基于表面增强拉曼光谱的重金属离子检测

以对巯基苯甲酸为拉曼标记和自组装修饰分子, 在光亮金基底上修饰后作为检测基底, 在金纳米粒子表面修饰后获得具有表面增强拉曼光谱信号的标记金溶胶. 修饰的基底及纳米离子通过重金属离子与羧基端的配位而发生相互作用, 最终形成“金属基底-对巯基苯甲酸/重金属离子/对巯基苯甲酸-金属纳米颗粒”的三明治结构. 采用扫描电镜表征纳米粒子的组装及以表面增强拉曼光谱检测表面标记分子的信号, 以此实现重金属离子的检测. 以强螯合剂EDTA溶液淋洗三明治结构, 使重金属离子与金属基底以及纳米颗粒上的羧基的配位作用断裂, 获得可再次利用的修饰金基底.     

苯硫酚及其衍生物在银电极表面的吸附取向

采用表面增强拉曼光谱技术研究了苯硫酚及其功能衍生物，对巯基苯胺和对苯硫酚在粗糙银电极上的吸附取向特征。结果表明：虽然3种分子的结构类似，但对位取代基直接影响各分子在电极上的吸附取向。3种分子都通过硫原子与银电极形成S-Ag键吸附在电极表面。苯硫酚采用倾斜的方式吸附，使得苯环与基底间表现一定程度的相互作用；吸附的对巯基苯胺则因质子化氨基间的静电相互作用而完全垂直于电极表面；而对苯硫酚则采用平躺于电极表面的方式吸附，致使苯环π体系与基底银之间具有较强的相互作用。     

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。     

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.     

空间稳定的SERS标记金纳米棒探针用于免疫检测

报道了空间稳定的表面增强拉曼散射(SERS)标记的金纳米棒探针在免疫检测方面的应用.该探针是将拉曼活性分子4-巯基苯甲酸和生物亲和性高分子α-巯基-ω-羧基聚乙二醇共吸附于金纳米棒表面而制得.其中,聚乙二醇高分子链为探针提供保护作用和空间稳定,使之可以耐受较苛性的条件;其端位的羧基与抗体等靶向实体结合,从而赋予探针检测识别功能.当探针检测待测抗原时(通过固体基底上的捕获抗体、待测抗原和探针上的抗体之间的特异性结合,形成经典“三明治”夹心结构),探针上4-巯基苯甲酸的SERS信号就能示踪出这种识别.该探针对单组分抗原的检出浓度能低至1×10^-9mg·mL^-1.     

阻抗滴定法测定3-巯基丙酸自组装膜的表面酸度

利用交流阻抗和循环伏安法研究了巯基丙酸自组装膜的组装过程及表面羧基的解离性质.研究表明,由于巯基丙酸的链长较短,自组装膜的组装过程表现为快吸附,然后表现为缓慢组装的过程.利用阻抗值随溶液pH的变化绘制出阻抗滴定曲线,得出了自组装膜表面巯基丙酸的表面酸度,研究了饱和吸附与不饱和吸附对表面酸度的影响.利用氢键作用和静电相互作用对实验结果进行了解释.     

钴岛膜上对巯基苯甲酸的表面增强红外吸收光谱

通过置换反应在金属铝表面制备了表面没有任何保护剂且具有红外增强作用的钴岛膜,用SEM、XRD和表面增强红外光谱对其形貌和性质进行表征。 结果表明,铝片上沉积出的钴呈岛状结构,钴岛膜由二次钴粒子和一次钴粒子通过密堆积的方式构成;首次发现具有这种特殊结构的钴对吸附于其表面的有机分子的红外吸收光谱有较大的增强作用,用此钴岛膜对1 mmol/L的对巯基苯甲酸的红外光谱研究时得到很好的红外增强信号,使得表面增强红外光谱可以用于痕量分析、检测。     

改性活性炭表面羧基的催化动力学分析

采用催化动力学分析法测定了浓HNO3或H2O2改性处理的活性炭表面羧基。选择环氧苯乙烷和甲醇在苯甲酸或改性活性炭催化下的加成反应为指示反应，采用固定时间法考察了环氧苯乙烷转化率与催化剂用量关系。结果表明：在反应初始阶段（转化率低于25％），当苯甲酸用量在O．2～0．6mmol、活性炭用量在0．4～0．8g范围内时，环氧苯乙烷的转化率随反应时间的变化为过原点的直线。以苯甲酸羧基量为参照，浓HNO3与H2O2氧化改性活性炭的表面羧基的质量摩尔浓度分别为0．67mmol／g和0．34mmol／g。与经典的Boehm滴定法相比，此法准确地反映了实际液-固反应中活性炭的表面羧基量。     

基于2-巯基苯甲酸及其原位氧化配体的两种金属配位聚合物的合成、结构及发光性质（英文）

由水热法得到2个新颖配位聚合物[Cd(2-mba)(bimb)]_n(1)和[Pb(2-sb)]_n(2)(H_2(2-mba)=2-巯基苯甲酸,bimb=4,4-双(1-咪唑基)联苯,sb2-=2-亚磺基苯甲酸酯)通过元素分析、红外光谱、X射线粉末衍射和单晶衍射对其进行了表征。配合物1为二维网状结构,由一维的[Cd(2-mba)]_n链与bimb连接形成。在配合物2中配体2-巯基苯甲酸在溶剂热的条件下通过原位反应被氧化成2-亚磺基苯甲酸酯,其结构为一种由配体2-亚磺基苯甲酸酯中的羧基与亚磺基桥联金属铅离子形成的二维(4,4)连接的层状结构。此外,2个配合物展示了良好的热稳定性和光致发光性能。     

纳米/微米碳酸钙的结构表征和热分解行为

采用棕榈酸对纳米碳酸钙进行有机表面改性, 运用SEM﹑TEM、XRD、FTIR 及TG-DTG 对表面改性前后的纳米碳酸钙进行表征, 并与微米碳酸钙的微晶结构及热分解特性进行比较. FTIR 分析结果确证了棕榈酸与纳米碳酸钙表面是以化学键合和物理吸附方式相结合, 粒子表面存在羧基等有机官能团的红外吸收特征. 对比研究发现, 碳酸钙微晶纳米化后, 其红外V3特征吸收峰出现约35 cm-1 的蓝移现象, 并且明显窄化. 初步解释了纳米碳酸钙红外吸收峰蓝移的原因, 认为尺寸效应和晶体场效应是影响纳米碳酸钙红外光谱特征的主要因素. 微晶结构的变化使得纳米碳酸钙的热分解反应表现出反常特性, 热分解温度较微米碳酸钙下降了40.6 ℃.     

Frequency Shift in Graphene‐Enhanced Raman Signal of Molecules

Graphene‐enhanced Raman scattering (GERS) is emerging as an important method due to the need for highly reproducible, quantifiable, and biocompatible active substrates. As a result of its unique two‐dimensional carbon structure, graphene provides particularly large enhanced Raman signals for molecules adsorbed on its surface. In this work, the GERS signals of a test molecule, 4‐mercaptobenzoic acid (4‐MBA), with reproducible enhancement factors are discussed and compared with surface‐enhanced Raman scattering (SERS) signals from highly active substrates, covered with spherical silver nanoparticles. It is shown that chemical interactions between the molecule and graphene can result in a frequency shift in the graphene‐enhanced Raman signal of the molecule.     

Adsorption kinetics, orientation, and self-assembling of N-acetyl-L-cysteine on gold: a combined ATR-IR, PM-IRRAS, and QCM study

The adsorption of N-acetyl-L-cysteine from ethanol solution on gold has been studied by in situ attenuated total reflection infrared (ATR-IR) spectroscopy, polarization modulation infrared reflection absorption spectroscopy, and a quartz crystal microbalance. After an initial fast adsorption, in situ ATR-IR revealed two considerably slower processes, besides further adsorption. The appearance of carboxylate bands and the partial disappearance of the carboxylic acid bands demonstrated that part of the molecules on the surface underwent deprotonation. In addition, the C=O stretching vibration of the carboxylic acid group shifted to lower and the amide II band to higher wavenumbers, indicating hydrogen-bonding interactions within the adsorbate layer. Based on the initial ATR-IR spectrum, which did not reveal deprotonation, the orientation of the molecule within the adsorbate layer was determined. For this, density functional theory was used to calculate the transition dipole moment vectors of the vibrational modes of N-acetyl-l-cysteine. The projections of the latter onto the z-axis of the fixed surface coordinate system were used to determine relative band intensities for different orientations of the molecule. The analysis revealed that the amide group is tilted with respect to and points away from the surface, whereas the carboxylic acid is in proximity to the surface, which is also supported by a shift of the C-O-H bending mode. This position of the acid group favors its deprotonation assisted by the gold surface and easily enables intermolecular interactions. Periodic acid stimuli revealed reversible protonation/deprotonation of part of the adsorbed molecules. However, only non-hydrogen-bonded carboxylic acid groups showed a response toward the acid stimuli.     

Investigating Alanine–Silica Interaction by Means of First‐Principles Molecular‐Dynamics Simulations

In our attempts to achieve a detailed understanding of protein–silica interactions at an atomic level we have, as a first step, simulated a small system consisting of one alanine in different protonation states, and a hydroxylated silica surface, using a first‐principles molecular‐dynamics technique. The simulations are carried out in vacuo as well as in the presence of water molecules. In the case of a negatively charged surface and an alanine cation, an indirect proton transfer from the alanine carboxylic group to the surface takes place. The transfer involves several water molecules revealing an alanine in its zwitterionic state interacting with the neutral surface through indirect hydrogen bonds mediated by water molecules. During the simulation of the zwitterionic state the ammonium group eventually establishes a direct ? N? H???O? Si interaction, suggesting that the surface–amino group interaction is stronger than the interaction between the surface and the carboxylic group. In vacuum simulations, the amino group exhibits clearly stronger interactions with the surface than the carboxylic group.     

On the nature of the Brønsted acidic groups on native and functionalized mesoporous siliceous SBA-15 as studied by benzylamine adsorption from solution

The concentration and Br?nsted acidity of surface silanol groups on mesoporous silica (SBA-15) has been studied by following the adsorption of benzylamine, BA, from water as a function of pH. The adsorbed amount of BA from water was compared to the maximum amount of BA that could be adsorbed from cyclohexane. Furthermore, the surface concentration and acidity of carboxylic acid functions on surface-functionalized SBA-15 was also studied, which allowed the relative surface concentration of remaining silanols to be obtained. Two types of silanols can be identified, where about 1/5 of the silanols have a pKa 相似文献   

A multinuclear solid-state magnetic resonance study of the interactions between the inorganic and organic coatings of BaSO4 submicronic particles

Silica-coated BaSO4 submicronic particles, modified on the surface by treatment with stearic acid, have been characterized by means of 29Si, 13C, and 1H magic-angle-spinning (MAS) high-resolution techniques, and low-resolution 1H-FID analysis. Two types of adsorbed water were identified; adsorbed either inside or on the surface of BaSO4, most of the latter being removed by the silica coating. Evidences of silica-stearic acid interactions were found involving either carboxylic acid or carboxylate functional groups, and occurring by means of hydrogen and/or covalent bonds. Stearic acid was present as monolayer only, its chain being mostly rigid, even though a small fraction was subjected to fast inter-conformational motions.     

An ATR-FTIR study of different phosphonic acids adsorbed onto boehmite

An ATR-FTIR study of the vibrational spectra of N,N-bis(2-hydroxyethyl) aminomethylphosphonic acid (BHAMP), 1-hydroxyethane-1,1′-diphosphonic acid (HEDP) and nitrilotris(methylenephosphonic acid) (NTMP) adsorbed onto boehmite is presented. The study was performed in the pH range from 5 to 9, and bands assignments are given in the 1200–900 cm^?1 wavenumber range, where the bands associated with various P–O(H) vibrations can be found. The three phosphonic acids adsorb onto boehmite by forming inner-sphere surface complexes. ATR-FTIR data indicates the presence of both protonated and deprotonated mononuclear surface species. In all cases, the surface-bound ions undergo protonation reactions as pH is decreased. The results are in good agreement with previously proposed surface complexation models.     

Competitive adsorption of organic matter with phosphate on aluminum hydroxide

The effects of orthophosphate on the adsorption of natural organic matter (NOM) on aluminum hydroxide were investigated using three organic compounds as surrogates, including humic acid (HA), phthalic acid, and 2,3-dihydroxybenzoic acid (2,3-DHBA). The adsorption of phthalic acid and 2,3-DHBA was very limited compared to that of HA, whereas their adsorption was reduced much more significantly than that of HA by phosphate. The efficiency of phosphate in reducing HA adsorption increased with increasing phosphate concentration. Phosphate adsorption was slightly reduced by phthalic acid and 2,3-DHBA but moderately suppressed by HA. The adjacent carboxylic groups mainly contributed to the adsorption of humic acid at low pH, while the adjacent phenol groups were responsible for the adsorption of humic acid at high pH. HPLC-SEC and SUVA analysis revealed that HA molecules with high molecular weight were adsorbed preferentially but were easily displaced by the specifically adsorbed phosphate. TM-AFM images revealed that the aggregation of HA molecules and the protonation of carboxylic groups at low pH facilitated the adsorption under acidic conditions. The presence of phosphate increases the coagulant dosage for NOM removal as some sites on the coagulant precipitates become utilized by phosphate.     

FTIR spectroscopy of alcohol and formate interactions with mesoporous TiO2 surfaces

The effects of pH and ultraviolet (UV) light with ligated formic acid on mesoporous TiO2 were characterized by transmission Fourier transform infrared (FTIR) spectroscopy and compared with adsorbed formate complexes. Surface-modified anatase thin films were prepared from acidic aqueous nanoparticulate anatase suspensions diluted with methanol and ethanol. Bands assigned to carboxylic acid groups displayed unique bonding character in the ligated formic acid on the anatase surface. For increased proton concentrations in the films, separation in -COO stretching bands (delta nu) for formic acid increased (increase in frequency for nuC=O and decrease in frequency for nuC-O). With UV exposure, surface-bound organics were rapidly removed by photocatalytic oxidation at 40 degrees C and 40% relative humidity (RH). In addition, the delta nu of the formic acid bands decreased as organics were mineralized to carbonates and CO2 with UV light. Aqueous formic acid adsorption experiments showed a distinctly different bonding environment lacking carbonate, and the delta nu for the carboxylic groups indicated a bridging bidentate coordination. The delta nu of the bands increased with increasing proton concentration, with both bands shifting to higher wavenumbers. The shifts may be ascribed to the influence of protonation on surface charge and the effect of that charge on the electronegativity of carboxylate groups bound to the surface. As alcohols are used in the mesoporous TiO2 solar cell preparation, implications of these surface modifications to dye-sensitized photovoltaics are discussed.     

ADSORPTION BEHAVIOUR AND RHEOLOGICAL PROPERTIES OF NON-AQUEOUS LANTHANUM CHROMITE SUSPENSIONS

Adsorption studies of monosubstituted benzene molecules with various functional groups on doped lanthanum chromite/cyclohexane surface have been performed. The results from the adsorption study can be used in selecting appropriate anchoring groups on the dispersant. It was found that high amount of O relative lo La on the LaCrO₃ surface correlated with high amounts of adsorbed benzoic acid. Increase in the La content relative to the O on the powder surface increased the amount of adsorbed benzylamine. The high amount of benzoic acid adsorbed on 20% Ca-doped lanthanum chromite powder (Al)lated well with good colloidal stability caused by a carboxylic acid containing dispersant. Rheology experiments showed that a low degree of agglomeration is obtained using only a small amount of the carboxylic acid containing dispersant (Hypermer LP1). Etectrophoretic mobility measurements in water of this powder coated with the LP1 dispersant indicated electrosteric stabilisation.     

Ag/ZrO2-NT/Zr hybrid material: A new platform for SERS measurements

In this paper, we present recent results of our attempts to produce nanoporous zirconia, as well as our investigations of a hybrid material consisting of nanoporous zirconia loaded with Ag-nanoparticles, Ag-n/ZrO₂-NT/Zr, which could be used as an active SERS substrate. The Zr-based hybrid material, as our investigations have shown, is an active and stable substrate in SERS investigations aimed at detecting various organic molecules: mercaptobenzoic acid, pyridine and two different dyes – rodhanine derivatives. The SERS spectra for the probe molecules adsorbed on silver nanoparticles on a ZrO₂-NT/Zr platform display characteristic intensity ratios different from those measured on previously studied nanoporous substrates based on Ti and Al, which ensure a different (alternative) interaction between the investigated adsorbate and adsorbent. In order to characterize our new substrate we used high-resolution SEM and surface analytical techniques: XPS (X-ray photoelectron spectroscopy) and SERS (surface enhanced Raman spectroscopy).