Functionalization of mesostructured inorganic–organic and porous inorganic materials

The capability to functionalize the interior channels and/or high internal surface areas of mesostructured inorganic–organic or porous inorganic solids with specific organic or inorganic moieties has dramatically expanded the potential applications for these versatile materials in catalysis, separations, optical and opto-electronic devices, drug delivery, sensors, and energy conversion. Key to the widespread application of these materials are the various synthetic schemes that have been developed to provide control over the types of species incorporated and, more importantly, their distributions within the mesostructured hosts. Furthermore, multiple active species can often be independently incorporated and collectively optimized to yield multifunctional properties that widen application prospects. Several recent developments and examples in this rapidly growing field of materials chemistry and engineering are highlighted and discussed.     

Self-assembly of functionalized inorganic–organic hybrids

Recent advances on the synthesis and self-assembly of hybrid inorganic–organic materials have been reviewed in terms of the synthetic strategies and emerging techniques, including in-situ self-assembly, template-induced self-assembly, evaporation-induced self-assembly, and layer-by-layer assembly for assembling functional hybrids. The perspectives and outlook on this research topic are given.     

Sedimentation analysis of organic–inorganic hybrid colloids

Hybrid organic–inorganic latex particles are synthesized to combine the beneficial properties of the constituents which thus lead to synergistic improvement in the properties. The properties of hybrid particles are dependent on the successful hybridization process, thus controlling or tuning of such processes by effective characterization is immensely important. Analytical ultracentrifugation provides these characterization possibilities owing to its high statistical capability and ability to characterize multiple parameters. The use of different detection methodologies can help in generating valuable information on the overall size and density distributions of the particles. Apart from that, it is also possible to quantify the presence of any free polymer and inorganic particles in the hybrid latex which would affect the properties of hybrid latexes. By following the densities of the pure and hybrid particles, it is also possible to quantify the amounts of the constituent phases in the hybrid particles. The density gradients generated in preparative ultracentrifugation also provide additional possibilities for the characterization of the hybrid particles which have densities higher than the measurable range in the analytical ultracentrifuge. Evolution of hybrid particles can also be studied as a function of time. It also provides advantage of separation of the various fractions for further characterization.     

Properties of wood–plastic composites: effect of inorganic additives

Wood–plastic composites from Syrian tree species (white poplar, cypress tree, and white willow) were prepared using gamma-ray irradiation. Dry wood was impregnated with acrylamide or butylmethacrylate at various methanol compositions as the swelling solvent. Effect of inorganic additives and co-additives such as lithium nitrate (LiNO₃), copper sulfate (CuSO₄) and sulfuric acid (H₂SO₄), used at a very low concentration (1%), on the polymer loading (PL) and the compression strength (CS) was also investigated. It has been found that all the additives and co-additives, except Cu²⁺, increase the PL values and only Li⁺ has a positive effect on CS.     

Flexible inorganic–organic hybrids with dual inorganic components

Combining multiple inorganic components is an effective approach to improve the mechanical properties of inorganic–organic hybrid materials. The inorganic components can form interactions with the organic polymer matrix, and there is thus a need to understand the reinforcement mechanism under the optimal combination of organic polymer and inorganic particles. In this work, we prepared a series of dual inorganic particle–based titania/silica–poly(tetrahydrofuran)–poly(ε-caprolactone) (TiO₂/SiO₂–PTHF–PCL) hybrids by means of simultaneous cationic ring-opening polymerization and sol–gel reaction. In addition to constructing hybrid networks, the SiO₂ and TiO₂ components play important roles in multiple toughening mechanisms. The prepared dual inorganic hybrids feature enhanced thermal stability and mechanical properties when compared with the ones with a single inorganic component. The optimized mixing of such two inorganic components is identified through mechanical tests, revealing that the hybrid polymer₇₀/(Si_0.6Ti_0.4)₃₀ (70/18/12 mass ratio) has the highest compressive failure strain (80%) and compressive ultimate strength (1.3 MPa) as well as storage modulus (120 kPa), enabling elongation of up to 37% when compared with its original length. We thus find that the dual inorganic component approach is an effective strategy to enhance the mechanical properties of hybrid materials, suggesting potential applications as scaffolds for tissue engineering and soft robotics.     

Polarographic catalytic wave of hydrogen——Parallel catalytic hydrogen wave of bovine serum albumin in the presence of oxidants

A polarographic catalytic hydrogen wave of bovine serum albumin (BSA) at about -1.80 V (vs. SCE) in NH4CI-NH3 · H2O buffer is further catalyzed by such oxidants as iodate, per-sulfate and hydrogen peroxide, producing a kinetic wave. Studies show that the kinetic wave is a parallel catalytic wave of hydrogen, which resulted from that hydrogen ion is electrochemically reduced and chemically regenerated through oxidation of its reduction product, atomic hydrogen, by oxidants mentioned above. It is a new type of poralographic catalytic wave of protein, which is suggested to be named as a parallel catalytic hydrogen wave.     

Electrochemical methods of analysis of inorganic substances. Publications for 1990–1999

The data of the scientometric study of publications in inorganic electrochemical analysis for 1990– 1999 were presented. Most of the published papers (from 60 to 80%) deal with voltammetry and potentiometry. Since 1997, the number of papers on voltammetry has been higher or equal to the number of papers on potentiometry, which is due to the successive development of modified electrodes, the use of ultramicroelectrodes, and the development of stripping voltammetry, including adsorption voltammetry. The role of electrochemical analysis in the development and production of sensors was discussed. The most advantageous methods are potentiometry and conductometry; the role of amperometry is also significant. It was underlined that, although the number of papers on coulometry is low, this method is the most precise absolute method of analytical chemistry. The contribution of conferences on analytical chemistry to the publications on electrochemical methods and the elements leading in the number of publications are considered. Presented at the V All-Russian Conference with the Participation of CIS Countries on Electrochemical Methods of Analysis (EMA-99), Moscow, December 6–8,1999.     

Synthesis of polymer–inorganic patchy microcapsules with tunable patches

We introduce a facile and versatile approach for the formation of ball-like polymer–inorganic patchy microcapsules with a tunable shell by combining sol–gel chemistry of silica precursor and phase separation between the polymer and the precursor. Firstly, chloroform-in-water emulsion droplets containing poly(methyl methacrylate) (PMMA), silica precursor [tetraethyl orthosilicate (TEOS)] and co-surfactant sodium dioctyl sulfosuccinate (Aerosol OT or AOT) were prepared by shaking the mixture by hand. Due to the added AOT, water molecules diffuse into the chloroform droplets, and the tiny water droplets would coalesce gradually, triggering the formation of double emulsion droplets. Upon further solvent evaporation, the concentration of the polymer and the silica precursor in the oil shell of the double emulsions increases, leading to the phase separation between the polymer and the precursors (and partially formed silica through the hydrolysis and condensation of TEOS). Because of the confined geometry of the oil shell in the double emulsions, polymeric disc-like structures, stabilized by AOT, were dispersed in the silica precursors. Meanwhile, the silica precursor hydrolyzed and condensed when brought in contact with the aqueous solution, ultimately leading to the formation of a mineralized shell around the polymer domains and the hybrid patchy microcapsules. Effect of synthesis conditions, such as the amount of TEOS, AOT, and PMMA used, the pH value, and solvent evaporation rate on interfacial behavior of the solvent/water; and the morphology of the patchy microcapsules were investigated. Patchy microcapsules with tunable patch size and shape can be generated through tailoring the experimental parameters. Our study indicates that the hybrid patchy microcapsules can be formed by taking advantage of the sol–gel chemistry and the phase separation process, and the underlying generality of the synthesis procedure allows for a variety of applications, including drug storage, coatings, delivery, catalysis, and smart building blocks in self-assembling systems.     

Effect of modified organic–inorganic hybrid materials on thermal properties of cotton fabrics

Phosphorus-modified siloxanes monomer DOPO-IPDI-AMEO (DIA) was synthesized and characterized by ¹H nuclear magnetic resonance (H NMR), ³¹P NMR, and Fourier transform infrared spectra (FTIR). It hydrolyzed and grew an organic–inorganic hybrid coating on the surface of cotton fabrics via sol–gel process. The conversion of gel reaction was characterized by solid-state ²⁹Si NMR. The effect of the modified organic–inorganic hybrid materials on thermal properties of cotton fabrics was investigated by thermogravimetric (TG) analysis, real time Fourier transform infrared (RT-FTIR), and microscale combustion calorimetry (MCC) experiments. In addition, thermogravimetry-Fourier transform infrared spectra (TG-FTIR) were used to investigate the released degradation products. The characterization information represented that DIA has been prepared successfully. Also the conversion of gel reaction was fairly high. The TG data showed that char residues increased with the addition of the DIA coating. While the peak heat release rate (PHRR) decreased with the presence of the coating in MCC test. Moreover, the flammable degradation products dropped obviously, which can be observed from the data of TG-FTIR.     

Modes of coordination and stereochemistry of the NO3 − anions in inorganic nitrates

Stereochemical features of 950 nitrate groups in the structures of 365 inorganic nitrates were analyzed using TOPOS software. The types of coordination of nitrate groups are systematized by means of Voronoi-Dirichlet polyhedra and the method of intersecting spheres. Terminal coordination (53% of the total number of nitrate groups), most of all terminal bidentate coordination (47%) was found to prevail. Bridging nitrate groups occur less frequently (20%). A considerable number of nitrate groups are not incorporated in the coordination sphere of the complexing atom but form H-bonds or bonds of mainly ionic nature (27%). A number of metal cations show clear-cut tendency for a certain mode of coordination of the NO₃ group. Criteria for classification of nitrate groups into four types (slightly distorted groups and groups with monodentate, bidentate and asymmetric type distortion) are proposed. Structural features of nitrate groups depending on the mode of coordination are considered. The geometry of mono- or bidentate nitrate groups can differ appreciably from the typical one because of participation of terminal oxygen atoms in ionic or hydrogen bonds. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 429–440, March, 2008.     

Inkjet printing of inorganic sol–gel ink and control of the geometrical characteristics

In this article we have shown the possibility to inkjet an ink on glass substrates for high resolution or on large area by varying the geometrical characteristics such as the dried droplet diameter and the line width. We formulated an inorganic sol–gel ink based on tetraethyl orthosilicate with a suitable mixture of organic solvents and investigated the thermal stability of the ink. The influence of the applied voltage during the jetting process as well as the surface free energy of the coated glass substrates were studied for tailoring the droplet diameter and line width of the dried inkjet-print.     

Synthesis and properties of organic–inorganic hybrid liquid crystal gels

Organic–inorganic hybrid liquid crystal (LC) gels have been synthesised by the thiol-ene reaction of a multifunctional cyclic siloxane, 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane (TVMCTS) and alkane dithiols, 1,6-hexanedithiol (HDT) or 1,9-decanedithiol (DDT), in LC matrices, 4-cyano-4?-pentylbiphenyl (5CB) or 4′-n-octyl-4-cyano-biphenyl (8CB). The LC gels were prepared in an isotropic phase at 70°C or mesophases at 25°C using radical initiators. The phase transition temperatures from a mesophase to an isotropic phase of the resulting gels were lower than those of the original LCs. The gels containing 8CB (8CB gels) prepared at 25°C showed two phase transitions: smectic-to-nematic and nematic-to-isotropic transitions. By contrast, the 8CB gels synthesised in the isotropic phase showed only one phase transition from smectic phase directly to isotropic phase. Reaction conversions in the LC gels prepared at 70°C were higher than that in the gels prepared at 25°C. Scanning microscopic light scattering analysis of the LC gels cleared homogeneous small size mesh with a small amount of large defect. Polarisation micrographs of the LC gels showed framed optical textures derived from the LC molecules at room temperature. The LC gels containing more than 90 wt% of LC showed electro-optic response.     

Zeta potential of inorganic fine particle—Na-bentonite binder mixture systems

The zeta potential of single and multi-inorganic fine particle mixtures (hematite and gangues, i.e., SiO₂ + Al₂O₃) with Na-bentonite was investigated to understand and properly control the mineral surface properties relevant to pelletization of low-grade fine iron ores. The zeta potential of hematite-bentonite mixture showed more negative charge up to 1 wt.% bentonite dosage and became constant. In the multiparticle mixture systems with bentonite, the SiO₂ amount in the system controlled the changes in zeta potential due to its high negative charge (−54.9 mV at natural pH) and the bentonite attachment on its surface based on the electrostatic interaction while Al₂O₃ had no effect due to its negligible surface charge (−1.6 mV at natural pH). This article reports the new insight into the characterization of surface chemistry of inorganic/mineral mixture systems to understand their surface charge properties in relation to fine mineral particle processing, and to show a direction toward the elucidation of particle dispersion/aggregation mechanism in complex ore systems aiming for their beneficiations.     

Structure and surface properties of fluorinated organic–inorganic hybrid films

Fluorinated organic–inorganic hybrid films were prepared by sol–gel process from tridecafluoroctyltriethoxysilane (PFAS), 3-glycidoxypropyltrimethoxysilane, and tetraethoxysilane (TEOS). It has been found that the fluorinated hybrid films possessed fluorinated side chains originating from PFAS as top layer, and silica network as bottom layer, which had very low surface energy and could be used as water repellent functional coatings. The outermost layer of the water-repellent film may be fully covered by the perfluoroalkyl side chains as the molar ratio of PFAS/TEOS increases up to about 0.005:1. The addition of BPA can enhance the cross-link density of fluorinated hybrid films, and make more perfluoroalkyl groups enriching at the coating film-air interface to lower the surface free energy. However, the improvement of the cross-link density of fluorinated hybrid films tends to exhibit brittleness and micro-cracks. Consequently, it can be concluded that a small BPA additive content is preferred for the formation of fluorinated hybrid films with a smooth surface and less detectable cracks.     

Syntheses and structural characterization of inorganic–organic hybrid solids of bis-imidazolium chlorocadmate complexes

Six organic–inorganic complexes derived from bis-imidazole derivatives ([(H₂L1)(CdCl₃ ? H₂O)₂] (1), L1 = 1-(3-(1H-benzimidazol-1-yl)propyl)-1H-benzimidazole; [(H₂L2)CdCl₄] (2), L2 = 1,1′-bis(benzimidazolyl)methane; [(H₂L3)CdCl₄] (3), L3 = 1-(2-(1H-benzimidazol-1-yl)ethyl)-1H-benzimidazole; [(H₂L4)₄(CdCl₄)₄] ? 13H₂O (4), L4 = 1,5-bis(1-benzimidazolyl)-3-oxapentane; [(H₂L5)CdCl₄] (5), L5 = 1-(4-(1H-benzimidazol-1-yl)butyl)-1H-benzimidazole; [(H₂L6)(Cd₂Cl₈)_0.5] ? H₂O (6), L6 = 3,6-bis(imidazol-1-yl)pyridazine), and cadmium(II) chloride dihydrate were prepared and characterized by IR, X-ray structure analysis, elemental analysis, and TG analysis. The imidazolyl moieties in all six compounds are essentially planar. X-ray diffraction analysis revealed that complexes 1–6 have 3-D network structures built from hydrogen bonds between imidazolium cations, chlorocadmate anions, and water. The arrangements of the anions and cations in their solid state are dominated not only by the size and symmetry of the imidazolium cations, but also by the different structure types of the chlorocadmate anions as well as the hydrogen-bonded interactions existing in the crystal structures. All of the complexes are thermally stable.     

Specific features of the salting-out of oxyethylated nonylphenols using inorganic salts at 25°С

The solubility of oxyethylated nonylphenols (neonol AF 9-12 and neonol AF 9-25) in aqueous solutions of inorganic salts is studied at 25°С. Cation and anion abilities to salt out neonols from aqueous solutions are examined. It is found that anions are able to salt out neonols while cations are able to salt in neonols. The concentration parameters of extraction in water–neonol AF 9-12 (neonol AF 9-25)–(NH4)2SO4 systems are optimized.     

Structure of the catalytic, inorganic core of oxygen-evolving photosystem II at 1.9 Å resolution

The catalytic center for photosynthetic water-splitting consists of 4 Mn atoms and 1 Ca atom and is located near the lumenal surface of photosystem II. So far the structure of the Mn(4)Ca-cluster has been studied by a variety of techniques including X-ray spectroscopy and diffraction, and various structural models have been proposed. However, its exact structure is still unknown due to the limited resolution of crystal structures of PSII achieved so far, as well as possible radiation damages that might have occurred. Very recently, we have succeeded in solving the structure of photosystem II at 1.9 ?, which yielded a detailed picture of the Mn(4)CaO(5)-cluster for the first time. In the high resolution structure, the Mn(4)CaO(5)-cluster is arranged in a distorted chair form, with a cubane-like structure formed by 3 Mn and 1 Ca, 4 oxygen atoms as the distorted base of the chair, and 1 Mn and 1 oxygen atom outside of the cubane as the back of the chair. In addition, four water molecules were associated with the cluster, among which, two are associated with the terminal Mn atom and two are associated with the Ca atom. Some of these water molecules may therefore serve as the substrates for water-splitting. The high resolution structure of the catalytic center provided a solid basis for elucidation of the mechanism of photosynthetic water splitting. We review here the structural features of the Mn(4)CaO(5)-cluster analyzed at 1.9 ? resolution, and compare them with the structures reported previously.     

Role of electronegativity in the qualitative inference of the TOF–SIMS fragment pattern of inorganic compounds

The role of the electronegativity of atoms in inorganic compounds in TOF–SIMS fragmentation is discussed. From a study of approximately 30 inorganic compounds – chlorides, oxides, nitrates, and sulfates – a simple rule has been proposed for the dependence of fragment pattern appearance on the electronegativity (electron affinity), which can be easily obtained from handbooks, and the valence of positive and negative ions in these compounds. TOF–SIMS measurements of metal and alloy surfaces, should be corrected for the ionization potentials and/or electronegativities of atoms present in surface contaminants. Received: 9 October 2000 / Revised: 26 February 2001 / Accepted: 1 March 2001     

Synthesis of organic–inorganic sorbent containing phenylboronic acid as glucose-binding ligand

A copolymer with N-allylaminophenylboronic acid has been synthesized from a water-soluble N-vinylpyrrolidone–acrolein diethyl acetal copolymer. Immobilization of the obtained copolymer on silica gel afforded an organic–inorganic sorbent capable of sorbing glucose from model solutions.     

Strong inclusion of inorganic anions into β-cyclodextrin immobilized to gold electrode

The inclusion of inorganic anions such as SO(4)(2-), NO(3)(-), and HPO(4)(2-) into the cavity of β-cyclodextrin monolayers on Au was examined by X-ray photoelectron spectroscopy (XPS), a quartz crystal microbalance (QCM), and chronocoulometric measurements of the competitive inclusion with ferrocene. The inclusion amounts of ferrocence in 0.2 M Na(2)SO(4), NaNO(3), and Na(2)HPO(4) solutions were less than 6% of the adsorption amount of β-cyclodextrin on Au, resulting in the apparent inhibition of the ferrocene redox reaction. The surface association constants of these anions reached about 10 on a logarithmic scale and were much higher than those for the inclusion of common organic guest compounds. A stronger anion inclusion was also demonstrated by the QCM response corresponding to the replacement of a preincluded organic guest with sulfate upon the injection of the sulfate solution. Quantitative analysis of the XPS data suggested a 1:1 association for each of these anions per surface β-cyclodextrin. There was no detectable inclusion for ClO(4)(-), Cl(-), and Br(-).