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The present study reports a systematic analysis of morphology and hydrogen sorption capacity of mesoporous organic-inorganic silica prepared by varying the silica synthesis parameters. Cationic surfactants of different chain lengths and different proportions of functionalised precursors were introduced in the synthesis mixture. Improved hydrogen storage properties have been obtained, already below 20 bar, reaching a maximum storage capacity around 4.75 wt% at 80 bar. The textural characteristics were analysed by nitrogen sorption and small angle X-ray scattering, and the thermal stability has been characterized by thermogravimetric analysis. The materials show specific surface area between 400 and 700 m2/g and a weakly ordered mesoporosity induced by the short chain surfactant template.

Iron oxide-silica nanocomposites were prepared by sol-gel method using ammonia (NH3), acetic acid (CH3COOH) and hydrochloric acid (HCl) catalysts to generate different pH values for the reaction conditions. As starting precursors, for the silica, respectively, for the iron oxide, tetraethylorthosilicate (TEOS) and iron-III-acetylacetonate were used. The physico-chemical characterization of the materials revealed that the sample obtained with HCl catalyst displays the largest surface area (300 m2/g), the most compact network structure, highest surface roughness, biggest crystallite size (14 nm), magnetization (7 emu/g) and superparamagnetic behavior. These materials were tested for adsorption of Cr6+ and Zn2+ from aqueous solution. Sample M-HCl presented the highest surface area and was further used for adsorption of metal ions. Kinetic, thermodynamic and equilibrium adsorption measurements studies were made for Cr6+ and Zn2+. To establish the material behavior from a thermodynamic point of view, temperature and contact time of adsorption process, activation energy, free energy, of standard enthalpy and entropy were calculated. The kinetic behavior was modelled by pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models and the adsorption characteristics were determined by modelling the experimental data with Langmuir, Freundlich and Sips isotherms.

Water pollution by synthetic organic dyes is mainly regarded as environmental and ecological issues worldwide and requires feasible solutions in face of the short-term risk to human health and stability of eco-systems. Therefore, in this paper, the magnetic mesoporous composites (MMC) were synthesized by surfactant template sol–gel method, using cetyl-trimethylammonium bromide (CTAB) as mesoporous structure generator and investigated for anionic and cationic dyes removal from aqueous solutions. The magnetic iron oxide nanoparticles were obtained by reverse co-precipitation, followed by mesoporous silica coating through modified sol–gel method. The obtained materials were characterized by FT-IR spectroscopy, X-ray diffraction, transmission electron microscopy, Mossbauer spectroscopy, nitrogen adsorption, small-angle X-ray scattering and magnetization measurements. The influence of CTAB amount on the morpho-textural and structural properties of nanocomposites was studied. XRD and Mossbauer spectroscopy showed that the obtained nanocomposites were composed of pure maghemite nanoparticles, and TEM images revealed particles size around 10 nm, embedded in silica matrix. The combination of magnetic properties and high surface area values, up to 695 m2/g, made suitable the obtained nanocomposites to be used as adsorbents. The dye removal efficiency was higher than 90% after the first adsorption and remained above 65% after four adsorption–desorption cycles, indicating that the as-prepared magnetic mesoporous nanocomposites can be considered excellent adsorbent materials for the removal of both anionic and cationic dyes from wastewaters, and the recycling performance revealed the stability of MMC.

The present paper reports a one-pot synthesis of magnetic nanocomposites samples through acid catalyzed sol-gel method. Fe(III) acetylacetonate was used as precursor of the iron oxide phase: tetraethylortosilicate for the silica phase and polyvinyl alcohol (PVA, molecular mass 49000) as pore former. Different concentrations of Fe2O3 in composites matrices were prepared and studied ranging from 0% to 20%. All reactions took place in one pot at room temperature; the materials were subsequently heat treated at 300°C, to ensure the crystallinity for the iron oxide having spinel structure, forming nanoparticles confined in the silica matrix. The materials were characterized using X-ray diffraction, small-angle neutron scattering, FT-IR spectroscopy, nitrogen adsorption, Mossbauer spectroscopy and magnetization measurements. The maximum value of room temperature saturation magnetization of ∼54 emu/g and 0.11 kOe coercive field was achieved for the magnetic nanocomposite sample with 20% Fe2O3. The highest surface area of 680m2/g was obtained for the sample with 10% Fe2O3. The potential applicability of the obtained materials was studied for adsorption performance for cadmium in aqueous solutions. The Langmuir isotherm model described well the adsorption data, indicating monolayer adsorption of Cd(II) on the heterogeneous composite surface.

Mesoporous silica particles have been prepared with functionalized precursors, used either in situ co-condensation process or as post-synthesis grafting agents, in order to deliver surface function...

Multifunctional hybrid materials with applications in gas sensing or dye removal from wastewaters were obtained by incorporation into silica matrices of either Pt(II)-5,10,15,20-tetra-(4-allyloxy-phenyl)-porphyrin (PtTAOPP) or platinum nanoparticles (PtNPs) alone or accompanied by 5,10,15,20-tetra-(4-allyloxy-phenyl)-porphyrin (TAOPP). The tetraethylorthosilicate (TEOS)-based silica matrices were obtained by using the sol-gel method performed in two step acid-base catalysis. Optical, structural and morphological properties of the hybrid materials were determined and compared by UV-vis, fluorescence and FT-IR spectroscopy techniques, by atomic force microscopy (AFM) and high resolution transmission electron microscopy (HRTEM) and by Brunauer&ndash, Emmett&ndash, Teller (BET) analysis. PtTAOPP-silica hybrid was the most efficient material both for CO2 adsorption (0.025 mol/g) and for methylene blue adsorption (7.26 mg/g) from wastewaters. These results were expected due to both the ink-bottle mesopores having large necks that exist in this hybrid material and to the presence of the porphyrin moiety that facilitates chemical interactions with either CO2 gas or the dye molecule. Kinetic studies concerning the mechanism of dye adsorption demonstrated a second order kinetic model, thus it might be attributed to both physical and chemical processes.

Metalloporphyrins are highly recognized for their capacity to act as sensitive substances used in formulation of optical, fluorescent, and electrochemical sensors. A novel compound, namely Pt(II)-5,10,15,20-tetra-(4-allyloxy-phenyl) porphyrin, was synthesized by metalation with PtCl2(PhCN)2 of the corresponding porphyrin base and was fully characterized by UV-vis, fluorimetry, FT-IR, 1H-NMR, and 13C-NMR methods. The fluorescence response of this Pt-porphyrin in the presence of different concentrations of hydrogen peroxide was investigated. Besides, modified glassy carbon electrodes with this Pt-porphyrin (Pt-Porf-GCE) were realized and several electrochemical characterizations were comparatively performed with bare glassy carbon electrodes (GCE), in the absence or presence of hydrogen peroxide. The Pt-porphyrin demonstrated to be a successful sensitive material for the detection of hydrogen peroxide both by fluorimetric method in a concentration range relevant for biological samples (1.05&ndash, 3.9 &times, 10&minus, 7 M) and by electrochemical method, in a larger concentration range from 1 &times, 6 M to 5 &times, 5 M. Based on different methods, this Pt-porphyrin can cover detection in diverse fields, from medical tests to food and agricultural monitoring, proving high accuracy (correlation coefficients over 99%) in both fluorimetric and electrochemical measurements.

Magnetic iron oxide-silica shell nanocomposites with different iron oxide/silica ratio were synthesized and structurally characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), small-angle neutron scattering, magnetic and N2-sorption studies. The composite that resulted with the best properties in terms of contact surface area and saturation of magnetization was selected for Pb2+ adsorption studies from aqueous media. The material presented good absorption capacity (maximum adsorption capacity 14.9 mg&middot, g&minus, 1) comparable with similar materials presented in literature. Its chemico-physical stability and adsorption capacity recommend the nanocomposite as a cheap adsorbent material for lead.

A new and "flexible" microwave-assisted hydrothermal (MWH) synthesis of crednerite CuMnO 2 materials is proposed. Single-phase compounds are synthesized by means of the MWH method in a significantly shorter time than by conventional hydrothermal heating. CuMnO 2 single-phase compounds are obtained in the 80–180 °C temperature range, with times ranging from 5 min to 1 h, starting from nitrate reactants. The structure and the phase composition were studied by X-Ray diffraction and FT-IR spectroscopy, and reveal that all samples crystallize within the crednerite structure with the C2/m space group and without other impurities. The surface area is 59.5 m 2 /g for the sample obtained at 120 °C, 5 min, and 76.8 m 2 /g for the sample obtained at 80 °C, 5 min, respectively. The morphological analysis by transmission electron microscopy revealed plate-like nanoparticles, 20–50 nm in diameter. As application, in the case of the as-obtained products the catalytic activity was tested for hydrogen evolution in aqueous sulphide solution.

Fe(acac)3/silica/PVA hybrid xerogel nanocomposite was obtained by one pot acid catalysed sol-gel synthesis using the homogeneous mixture of iron(III) acetylacetonate (Fe(acac)3), tetraethylorthosilicate (TEOS), and polyvinyl alcohol (PVA). Nominal composition ratio of iron oxide/silica was 15/85 (weight percent). Nitric acid was used as catalyst. Another sample of Fe(acac)3/silica xerogel without PVA addition was prepared in the similar processing conditions. Based on thermal analysis studies, the thermal behaviour of both xerogel samples was unveiled and it allowed choosing the optimal calcination temperatures in order to obtain iron oxide silica magnetic nanocomposite samples. The two xerogel (with and without PVA) samples were thermally treated, in air, at 220, 260 and 300?C and characterized by different techniques. XRD investigations revealed phase composition evolution with calcination temperature, from cubic spinel phase (maghemite) to hexagonal stable hematite containing nanocomposite of 10-20 nm average crystallite size. These findings were confirmed by M?ssbauer spectroscopy. Up to 300?C, the surface area and total pores volume increased with temperature for all samples. By calcination at the same temperature, the hybrid xerogel containing PVA resulted in significantly higher magnetization and free volume values in comparison with the sample without PVA.

A fast and effective method for the preparation of NaTaO3 nanomaterials reported here is ultrasonic method with immersed sonotrode in the reaction medium followed by annealing at 600 °C. In order to remove the organic material and increase phase crystallinity, the materials were annealed at different temperatures (400, 600, 800 °C), for 6 h. The as-prepared samples were characterized by X-ray diffraction (XRD), thermal analysis (TG/DTG/HF), IR spectroscopy, surface area analysis (BET), and scanning electron microscopy (SEM/EDX). The structural characterization by X-ray powder diffraction revealed that heat-treated materials at 600 °C are well crystallized and the average size of the crystallites being approximately 60 nm, confirmed also by scanning electron microscopy. Thermal analysis has revealed five transformations process of NaTaO3, the highest mass loss (10.67 %) taking place in the range 23–323.5 °C. It was found that the BET surface area decreases with temperature increasing which indicates a change in pores due to the removal of organics. From morphological analysis, it can be seen that particles have spherical shape and EDX revealed the purity of obtained materials.

A series of heteropolyacids (HPA)–silica composites were prepared from H3PMo12O40 (HPM) and H4PVMo11O40 (HPVM) by chemically anchoring to the amine-functionalized mesoporous MCM-41 and SBA-15. These composites were characterized by FT-IR, XRD, N2 adsorption, SEM, and TEM for their structural integrity and physicochemical properties. The effect of the support on thermal stability was investigated by TG–DTG and DTA. The evolved gases during the thermal analysis of prepared composites were identified by online mass spectrometry coupled with TG technique. It was evidenced that HPAs species were finely dispersed on amine-functionalized molecular sieves via chemical immobilization and the structure of the HPAs is preserved over mesoporous materials. From thermal analysis of HPA–silica composites was observed an important mass loss above 553 K which is due to the decomposition of amino propyl functional group. For this reason prepared composites can be utilized as dispersed catalysts for the reactions performed below 553 K. Catalytic properties of these composites were studied by using ethanol conversion at different temperatures. The HPA supported on molecular sieves exhibited an enhanced oxidation catalytic activity (formation of acetaldehyde) and a lower acid catalytic activity (formation of ethylene and diethyl ether) compared to the parent catalysts. The favorable effect of HPAs deposition on silica supports for oxidehydrogenation pathway to acetaldehyde results from the examination of and reaction rate values. For all reaction temperatures, the reaction rates of acetaldehyde formation are higher for supported samples than unsupported ones.

A novel hybrid mesoporous silica–Mn–porphyrin nanomaterial and its application for fluorescent detection of H2O2 is reported. The hybrid was obtained by sol–gel method in two steps acid-base catalysis and was completely characterized by UV–vis, FT-IR, fluorimetric, DRX, BET, AFM, TEM and conductivity investigations. The influence of adding H2O2 to the silica–Mn–porphyrin hybrid generates major differences regarding the optical, textural and morphological properties of the material. The dependence between H2O2 concentration and the fluorescence intensity, measured at the emission maximum at the wavelength 655 nm, is linear with an excellent correlation coefficient of 0.9945. The high sensitivity for hydrogen peroxide in wet media noticed for this hybrid, accompanied by changes in color, justifies further investigations towards design of fluorimetric and colorimetric O2 gas sensors. The low conductivity of the manganese(III)porphyrin–silica hybrid (0.694 × 10−8 S/cm) can be improved, so that this material may become a promising one for electrochemical cells (batteries).

The adsorptive potential has been evaluated for the aminopropyl functionalized mesoporous silica materials obtained by co-condensation and post grafting methods. Nitrogen sorption, small angle neutron and X-ray scattering (SANS and SAXS) demonstrated high surface area and well-ordered hexagonal pore structure suitable for applications as adsorbents of metals from waste waters. A comparison of Cr(VI) adsorption properties of the materials prepared by different functionalization methods has been performed. The obtained results demonstrated the adsorption capacity due to the affinity of the chromium ions to the amino groups, and showed that co-condensation of tetraethoxysilane (TEOS) and 3-aminopropyl triethoxysilane (APTES) resulted in higher metal sorption capacity of the materials compared to post-synthesis grafting of aminopropyl groups onto the mesoporous silica particles.

H2 adsorption properties of ordered mesoporous silica prepared with different ratios of functionalized precursors have been studied. Silica particles were synthesized by sol-gel method, with tetradecyltrimethyl ammonium bromide (C14) or dodecyl trimethyl ammonium bromide (C12) as structure directing agents, and tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES), by varying the molar ratio of the two precursors. The porosity and microstructure of the materials in function of the MTES/TEOS ratio were evaluated by using nitrogen adsorption and X-ray diffraction and showed that the samples contained amorphous and ordered porous domains. Stable porous structure able to hold H2 molecule and give them back when required has been obtained. The higher hydrogen adsorption capacities measured at 77 K were obtained for the samples synthesized with reduced amount of MTES, followed by the samples with no MTES, with both C12 and C14 directing agents. Increased amount of MTES precursor led to lowering of the adsorption capacity. The increase of the adsorption capacity already below 20 bar, observed for all samples, could be an advantage for practical application since a lower pressure is preferable. The study revealed the influence of the synthesis parameters to the hydrogen sorption performance and serves as guidance for applications as hydrogen adsorptive materials.

Magnesium silicate functionalized with tetrabutyl ammonium dihydrogen phosphate was developed as a new adsorbent for La(III) removal from aqueous solutions. The functionalized material was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis, and determination of the specific surface area (194 m2·g–1). The influence of several experimental parameters (amount of adsorbent, contact time, temperature,and initial concentration of lanthanum ions) on the adsorption process was examined. The optimum dose of adsorbent was established as 4 g·L–1. The optimum contact time of 15 min ensured a ∼95% La(III) removal efficiency at 298.15 K. The pseudo-second-order kinetic model was the best fit of the experimental data. The positive value of activation energy (10.7 kJ·mol–1) suggested that the adsorption process was endothermic and the mechanism was chemisorption. Thermodynamic parameters (ΔG°, ΔH°, ΔS°) showed that the adsorption process was endothermi...

Mesoporous silica matrices have been prepared via classic acid catalyzed and sono-catalyzed sol-gel routes. Tetramethoxysilan (TMOS) and methyl-trimethoxysilane (MTMS) were used as silica precursors, and N-butyl-3-methylpyridinium tetrafluoroborate ([bmPy][BF4]) was employed as co-solvent and pore template. The ionic liquid (IL) to silica mole ratio was varied between 0.007 and 0.07. Nitrogen adsorption-desorption and small-angle neutron scattering measurements were used to characterize the obtained materials. The ionic liquid played the role of catalyst that affected the formation of the primary xerogel particles, and changed the porosity of the materials. Ultrasound treatment resulted in microstructure change on the level of the colloid particle aggregates. In comparison with IL containing xerogels, the IL containing sonogels show increased pore diameter, bigger pore volumes and diminished surface areas.

Mesoporous silica particles have been synthesized by sol-gel method from tetraethoxysilane (tetraethylorthosilicate, TEOS) and methyltriethoxysilane (MTES), in ethanol and water mixture, at different ratios of the of the silica precursors. Ammonia was used as catalyst at room temperature and hexadecyltrimethylammonium bromide (cetyltrimethylammonium bromide, CTAB) as the structure directing agent. Nitrogen sorption, X-ray diffraction and small-angle neutron scattering gave information on the evolution of the gel structure and pore morphologies in the function of MTES/TEOS molar ratio. Thermogravimetric and differential thermal analysis showed that with addition of MTES the exothermic peak indicating the oxidation of the low molecular weight organic fragments shift to higher temperature. A room-temperature, one-pot synthesis of MCM-41 type materials is presented, in which the variation of the MTES concentration allows to change the hydrophobicity, preserving the specific properties materials, like the ordered pore structure, large specific surface area and high porosity, making them suitable for selective uptake of guest species in drug loading applications. Specifically, the obtained materials had cylindrical pores, specific surface areas up to 1101 m2/g and total pore volumes up to 0.473 cm3/g. The obtained mesoporous materials are susceptible for further functionalization to improve their selective uptake of guest species in drug delivery applications.