyridinium amine occurs only in the π,π* excited singlet state in the acetic acid and isooctane mixed solvent. On the other hand, the fluorescence spectrum of 2-pyridinamine in the pH ⪢ 11 controlled solution was assigned to the monoanion species, that is, the 2-pyridylamide ion which was formed in the first π,π* excited singlet state.     

Infrared study of the kinetics and mechanism of adsorption of acrylic polymers on alumina surfaces

In this paper, we studied the kinetics of the adsorption of poly(methyl methacrylate), PMMA, onto native aluminum oxide surfaces by X-ray photoelectron spectroscopy and reflection-absorption infrared spectroscopy, with the intent of tracking the various changes observed in the infrared spectrum of the adsorbed polymer layer as a function of adsorption time. Specifically, we utilized the relative changes in the absorption bands of the carbonyl, carboxylic acid, and carboxylate groups to determine the sequence of events that culminate in the formation of bonds between carboxylate groups on hydrolyzed PMMA and specific sites on the aluminum oxide surface. We have shown that the adsorption process involves the hydrolysis of a fraction of the methoxy groups of the PMMA to generate COOH groups. Unlike previous assumptions, the formation of COOH groups on the PMMA chains does not constitute a sufficient condition for the actual chemisorption of the polymer chains onto the metal oxide surface. To promote bonding, the acid groups must undergo dissociation to form the carboxylate groups, followed subsequently by actual bond formation, that is, active anchoring, on the surface. This process is mediated by the aluminum oxide sites on the surface in the presence of water. Hence, the adsorption process occurs via a two-step mechanism, in which the first step, that is, the hydrolysis step, is a necessary but insufficient condition and the second step, that is, the anchoring step, is largely dependent on the type of interfacial chemistry possible for a particular polymer-metal oxide surface, the polymer conformation, the molecular weight, and the flexibility of the adsorbing molecules.     

Electronic properties and ultraviolet absorption and fluorescence spectra of 2,6-pyridinediamine

The u.v. absorption and fluorescence spectra of 2,6-pyridinediamine and its carboxylate salts were measured in various solvents [isooctane (2,2,4-trimethylpentane), methylcyclohexane and isopentane mixed solvent, ethanol and isooctane mixed solvent, and pH adjusted solvent] at room temperature and 77 K. These spectral data were interpreted by the molecular orbital method. From these results it was found that the formation of 6-amino-2(1H)-pyridinimine through the 2,6-pyridinediamine hydrogen bonded complex with ethanol occurs only in the π,π* excited singlet state in the ethanol and isooctane mixed solvent. On the other hand, the fluorescence spectrum of 2,6-pyridinediamine in the pH > 13 controlled solution was assigned to the monoanion species, that is, the 6-amino-2-pyridylamide ion which was formed in the first π,π* excited singlet state.     

Water dynamics in small reverse micelles in two solvents: two-dimensional infrared vibrational echoes with two-dimensional background subtraction

Water dynamics as reflected by the spectral diffusion of the water hydroxyl stretch were measured in w(0) = 2 (1.7 nm diameter) Aerosol-OT (AOT)/water reverse micelles in carbon tetrachloride and in isooctane solvents using ultrafast 2D IR vibrational echo spectroscopy. Orientational relaxation and population relaxation are observed for w(0) = 2, 4, and 7.5 in both solvents using IR pump-probe measurements. It is found that the pump-probe observables are sensitive to w(0), but not to the solvent. However, initial analysis of the vibrational echo data from the water nanopool in the reverse micelles in the isooctane solvent seems to yield different dynamics than the CCl(4) system in spite of the fact that the spectra, vibrational lifetimes, and orientational relaxation are the same in the two systems. It is found that there are beat patterns in the interferograms with isooctane as the solvent. The beats are observed from a signal generated by the AOT/isooctane system even when there is no water in the system. A beat subtraction data processing procedure does a reasonable job of removing the distortions in the isooctane data, showing that the reverse micelle dynamics are the same within experimental error regardless of whether isooctane or carbon tetrachloride is used as the organic phase. Two time scales are observed in the vibrational echo data, ~1 and ~10 ps. The slower component contains a significant amount of the total inhomogeneous broadening. Physical arguments indicate that there is a much slower component of spectral diffusion that is too slow to observe within the experimental window, which is limited by the OD stretch vibrational lifetime.     

水和甲醇混合溶剂氢键相互作用及对高分子链溶解能力的理论研究

用密度泛函理论对水和甲醇混合溶剂体系的氢键结构进行了详细研究.通过构象和频率分析发现在水团簇中五聚体和六聚体环状结构最为稳定,同时发现一个全新的特征,即甲醇分子能与水五聚体和六聚体形成双氢键.根据各相互作用的稳定化能,分析了水和甲醇混合溶剂对PNIPAM溶解能力的影响,并对实验现象给予了合理解释.