Quantum-dots containing Fe/SBA-15 silica as “green” catalysts for the selective photocatalytic oxidation of alcohol (methanol,under visible light)

Fe/SBA-15 catalysts containing iron oxide nanoparticles confined inside silica pores (replicated, internal, poorly crystalline) and grown outside silica grains (external, mainly crystalline hematite) in different proportions are prepared using a single silica support. Fe-species are deposited by the two-solvent technique with two iron salts precursors (Fe(NO₃)₃·9H₂O, FeCl₃·6H₂O) and two solvents (cyclohexane, hexane) for 11 wt% of iron. Calcination is performed in reproducible conditions (700 °C, 2 °C/min, thin bed, in air). SAXS measurements are used to show that the 2D hexagonal structure of the used silica is maintained after Fe-loading and calcination. Ar sorption measurements show that the pores are partially plugged. The oxidation of pure methanol is used as a test reaction to compare photocatalytic properties. H₂O₂ and visible light both activate the reaction. More active catalysts are formed with hexane associated with FeCl₃·6H₂O than with Fe(NO₃)₃·9H₂O. A reversed situation is observed with cyclohexane. Iron leaching (after 1 h 30 of test, up to 3 mg of Fe by mL) is important. These results are expected to be of interest in the exploration of size and shape “nanocatalysis” and to provide a further understanding for the reactions that take place when porous silicas are used as supports.     

Effect of the order of Ni and Ce addition in SBA-15 on the activity in dry reforming of methane

Dry reforming of methane has been carried out on SBA-15 catalysts containing 5 wt% Ni and 6 wt% Ce. The effect of the order of Ni and Ce impregnation on the catalytic activity has been studied. Both metals were added using the “two-solvent” method that favors metal dispersion inside the pores. Characterizations by XRD (low and high angles), N₂ sorption, SEM and TEM of the materials after metal addition and calcination indicate good preservation of the porosities and high NiO and CeO₂ dispersion inside the porous channels. Reduction was carried out before the catalytic tests and followed by TPR measurements. The most active reduced catalyst was the Ni–Ce/SBA-15 sample prepared by impregnating cerium first, then nickel. All catalysts were highly active and selective towards H₂ and CO at atmospheric pressure. Full CH₄ conversion was obtained below 650 °C. The higher performances compared to those reported in the literature for mesoporous silica with supported Ni and Ce catalysts are discussed.     

Physical properties,biological applications and biocompatibility studies on biosynthesized single phase cobalt oxide (Co3O4) nanoparticles via Sageretia thea (Osbeck.)

Cobalt oxide nanoparticles were successfully biosynthesized by complete green process using aqueous leaf extracts of Sageretia thea as chelating agent. Diverse techniques were applied for characterization. Antibacterial (with and without UV illumination), antileishmanial, antioxidant and enzyme inhibition applications were assessed, while freshly isolated macrophages and red blood cells were used for biocompatibility studies. Good antibacterial nature and enhancement of bactericidal nature upon UV modulation is reported. Staphylococcus aureus and Escherichia coli are indicated as most susceptible bacterial strains. Significant cytotoxic potential is revealed with IC₅₀ calculated as 12.82 µg/ml and 3.16 µg/ml against the axenic leishmanial promastigote and amastigote cultures respectively. Biogenic cobalt oxide nanoparticles indicated DPPH free radical scavenging potential, while moderate antioxidant capacity and reducing power was demonstrated. Bioinspired cobalt oxide also demonstrated alpha amylase and protein kinase inhibition at higher concentrations. Biogenic cobalt oxide was found as more cytotoxic to macrophages (IC₅₀ = 58.55 µg/ml) then to RBC’s (IC₅₀ >200 µg/ml). Our results indicate green synthesis as an alternative, effective and eco-friendly method for the biosynthesis of cobalt oxide nanoparticles with numerous biological applications.     

Unusual phase behavior of decane-dodecane mixtures confined in SBA-15:Size effect on binary phase diagram

Phase behavior of normal decane-dodecane(n-C₁₀H₂₂-C₁₂H₂₆,C₁₀-C₁₂) system confined in SBA-15（Santa Barbara Amorphous,pore diameters 3.8,7.8,and 17.2 nm） has been studied by using differential scanning calorimetry.It has been found solid-liquid phase diagram of the C₁₀-C₁₂/SBA-15 system is composed of a straight line（3.8 nm）,a curve（7.8 nm） and a loop line （17.2 nm）.The growth of the phase diagram clearly shows the size effect on phase behavior of binary alkanes.Phase behavior has been compared among the systems C₁₀H₂₂-C₁₂H₂₆/SBA-15,C₁₂H₂₆-C₁₄H₃₀/SBA-15 and C₁₄H₃₀-C₁₆H₃₄/SBA-15.     

The effect of copper content on the reactivity of Cu/Co6Al2 solids in the catalytic steam reforming of methane reaction

The steam reforming of methane over Cu/Co₆Al₂ mixed oxides with different copper contents was studied. The Co₆Al₂ support was prepared via the hydrotalcite route. It was thermally stabilized at 500 °C, impregnated with 5 wt.%, 15 wt.% or 25 wt.% copper using copper (II) nitrate Cu(NO₃)₂·3H₂O precursor and then calcined again at 500 °C under an air flow. The impregnation of copper enhanced significantly the reactivity of the solids in the considered reaction. The 5Cu/Co₆Al₂ solid was the most reactive one, with a methane conversion of 96% at 650 °C. The selectivities of H₂ and CO₂ were also better for the catalyst containing 5 wt.% copper compared to higher copper loadings. The decrease in the catalytic reactivity with increasing the copper content was attributed to the formation of agglomerated and less reactive CuO species, which were detected by XRD and TPR analyses.     

CO oxidation catalyzed by Ag/SBA-15 catalysts: Influence of the hydrothermal treatment

Four types of SBA-15 were prepared with different times and temperatures of treatment in order to obtain a range of micropore sizes. CO oxidation was used as a probe reaction in order to evaluate the nature of the active species when SBA-15s were doped with ca 10% Ag deposited from an AgNO₃ solution and calcined or reduced at 350 °C. The texture (TEM, nitrogen physisorption), structure (XRD) and reducibility (TPR) of the various catalysts (Ag/SBA-15) were studied and compared to those of a catalyst prepared by deposition of silver on fumed silica as a reference. These catalysts differ initially by the nature of silica and by pore sizes. In CO oxidation, pre-reduced catalysts are more active than pre-oxidised ones. This has to do with two phenomena, i.e. sintering, which produces large inactive silver particles, and formation of active silver species in the form of small Ag₂O particles.     

Immobilization of acetylcholinesterase on functionalized SBA-15 mesoporous molecular sieve for detection of organophosphorus and carbamate pesticide

A novel method for the immobilization of acetylcholinesterase (AChE) on amino modified SBA-15 mesoporous molecular sieves was developed via electrostatic adsorption and glutaraldehyde crosslinking. The immobilized AChE could be exploited as a fast, sensitive and low-cost biocatalyst towards the detection of pesticides residues which could be stored at room temperature for a long time.     

Synthesis,characterization, single crystal XRD,in vitro antimicrobial and cytotoxicity study of tris(ethylenediamine)cobalt(III)chloride oxalate trihydrate

The complex tris(ethylenediamine)cobalt(III)chloride oxalate trihydrate [Co(en)₃]Cl(C₂O₄)·3H₂O crystallizes in the monoclinic space group C₂/c with the following unit cell parameters a = 19.9318 (13), b = 9.3344 (4), c = 19.0881 (13) Å β = 96.846(3)°, Z = 8. The crystal structure was solved by direct methods and refined by full matrix least squares procedures to a final R value of 0.0314 for 4330 observed reflections. The reported cobalt complex is six co-ordinated through amine nitrogen with distorted octahedral geometry. There are uncoordinated chloride and oxalate ions along with the water molecules. In-vitro antimicrobial activity was studied against various test organisms and found to be good. From in-vitro cytotoxic activity of the synthesized complex, the IC₅₀ value was found to be 55.85 μg/ml.     

Synthesis and characterization of high surface area TiO2/SiO2 mesostructured nanocomposite

Recently titania synthesis was reported using various structuration procedures, leading to the production of solid presenting high surface area but exhibiting moderate thermal stability. The study presents the synthesis of TiO₂/SiO₂ nanocomposites, a solid that can advantageously replace bulk titania samples as catalyst support. The silica host support used for the synthesis of the nanocomposite is a SBA-15 type silica, having a well-defined 2D hexagonal pore structure and a large pore size. The control of the impregnation media is important to obtain dispersed titania crystals into the porosity, the best results have been obtained using an impregnation in an excess of solvent. After calcination at low temperature (400 °C), nanocomposites having titania nanodomains (～2–3 nm) located inside the pores and no external aggregates visible are obtained. This nanocomposite exhibits high specific surface area (close to that of the silica host support, even with a titania loading of 55 wt.%) and a narrow pore size distribution. Surprisingly, the increase in calcination temperature up to 800 °C does not allow to detect the anatase to rutile transition. Even at 800 °C, the hexagonal mesoporous structure of the silica support is maintained, and the anatase crystal domain size is evaluated at ～10 nm, a size close to that of the silica host support porosity (8.4 nm). Comparison of their physical properties with the results presented in literature for bulk samples evidenced that these TiO₂/SiO₂ solids are promising in term of thermal stability.     

Self-assembled Nafion–silica nanoparticles for elevated-high temperature polymer electrolyte membrane fuel cells

In this paper, a novel Nafion/SiO₂ nanocomposite membrane based on the self-assembled Nafion–SiO₂ nanoparticles was developed. The average particle size of Nafion–SiO₂ nanoparticles prepared by self-assembly process was 2.8 ± 0.5 nm. The self-assembled Nafion–SiO₂ nanoparticles significantly enhance the durability of the Nafion/silica nanocomposite membrane as compared to that of conventional Nafion/silica composite and Nafion 212 membranes under wet/dry cyclic tests at 90 °C. With an addition of 5 wt% self-assembled Nafion–SiO₂ nanoparticles, the Nafion/SiO₂ nanocomposite membrane shows a significantly improved performance stability at cell/humidifying temperatures of 100 °C/60 °C under a current density of 600 mA/cm², and the degradation rate is 0.12 mV/min, almost 20 times lower than 2.33 mV/min measured on the pristine Nafion 212 membrane under the same conditions. The present results demonstrate the promises of the self-assembled Nafion/SiO₂ nanocomposite membrane for elevated-high temperature PEM fuel cells applications.     

Silylated Co/SBA-15 catalysts for Fischer-Tropsch synthesis

A series of silylated Co/SBA-15 catalysts were prepared via the reaction of surface Si-OH of SBA-15 with hexamethyldisilazane (HMDS) under anhydrous, vapor-phase conditions, and then characterized by FT-IR, N₂ physisorption, TG, XRD, and TPR-MS. The results showed that organic modification led to a silylated SBA-15 surface composed of stable hydrophobic Si-(CH₃)₃ species even after calcinations and H₂ reduction at 673 K. Furthermore, the hydrophobic surface strongly influenced both metal dispersion and reducibility. Compared with non-silylated Co/SBA, Co/S-SBA (impregnation after silylation) showed a high activity, due to the better cobalt reducibility on the hydrophobic support. However, S-Co/SBA (silylation after impregnation) had the lowest FT activity among all the catalysts, due to the lower cobalt reducibility along with the steric hindrance of grafted -Si(CH₃)₃ for the re-adsorption of α-olefins.     

High performance solid oxide electrolysis cell with impregnated electrodes

Here we report a solid oxide electrolysis cell (SOEC) employing impregnated electrodes. The cell structure consisted of a porous 430 L metal support, a Ni-Ce_0.8Sm_0.2O_2 − δ (SDC) impregnated 430 L-zirconia stabilized zirconia (YSZ) hydrogen electrode, a scandia stabilized zirconia (SSZ) electrolyte and a Nd₂O₃-Nd₂NiO_4 + δ (Nd₂O₃-NNO) impregnated SSZ oxygen electrode. The cell is prepared by tape casting, co-firing and impregnation techniques. At an applied voltage of 1.3 V and 50% steam content, current density of 2.05 A cm^− 2 is obtained at 800 °C. The effect of the variation of H₂O/H₂ ratio (3/97 to 70/30) on electrolysis performance at 750 °C is evaluated and the long-term stability in electrolysis mode is also investigated.     

Polyol-mediated synthesis of ultrafine tin oxide nanoparticles for reversible Li-ion storage

A simple, cheap and versatile, polyol-mediated fabrication method has been extended to the synthesis of tin oxide nanoparticles on a large scale. Ultrafine SnO₂ nanoparticles with crystallite sizes of less than 5 nm were realized by refluxing SnCl₂ · 2H₂O in ethylene glycol at 195 °C for 4 h under vigorous stirring in air. The as-prepared SnO₂ nanoparticles exhibited enhanced Li-ion storage capability and cyclability, demonstrating a specific capacity of 400 mAh g⁻¹ beyond 100 cycles.     

Impact of reforming catalyst on the anodic polarisation resistance in single-chamber SOFC fed by methane

This paper emphasises the electrochemical and catalytic properties of a Ni–10% GDC (10% gadolinium-doped ceria) cermet anode of a single-chamber solid oxide fuel cell (SC-SOFC). Innovative coupling of electrochemical impedance spectroscopy with gas chromatography measurements was carried out to characterise the anode material using an operando approach. The experiments were conducted in a symmetric anode/electrolyte/anode cell prepared by slurry coating resulting in 100 μm-thick anode layers. The electrochemical performance was assessed using a two-electrode arrangement between 400 °C and 650 °C, in a methane-rich atmosphere containing CH₄, O₂ and H₂O in a 14:2:6 volumetric ratio. The insertion of a Pt–CeO₂ based catalyst with high specific surface area inside the cermet layer was found to promote hydrogen production from the Water Gas Shift reaction and consequently to improve the electrochemical performances. Indeed, a promising polarisation resistance value of 12 Ω cm² was achieved at 600 °C with a catalytic loading of only 15 wt.%.     

Encapsulation hemoglobin in ordered mesoporous silicas: Influence factors for immobilization and bioelectrochemistry

The encapsulation of hemoglobin (Hb) on the mesoporous silicas SBA-15 and Au-doped SBA-15 (Au-SBA-15) has been studied as a model protein adsorption system. The influences of solution pH, structure of mesoporous silicas and gold nanoparticles incorporation on Hb immobilization are investigated in detail. The spectral characteristics of Hb/SBA-15 and Hb/Au-SBA-15 nanoconjugate show an absorption curve quite similar to that of native Hb, indicating that Hb retains its higher-order structure in the mesopores of SBA-15. Direct electrochemistry of Hb is obtained when Hb is adsorpted by mesoporous silicas SBA-15 or Au-SBA-15. Moreover, Hb/Au-SBA-15 exerts enhancing electron transfer ability because of the Au incorporation. Additionally, the Hb/Au-SBA-15 displays good electrocatalytic reduction of hydrogen peroxide with a detection limit of 1.0 μM, about 3 times as low as that for the Hb/SBA-15. The Hb/Au-SBA-15 exhibits higher peroxidase-like activity with the apparent Michaelis–Menton constant (K_m) of 2.87 mM, significantly lower than the 7.78 mM value for the Hb/SBA-15.     

Influence of FCC catalyst steaming on HDPE pyrolysis product distribution

A commercial FCC catalyst based on a zeolite active phase has been used in the catalytic pyrolysis of HDPE. The experimental runs have been carried out in a conical spouted bed reactor provided with a feeding system for continuous operation. Different treatments have been applied to the catalyst to improve its behaviour. This paper deals with the optimization of catalyst steaming and pyrolysis temperature in order to maximize the production of diesel-oil fraction. The performance of the fresh catalyst has been firstly studied at 500 °C. This catalyst gives way to 52 wt% gas yield, 35 wt% light liquid fraction and a low yield of C₁₀⁺ fraction (13 wt%). After mild steaming (5 h at 760 °C) the results show a significant improvement in product distribution. Thus, gas yield decreases to 22 wt%, the yield of light liquid is similar to that of the fresh one (38 wt%), whereas the yield of the desired C₁₀⁺ fraction increases to 38 wt%. Nevertheless, the best results have been obtained when a severe steaming is applied to the catalyst (8 h at 816 °C) and pyrolysis temperature is reduced to 475 °C. There is a significant reduction in the gaseous fraction (8 wt%). The light liquid fraction has also been reduced to 22 wt%, but the yield of diesel fraction increases to 69 wt%. Moreover, the deactivation of the catalyst has also been studied under the optimum conditions.     

Preparation of conducting silver paste with Ag nanoparticles prepared by e-beam irradiation

Conducting silver paste was prepared by using Ag nanoparticles which were synthesized by e-beam irradiation method (from KAERI); its conductivity was comparatively determined with Ag nanoparticles which were prepared by thermolysis method (commercial). The silver nanoparticles with the diameter of approximately 150 nm size prepared by e-beam irradiation were mixed with glass frit and sintered for 1 h at 500 °C. It is presumably concluded that the wt% of silver nanoparticle, size distribution and homogenous dispersibility of Ag nanoparticles in the pastes are the critical factors for the high conductivity of the paste. Among the various wt% of silver nanoparticle in the conducting silver pastes, silver paste with 90 wt% of silver nanoparticle has the highest conductivity as 1.6×10⁴ S cm^?1. This conductivity value is 1.6 times higher than the Ag pastes which were prepared with silver nanoparticles obtained by thermolysis method.     

Catalytic effects of copper(II) chloride and aluminum chloride on the pyrolytic behavior of cellulose

The cellulose without and with catalyst (CuCl₂, AlCl₃) was subjected to pyrolysis at temperatures from 350 to 500 °C with different heating rate (10 °C/min, 100 °C/s) to produce bio-oil and selected chemicals with high yield. The pyrolytic oil yield was in the range of 37–84 wt% depending on the temperature, the heating rate and the amount of metal chloride. The non-catalytic fast pyrolysis at 500 °C gives the highest yield of bio-oil. The mixing cellulose with both metal chlorides results with a significant decrease of the liquid product. The non-catalytic pyrolysis of cellulose gives the highest mass yield of levoglucosan (up to 11.69 wt%). The great influence of metal chloride amount on the distribution of bio-oil components was observed. The copper(II) chloride and aluminum chloride addition to cellulose clearly promotes the formation of levoglucosenone (up to 3.61 wt%), 1,4:3,6-dianhydro-α-d-glucopyranose (up to 3.37 wt%) and unidentified dianhydrosugar (MW = 144; up to 1.64 wt%). Additionally, several other compounds have been identified but in minor quantities. Based on the results of the GC–MS, the effect of pyrolysis process conditions on the productivity of selected chemicals was discussed. These results allowed to create a general model of reactions during the catalytic pyrolysis of cellulose in the presence of copper(II) chloride and aluminum chloride.     

Effects of phosphoric acid as additive in the preparation of activated carbon fibers from poly(p-phenylene benzobisoxazole) by carbon dioxide activation

Poly(p-phenylene benzobisoxazole) (PBO) was impregnated with small amounts of H₃PO₄, and the effects of this additive on the porosity and other characteristics of chars and activated carbon fibers (ACFs) derived from this polymer were investigated. To this end, PBO-AS impregnated with 5, 10 or 15 wt.% H₃PO₄ was pyrolyzed at 850 °C, and the resulting chars were physically activated with carbon dioxide at 800 °C to different burn-off (BO) degrees. Thermal analysis techniques only detected minor effects of H₃PO₄ on PBO pyrolysis. The char yield and char reactivity towards CO₂ increased following PBO-AS impregnation with H₃PO₄. Structural (X-ray diffraction), porous textural (CO₂ adsorption) and surface chemical (temperature-programmed desorption, X-ray photoelectron spectroscopy) characterizations of the pyrolysis chars indicated that the increase in char reactivity is probably associated with a higher content of oxygenated functionalities. Following CO₂ activation, the surface area and pore volume of the obtained ACFs chiefly depended on the BO degree, but impregnation with H₃PO₄ restricted the pore size to the micropore and narrow mesopore range, thus producing adsorbents with a slightly narrower pore size distribution than in the absence of H₃PO₄. The results are compared with those previously obtained under equivalent conditions with other high-crystallinity polymers as precursors for ACFs.     

Fabrication by Co-extrusion and electrochemical characterization of micro-tubular hollow fibre solid oxide fuel cells

A phase inversion process was used to co-extrude cerium–gadolinium oxide (Ce_0.9Gd_0.1O_1.95)/NiO–CGO dual-layer hollow fibres (HF), which were then sintered to form, respectively, the electrolyte and high porosity anode precursor of a solid oxide fuel cell (SOFC) with anode inner diameter of 0.8 mm. Graded CGO–lanthanum strontium cobalt ferrite (La_0.6Sr_0.4Fe_0.8Co_0.2O₃) cathode layers were then painted onto the CGO electrolyte to form a micro-tubular HF-SOFC. With a carefully designed anode current collector, this produced maximum power densities of 1186–5864 W m^? 2 at 450–570 °C. High magnification imaging analysis revealed large three-phase boundary regions within the anode, a dense electrolyte layer and clearly highlighted the multiple CGO–LSCF cermet and pure LSCF cathode layers. The performance of the HF-SOFC with a twenty millimetre active length showed no degradation after four thermal cycles between 300 °C and 570 °C.