Sol-Gel Methods for Materials Processing

Here we consider the routes of synthesis (which is performed by use of sol-gel method) of a new class of sorbents, namely: polysiloxane xerogels functionalized with nitrogen-, oxygen-, phosphorus- and sulfur chapter ligand groups. Applying a number of physical methods (SEM, TEM, AFM, IR and Raman spectroscopy,

1

H,

13

C,

29

Si and

31

P CP/MAS NMR, EPR spectroscopy, ERS, thermal analysis) we established the structure of both: the xerogels and their surface. An influence of some factors on the structural-adsorption characteristics of such xerogels and their sorption properties is analyzed.

This chapter will illustrate how solid-state NMR techniques can provide extremely valuable information on the interactions between pollutant and adsorbent in depollution-related systems. In a first sub-chapter, NMR techniques based on dipolar coupling and well-adapted to probe spatial proximities between species, will be briefly introduced. The second sub-chapter deals with the role of solid-state NMR technique in two fields: (1) accidental dispersion of pollutant in soil matter and (2) volunteer adsorption within specially conceived hybrid organic/inorganic materials for depollution applications. Experimental data will be given to illustrate this last point.

Molecular separation using membranes is widely considered as an energy-efficient alternative for conventional industrial separation techniques. For the preparation of such membranes sol-gel technology is highly suitable. Using sol-gel techniques thin (50–100 nm) amorphous nanoporous layers having pore sizes in the micropore (<2 nm) or fine mesoporous (<5 nm) region can be prepared on a porous substrate. These layered porous systems, usually in tubular form, can be used for nanofiltration, pervaporation and gas separation applications. The application window is dependent on the material properties, such as the pore size and pore size distribution, the interfacial properties of the pores, and the defect density. The success of this technology in actual industrial applications strongly depends on reproducible large scale production of the sol-gel membranes and on a sufficient stability of the membranes with respect to flux and selectivity. In addition the production cost of the full membrane system is an important aspect. Here, we will focus on the more chemical aspects in the membrane preparation. Main topics are synthesis and properties of the sols, the preparation of microporous thin films, and the search for membrane materials that have a high hydrothermal stability.

Sol gel method is an important technology for the synthesis of TiO

2

films for water treatment. In this chapter, we will discuss the critical issues on the sol gel synthesis of TiO

2

films with high photocatalytic activity and good long-term mechanical stability. The aspects will mainly include the following: (1) design of film structure for increasing the number of electron-hole pairs generated and number of hydroxyl radicals produced, (2) tailor-design of the film pore structure for increasing adsorption of treated contaminants and enhancing mass transfer between the contaminants and catalyst active sites, and (3) improvements in the long-term mechanical stability of the TiO

2

films by achieving good adhesion of immobilized TiO

2

films on the support (substrate). Important achievements of our research works related to sol gel synthesis of TiO

2

films and membranes and the application of these TiO

2

photocatalysts in promising photocatalytic reactors are summarized. Current challenges and future directions on the sol gel synthesis of TiO

2

films for water purification are also discussed.

The development and potential application of various biosystems based on enzymes and living cells of microorganisms, immobilized into gelcontaining carriers and capable of detoxifying neurotoxic agents such as organophosphorous pesticides and chemical warfare agents as well as products of their destruction are discussed.

The preparation of porous hierarchical architectures that have structural features spanning from the nanometer to micrometer and even larger dimensions which in addition exhibit defined functionalities is one of today’s challenges in materials chemistry. Sol-gel chemistry is a versatile tool for the formation of inorganic as well as inorganic-organic hybrid materials. Controlled hydrolysis and condensation reactions of (organo)alkoxysilanes allow the combination with organic entities and even their deliberate positioning in an inorganic network on the nanometer level. Moreover, not only the chemical composition, but also the structure of the final material is easily controlled on different length scales from the nanometer level up to the macroscopic morphology. In the present paper, opportunities from the application of novel diolmodified silanes are discussed for the synthesis of hierarchically organized inorganic, but also inorganic-organic porous monoliths. In addition, strategies for macroscopic shaping of hybrid materials with hierarchical porosity as well as exotemplating approaches are presented. In addition, strategies for macroscopic shaping of hybrid materials with hierarchical porosity as well as exotemplating approaches are presented.

Mesoporous films are a fine example of a self-assembled nanosystem, containing ordered porosity in the 2–50 nm range. A great number of characteristics, including framework nature (composition, crystallinity), high surface area, pore dimension, shape, surface, accessibility and pore array symmetry and interconnection can be tuned using green chemistry synthetic techniques. These materials present potentials in several fields where a large functional interfacial area contained in a robust framework is required. The capability of changing in a separate way the characteristics of the inorganic framework and the pore surface leads to an amazing potential in tuning functional properties, due to the combined properties of a thoroughly tailored pore system and the inherent features of thin films. These properties can be tailored to respond to changes in the environment, such as relative humidity, making mesoporous hybrid thin films an exciting prospect for several nanotechnology applications (e.g. sensors, actuators, separation devices). Here we present some basic concepts revolving around mesoporous films. We will first comment on the synthetic approach in the fabrication of these materials. Second, we will discuss the aspects regarding template organization and surface functionalization. Third, we will review some applications illustrating the potentialities of theses self-assembled nanomaterials.

Sol-gel technology has attracted considerable attention due to possibility of obtaining submicron and nano-sized materials. The method of silica and titania nanopowders and thin films obtaining will be presented. Also properties and prospective application of these materials will be express. Additionally, methods of obtaining nanomaterials with different grains shape and specific properties (submicron spherical silica powders, titania nanofibers) will be showed. One of the main advantages of the sol-gel technique is the easiness of doping of the obtained materials with various substances (inorganic, organic, biological). Materials activated this way possess several useful properties. For example, silica spherical matrices with metallic nano-islands on their surface will be presented. Such silver-doped silica powders display anti-microbial capabilities and can be used to obtain doped thin-film coatings e.g. for the production of bacteriostatic textiles. Moreover, materials obtained by the sol-gel method have found wide application in the area of sensors. Examples of optical sensors based on sol-gel derived thin films and optical fiber or planar wave-guide will be also presented.

The review considers principal mechanisms in solution transformations, hydrolysis and condensation of alkoxysilanes and metal alkoxide complexes and the pathways of further transformations of the thus formed colloid systems. The versatility of silica sol-gel is provided by the possibility to direct the kinetically controlled process towards either polymeric or micellar colloids. The hydrolysis of metal alkoxides is kinetically unhindered and results in formation of Micelles Templated by Self-Assembly of Ligands (MTSALs) under the local equilibrium conditions. The morphology, reactivity, long term stability and biocompatibility of MTSALs can be efficiently controlled by the choice of metal cations, ligands and the conditions of hydrolysis. Application of the MTSAL concept for the synthesis of hierarchically porous materials and the prospects of their use in bioencapsulation and biodelivery for water and soil remediation processes are discussed.

This review provides an overview of some exciting, new as well as somewhat older, directions in sol-gel electrochemical applications of silicates and composite silicate electrodes. Rather than provide an exhaustive account of all the many papers that have been published on sol-gel electrochemistry and composite sol-gel electrodes, we prefer to illustrate the versatility of sol-gel chemistry by a few select examples which on the one hand illustrate the power entailed in sol-gel technology for electrochemical applications, and on the other hand point to hot electrochemical fields in which more research is due and exciting developments are to be expected. We start this review with a brief historical perspective. The inorganic sol-gel and silicone electrochemistry fields are both rather old though never extensively dealt with particularly when it comes to sensing applications. In contrast, the sol-gel electrochemistry of inorganic-organic hybrids is a relatively young field whose importance was recognized only in the last 30 years, and despite, or maybe even owing to the late recognition it is being very extensively studied nowadays. The use of composite electrodes for sensing and other applications is emphasized in this review, and the fast evolving electrodriven deposition techniques are reviewed.

The development of mesoporous silicas containing organic functionality via templated sol-gel methodology has led to a great deal of interest, primarily as catalysts, but also in applications such as adsorbency.

It is possible to prepare materials with a mechanically stable silica backbone, with mesopores having narrow pore size distribution, and which can be coated with a wide range of functionality. They are promising adsorbents due to their controllable surface chemistry and their significant pore volumes.

We have also demonstrated that starch can be expanded to give a gel, which can be converted to a novel range of mesoporous carbons, with tuneable surface functionality, high surface area and good pore volume.

They display remarkable catalytic activity (for example, they can completely esterify succinic acid in

aqueous

environments). We believe that this unusual behaviour can be related to their adsorbency properties.

We present details of the properties of these materials, as well as preliminary results on their ability to adsorb a range of compounds.

Recent developments of calorimetric techniques for the characterization of porous materials and gels are presented. In particular thermoporosimetry is introduced along with recent applications to soft materials like gels and polymers. In a second part, photo-DSC technique is presented with the new developments for the study of gels networks and photo-ageing of polymers. An overview of the potential of the two techniques towards sol-gel materials is finally given.

The tremendous developments of materials with fine tuning of the composition, shape, size and chemical functionalities at the nanometre scale has opened a wide range of applications in medicine. An overview of hybrid nanomaterials for applications in biological environment will be presented. The use of functional particles for medical imaging and therapy will be especially discussed. These functional systems usually require combination of different properties such as luminescence (imaging) or molecular recognition (targeting) and non-linear optical properties (therapy), together with size/shape control and biocompatibility (cells diffusion, solubility, biochemical stability). For example series of hybrid metal or oxide nanoparticles can be prepared for medical imaging. Some of them are already commercially available. The most recent work in this field will be presented and the future developments will be discussed. For example one can expect to combine several imaging techniques (multimodal contrast agents) or imaging and therapy in the same nanocomposite. The use of hybrid systems combining inorganic (metal or oxide) with their organic counterparts shows the most promising routes towards such applications in biological environment. New trends in the field of phototherapy will be discussed.

An original method of competing ions has been proposed and experimentally tested permitting a sol-gel process to be conducted only with water solutions of simplest salts, alkalis and acids without using chelating reagents.

The data are also presented on the “oil-drop” and “air-drop” technologies for continuous sol-gel production of spherically granulated inorganic ion exchangers such as titanium and zirconium phosphates as well as solid highporous acid catalysts based on sulfonated zirconium and titanium dioxide. The information is given about selective sorption of trace amounts of heavy metals, radionuclides, and uranium from a variety of technological solutions and drinking water on the prepared titanium and zirconium phosphates.

Sol-gel derived silica and titania have a specific interaction with many biological molecules, microbes, algae, cells and living tissue. The specific interactions mean that they differ from common reactions between non-viable materials and biomolecules or living tissues and the interactions are mostly beneficial from the viewpoint of biotechnical applications. Pepetides and proteins may preserve their activity and bacteria, algae and cells may preserve their viability and viruses their infectivity as encapsulated in sol-gel derived silica. Silica and titania are known to form a direct bond with living tissue which can be utilized in the biomaterial applications. Other application areas of silica and titania are in biosensing, tissue engineering, gene therapy, controlled delivery of therapeutic agents and environmental protection.

The influence of pH, nature of alcohol and initial components concentrations in micellar solution on the structural-adsorption characteristics of spherical mesoporous silicas has been investigated. The peculiarities of template synthesis of mesoporous silicas inside large pores of silica gel were also studied. Synthesized silicas were characterized by low-temperature nitrogen adsorption-desorption, X-ray diffraction and scanning electronic microscopy.

Heparin is an anticoagulant which is widely used during blood-dialysis. To now, there is not a commercial device able to “filter” heparin from blood after or during the medical treatment. Heparin can give, on life-long treatments, several health problems. We prepared siloxane-modified hybrid poly(aminoamides) which can be obtained from water solution. They shown good heparin absorption properties.

Sol-gel silica films doped with Cr(acac)

3

and having

ca

. 100 nm thickness on aluminium substrate were synthesised by dip-coating from the precursor composition prepared by TEOS acidic hydrolysis. It has been found out the that the C = O groups of doping Cr(acac)

3

molecules are involved into interaction with silica network terminated with silanol groups. Upon thermal treatment of Cr(acac)

3

-SiO

2

film in air, the ligand elimination from doping Cr(acac)

3

molecules took place, resulting in complete thermolysis at 613 K. The latter was accompanied by oxidation of Cr (III) to Cr (VI).

Polysiloxane materials containing residual thiophosphonic acid groups ≡Si(CH

2

)

3

NHP(S)(OC

2

H

5

)

2

in the surface layer have been prepared by sol-gel template methods (S

sp

= 240 – 670 m

2

/g; V

s

= 0.19 – 0.41 cm

3

/g; d = 3.3 – 4.5 nm). It was supposed that synthesized silicas are able to adsorb mercury(II) ions from nitric acid solutions (their SSC can be close to 450 mg/g). It was shown that the complexes in 1:1 ratio were formed in the surface layer. The excessive sorption of metal ions was shown to be due to partial hydrolysis of ethoxy-groups attached to the phosphorus atom.

The development of new high-performance materials for electronic, optical-mechanical and other industries is restrained by traditional mode of their production. It concerns materials technologies based on physical processes, for example, fusion and sintering, which require heat treatment and high pressure. The synthesis of materials with new properties is possible using chemical, colloid processes. In this respect the processes of transition of a sol into a gel, and further into a solid body with particular properties, is the basis of development of new sol-gel technologies.

The report summarizes peculiarities of synthesis and optical properties of the structures xerogel/porous anodic alumina doped with Er, Tb and Eu. Porous anodic alumina is considered as attractive material for sol-gel synthesis from viewpoint of luminescence properties of the structure xerogel/porous anodic alumina. Origin of strong luminescence of lanthanides from xerogels in mesoporous matrices is discussed.

Mesoporous TiO

2

films were prepared by template assisted sol-gel method and used as support for deposition of CdS particles on its surface to produce visible light sensitive nanocomposites. The influence of the surface morphology of mesoporous titania matrix onto the TiO

2

/CdS heterostructure formation was investigated using UV-Vis, IR, low-angle XRD, SEM and AFM methods.

The obtaining of hybrid mineral-polymer sorbents, based on wideporous microspherical silica gels (with 30 nm average pore diameter) and polymer components, has been discussed. The possibility to apply the obtained sorbents in reversed-phase high performance liquid chromatography has been studied. Introducing the polymer layer onto the surface of micro-spherical silica gel has been realized by means of “dry polymerization” of the corresponding monomers in the adsorbed layer of the porous matrix surface.

The 5% Co-M/SiO

2

catalysts (M – VIII Group metal) prepared by sol-gel method have been tested in dry reforming of methane by carbon dioxide and in bi-reforming of methane by both carbon dioxide and water steam. The conditions for formation of stable bimetallic nano-sized particles have been determined. The activity and selectivity of catalysts depend on the nature of the second metal. Presence of water in initial CO

2

+ CH

4

mixture causes a decrease in the catalyst activity.

Cationic and anionic surfactants are used for structuring of the negatively charged silica species during the formation of ordered mesoporous silicas from stable dilute silica sols, obtained by ion-exchange method. Isotherms of nitrogen adsorption-desorption at 77 K on silicas, which are prepared by the thermal decomposition of silica hydrogels, obtained at different pH using sodium dodecylsulfate or cetylpyridinium chloride as surfactants, are measured. The shape of the capillary condensation hysteresis and the type of the sorption isotherms are identified using the IUPAC classification. It is found that the adsorption and textural properties of the silica gels depend on the concentration and the type of surfactant (SAA), and also on pH.

The adsorbents (polysiloxane xerogel, silicagel Davisil, mesoporous silica SBA-15) containing macroligands, such as calix[4]arenes, diaminodibenzo-18-crown-6-ethers, α- and β-cyclodextrins, have been obtained by the sol-gel method and the surface modification method. The influence of the synthesis conditions, the nature of macrocyclic compounds and routes of their grafting on the structural-adsorption characteristics of the obtained polysiloxane materials and their sorption properties toward Cs

+

(

137

Cs) and Na

+

, K

+

, Sr

2+

(

90

Sr), and organic compounds of different kind, has been investigated.

The paper presents characteristics of biosensors with biorecognition elements entrapped in silica based polymers developed and tested in the Institute of Chemical Process Fundamentals ASCR, Prague (ICPF). Prepolymerized alkoxysilanes were used for preparing whole cell biosensors of phenol, naphthalene or salicylic acid intermediate, and polychlorinated biphenyls (PCB). Modifications of prepolymer composition and immobilization procedure could increase viability of entrapped cells but can also influence sensors properties. UV curable polymers with silica skeleton, ORMOCER

®

s, have been matrices of a sensitive element of optical sensor for the in-situ continuous monitoring of glucose in bioreactors. This enzymatic sensor, developed within the project MATINOES, displayed 3 week stability during fermentation in a laboratory bioreactor.

Sol-gel derived silica films are promising for application as working elements of sensors for environment control. The goal of the present work was to examine the difference in the post-synthesis functionalisation of nanometer-scale silica films prepared on glass substrates

via

template and template-free sol-gel routes. The films were prepared by dip-coating from TEOS sol-gel precursor in the absence or presence of CTAB template. It has been found out that the template-structured silica films can be functionalised with Ag nanoparti-cles

via

[Ag(NH

3

)

2

]NO

3

ion-exchange or with adsorbed Methylene Blue (MB) cationic dye due to the presence of the well-organised mesopores after template removal. In contrast, only the external geometric surface of the template-free silica films appeared to be accessible for modifier molecules.

SBA-15 mesoporous organosilicas with the

p6m

symmetry were synthesized by sol-gel co-condensation of tetraethyl orthosilicate with mercaptopropyltriethoxysilane, bis[3-(ethoxysilyl)propyl]ethane, bis[3-(ethoxy-silyl) propyl]disulfide, and bis[3-(ethoxysilyl)propyl]tetrasulfide. Final samples were characterized by X-ray diffraction and nitrogen sorption measurements. Depending on the monomers used, the resulted materials exhibit well or poorly ordered structures. All materials have a well-developed porous structure and high chapter of sulfur-containing moieties introduced by co-condensation.

Molecular sieve adsorbents have been prepared by the sol-gel route comprising simultaneous hydrolysis of tetraethylorthosilicate (TEOS) and polymerization of furfuryl alcohol (FA). The mixtures of TEOS (10%) and FA (90%) have been forced to interaction in the presence of small amounts of water (hydrolyzing agent) and sulfuric acid (polymerization catalyst) under ambient conditions, and successive carbonization at 923–1,023 K under argon. Adsorption of nitrogen at 77 K appears to be essentially non-equilibrium indicating activated character of diffusion. The ratio of CO

2

/N

2

adsorption uptake at 1 bar changes from 9:1 for carbon, obtained without TEOS additives under other similar conditions, to ∼1:3 for carbon-silica composite, indicating the reciprocal change of the adsorption selectivity factor.

The mesoporous silicas with thiourea functional group =Si(CH

2

)

3

NHC(S)NHC

2

H

5

were synthesized using sol-gel and template methods (with cetylpyridinium chloride as template). It has been found that the sorption properties of these mesoporous silicas are influenced both by the functional group chapter and the character of the sorbent’s porous structure. At low density of ligand groups all of them are accessible for Hg

2+

sorption with formation, as a rule, of the simplest complexes (1:1 composition). The rising density of functional groups in the surface layer of sorbents results in the reduction of their accessibility and complicates the complex formation process. This, causes reducetion of static sorption capacity of such materials (from 357 to 46 mg/g). It was shown that mesoporous materials with thiourea groups synthesized by template method and possessing highly ordered structures have superior kinetic characteristics compared to xerogels with the same functional groups is stable.

Sol-gel method was used to synthesize polysiloxane hydrogel with encapsulated urease (immobilization degree in the range of 79–88%) which preserved the enzymatic activity at the level of 56–84%. The nature of functional groups was shown to influence the pore structure parameters. Immobilization degree and preservation of adsorbed urease activity depend on the structural-adsorption characteristics of matrices. The possibility of “double immobilization” of urease on silica gel by sol-gel method and the opportunity of reuse of the synthesized formulations was investigated. Urease immobilization on the surface of magnetite (FeO·Fe

2

O

3

) was also studied by adsorption method.

Enzyme encapsulation in ordered porous silica has been modified by introducing a natural surfactant such as lecithin during the sol-gel process. β-lactose has been used as the enzyme protecting agent and tetraethoxysilane as the source of silica in an hydroalcoholic media. In the present study, the EPR spectroscopy of paramagnetic probes has allowed to monitor the formation of mesophases and the condensation of silica in an isotropic three-dimensional structure, named Sponge Mesoporous Silica, with a pore size of 6 nm and a specific surface area of 600 m

2

/g. Different techniques of characterization (nitrogen sorption, XRD, TEM, SEM) have been used to study the influence of the different reactants on the structure of the materials. Hemoglobin has been encapsulated in the different materials and its catalytic pseudo peroxydase activity has been evaluated.

Cation-doped perovskite materials based on barium titanate, such as (Ba,Sr)(Ti,Nb)O

3

, are of interest as transparent ceramic semiconductors with conductivity strongly dependent both on the cation and the oxygen stoichiometry. Development of precursor systems offering proper control over the cation stoichiometry and permitting to efficiently avoid residual carbon impurities is therefore an important problem. In the present communication we report the synthesis and structural characterization of a series of hetero-metallic precursors of these materials with the general formulae M

2

II

Ti

2

(L)

4

(OR)

8

(ROH)

2

and M

2

II

M

2

V

(L)

2

(OR)

12

(ROH)

2

, where R = Et,

n

Pr; M

II

= Ba, Sr; M

V

= Nb, Ta; L = thd or R’OAcAc (R’ =

t

Bu,

i

Pr). The compounds have been characterized by single crystal and power X-ray and by

1

H and

13

C NMR, vibration spectroscopy and mass-spectrometry. These species are very stable in solution and display even considerable gas phase stability. Solution microhydrolysis of the molecules in these series leads most often to oxo-aggregates with the cation stoichiometry rather close to 1:1, which additionally simplifies handling of solutions based on these precursors. The obtained precursors have been used for preparation of powders and films (on Si substrates), which were characterized by SEM-EDS and X-ray powder techniques.

Sol-gel method allows production of effective adsorbent systems from fine SiO

2

powder and magnetite. The protolytic exchange capacity of synthesized gels was studied within the pH range of 4–12. The main characteristics of the synthesized silica gel are: surface – 250–350 m

2

/g; density – 0.9 g/cm

3

; thermal stability – 900°C; sorbent capacity – 0.8–1.2 mmol-eq/g.

Synthesized silica gels have high sorption capacitance in relation to Pb

2+

and Sr

2+

ions and provide steep withdrawal of these ions from liquid environments. The isotherms of ion sorption on SiO

2

–Fe

3

O

4

as sorbent display two steps of sorption. The first step is responsible for the main contribution to capacitance of sorption, the second step provides complete extraction of metal from depletion at the maiden stage of solution.

With increase of the chapter of magnetite in the SiO

2

–Fe

3

O

4

sorbent, the sorption capacity of metals and depth of their withdrawal increases, indicating prospects to apply the data on such sorbents in geochemical research.

Functionalized nanocomposite sorbtional material was prepared by sol-gel method based on of chitosan and polyethoxysilane oligomer. The resulting product was characterized by microscopy, FTIR-spectrometry, XRD and chromatography. XRD analysis has shown the suppression of crystallinity of chitosan included into silica network.

In the present study a new type of continuous photo-reactor is developed in which the TiO

2

catalyst is immobilized on the surface of quartz tubes surrounding the UV lamps. The paper presents the results of an initial investigation of the performance of a laboratory scale photo-reactor using chloroform as a model compound. The study showed that an initial chloroform concentration of 7 mg/1 was degraded to under the detection limit in a period of 350 h. The half time t

1/2

for the photo-reactor was found to be 8 h.

TiO

2

and TiO

2

/ZnO films with silver nanoparticles (Ag NP’s) distributed in the matrix and on the surface were characterized by TEM, AFM and UV-Vis spectroscopy. Direct photoelectrochemical investigations of the TiO

2

/Ag and TiO

2

/ZnO/Ag heterojunctions showed the cathodic shift of the flat-band potential position and the increase of photocurrent quantum yield in comparison with unmodified TiO

2

electrodes. Photocatalytic activity of Ag/TiO

2

and Ag/ TiO

2

/ZnO films estimated in the process of Rhodamine B dye degradation is coincides with photoelectrochemical data.

A series of microporous-mesoporous mechanical mixtures of zeolite NaY and γ-alumina was used for testing the applicability of the modified (three-parameter) BET isotherm equation. Nitrogen adsorption isotherms (77 K) of NaY+ γ-alumina samples were analyzed by this equation and the results compared with the independent textural information obtained from t-plots (with the standard isotherm of nonporous α-alumina and the standard isotherms of Lecloux-Pirard). It appeared that the use of the modified BET equation as same as the standard t-plot method provided good micropore volumes and mesopore surface areas contrary to the incorrect results of the classic BET equation.

Thin nanolayers of titania prepared by repeated dip-coating of silica glass into transparent homogeneous sol from nonionic surfactants with various number of oxyethylene units were studied. Calcination in the air flow and/or extraction by supercritical CO

2

, subcritical H

2

O and subcritical CH

3

OH were used to convert transparent gel layers into anatase layers. The influence of individual surfactants on the surface morphology, roughness, structural and textural properties was evaluated.

Mesoporous sol-gel materials are among the ideal host matrixes for immobilizing enzymes because of their large pore volumes and controllable pore sizes appropriate for inclusion compounds. Although indirect enzyme immobilization in mesoporous materials has been achieved by impregnating of the MCM41 matrix with an enzyme, there are only few reports on one-step direct immobilization of bioactive species in surfactant-templated mesoporous sol-gel materials. We demonstrate here the principle by immobilization of 2,4D herbicide and mycotoxins T2 as model system. With that goal in view, various silica matrices with miscellaneous structural parameters were prepared and characterized.

The Ag/TiO

2

materials synthesised by a pH-controlled photocatalytic process and triblock copolymer-induced reduction of the [Ag(NH

3

)

2

]

+

ions under ambient light illumination appeared to be active and selective catalysts for the photocatalytic reduction of the nitrate ions in water. High efficiency of such Ag/TiO

2

catalysts was attributed to the presence of both the highly dispersed silver nanoclusters on the surface of titania and the hetero-junctions in the TiO

2

support. The influence of the structural features and the phase composition of the titania support on catalytic properties of the Ag/TiO

2

materials is discussed.

In this communication, a different approach to the preparation of mesoporous SiO

2

and TiO

2

thin films and nanocomposites has been adopted, aimed at preparation of oriented mesoporous thin films with highly stable roughness of the film surface and controlled pore dimension. We describe the preparation and compositional analysis of thin film coatings prepared using sol-gel techniques (thickness 50–500 nm, roughness ± 0.5 nm with pore distribution 2.4–8 nm for silica oxide and up to 300 nm for titanium oxide and porosity 30–50%). Analyses of these systems were based on XRD, AFM, FTIR, and elipsometry porosimetry data. The structural evolution of the film during thermal treatment was observed by FTIR spectroscopy and XRD.

The modification by cationic surfactants of sorbents based on hydromica and kaolinite – layered silicates with rigid structural cell – was performed by a modified sol-gel method. It was shown that the modification leads to sharp decrease of the minerals hydrophilicity, and to the increase of their affinity to the molecules of anionic and non-ionic surfactants. Significant increase of the sorption capacity of modified minerals with respect to non-ionic surfactants was ascribed to the formation of bulk associates of cationic and non-ionic surfactants.

The Ag-Au alloy and core-shell bimetallic nanoparticles (BMNP) in colloids can be successfully prepared by photoinduced reduction of corresponding salts in the presence of SiO

2

/BP

ads

(silica film with adsorbed Benzophenone) photocatalyst in water-IPA solution as a source of ketyl radicals and BP anionradicals as the reductive agents, and CTAB as a stabilizer. Generation of BMNP during the photochemical process happens right away of UV-irradiation. The ageing of bimetallic colloids related with formation and stabilization of the alloy-to-core-shell structure occurs with time (from hours to days) and depends on the order of metal ions photoreduction, viz simultaneous or successive UV irradiation of silver and gold ions in solution, and varying of Ag/Au mole ratio. Ageing of photoproduced colloid nanocomposites accompanied by the change of structure from alloy to core-shell what is proved with UV-vis absorption spectra. Optical spectra demonstrate formation of core-shell structures, where the shell is enriched with the core atoms. For now, first conclusion should be that BMNP Ag:Au 1:1 in colloids are formed mainly with Au NP’s in the shell. Photochemically produced and stabilized within pores of silica film Ag/Au BMNPs are formed as separate Ag and Au NP’s, together with the big aggregates.

Determination of the chemical mechanisms and the influence of solvation-desolvation phenomena on the gel formation in methylsilicic acid sol-gel processing, based on theoretical modeling and modern physicochemical investigation techniques, led to creation of a new industrial technology for direct synthesis of materials and formulations for industrial and medicinal use. An industrial technology of synthesis of stable pastes characterized by selective adsorption properties has been developed. Medical aspects of application of «Enterosgel» developed on the basis of methylsilicic acid hydrogels, a new effective and safe medical formulation for organism detoxication have been presented.

The thickness of the modified silica coatings and their transparency at specified wavelength were easily controled by changing sol concentration and the parameters of the spin-coating formation process. It was demonstrated that the modification of sols changes the maximum of the transmittance for the certain range of wavelength. Using modification process of the sols in the technology of preparation of transparent coatings, their hydrophobic properties and resistance to humidity increased. The transmittance spectra of the 3% SiO

2

coatings, which were applied on different glass substrates, showed that the usage of suitable sol and coating program will result a formation of films which possess antireflective properties

Several triethoxysilylated ligands have been synthesized and after complexation with a metal followed by the hydrolysis, efficient and recyclable heterogeneous catalysts were obtained. Three examples of catalytic reactions have been studied with these organic-inorganic hybrid materials obtained by the sol-gel process: (1) asymmetric reduction of prochiral ketones by hydride transfer, (2) Suzuki’s coupling reaction and (3) metathesis of dienes and enynes.