Hybrid organic–inorganic materials on paper: surface and thermo-mechanical properties

In this work a new simple method to improve the bulk properties of paper is presented. Co-polymerization of vinyl functionalised zirconia oxoclusters with vinyl trimethoxysilane was carried out onto paper. The coating process was evaluated also taking into account the specific weight of hybrid polymer left on the paper after one or two deposition steps, and with or without a thermal treatment of curing. The effectiveness of the coating process in consolidating and protecting paper was investigated by measurements with High Temperature Differential Scanning Calorimetry, Dynamical Mechanical Spectroscopy, tensile testing, contact angle, along with Environmental Scanning Electron Microscopy. The coating process does not affect the morphology and appearance of the paper, but modifies its mechanical, surface and thermal properties.     

Nanoscale oxide surface modification of inorganic materials

A method of synthesis of metal oxide films by carboxylate pyrolysis on a substrate surface is developed. The optic physical properties of the obtained films are studied by spectrophotometry using specialdesign fiber-optic probes.     

Charge effects during surface analysis of poorly conducting inorganic materials

Summary The properties of surfaces and interfaces often determine the behaviour of materials in a given application: typical examples are all kinds of corrosion, segregation, sensor activity, wear and friction, adhesion of coatings, joining processes, sintering, etc. It is the aim of this paper to provide materials scientists with a better understanding of the limits of applying modern surface analysis methods (SIMS, AES, etc.) to materials with low room temperature electrical conductivity like most ceramics and glasses. One feature common to all methods deserves special attention: this is the influence of surface and near surface charges on the distribution of mobile ionic species in the near surface region of the sample to be analyzed. The origin of these charges and their order of magnitude as a function of the experimental parameters can be deduced from charge balance considerations: the main result is that self-compensating methods should be most favorable.     

Analysis of inorganic materials by beam techniques — the challenge of high technology

For property-related characterization of inorganic materials, information is needed about bulk composition, distribution of elements, compounds, phases and structural features. Photons, electrons, charged ions or neutrons, often used as focused beams provide access to this information. The major trends in this field are the development or improvement of methods to obtain new information or to increase spatial resolution, detection power, precision and accuracy of analysis. The present state of the analysis of inorganic materials by using beam techniques is discussed in a selective manner. Emphasis is placed on the following problems, which are important for basic research and for development of high-technology materials: ultratrace bulk analysis in the pg g^?1 to ng g^?1 range; analysis for phases, trace elements and isotopes, including structural characterization; and surface analysis, with emphasis on the characterization of trace elements at surfaces, quantitative distribution of trace elements in heterogeneous structures, and surface structural analysis with atomic resolution.     

无机钙材料在石灰岩文物表面防护中的应用

由于碳酸盐矿物的质地特点,石灰岩文物在露天环境中极易发生表面溶蚀,其上赋存文化信息的文字、纹饰和符号等雕刻痕迹也随之湮灭,对其文物价值造成了严重减损。从耐候性和兼容性角度考虑,无机保护材料显然更适合于石灰岩文物的表面防护处理。近年来,基于草酸钙、磷灰石和碳酸钙等钙基材料的石灰岩文物表面防护研究逐渐兴起并开始走向应用。本文就上述钙基保护材料的特点、防护膜制备和应用实践等做了归纳和评述,以期为石灰岩文物保护研究提供参考和借鉴。     

无机钙材料在石灰岩文物表面防护中的应用

由于碳酸盐矿物的质地特点,石灰岩文物在露天环境中极易发生表面溶蚀,其上赋存文化信息的文字、纹饰和符号等雕刻痕迹也随之湮灭,对其文物价值造成了严重减损。从耐候性和兼容性角度考虑,无机保护材料显然更适合于石灰岩文物的表面防护处理。近年来,基于草酸钙、磷灰石和碳酸钙等钙基材料的石灰岩文物表面防护研究逐渐兴起并开始走向应用。本文就上述钙基保护材料的特点、防护膜制备和应用实践等做了归纳和评述,以期为石灰岩文物保护研究提供参考和借鉴。     

用连接性指数估算与预测无机物晶格能

提出原子点价连接性指数（ ｍＸ） 及其逆指数（ ｍ－ｘ）．采用逐步回归方法,建立４７ 种无机物晶格能Ｕ 与１ Ｘ,０－ｘ 的回归方程为： Ｕ＝ １ ３２１ ．８２ ＋３３７ ．０７１ Ｘ－２ ３８０ ．１００－ｘ ,Ｒ＝０．９９９ ６．其估算值优于Ｕ 的理论值,对１０ 种无机物晶格能的预测值与其实验值非常吻合     

On the calculation of surface energies

A simple formalism based on response theory is used to evaluate expressions for the surface energy of a uniform dielectric or metallic medium and the change in surface energy of a dielectric solvent when a dilute electrolyte is dissolved in it. The latter result coincides with the result of Onsager and Samaras.     

Modification of inorganic supports with nickel acetylacetonate: The effect of their surface properties

The mesostructured silica SBA-15, γ-Al₂O₃, and amorphous silica-alumina are modified with Ni(acac)₂ in the liquid and gas phases. This process depends crucially on the nature of active sites on the support surface. In the modification of materials containing weakly acidic or weakly basic hydroxyl groups, it is necessary to use low-polarity solvents. The dominant Ni(acac)₂ chemisorption sites on amorphous silica-alumina are the acid hydroxyls of ≡Si-OH-Al= bridges. The covalent bonding resulting from the replacement of the acetylacetonate ligand favors the fixation of the adsorbed complex on the support surface. The coordinatively unsaturated sites formed by Al³⁺ ions play an insignificant role in Ni(acac)₂ chemisorption. The degree of dispersion of the oxide phase in the resulting catalysts depends strongly on the strength of the interaction between the modifier molecules and the active sites of the support. This is not the case with the aluminum acetylacetonate complexes that form upon the modification of the Al-containing supports. Gas-phase modification affords finer NiO particles than liquid-phase modification.     

Bipolar molecules with high triplet energies: synthesis, photophysical, and structural properties

This article sheds new light on the interplay of electronic and conformational effects in luminescent bipolar molecules. A series of carbazole/1,3,4-oxadiazole hybrid molecules is described in which the optoelectronic properties are systematically varied by substituent effects which tune the intramolecular torsion angles. The synthesis, photophysical properties, cyclic voltammetric data, X-ray crystal structures, and DFT calculations are presented. Excited state intramolecular charge transfer (ICT) is observed from the donor carbazole/2,7-dimethoxycarbazole to the acceptor phenyl/diphenyloxadiazole moieties. Introducing more bulky substituents onto the diphenyloxadiazole fragment systematically increases the singlet and triplet energy levels (E(S) and E(T)) and blue shifts the absorption and emission bands. The triplet excited state is located mostly on the oxadiazole unit. The introduction of 2,7-dimethoxy substituents onto the carbazole moiety lowers the value of E(S), although E(T) is unaffected, which means that the singlet-triplet gap is reduced (for 7bE(S) - E(T) = 0.61 eV). A strategy has been established for achieving unusually high triplet levels for bipolar molecules (E(T) = 2.64-2.78 eV at 14 K) while at the same time limiting the increase in the singlet energy.     

Cranberry changes the physicochemical surface properties of E. coli and adhesion with uroepithelial cells

Cranberries have been suggested to decrease the attachment of bacteria to uroepithelial cells (UC), thus preventing urinary tract infections, although the mechanisms are not well understood. A thermodynamic approach was used to calculate the Gibbs free energy of adhesion changes (DeltaG(adh)) for bacteria-UC interactions, based on measuring contact angles with three probe liquids. Interfacial tensions and DeltaG(adh) values were calculated for Escherichia coli HB101pDC1 (P-fimbriated) and HB101 (non-fimbriated) exposed to cranberry juice (0-27 wt.%). HB101pDC1 can form strong bonds with the Gal-Gal disaccharide receptor on uroepithelial cells, while HB101-UC interactions are only non-specific. For HB101 interacting with UC, DeltaG(adh) was always negative, suggesting favorable adhesion, and the values were insensitive to cranberry juice concentration. For the HB101pDC1-UC system, DeltaG(adh) became positive at 27wt.% cranberry juice, suggesting that adhesion was unfavorable. Acid-base (AB) interactions dominated the interfacial tensions, compared to Lifshitz-van der Waals (LW) interactions. Exposure to cranberry juice increased the AB component of the interfacial tension of HB101pDC1. LW interactions were small and insensitive to cranberry juice concentration. The number of bacteria attached to UC was quantified in batch adhesion assays and quantitatively correlated with DeltaG(adh). Since the thermodynamic approach should not agree with the experimental results when specific interactions are present, such as HB101pDC-UC ligand-receptor bonds, our results may suggest that cranberry juice disrupts bacterial ligand-UC receptor binding. These results help form the mechanistic explanation of how cranberry products can be used to prevent bacterial attachment to host tissue, and may lead to the development of better therapies based on natural products.     

Kinetic adhesion of bacterial cells to sand: cell surface properties and adhesion rate

Correlation between microbial surface thermodynamics using the extended DLVO (XDLVO) theory and kinetic adhesion of various bacterial cells to sand was investigated. Two experimental setups were utilized. Adhesion tests were conducted in batch reactors with slow agitation. Also, bacteria were circulated through small sand columns in a closed loop and the results were analyzed with a simple model which accounted for the rate of the adhesion phenomena (omega in h(-1)) and adhesion percentage. Cells surface properties were derived from contact angle measurements. The wicking method was utilized to characterize the sand. Zeta potentials were measured for the sand and the cells. Kinetic of bacterial retention by the porous media was largely influenced by the electrostatic interactions which are correlated with omega from the model (R(2)=0.71). Negative zeta potentials resulted in electrostatic repulsions occurring between the sand and the bacterial cells which in result delayed bacterial adhesion. While no correlation was found between the adhesion percentage and the total interaction energy calculated with the XDLVO theory the respective behavior of hydrophobic and hydrophilic bacteria as well as the importance of electrostatic interactions was evidenced. All the bacterial strains studied adhered more in the column experiments than in the adhesion tests, presumably due to enhanced collision efficiency and wedging in porous media, while filtration could be ignored except for the larger Bacillus strains. Approximate XDLVO calculations due to solid surface nanoscale roughness, retention in a secondary minimum and population heterogeneity are discussed. Our results obtained with a large variety of different physicochemical bacterial strains highlights the influence of both surface thermodynamics and porous media related effects as well as the limits of using the XDLVO theory for evaluating bacterial retention through porous media.     

Thermal stability of high surface area silicon carbide materials

The synthesis of mesoporous silicon carbide by chemical vapor infiltration of dimethyl dichlorosilane into mesoporous silica SBA-15 and subsequent dissolution of the silica matrix with HF was investigated. The influence of the synthesis parameters of the composite material (SiC/SBA-15) on the final product (mesoporous SiC) was determined. Depending on the preparation conditions, materials with specific surface areas from 410 to 830 m² g⁻¹ and pore sizes between 2 and 10 nm with high mesopore volume (0.31-0.96 cm³ g⁻¹) were prepared. Additionally, the thermal stability of mesoporous silicon carbide at 1573 K in an inert atmosphere (argon) was investigated, and compared to that of SBA-15 and ordered mesoporous carbon (CMK-1). Mesoporous SiC has a much higher thermal textural stability as compared to SBA-15, but a lower stability than ordered mesoporous carbon CMK-1.     

Cell adhesion and surface properties of polystyrene surfaces grafted with poly(N-isopropylacrylamide)

Cell adhesion plays a key role in various aspects of biological and medical sciences. In this study, poly(Nisopropylacrylamide) (PNIPAM) was grafted on polystyrene surfaces using different solvents under UV radiation. Moreover, the relation between surface roughness and cell adhesion were evaluated by gravimetric, SEM, AFM, contact angle measurement and cellular analyses. The gravimetric analysis clearly indicated an increase in the grafting by adding 10% methanol to water. The study of surface topography by AFM images showed an increase in the surface roughness and as a result of which, a decrease in wettablity was observed. At 37 °C, epithelial cells were well attached and proliferated on the grafted surfaces, while these cells were spontaneously detached below 32 °C in the absence of any enzymes. Moreover, MTT assay and SEM images indicated good cell viability and an increase in cell adhesion caused by the roughness increase. The results of this study reveal the great potential of PNIPAM-grafted polystyrene for being used in the biomedical fields such as drug delivery systems, tissue engineering and cell separation.     

Development of new high transparent hybrid organic–inorganic monoliths with surface engraved diffraction pattern

Flexible hybrid xerogels bringing together high optical transparency up to 96%, low shrinkage down to 5.5%, very smooth surface (average roughness of about 0.3 nm) and thermal stability up to 200 °C were achieved as a result of the optimization of sol‐gel preparative method and a new combination of sol‐gel precursors. Two types of hybrid materials (hereafter referred, respectively, as urea‐silicate and amino‐alcohol‐silicate gels) were synthesized in this work. The shrinkage and the transparency of these materials have been drastically improved by using two different derived siloxanes (3‐isocyanate propyltriethoxysilane and 3‐glycidoxypropyltrimethoxysilane) and two amine‐terminated polyether precursors with different molecular weights. A drying process was implemented to minimize yellowing of prepared samples. Under these conditions, we were able to efficiently reproduce a well‐defined imprinted pattern at materials surface by using an original casting mould. The study of the diffraction characteristics of the obtained grating revealed a good reproducibility of the imprinted grating that shows to be comparable with the original mould. The developed methodology opens the possibility to produce diffraction lenses with a wide range of forms by a simple method based on sol‐gel process. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Influence of surface properties of particles on their adhesion and removal

The effect of surface properties of particles on their adhesion and removal was investigated using an immersed system consisting of nylon particles and a quartz plate. The nylon particles were dyed with a reactive dye in order to change their properties and were used for the adhesion and removal experiments in comparison with undyed particles. The electrokinetic potentials of the particles were measured by micro-electrophoresis and the Hamaker constants were independently evaluated using experimental values of dispersive component of surface free energy determined by the Wilhelmy technique. The experimental results were used for the discussion of particle adhesion and removal on the basis of the heterocoagulation theory. The differences in adhesion and removal efficiencies between dyed and undyed particles were explained in terms of the electrostatic and dispersive van der Waals interaction by considering the differences in thier properties, the electrokinetic potential and the Hamaker constant, due to dyeing.     

Evaluation of multi-modal high salt binding ion exchange materials

The performance and selectivity of novel cation and anion exchange multi-modal chromatographic materials were evaluated. Desorption profiles of 13 proteins possessing a range of properties (e.g. size, charge and hydrophobicity) were determined on the cation exchange materials. Batch experiments were carried out by loading individual proteins on each resin at low salt, and examining the desorption of the proteins during sequential washes with increasing salt concentrations. While all of the resins exhibited some binding of proteins at elevated salt concentrations, this effect was more pronounced on the resins with aromatic ligands as compared to the materials with aliphatic ligands. As expected, materials with higher ionic capacities exhibited higher binding at elevated salts. In addition, some proteins exhibited high binding at elevated salt concentrations to all of the resins. The combined effect of charge and other secondary interactions with these multi-modal chromatographic materials enables high salt binding of a range of proteins as well as unique selectivities for the recovery of certain classes of proteins. Since the anion exchange materials all exhibited high binding at elevated salt concentrations the work with these materials focused on a study of elution strategies to remove proteins from these aromatic based materials. After evaluating various elution protocols, a combined strategy of pH change and chaotropic salt were shown to minimize electrostatic and hydrophobic interactions and was found to be an effective elution strategy for this class of anion exchange materials using peanut lectin as a model protein.     

Organic templates for the generation of inorganic materials

Mankind's fascination with shapes and patterns, many examples of which come from nature, has greatly influenced areas such as art and architecture. Science too has long since been interested in the origin of shapes and structures found in nature. Whereas organic chemistry in general, and supramolecular chemistry especially, has been very successful in creating large superstructures of often stunning morphology, inorganic chemistry has lagged behind. Over the last decade, however, researchers in various fields of chemistry have been studying novel methods through which the shape of inorganic materials can be controlled at the micro- or even nanoscopic level. A method that has proven very successful is the formation of inorganic structures under the influence of (bio)organic templates, which has resulted in the generation of a large variety of structured inorganic structures that are currently unattainable through any other method.     

Diversity of the surface properties of Lactococci and consequences on adhesion to food components

Bacteria possess surface properties, related to their charge, hydrophobicity and Lewis acid/base characteristics, that are involved in the attachment processes of microorganisms to surfaces. Fermentation bulks and food matrixes are complex heterogeneous media containing various components with different physicochemical characteristics. The aim of the present study was to investigate whether (i) bacteria present in a food matrix, interacted physicochemically at their surface level with the other constituents and (ii) the diversity of bacterial surface properties could result in a diversity of microbial adhesion to components and thus in a diversity of tolerance to toxic compounds. The surface properties of 20 lactic acid bacteria were characterized by the MATS method showing their relatively hydrophilic and various basic characteristics. The results obtained from a set of representative strains showed that (i) the strains with higher affinity for apolar solvents adsorbed more to lipids and hydrophobic compounds, (ii) the more the strains adsorbed to a toxic solvent, the less they were tolerant to this solvent. A diversity of bacterial surface properties was observed for the strains in the same species showing the importance of choosing bacteria according to their surface properties in function of technological objectives.