Degradation of bare and silanized silicon wafer surfaces by constituents of biological fluids

The surface hydroxyl content and surface structure of silica and other oxides with and without surface modification were systematically studied by solid state (29)Si NMR, thermogravimetric analysis, and the lithium alanate method. Aerosil 90 as a well described reference system and functionalized zirconia-silica particles were used in the validation of the lithium alanate method. 3-Methacryloxypropyltrimethoxysilane and dodecylphosphonic acid were applied as surface modifiers. The determination of silanol content of Aerosil 90 by (29)Si NMR and TGA confirms the results obtained by the lithium alanate method, which also allows for the determination of the remaining surface hydroxyl content after surface modification. For both silane coupling agents, the residual hydroxyl content of modified zirconia-silica is decreased by a factor of approximately 2 compared with that of the unmodified mixed oxide, whereas after modification with dodecylphosphonic acid, the hydroxyl content is slightly higher. These results are again in good agreement with those by (29)Si NMR confirming that the lithium alanate method is a reliable and easily practicable method for surface hydroxyl determination.     

2-Amino-5,7-dimethyl-1,8-naphthyridine as a fluorescent reagent for the determination of nitrite

A new fluorescent reagent 2-amino-5,7-dimethyl-1,8-naphthyridine (ADMND) was proposed for the determination of trace nitrite. The reaction is based on the diazotization of naphthyridine amine with nitrite to form a diazonium salt that hydrolyzed when boiling to give hydroxyl group substituted naphthyridine. Fluorescence quenching degree of ADMND by nitrite ion is linear in the nitrite concentration range of 1 x 10(-7) to 2.5 x 10(-6)mol l(-1) with a detection limit of 4.06 x 10(-8)mol l(-1). Reaction and determination acidity for nitrite is the same which made the method much simpler compared with the widely accepted fluorescence method with DAN as a fluorescence reagent.     

Reverse hydrophobic PDMS surface to hydrophilic by 1‐step hydrolysis reaction

Hydrophilic modification on the surface of polymer polydimethylsiloxane (PDMS) material is a key step for its application in biomaterial, bioengineering, and so on. In this article, a novel and effective method was proposed to reverse hydrophobic surface to hydrophilic by 1‐step hydrolysis of Si―O bond to produce hydrophilic hydroxyl group. The hydrophilizing reagent 2‐(trimethylsiloxy) ethyl methacrylate (TMSEMA) was used during the copolymerization of polydimethylsiloxane prepolymer (DMS U21). The prepared PDMS film was subjected to 1‐step surface hydrophilic reversal treatment using KOH solution to produce hydroxyl groups on the surface. The contact angle, attenuated total reflection Fourier transform infrared spectra, and equilibrium water content (EWC) measurements were conducted on PDMS films. The results showed that TMSEMA content had no obvious impact on the contact angle and EWC value of untreated PDMS. After reversal treatment, the contact angle decreased from 94° to 15°, and the EWC value increases to 10% when the TMSEMA content was 15 wt%. The spectrum proved that the reverse reaction produced hydroxyl and carboxylate on the surface. The hydrophilic stability, surface morphology, and protein adsorption properties of PDMS film were also investigated. This study can provide new ideas and further reference for improving the hydrophilicity of PDMS surface.     

马来酸酐(MAH)表面改性纳米碳酸钙粉体的制备及表面性能

通过在两相法制备纳米碳酸钙的过程中添加一定量的马来酸酐(MAH)的方法，在纳米碳酸钙的表面引入羧基、羟基、双键等活性基团对纳米碳酸钙进行表面改性，并通过调节马来酸酐的用量，有效地控制纳米碳酸钙的极性和表面能。接触角实验结果表明，当马来酸酐的加入量为2%时可以获得界面性能最理想的改性纳米碳酸钙。还在此基础上提出了马来酸酐(MAH)对纳米碳酸钙进行表面改性的过程机理，并以SEM，ATR-FTIR和TGA等手段对上述过程机理进行了验证。     

稀土固体超强酸SO42-/TiO2/La3+催化合成丁酸异戊酯

丁酸异戊酯是无色至淡黄色透明油状液体,有近似生梨和香蕉香甜气。天然品存在于椰子油、可可豆、苹果、香蕉、葡萄、草莓等中,是我国ＧＢ２７６０－８６规定允许使用的食用香料,主要用以配制香蕉、菠萝、杏、樱桃和杂锦水果等型香精;也可用作提取天然香料的溶剂、乙酸纤维素的溶剂及增塑剂。通常它是在硫酸催化下由丁酸和异戊醉酯化反应而得［１,２］,反应时间长,副反应多,对设备腐蚀严重,废水排放量大,后处理工艺复杂。为此,本实验选用稀土固体超强酸ＳＯ４２－／ＴｉＯ２／Ｌａ３＋作为催化剂进行某些酸与异戊醇的酯化反应。 …     

化学反应-顶空气相色谱法测定气相二氧化硅表面硅羟基

建立了一种基于化学反应-顶空气相色谱测定气相二氧化硅表面硅羟基含量的新方法.实验取气相二氧化硅放入顶空瓶中于105℃烘箱中加热2 h去除水分,将甲苯稀释的格氏试剂注入密闭的顶空瓶中,格氏试剂与气相二氧化硅表面硅羟基快速反应产生甲烷(CH4),甲烷量与气相二氧化硅表面硅羟基含量成正比.经过气相色谱-氢火焰离子化检测器测定...     

钛酸酯偶联剂对包硅铝钛白粉表面的有机改性

The surface organic modification of TiO2 particles with titanate coupling reagent,which was pre-coated with double layers of SiO2 and Al2O3,was studied.Experiments showed that the modified particles exhibited hydrophobic characteristics.The modification state of the particle surface was characterized by IR spectroscopic measurement,pyrolytic gas chromatography,thermogravimetric analysis and X-ray photoelectron spectra.The titanate coupling reagent binding with the hydroxyl on the particle surface was analyzed.The surface characteristics of pre-modification and post-modification particles were compared.     

Surface characterisation of chemically reduced electrolytic manganese dioxide

In this work a titration technique has been used to characterize the amphoteric surface properties of a series of chemically reduced electrolytic manganese dioxide (EMD) samples (MnO 1.97 to MnO 1.50). The surface of the EMD was found to consist of independent acidic and basic hydroxyl groups, which were able to be characterised by their respective equilibrium constants and site concentrations. For this chemically reduced series Kb varied from (1.81-8.43)x10(-10) as reduction proceeded, with the corresponding basic site concentration varying from (0.20-2.50)x10(-4) mol/m2 over the pH range considered. Ka was ranged from (1.23-9.23)x10(-6) over the reduction range considered. The increase in Kb suggested a weakening of the MnO bond via the introduction of the larger Mn3+ ions which will increase the length of this bond. Weakening the MnO bond results in a corresponding strengthening of the OH bond giving the surface hydroxyl group a basic nature which is supported by the increasing basic site concentration. For the samples with an x in MnOx value above 1.71 the total number of acidic sites decreased which supports the increase in the concentration of basic sites; however, below 1.71, the surface concentration of acidic sites increases slightly, which can be rationalised by the fact that the pyrolusite domains within the EMD (with relatively stronger MnO bonds) are accessible at this stage of the reduction. The number of surface oxide sites (Ns) and surface hydroxyl sites (Ns(OH)) were calculated crystallographically, and from the sum of the acid and basic hydroxyl groups determined by titration. Both methods produced data with the same order of magnitude, as well as indicated the expected increase in the number of surface hydroxyl groups with increasing degree of reduction. Electrochemical analysis of the samples in 9 M KOH showed the expected decrease in capacity with an increase in the degree of reduction. It also showed a decrease in the amount of charge contributed to the overall homogeneous reduction by Mn4+ ions in surface defects and within the ramsdellite domains over the entire x in MnOx range. However, the amount of charge contributed from the pyrolusite domains remained unchanged until after a x in MnOx value of 1.71.     

稀土固体超强酸SO42-/TiO2/La3+催化合成丁酸异戊酯

The synthesis of isoamyl butyrate with isoamyl alcohol and butyric acid as reactants and rare-earth solid superacid SO₄^2-/TiO₂/La³⁺ as catalyst had been studied.The influent actors of reaction were investigated.The results showed that the appropriate conditions should be: Weight of catalyst was 0.5g (weight of butyric acid if 0.2mol); molar ratio of isoamyl alcohol to butyric acid was 1.8: 1; reaction time was 2.0 h; the taking water reagent (Toluene) was 15mL.The yield of isoamyl butyrate was about 99.0%.     

High-affinity binding and direct electron transfer to solid metals by the Shewanella oneidensis MR-1 outer membrane c-type cytochrome OmcA

The purified outer membrane bacterial protein OmcA binds densely to the surface of hematite (Fe2O3), permitting direct electron transfer to this solid mineral to reduce Fe (III) with an electron flux of about 1013 electrons /cm2/s. In the presence of hematite, there is a substantial increase in the amplitude of internal protein motions that correlate with metal reduction. Binding is highly favorable, with a partition coefficient of approximately 2 x 105 (DeltaGo' = -28 kJ/mol), where approximately 1014 OmcA proteins bind per cm2 to the solid metal surface, indicating the utility of using purified OmcA in the construction of a biofuel cell.     

Potential of thermo-optical methods for the study of molecular layers bonded to a flat glass surface

Thermal-lens spectrometry and photothermal deflection spectroscopy (mirage-effect spectroscopy) are used to study active bright red 5SKh bonded to a glass surface. The theoretically calculated dependence of the thermal-lens signal on the absorbance of the surface-absorbing layers on a nonabsorbing substrate is used to evaluate the concentration of the reagent in the bonded layer. The concentration of the reagent varies in the range of (2–8) × 10^?11 mol/cm², depending on the method of surface modification. Using photothermal deflection spectroscopy, it is shown that the thickness of the layer on the glass surface does not exceed 700 nm. Data obtained by the thermo-optical methods are supplemented with the results of the analysis of the surface relief obtained using electron microscopy in the secondary electron emission mode, and the uniformity of the modification of the sample surface is characterized. Based on the obtained data, a comparative analysis is performed for the potential of the considered methods for the investigation of the molecular layers bonded to the flat glass surface.     

Biphenalenylidene: the forgotten bistricyclic aromatic ene. A theoretical study

The Lawesson reagent and P(2)S(5) mediated reductive coupling of phenalenone (6) gives LPAH peropyrene (5) in 47% and 54% yields. The mechanism of the reaction involves the formation of phenalenethione (10), Z- and E-1,1'-biphenalenylidene (3), and 9 as intermediates. The electrocyclization reaction of Z-3 to 9, followed by aromatization, gives 5. The results of an ab initio and DFT study of 3 and 2,2'-biphenalenylidene (12) are reported. E-3 and Z-3 have a diradical character with twist angles of 44.8 degrees and 57.8 degrees (at UB3LYP/6-311G**). Delta E(++)(Tot) = 10.2 kJ/mol and Delta G(++)(298) = 10.6 kJ/mol for E-3 <==> Z-3 diastereomerization. These unusually low energy barriers are due to the ground-state diradical destabilization and the aromatic stabilization of the transition state TS-3. Triplet Z-3 is higher in energy than singlets E-3 and Z-3 by 10.4 and 3.1 kJ/mol. In the concealed non-Kekulé 12, singlet 12 is more stable than the triplet by 1.3 kJ/mol. Singlet 12 is more stable than singlet E-3 by 2.0 kJ/mol, and orthogonal singlet TS-12 is lower in energy than singlet TS-3 by 6.0 kJ/mol. The energy barriers for the hexatriene-cyclohexadiene electrocyclization Z-3 --> 9 are Delta E(++)(Tot) = 94.8 and Delta G(++)(298) = 98.3 kJ/mol (at (U)B3LYP/6-31G). The reaction occurs thermally in a conrotatory mode.     

Trace analysis of surfactants derived from fatty alcohols I. Optimization of derivatization reaction

Summary Pre-column derivatization of the primary hydroxyl group in fatty alcohols and fatty alcohol ethoxylates using carbazole-9-carbonyl chloride (CC−Cl) and FMOC-Cl is described and compared with derivatization with 1-naphthoyl chloride (N−Cl). As the excess of derivatization reagent leads to a broad and strongly tailing reagent peak, it hinders trace determination of fatty alcohols and fatty alcohol ethoxylates. Therefore, an off-line as well as an on-line solid-phase extraction (SPE) method for removal of excess reagent are described. The on-line method which is based on column switching, shows better reproducibility higher pre-concentration, lower risk of contamination and can be easily automated, while the off-line method is better suited for the analysis of derivatized, fatty alcohol ethoxylates. An example of the trace analysis of fatty alcohols with a concentration of 2 ppb is given.     

二苯并-18-冠-6的氯甲基化及其在交联聚乙烯醇微球表面的固载化

在Lewis酸催化剂存在下,1,4-二氯甲氧基丁烷对冠醚二苯并-18-冠-6(1)进行氯甲基化修饰使其转变成氯甲基化冠醚(2),其结构经1HNMR,13C NMR,IR及MS表征。2与交联聚乙烯醇(CPVA)微球表面的羟基发生亲核取代反应实现冠醚的固载化,制得固载有冠醚的功能微球(3)。实验结果表明,1的氯甲基化反应易于进行,在两个苯环上分别发生了对称的氯甲基化反应,2为对称的四取代产物。通过2的氯甲基与CPVA的羟基之间的亲核取代反应,1可容易地化学固载到CPVA表面。     

羟基化对Si3N4粉体水相分散性的影响

过施加硝酸有效地使氮化硅（Si₃N₄）粉末的表面羟基化,以改善在水性介质中的分散性。与天然粉末相比,羟基化粉末在水性介质中产生更稳定的胶体分散。傅里叶变换红外光谱和X射线光电子能谱结果表明,随着羟基改性,Si₃N₄粉末的羟基含量显著增加。这有助于防止Si₃N₄粉末在水性介质中聚集。此外,热重分析表明羟基化Si₃N₄粉末的羟基含量比天然粉末高68.8%。Si₃N₄粉末的表面亲水性通过羟基改性而增强,并且粉末分散性随着羟基含量的增加而提高。     

羟基化对Si3N4粉体水相分散性的影响

通过施加硝酸有效地使氮化硅（Si₃N₄）粉末的表面羟基化,以改善在水性介质中的分散性。与天然粉末相比,羟基化粉末在水性介质中产生更稳定的胶体分散。傅里叶变换红外光谱和X射线光电子能谱结果表明,随着羟基改性,Si₃N₄粉末的羟基含量显著增加。这有助于防止Si₃N₄粉末在水性介质中聚集。此外,热重分析表明羟基化Si₃N₄粉末的羟基含量比天然粉末高68.8%。Si₃N₄粉末的表面亲水性通过羟基改性而增强,并且粉末分散性随着羟基含量的增加而提高。     

SiO2表面吸附层中钛酸丁酯的反应过程

研究了硅胶表面富含水吸附层中钛酸丁酯的反应过程.在不同条件的吸附相反应制备中,首先利用分光光度计测定了乙醇体相中Ti含量随反应进行的变化过程.结果表明由于吸附层中钛酸丁酯的快速水解,乙醇体相中的Ti含量在反应前60 min快速减少.钛酸丁酯与硅胶表面羟基、化学吸附层和物理吸附层中的水分子的反应活性均不相同,这导致了Ti含量曲线的不同变化.EDAX的分析结果表明温度对乙醇体相中钛酸丁酯的反应过程影响很小,但对吸附相反应有着较为复杂的影响,Ti含量和TiO2形貌都随着温度升高出现了两类变化.本文提出了温度对化学吸附和物理吸附的不同影响来解释样品中Ti含量和TiO2形貌的不同变化.     

沉淀温度对K-CuLaZrO_2催化剂上合成气直接合成异丁醇的影响

合成气制备异丁醇是一个非常复杂的过程,催化剂性质与异丁醇形成之间的关系仍未完全理解。共沉淀法是合成固体复合氧化物常用的制备方法,分散度高、相互作用强、制备工艺简单,但是影响制备过程的因素很多。本研究深入考察沉淀反应开始时沉淀温度对催化剂性质的影响,进而通过不同的表征手段,结合评价结果建立催化剂性质与异丁醇形成的联系,进一步完善异丁醇形成机制。结果表明,低温(30℃)有利于CuO-ZrO_2固溶体的形成,两者分散性好,且彼此之间相互作用较强,有利于氧化铜还原。同时,在低温下,催化剂表面含有较多的羟基,与CO反应后形成较多的表面C_1物种,促进了碳链增长,提高了异丁醇选择性。提高沉淀温度后,CuO颗粒粒径增大,CuO-ZrO_2固溶体逐渐被破坏,两者相互作用减弱,且表面羟基含量降低,导致表面C_1物种减少,异丁醇选择性明显降低。在CLZ-30(沉淀温度为30℃)催化剂上,异丁醇的选择性最高可达38.7%。     

Mobility of solid tert-butyl alcohol studied by deuterium NMR

The molecular mobility of solid deuterated tert-butyl alcohol (TBA) has been studied over a broad temperature range (103–283 K) by means of solid-state 2H NMR spectroscopy, including both line shape and anisotropy of spin–lattice relaxation analyses. It has been found that, while the hydroxyl group of the TBA molecule is immobile on the 2H NMR time scale (τC > 10(–5) s), its butyl group is highly mobile. The mobility is represented by the rotation of the methyl [CD3] groups about their 3-fold axes (C3 rotational axis) and the rotation of the entire butyl [(CD3)3-C] fragment about its 3-fold axis (C3′ rotational axis). Numerical simulations of spectra line shapes reveal that the methyl groups and the butyl fragment exhibit three-site jump rotations about their symmetry axes C3 and C3′ in the temperature range of 103–133 K, with the activation energies and preexponential factors E1 = 21 ± 2 kJ/mol, k(01) = (2.6 ± 0.5) × 10(12) s(–1) and E2 = 16 ± 2 kJ/mol, k(02) = (1 ± 0.2) × 10(12) s(–1), respectively. Analysis of the anisotropy of spin–lattice relaxation has demonstrated that the reorientation mechanism of the butyl fragment changes to a free diffusion rotational mechanism above 173 K, while the rotational mechanism of the methyl groups remains the same. The values of the activation barriers for both rotations at T > 173 K have the values, which are similar to those at 103–133 K. This indicates that the interaction potential defining these motions remains unchanged. The obtained data demonstrate that the detailed analysis of both line shape and anisotropy of spin–lattice relaxation represents a powerful tool to follow the evolution of the molecular reorientation mechanisms in organic solids.     

Immobilization of η-cyclopentadienyltris(dimethylamido)zirconium polymerization catalysts on a chlorosilane- and HMDS-modified mesoporous silica surface: a new concept for supporting metallocene amides towards heterogeneous single-site-catalysts

The modification of a mesoporous silica surface with Si(Ind)(CH₃)₂Cl and the immobilization of CpZr(NMe₂)₃ on this surface was studied via IR-spectroscopy. To reduce side reactions, the indenyl-modified silica was reacted with hexamethyldisilazane (HMDS) under IR-control before the CpZr(NMe₂)₃-immobilization. The role of the hydroxyl group protection with HMDS is discussed. The surface modifications have been repeated via Schlenk technique at the same conditions and the surface modifications were studied with ¹³C CP MAS–NMR, ¹H MAS–NMR, elemental-, SEM- and BET-analysis. The surface species of the resulting catalysts are discussed. The precatalysts have been treated with methylaluminoxane (MAO) (Al:Zr (mol:mol)=500:1) and the resulting Zr contents (leaching-effect) are discussed. All catalysts have been tested in ethylene and propylene polymerization.