Silica gels containing embedded heteropolyacids were synthesized in acidic media by co-condensation of tetraethoxysilane with phosphotungstic or phosphomolybdic acids using the sol-gel technique. Surfactants dodecylamine, sodium dodecylsulfate, trimethylstearylammonium chloride, and Pluronic P123 were used as templates. The effect of the synthesis conditions on their structure and morphology was studied. All materials were mesoporous but contained micropores in their structures. Presence of bands of Keggin structures in fourier transform infrared spectroscopy spectra along with absence of X-ray diffraction patterns of crystalline heteropolyacids confirmed their fine incorporation into silica network. Particle sizes of modified materials were 500–1100 nm except for the W-containing sample obtained with trimethylstearylammonium chloride, which was significantly lower. This unusual effect was attributed to stabilization of primary silica nanoparticles by interactions between the surfactant and heteropolyacid. High ratio heteropolyacid/tetraethoxysilane resulted in partial loss of porosity. Obtained results might be used for optimization of synthesis of effective catalysts and adsorbents containing heteropolyacids in mesoporous structure.Open image in new window

The adsorption of cesium on mesoporous silica materials containing embedded phosphotungstic acid (PTA) was studied. The materials contained active adsorbent and binders: γ-Al2O3, kaolin, or charcoal. The presence of Keggin units of PTA in the bound materials was confirmed by FT-IR spectroscopy. Among all materials, the formulation with γ-Al2O3 demonstrated the highest porosity and effectiveness in adsorption. Pure PTA/SiO2 contained a significant fraction of small particles between 100 and 300 nm. However, in the alumina-bound material, they were not detected. SEM imaging showed that these particles occupied interparticle space between larger γ-Al2O3 particles. The material was stable up to 540 °C. In most materials, the adsorption of cesium decreased with increase of the binder contents but not proportionally. The adsorption capacity of all materials depended on the concentration of cesium in the solutions. Maximum adsorption was achieved after 1 h. The adsorption of cesium is controlled by intraparticle diffusion while its rate can be described by the pseudo-second-order model.

•Silver/polymer nanocomposites were obtained by silver surface coating with PLA and PLGA.•Obtained products contained silver nanoparticles finely dispersed in a polymer matrix.•Ester-terminated polymer did not provide high dispersibility.•The materials demonstrated X-ray contrast and bactericidal properties.The objective of this research was the development of a novel synthetic method for preparation of silver/polymer nanocomposites containing finely dispersed silver nanoparticles. The surface of nanosilver was functionalized by amino groups, which then reacted with end acidic groups of polylactide (PLA) and its co-polymer with polyglycolide (PLGA). The condensation reaction was conducted in the presence of diisopropylcarbodiimide. Nanosilver coating with the polymers was confirmed by FT-IR and UV–vis spectroscopy. It was found that not only acid-terminated but also ester-terminated polymers can react with functionalized nanosilver. However, high dispersibility of the nanoparticles was achieved with acid-terminated polymers only. Obtained materials demonstrated X-ray contrast and bactericidal properties that makes possible their prospective application in biology and medicine.

Mesoporous amino-functionalized adsorbents for post-combustion CO2 capture were synthesized by grafting and sol–gel methods. The silsesquioxane obtained by polycondensation of bis[3-(trimethoxysilyl)-propyl]amine without a cross-linker had the highest amount of surface amino groups. Their content was 8.4 times higher than in the grafted material prepared with the same precursor. All obtained materials were tested in CO2 reversible adsorption from a gas stream. The bridged silsesquioxane adsorbent had the adsorption capacity 4.7 times higher than the grafted sample obtained from the same precursor. Porosity study of this material revealed wide pore size distribution with notable fraction of macropores. The nature of adsorbed species was determined from the FTIR spectrum after adsorption. It was found that CO2 formed carbamate and bicarbonate species on the surface.

The reaction of base-free Chan–Lam coupling was successfully used for functionalization of surface of mesoporous silica gel. Various aromatic, aliphatic, and heterocyclic compounds were immobilized by a copper-catalyzed reaction of corresponding boronic acids with surface amino groups at mild conditions. Obtained functionalized materials were mesoporous although their surface area decreased after immobilization. The reactivity of some surface functional groups was tested in their characteristic reactions.

•Nanosilver was modified for preventing agglomeration in organic media.•Modified silver nanoparticles form a stable colloidal dispersion in a polymer matrix.•High dispersibility of the nanoparticles can be achieved at high silver contents.•The method can be used for preparation of nanosilver dispersions in polyacids.Silver–polymer composite material containing highly dispersed silver nanoparticles (AgNPs) of 20–100 nm diameter can be obtained from bare nanosilver. The synthesis consists of three steps. The first step is modification of AgNPs by 2-aminoethanethiol. Second, polyacrylic acid is bonded to the silver 2-aminoethanethiolate by the carbodiimide method. Then esterification of the remaining carboxyl groups of the product by methanol results in formation of a stable colloidal dispersion of AgNPs in the polymer matrix. The method allows obtaining of nanocomposites with silver contents up to 1.4 wt%.

Four ethylene bis-indenyl ligands containing tethers of various lengths were successfully immobilized on the surface of functionalized silica gel. The strategy of immobilization was based on catalytic thiol–ene coupling of terminal alkene groups in the tethers with surface thiol groups. Obtained materials have high BET surface area and pore volume. The method developed can be used for immobilization of catalytically active bis-indenyl metallocene complexes, thus preventing their dimerization and deactivation.

The objective of this work is the synthesis of highly functionalized hybrid organic/inorganic materials by the polycondensation of bis[3-(trimethoxysilyl) propyl]amine in the presence of surfactants. High contents of amine groups were achieved by carrying out the syntheses without an inorganic cross-linker. The silsesquioxanes obtained had a mesoporous structure. The stability of their porous system in the absence of an inorganic cross-linker was enhanced by the precursor’s bridged structure. The material structures were studied by FT-IR spectroscopy, Porosimetry, X-Ray Diffraction and Small Angle X-Ray Scattering methods. A material prepared in the presence of dodecylamine as a template had a higher surface area and narrower pore size distribution while the use of sodium dodecyl sulfate resulted in the formation of mesopores with a wide size distribution. Surface amine groups in silsesquioxanes were accessible for adsorption of small molecules of acidic nature.

Coating of organophobic silver nano-particles with thiols was applied to facilitate their dispersing in aprotic organic solvents and solutions of polyacrylic acid and polylactide. Impact of chemical nature of thiols and dipole moment of the solvents on dispersibility of the modified silver particles was studied by UV–Vis spectroscopy (surface plasmon resonance) and scanning electron microscopy. It was shown that thiols’ grafting to the surface of metal nanoparticles is an effective route to improve and stabilize dispersions in organic systems.Graphical abstractHighlights► Silver nanoparticles were coated by thiols with various terminal functional groups. ► UV–Vis spectroscopy of surface plasmon resonance and SEM were used to study their dispersibility in organic media. ► Nature of functional groups in thiol molecule deposited on nanosilver surface strongly affects its tendency to agglomeration. ► Dispersibility of coated nanosilver in aprotic solvents depends on their dipole moments. ► Presence of polar groups in polymer increases dispersibility of coated nanosilver.

•Silica-embedded phosphotungstic acid has excellent adsorption capacity to cesium.•Keggin units covalently bonded to silica gel can immobilize cesium cations irreversibly.•The cesium adsorption isotherm follows Langmuir and Temkin models.•Adsorption results in increase of the adsorbent porosity.•The material can be used for decontamination of water containing radioactive cesium-137.Mesoporous silica gel containing embedded phosphotungstic acid (PTA) was synthesized by sol-gel co-condensation of tetraethoxysilane with PTA in acidic media. The obtained material had high BET surface area and pore volume. A characteristic band of the Keggin structure of PTA was present in its FT-IR spectrum while its XRD patterns were absent. This proved the embedding of PTA on a sub-molecular level. The material demonstrated high adsorption capacity of Cs. Unexpectedly, porosity of the adsorbent increased after substitution of most protons by cesium cations. Cation exchange also favored agglomeration of the material particles. Kinetic studies showed that the adsorption data correlates strongly with the pseudo-second order model. The adsorbent had two types of adsorption sites: heteropolyacid anions and silanol groups. However, adsorption on silanol groups was very sensitive to the temperature. At the increased temperature, the nature of adsorption fit the Langmuir model extremely well. The obtained results can be used in the development of an effective adsorbent for clean-up of water contaminated by radioactive cesium-137.