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Mesoporous structure of silica is determined by the type of template, but the introduction of functional groups during the synthesis has additional influence. The structure of SBA-15 may be violated by the introduction of long functions, such as ≡Si(CH2)3NHC(=S)NHC2H5. These ethylthiocarbamidepropyl groups can form complexes with metal ions in thiol or thione tautomeric forms. We determined that the 2D hexagonal p6 mm structure is preserved for SBA-15 with thiourea groups at maximal TEOS:trifunctional silane ratio (mol) = 10:2, which was confirmed by TEM and by the presence of an intense reflex in the small-angle region of diffractograms of the final product. It was shown that the obtained sorbents possess high kinetic characteristics. The experimental data fit pseudo-second-order kinetic equation, but the rate constants depend on the content of functional groups in the surface layer. Template Pluronic P-123 defines the porosity of functional mesoporous silica materials even at increasing content of trifunctional silane in the initial solution. Infrared spectroscopy analysis showed that thione form of thiourea ligand is prevalent on the surface of pores of mesoporous samples. However, during the sorption of silver(I) ions, there are both thione and thiol forms on the surface. Thione form is transformed into thiol with increasing concentration of mercury(II) ions in the sorption solution. Adsorption experiments showed that the SBA-15 silicas functionalized with ethylthiocarbamidepropyl groups had high selectivity for silver(I) ions and could concentrate Ag(I) ions from metal ions mixture at pH ~ 2.

The direct template method was used for the synthesis of mesoporous organosilica sorbents of SBA-15 type with phosphonic acid groups using sodium metasilicate (SS) as a source of silica. The presence of functional groups in the synthesized samples was confirmed by IR spectroscopy and elemental analysis. This approach allowed producing relatively cheap materials with ordered structure, developed specific surface (550-700 m2/g) and high sorption volume (0.74-0.81 cm3/g). The optimal sodium metasilicate (SS):diphosphoethyltriethoxysilane (DPTS) ratio for the synthesis of SBA-15 type organosilicas with phosphonic acid residues was found to be 10:2.

The chapter is a self-review devoted to the features of synthesis and structure of spherical particles functionalized with amino-containing groups, which are produced by the sol-gel method. This review consists of three main parts in addition to introduction and conclusions. The first part deals with the features of the synthesis techniques, identification of the functional groups and silica skeleton by vibrational spectroscopy and with the structure of particles and their surfaces on the basis of the physical and chemical methods. In the second part, the sorption properties of functionalized silica particles towards copper(II) ions and some anionic dyes are discussed and analyzed. Finally, in the third part, the cause of antibacterial properties of amino- as well as copper- amino-containing materials was highlighted, including overview of data by other authors.

The chapter provides an overview of synthetic approaches and applications in sorption and catalysis of mesoporous surface-functionalized silicas. We have synthesized a series of the mono- and bifunctional SBA-15 samples with thiol, phosphonic and amino groups in their surface layer. All of them were obtained by direct template method using P123. To determine the concentration of chemically available functional groups on the surface of silica samples the method of potentiometric titration was used. The samples with phosphonic and thiol groups for lead (II) sorption were used and cumulative effect of them was described. The value of the distribution coefficient and the exchange constant for lead (II) ions for bifunctional samples were higher than for monofunctional analogues. This indicates that the bifunctional samples are more versatile sorbents. The maximum value of the static sorption capacity to Hg (II) ions was 390 mg/g, to Pb(II) ions ‒ 150 mg/g, to uranyl-ions – 201 mg/g, and to Nd(III) ions ‒ 78 mg/g. Catalytic tests of ethanol conversion have shown that the anchoring of phosphomolybdic acid on SBA-15 functionalized with aminopropyl groups enhances oxidizing properties of heteropolycatalysts. Accordingly, the supported catalysts are characterized by higher turnover frequency values in aerobic oxidation of cyclooctane to cyclooctanone and cyclooctanol.

The magnetite nanoparticles were functionalized with silica shells bearing mercaptopropyl (monofunctional) and mercaptopropyl-and-alkyl groups (bifunctional) by single-step sol-gel technique. The influence of synthetic conditions leading to increased amounts of active functional groups on the surface and improved capacity in the uptake of Ag(I), Cd(II), Hg(II), and Pb(II) cations was revealed. The physicochemical properties of obtained magnetic nanocomposites were investigated by FTIR, Raman, XRD, TEM, SEM, low-temperature nitrogen ad-/desorption measurements, TGA, and chemical microanalysis highlighting the efficiency of functionalization and mechanisms of the preparation procedures. The removal of the main group of heavy metal cations was studied in dependence from the pH, contact time and equilibrium concentration to analyze the complexes composition for the large scale production of improved adsorbents. It was demonstrated that introduction of the alkyl groups into the surface layer prevents the formation of the disulfide bonds between adjacent thiol groups. The obtained adsorbents were employed to treat real wastewater from Ruskov, Slovakia with concentration of Fe 319 ng/cm3, Cu 23.7 ng/cm3, Zn 36 ng/cm3, Mn 503 ng/cm3, Al 21 ng/cm3, As 34 ng/cm3, Pb 5.8 ng/cm3, Ni 35 ng/cm3, Co 4.2 ng/cm3, Cr 9.4 ng/cm3, Sb 6 ng/cm3, Cd 5 ng/cm3. These materials proved to be highly effective in the removal of 50% of all metal ions, espeсially Zn, Cd, and Pb ions from it and turned recyclable, opening for their sustainable use in water purification.

One-pot synthesis of highly ordered SBA-15 type silica-tethered phosphonic acid at weakly acidic pH (3.75) allows for higher loading of phosphonic functionality (up to 33%) without significant deterioration of the mesostructure. In this synthesis sodium metasilicate was used instead of tetraethylorthosilicate. The resulting samples featured high specific surface areas (362–533 m2/g) and well-developed mesoporosity. The hexagonal structure and high concentration of phosphonic acid groups (1.0–3.0 mmol/g) in the synthesized samples were established by XRD, TEM, EDS and elemental analysis methods. Since inexpensive sodium metasilicate was used as a source of silica, these materials can be of interest for large-scale applications. Experimental studies of the synthesized materials showed that they are effective for extraction of trace uranium species under weak basic conditions (pH 8.3), which are relevant for practical use such as uranium extraction from seawater.

The insight into the molecular aspects of ligand grafting and potential maximal capacity of hybrid organic–inorganic adsorbents bearing phosphonate ligand monolayers as active functions was obtained by single crystal X-ray studies of ligand-functionalized titanium alkoxide complexes. The attachment of molecules occurs generally in the tripodal vertical fashion with the minimal distance between them being about 8.7 A, resulting in 0.19 nm2 as the minimal surface area per function. In the present experimental work the theoretical loading capacity could almost be achieved for functionalization of mesoporous nanorods of anatase with imino-bis-methylphosphonic acid (IMPA, NH(CH2PO3H2)2) or aminoethylphosphonic acid (AEPA, H2NC2H4PO3H2). The products had the same morphology as the starting material, as was established by SEM and optical microscopy. The size and structure of the individual nanoparticles of the constituting inorganic component of the material were preserved and practically unchanged through the surface modification, as established by powder XRD and EXAFS studies. The surface area of the inorganic–organic hybrids decreased somewhat from the initial ∼250 m2 g−1, on adsorption of AEPA (0.21 mmol g−1) to ∼240 m2 g−1, and on adsorption of IMPA (0.17 mmol g−1) to ∼190 m2 g−1. The ligands were bound effectively to the surface according to TGA, EDS and FTIR analyses and remained in the mono-deprotonated form. The produced hybrid adsorbents had for the selected pH (3.5) high capacities towards adsorption of Rare Earth Element (REE) cations, but with equilibria achieved relatively slowly. The composition of the surface complexes was determined as M : L = 1 : 1 for IMPA, but varied for the AEPA from 1 : 3 to 1 : 1 dependent on the REE, which can be interpreted in terms of charge compensation as the major driving force behind binding. The cation desorption in strongly acidic media for recuperation of the adsorbed REE and the relative capacity of the re-used adsorbent have been quantified.

Spherical silica particles with bifunctional (≡Si(CH2)3NH2/≡SiCH3, ≡Si(CH2)3NH2/≡Si(CH2)2(CF2)5CF3) surface layers were produced by a one-step approach using a modified Stöber method in three-component alkoxysilane systems, resulting in greatly increased contents of functional components. The content of functional groups and thermal stability of the surface layers were analyzed by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, and 13C and 29Si solid-state NMR spectroscopy revealing their composition and organization. The fine chemical structure of the surface in the produced hybrid adsorbent particles and the ligand distribution were further investigated by electron paramagnetic resonance (EPR) and electron spectroscopy of diffuse reflectance (ESDR) spectroscopy using Cu2+ ion coordination as a probe. The composition and structure of the emerging surface complexes were determined and used to provide an insight into the molecular structure of the surfaces. It was demonstrated that the introduction of short hydrophobic (methyl) groups improves the kinetic characteristics of the samples during the sorption of copper(II) ions and promotes fixation of aminopropyl groups on the surface of silica microspheres. The introduction of long hydrophobic (perfluoroctyl) groups changes the nature of the surface, where they are arranged in alternately hydrophobic/hydrophilic patches. This makes the aminopropyl groups huddled and less active in the sorption of metal cations. The size and aggregation/morphology of obtained particles was optimized controlling the synthesis conditions, such as concentrations of reactants, basicity of the medium, and the process temperature.

Ordered mesoporous silicas with ester-type [ Si(CH2)2P(O)(OC2H5)2] and acidic [ Si(CH2)2P(O)(OH)2] functionalities were synthesized via co-condensation of suitable organosilanes in the presence of triblock copolymer, Pluronic P123, under acidic conditions. XRD and TEM analysis of the synthesized materials confirmed their hexagonally ordered mesoporosity similar to that in SBA-15. Namely, the materials prepared under microwave irradiation by using tetraethylorthosilicate (TEOS) as a framework-forming agent and diethylphosphatoethyltriethoxysilane as a source of functional groups exhibit adsorption properties (such as the specific surface area, pore size and pore volume) slightly different than those of the corresponding samples obtained by conventional hydrothermal synthesis. However, in the case of conventional hydrothermal synthesis, nitrogen adsorption isotherms resemble those for plugged hexagonally ordered mesoporous silicas. Also, the replacement of TEOS with sodium silicate and introduction of Si(CH2)2P(O)(OH)2 functionalities results in the samples with slightly higher specific surface area. Thus, the synthesis method does not have a significant impact on the porous structure and adsorption characteristics of the samples studied. A tangible advantage of the microwave-assisted synthesis vs. conventional hydrothermal preparation is its significantly shorter time.

Magnetically retrievable formulations of urease potentially promising for biomedical and environmental applications were constructed by immobilization of the enzyme on the surface of magnetite nanoparticles functionalized by siloxane layers with active thiol or thiol-and-alkyl moieties. The latter were deposited using a hydrolytic polycondensation reaction of tetraethoxysilane with either 3-mercaptopropyltrimethoxysilane, or with 3-mercaptopropyltrimethoxysilane and methyltriethoxysilane, or alternatively n-propyltriethoxysilane. Immobilization of urease was carried out in different ways for comparison: by adsorption, by entrapment during the hydrolytic polycondensation reaction, or by covalent bonding. For entrapment the enzyme was introduced into solution before functionalization of the magnetite. Entrapment bound high amounts of enzyme (more than 700 mg per g of carrier), but its activity was decreased compared to the native form to between 18 and 10%. In the case of covalent binding of urease using Ellman's Reagent, binding of the enzyme was almost as efficient as in the case of entrapment but its residual activity was 75%. The residual activity of urease immobilized by adsorption on the surface of thiol-functionalized particles was truly high as compared to that of the native enzyme (97%), but binding was significantly less efficient (46%). Introduction of alkyl functions permitted increase of the amounts of the adsorbed enzyme but its activity was somewhat decreased.

Iron-mediated synthesis of alkali metal iodides was quite unexpectedly demonstrated to be able to serve as a cost-efficient and reliable source of spherical single crystalline near-stoichiometric magnetite (Fe3O4) nanoparticles as revealed by TEM and XRD studies and also by XANES spectroscopic quantification of the Fe2+-content. Using the particles as nuclei for the Stoeber synthesis of silica nanoparticles, core-shell magnetic material has been produced. The nature of the magnetic component was probed by XANES spectroscopy. The size of the particles is dependent on the synthesis conditions and Si : Fe ratio but can be kept below 100 nm. It is the Si : Fe ratio that determines the stability of the particles in acidic medium. The latter was investigated spectrophotometrically as leaching of Fe3+-cations. Considerable stability was observed at Si : Fe > 10, while at Si : Fe >= 20 no measurable leaching could be observed in over 10 days. Magnetic nanoparticles with improved stability in acidic medium provide an attractive basis for creation of adsorbent materials for applications in harsh media.

We have investigated the removal of Pb2+ ions from water using thiol-functionalized, cobalt-ferrite, magnetic nanoparticles. These magnetic nanoparticles were prepared using the co-precipitation method and their surfaces were modified with tetraethoxy silane and 3-mercaptopropyl trimethoxysilane in order to provide a sufficient surface concentration of the thiol (–SH) functional groups. The adsorption of the Pb2+ ions from the aqueous solutions onto the thiol-functionalized, cobalt-ferrite, magnetic nanoparticles was studied. The investigated parameters include the pH value of the model water, the concentration of the adsorbent, the contact time and the temperature of adsorption. The removal of the Pb2+ was found to be greater at the higher pH values and increasing the temperature was also found to increase the removal of Pb2+ ions.

A new technique of synthesis of mesoporous silica with protonated amino groups avoiding microwave treatment of mesophase was developed using a template method. The block-copolymer P123 was used as a template and sodium meta-silicate with 3-aminopropyltriethoxysilane as precursors. After the removal of template from mesophase with boiling ethanol, the obtained sample displayed highly ordered hexagonal structure with attractive textural parameters: SBET = 460 m2 g−1, Vtotal = 0.79 cm3g−1 and d = 7.1 nm. FTIR and 13C CP/MAS NMR spectroscopy revealed the presence of alkyl ammonium groups (0.7 mmol g−1) that were able to attach anions of molybdophosphoric acid to the surface of the synthesized mesoporous material. The resulting anion-ion exchange phase can find applications in many areas (adsorption, catalysis, etc.).

The surface of magnetite nanoparticles was coated with functional polysiloxane layers using reaction of hydrolytic copolycondensation of tetraethoxysilane and 3-aminopropyltriethoxysilane (or N-[3-trimethoxysilylpropyl]ethylendiamine), and also that of tetraethoxysilane, 3-aminopropyltriethoxysilane and methyltriethoxysilane (or n-propyltriethoxysilane). It was shown that these functionalized magnetically controllable particles (about 60–150 nm in size as aggregates), as opposed to magnetite, adsorb urease well from aqueous solutions (up to 1 g/g), and that the level of residual activity of adsorbed layers is up to 84 % in the case of a bifunctional sample. It was established that the activity of immobilized urease is normally gradually reduced during storage of the samples, but in the case of ethylenediamine functional group is not decreased for 45 days. The synthesized samples are promising for use as magnetically directed biocatalysts.

In order to obtain amino-functionalized silica materials with magnetic core, one-step synthesis was carried out. Several materials, differ in number and structure of amino groups, were synthesized on the basis of sol-gel method. The synthesized materials were examined by several analytical techniques. The presence and content of amino groups were measured by using Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy and acid-base titration, respectively. Specific surface areas were measured by nitrogen/adsorption desorption isotherms. It was proved that sol-gel approach leads to obtain materials with high content of amino groups built into their surfaces (in the range 1.6-2.7 mmol/g). As-obtained materials were tested as potential adsorbents for copper(II) ions. The received maximum adsorption capacities were in the range 0.4-0.7 mmol/g.

The bifunctional layers of ≡Si(CH 2 ) 3 NH 2 /≡SiCH 3 and ≡Si(CH 2 ) 3 NH 2 /≡SiC 3 H 7 − n on the surface of Fe 3 O 4 magnetic particles are obtained by the developed method based on the reaction of hydrolytic polycondensation of tetraethoxysilane and appropriate trifunctional silanes. The DRIFT spectra indicate the formation of the silica bounds framework in the surface layers of magnetite nanoparticles and the presence of related functional groups. The content of amine groups at the level of 1.6–2.2 mmol/g is confirmed by the acid–base titration. The presence of the amine groups along with the methyl (or n -propyl) groups in the surface layer enhances the sorption capacity of samples towards the HSA. The resulting powder materials retain their magnetic properties and are perspective for the usage in medical practice.

Hydrolysis and polycondensation reactions of tetraethoxysilane (TEOS) with 3,3,3-trifluoropropyl-trimethoxysilane (TFMS) or 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFES) were used to synthesize xerogels functionalized with fluorine-containing groups. According to transmission electron microscopy, the skeletons of synthesized polysiloxane xerogels have globular structures and consist of agglomerates of particles with fluorinated groups on their surfaces. FTIR spectroscopy showed that primary xerogel particles possess spatial polysiloxane networks, with fluorinated groups along with silanol groups and water in the surface layer. According to thermal analyses, the water content was 3–8 wt.%, and it decreased with increasing length of the fluorinated chain. Thermal destruction of the surface layer starts above 300 °C. The sorbents that were obtained were predominantly mesoporous materials with well-developed porous structures ( S BET = 400–960 m 2 g −1 , V s = 0.66–0.93 cm 3 g −1 ). The influence of the TEOS/functional silane ratio and the natures of the functional groups on the structural and adsorptive properties were shown. The samples synthesized are organophilic. The affinity for n -hexane increases with increasing length of the fluorine-containing chain (PFES) and the content of fluorinated groups in the surface layer. The hybrid organic–inorganic materials that were obtained can be used for adsorption of hydrocarbons, including oil, from water.

Magnetic nanoparticles modified with siloxane layers bearing amino and thiol functions have been used for immobilization of urease either by adsorption or via surface grafting. The activity of the immobilized enzyme in the hydrolysis of urea extended to the levels typical of the native enzyme, while its long-term stability in combination with magnetic retraction opened for its repeated use in both analysis and detoxification of bio-fluids. The immobilized urease revealed strongly enhanced stability and 65% activity in the presence of 0.1mmol/l of Hg(2+) or 0.3mmol/l of Cu(2+) while the native urease did not retain any activity at all. The enzyme grafting was shown to be a potentially perspective tool in alleviation of heavy metal poisoning and to be providing an opportunity for use of the developed adsorbents as both biosensors and bio-reactants for removal of urea from biofluids.

The structure and texture characteristics of the hybrid organic–inorganic adsorbents, which were obtained by using of two-component systems of “structure-forming agent/trifunctional silane”, are compared as follows: the first component is Si(OC 2 H 5 ) 4 or (C 2 H 5 O) 3 Si–A–Si(OC 2 H 5 ) 3 , where A = –(CH 2 ) 2 – or –C 6 H 4 –; the second one is alkoxysilane with amine (–NH 2 , NH, –NH(CH 2 ) 2 NH 2 ) and thiol (–SH) groups. The adsorbents, derived from TEOS, have more accessible functional groups (2.6–4.2 mmol/g) than xerogels, which are based on bis(triethoxysilanes) (1.0–2.6 mmol/g). On another hand xerogels derived from bis(triethoxysilanes) have a more extended porous structure ( S sp =516–968 m 2 /g, V s = 0.418–1.490 cm 3 /g, d = 2.5–15.0 nm) than those that are based on TEOS ( S sp = 4–631 m 2 /g, V s = 0.005–1.382 cm 3 /g, d = 2.3–17.7 nm). The geometric dimensions of functional groups have a more essential effect on the parameters of porous structure in the case of TEOS-derived xerogels. Using solid-state NMR spectroscopy, it has been shown that in synthesis of xerogels with the use of TEOS, the molecular frame of globules is formed by structural units Q n ( n = 2,3,4), and the functional groups exist as structural units of T n ( n = 2,3). The xerogels obtained with using bis(triethoxysilanes) consist only of structural units of T n -type ( n = 1,2,3).

Xerogels containing thiol groups (1.0–2.7 mmol g– 1 ) and having high specific surface areas of 630–970 m 2 g– 1 were obtained by the sol–gel method using a structure-forming agent [1,2-bis(triethoxysilyl)ethane or 1,4-bis(triethoxysilyl)benzene] and a functionalising agent (3-mercaptopropyltrimethoxysilane).

One-step synthesis technique of mesoporous SBA-15 type silica with thiourea Si(CH 2 ) 3 NHC(S)NHC 2 H 5 groups in the surface layer was developed. According to elemental analysis, the content of surface groups is 1.25 mmol/g, which is consistent with TGA data. FT-IR spectra of the obtained sample contain characteristic absorption bands of thiourea groups ( NH C(S) NH ), as well as polysiloxane network ( Si O Si ). The synthesized sample was studied by XRD, TEM, SEM, and adsorption method. It was demonstrated that the sample features porous microspheres ∼0.5 μm with well-ordered internal spatial structure of the hexagonal lattice type due to the usage of template P123 during synthesis. According to XRD and TEM, the diameter of pores is 4.2–5 nm and the wall thickness between them is 2.6 nm. These data are consistent with the structural-adsorption characteristics calculated from nitrogen adsorption–desorption isotherms: S sp. = 510 m 2 /g, V s = 0.47 cm 3 /g, and d = 4.3 nm. Equilibrium is established within 60 min during sorption of silver(І) and mercury(ІІ) ions from acidified aqueous solutions for this sample, and with the complexes are formed 1.1/1 for Ag + and 0.8/1 for Hg 2+ at metal/ligand ratio.

The sorption properties towards dysprosium(III) ions of three samples of mesoporous silicas functionalized with phosphonic groups ≡ Si(CH2)2P(O)(OH)2 were studied. It was found that for the sample synthesized by spray-drying using OTAB as a template both sorption and desorption rate of Dy3+ ions is high, due to the defined porosity of the sorbent. Sorption of Dy3+ ions by bridged silsesquioxane xerogels with disordered structure is significantly hindered by diffusion processes, due to the chaotic packing of globules. Using a model for the chemical reactions, the composition of dysprosium(III) complexes with surface phosphonic groups were determined, and their formation constants were calculated. It was shown that xerogels with higher surface concentration of ligand groups (L), can form complexes DyL3 and DyL4 −. Meanwhile, the sample synthesized by spray-drying method forms only DyL2 + and DyL3 complexes. For this sample, complexes DyL3 are more stable than for xerogels. So, mesoporous silica derived by spray-drying method, with defined spatial porosity and relatively low surface concentration complexation groups, is characterized by the best sorption properties towards dysprosium(III) (adsorption and desorption kinetics, the value of the static sorption capacity).

We have shown that mesoporous silica microspheres with phosphonic groups ≡Si(СН2)2P(O)(ОН)2 in their pore surface layer have interesting properties for the sorption of neodymium(III) and dysprosium(III) from aqueous solutions, as well as for the adsorption of n-hexane, water, and triethylamine molecules from the gas phase. Such systems form the complexes LnL3 and LnL 2 + in the surface layer in case of Lanthanide sorption. We found that at low equilibrium concentrations of metal ions in the solution the composition of the formed complexes is mainly LnL3, quickly reaching their saturation limit in the surface layer. Therefore, the further increase of sorption with the growing equilibrium concentration is observed due to the formation of complexes LnL 2 + . However, the ratio between these two types of complexes for neodymium(III) and dysprosium(III) are different probably because of the differences in Lanthanide radius. The mesoporous microspheric sorbents used are easily regenerated by hydrochloric acid, without substantial changes in their structure and in the composition of their surface layer. During sorption from the gas phase (in the absence of water molecules on the surface) phosphonic group could form hydrogen bonds among themselves or with silanol groups, which prevents their interaction with the electron-donor molecules (e.g. triethylamine).

International audience; Porous silica-based microspheres with pore surfaces functionalized by phosphonic acids are obtained for the first time from a direct co-condensation route using two alkoxide precursors (Si(OEt)4 and Si(OEt)3(CH2)2P(O)(OEt)2), surfactant self-assembly and spray-drying methods. The synthesis employs octadecyltrimethylammonium bromide as template agent. The post-treatment of the microspheres in boiling concentrated hydrochloric acid insures the hydrolysis of the ethoxy groups initially bound to phosphorus in the organophosphonate-siloxane precursor, without destroying the morphological and textural properties. Final porous materials have the chemical structure [SiO1.81(OZ)0.38]0.91[SiO1.35(OZ)0.29 (CH2)2P(O)(OH)2]0.09 (with Z @ H or Et), and posses interesting textural properties: SBET = 747 m2 g-1, and dp = 2.3 nm.

International audience; 1H solid-state NMR is becoming a routine characterisation tool. In the case of materials textured by self-assembled amphiphile molecules, we present a multi-scale characterisation approach, which can be easily implemented in most recent spectrometers. Valuable information on the interfaces between amphiphile molecules and oxide-based networks is obtained through this approach, as shown in some selected examples: block copolymers, hybrid siloxane membranes, and mesoporous microspheres obtained from spray-drying. We also present new results on 14N and 81Br solid-state NMR and discuss the applicability of direct or indirect proton-detected experiments to the study of mesoporous materials textured by cationic surfactants.

The routes of synthesis of polysiloxane xerogels functionalized by nitrogen-, oxygen-, phosphorus- and sulphur content ligand groups were investigated. Applying a number of physical methods (SEM, TEM, AFM, IR and Raman spectroscopy, 1H, 13C, 29Si and 31P CP/MAS NMR spectroscopy, EPR spectroscopy, ERS and thermal analysis) the structure of xerogels and their surface was established. The influence of some factors on the structural-adsorption characteristics of such xerogels and their sorption properties were analysed.

Polysiloxane xerogels containing both –SH and –NH 2 functions have been prepared using the sol–gel method with alkoxysilane precursors [such as Si(OEt) 4 , (MeO) 3 Si(CH 2 ) 3 SH and (EtO) 3 Si(CH 2 ) 3 NH 2 ]. Molar ratios of 3.2:1, 1.1:1 and 0.4:1 for the two functions –SH and –NH 2 were employed. Xerogels which contain only one of the two functions were also synthesized for comparative purposes. It was shown that the use of stannic compounds as catalysts for xerogels with 3-mercaptopropyl groups resulted in a product which possessed a non-porous structure, while the use of fluoride ions allowed the synthesis of a sample with a porous structure (S sp = 216 m 2 /g, V s = 0.152 cm 3 /g, d = 3.5 nm). Xerogels with a bifunctional surface layer possess a bimodal structure. Infrared, Raman and multinuclear solid-state NMR ( 1 H, 13 C, 29 Si) spectroscopy data showed: (i) the absence of deprotonation for the 3-mercaptopropyl groups in the bifunctional surface layer of the xerogels; and (ii) that 3-aminopropyl groups form hydrogen bonds in these surface layers. The type of hydrogen bond formed depends on the ratio of the amount of water to the amount of 3-aminopropyl groups in the surface layer. When this ratio is about 1:1, the amino group forms a hydrogen bond with the silanol group associated with the water molecule. Re-organization of the surface layer is observed when the amount of water decreases, the amino groups forming hydrogen bonds between themselves. Hence, the system of hydrogen bonds in the surface layer of such xerogels depends primarily on the drying regime employed for the samples.

Polysiloxane materials containing residual thiophosphonic acid groups ≡Si(CH2)3NHP(S)(OC2H5)2 in the surface layer have been prepared by sol-gel template methods (Ssp = 240 – 670 m2/g; Vs = 0.19 – 0.41 cm3/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.

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, 1H, 13C, 29Si and 31P 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.

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.

The mesoporous silicas with thiourea functional group =Si(CH2)3NHC(S)NHC2H5 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 Hg2+ 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·Fe2O3) was also studied by adsorption method.

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.

Modification of filtration materials and sediments in order to change adsorption and adhesion surface properties are proposed. The structure and sorption characteristics of the resulting materials are discussed. Experimental investigation of their application in water treatment and sewage purification has been carried out. The improvement of the adsorption properties and of the effectiveness of water treatment from highly dispersed insoluble and soluble organic contaminations is observed.

A consideration has been given to salient features of synthesis of functionalized polysiloxane xerogels using one-, two-, and three-component (in terms of alkoxysilanes) systems. Possibilities have been revealed for potentialities of physical methods for characterizing nature of functional groups, types of structural units that form these xerogels and surface layer structure. Adsorption properties of such hybrid organic-inorganic materials have been described in detail.

Here we report a simple two-step synthesis of magnetite nanoparticles (NPs) coated with silica shell functionalized with 3-aminopropyl groups. The content of surface amino groups within the range of 0.7–2.8 mmol g −1 was established by elemental analysis and acid–base titration. The materials obtained are hydrolytically stable in acidic medium and are rapidly separated from the solution using an external magnetic field. It was shown that the prepared NPs efficiently extract palladium(II) ions in the form of [PdCl 4 ] 2– from the solution. The kinetics of adsorption was well described by the second-order model with the rate constant of approximately 0.76 g mmol −1 minute −1 . The isotherm of adsorption is fitted by the Langmuir model with the maximum [PdCl 4 ] 2– adsorption capacity of 0.158 mmol g −1 .

The chapter is a self-review devoted to features of synthesis and structure of spherical particles functionalized with amino-containing groups, which are produced by the sol-gel method. This review consists of three main parts in addition to introduction and conclusions. The first part deals with the features of the synthesis techniques, identification of the functional groups and silica skeleton by vibrational spectroscopy and with the structure of particles and their surfaces on the basis of the physical and chemical methods. In the second part, the sorption properties of functionalized silica particles towards copper(II) ions and some anionic dyes are discussed and analyzed. Finally, in the third part, the cause of antibacterial properties of amino-as well as copper-amino-containing materials was highlighted, including overview of data by other authors.