452 research outputs found
A versatile method for the production of monodisperse spherical particles and hollow particles: Templating from binary core-shell structures
Get PDFUsing the porosity of a binary exotemplate, with mesoporous core-shell structure (SiO2@ZrO2), opens a new pathway to produce hybrid core-shell spheres, composite hollow spheres, and porous hollow spheres – all monodisperse in size.Fil: Arnal, Pablo Maximiliano. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Schüth, Ferdi. No especifíca;Fil: Kleitz, Freddy. Universite Laval; Franci
Enzyme-responsive controlled release of covalently bound prodrug from functional mesoporous silica nanospheres
No full textI want to break free: Mesoporous silica nanoparticles are functionalized with sulfasalazine (SZ; see scheme), a prodrug of 5-aminosalicylic acid (5-ASA) and sulfapyridine, to generate enzyme-responsive nanocarriers. In the presence of the colon-specific enzyme azo-reductase (orange), 5-ASA and sulfapyridine are efficiently released.Amirali Popat, Benjamin P. Ross, Jian Liu, Siddharth Jambhrunkar, Freddy Kleitz, and Shi Zhang Qia
Immobilization of Agaricus bisporus Polyphenol Oxidase 4 on mesoporous silica: Towards mimicking key enzymatic processes in peat soils
Get PDFThe use of immobilized enzyme-type biocatalysts to mimic specific processes in soil can be considered one of the most promising alternatives to overcome the difficulties behind the structural elucidation of riverine humic-derived iron-complexes. Herein, we propose that the immobilization of the functional mushroom tyrosinase, Agaricus bisporus Polyphenol Oxidase 4 (AbPPO4) on mesoporous SBA-15-type silica could contribute to the study of small aquatic humic ligands such as phenols.The authors thank the University of Vienna (Austria) and the Austrian Science Research Fund (FWF, P32326 to A.R.) for financial support.Peer reviewe
Nitrogen-containing mesoporous carbons via nanocasting for CO2 capture and energy storage applications
No full textIn this work, nitrogen-containing ordered mesoporous carbons (NOMCs) are proposed as CO2 adsorbents. The nanocasting approach, using ordered mesoporous silica hard templates, was exploited for tuning the textural features of the carbonaceous adsorbents and therefore optimizing their capture performances and the kinetics of gas diffusion. Moreover, an eco-friendly nitrogen-containing carbon source was chosen as a precursor, in order to introduce basic sites useful to promote the interaction with the acidic CO2 molecule, thus fostering a selective adsorption in a gas mixture.
CMK-8 materials were prepared using KIT-6 templates, varying the pyrolysis temperature in order to evaluate the role of microporosity and nitrogen species (amount and type of N inclusions, i.e. pyridinic, pyrrolic and graphitic) in CO2 adsorption.
An extensive characterization of the ordered mesoporous architecture (low-angle XRD, FESEM, TEM and N2 physisorption at 77K), microporosity (CO2 isotherms at 273K) and surface chemical properties by XPS was carried out.
CO2 capture tests were performed in different conditions of temperature and pressure. An adsorption of 1.05 mmol/g (4.6% weight increase) was achieved at 30 °C and 90 kPa in a pure CO2 flow. Also selectivity in a mixture with N2 and reusability upon cycling was investigated.
The described NOMCs can be applied not only for CO2 up-take, but also in energy storage and conversion devices (e.g., lithium or sodium based batteries), photocatalysis or electrocatalytic reduction of CO2. For these applications, they can be used as-synthesized or decorated with specifically selected metal oxides and testing is now in progress in our laboratories
Nitrogen-containing ordered mesoporous carbons applied as CO2 adsorbents and anode materials in energy storage devices
No full textPorous carbons, thanks to their easily tunable features (porosity, surface chemical properties, etc.), can be employed for several applications: separation processes, as catalyst supports as well as electrode components in electrochemical energy storage/conversion devices. Among these, in the framework of strategies for the mitigation of global warming and climate changes, nitrogen-containing ordered mesoporous carbons (NOMCs) are proposed as CO2 adsorbents, thanks to their outstanding adsorption ability and selectivity. NOMCs can be synthesized with different pore architectures as nano-replications of a silica hard template, using a three-step procedure: i) infiltration of the carbon/nitrogen source inside the pore channels of silica, ii) pyrolysis of the hybrid system, and iii) template removal. This method is particularly useful for achieving the optimal textural properties, i.e. a hierarchical pore architecture composed of both micro- and mesopores able to promote at the same time improved capture performances and fast kinetics of gas diffusion, respectively.
In this work, the aforementioned approach, known for the preparation of the so-called CMK-type materials, is exploited for tuning the textural features of the carbonaceous adsorbents. Moreover, a natural occurring nitrogen/carbon source was chosen as a precursor, in order to introduce basic sites useful to promote the interaction of the carbon framework with the acidic CO2 molecule, thus also fostering a selective adsorption in a gas mixture. Therefore, the regular, ordered mesoporous architecture and the chemical surface properties were investigated to unveil their effect on the CO2 capture performances.
In addition, the described NOMCs can be applied not only for CO2 up-take, but also in energy storage and conversion devices (e.g., lithium or sodium-based batteries), photocatalysis or electrocatalytic reduction of CO2. For these applications, they can be used as-synthesized or eventually decorated with specifically selected metal oxides, and related results are here shown
Design of nitrogen-containing carbonaceous adsorbents for CO2 capture and energy storage applications
No full textThe increase of global CO2 concentration, mainly due to anthropogenic emissions from combustion of fossil fuels, is responsible for severe environmental issues, in particular global warming. Limitations in the use of polluting energy sources and the development of strategies for the reduction of CO2 emissions are therefore strictly urgent. Activated carbons can be employed for several applications: separation processes, as catalyst supports as well as electrode/electrolyte components in electrochemical energy storage/conversion devices. Among these, nitrogen-containing ordered mesoporous carbons (NOMCs) are proposed for CO2 up-take. Ordered mesoporous carbons (OMCs) can be synthesized with different pore architectures as nano-replications of a silica hard template, using a three-step procedure: i) infiltration of the carbon source inside the pore channels of silica, ii) pyrolysis of the hybrid system and iii) template removal. For example, this approach has been used to prepare the well-known CMK-type materials: CMK-1, CMK3, CMK-6 and CMK-8 are synthesized using MCM-48, SBA-15, SBA-16 and KIT-6 silica templates, respectively. NOMCs are here proposed as CO2 adsorbents in the context of the carbon capture and storage technologies. In this work, the aforementioned approach, known for the reparation of the so-called CMK-type materials, is exploited for tuning the textural features of the carbonaceous adsorbents and therefore optimizing their capture performances and the kinetics of gas diffusion. Moreover, a nitrogen-containing carbon source was chosen as a precursor, in order to introduce basic sites useful to promote the interaction with the acidic CO2 molecule, fostering in this way also a selective adsorption in a gas mixture. Therefore, the regular, ordered mesoporous architecture and the superficial chemical properties have been investigated in order to study their effect on the CO2 capture performances. The described NOMCs can be applied not only for CO2 up-take, but also in energy storage and conversion devices (lithium or sodium based batteries for instance), photocatalysis or electrocatalytic reduction of CO2. For these applications, they can be used as-synthesized or eventually decorated with specifically selected metal oxides
Zeolitic core@shell adsorbents for the selective removal of free glycerol from crude biodiesel
Get PDFSelective adsorption of free glycerol from crude biodiesel was investigated by using mesoporous silica spheres coated with a thin shell of microporous silicalite-1. A polycrystalline silicalite-1 shell was formed upon first covering the external surfaces of various core templates with discrete silicalite-1 nanocrystals, and this was followed by short hydrothermal treatment to ensure shell uniformity. Batch glycerol adsorption experiments were conducted to evaluate the ability of the sorbents to remove free glycerol selectively from crude biodiesel mixtures at various temperatures, also in comparison to that of conventional sorbents, for example, bare mesoporous silica gel spheres and zeolites. The silicalite-1 shell provided a microporous membrane that hindered the diffusion of fatty acid methyl esters into the mesopores of the composite sorbent, whereas the large pore volume of the mesoporous core enabled multilayer glycerol adsorption; this ultimately substantially enhanced the performance in terms of purification yield and adsorption capacity.Fil: Masoumifard, Nima. Laval University; CanadáFil: Arnal, Pablo Maximiliano. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Tecnología de Recursos Minerales y Cerámica; ArgentinaFil: Kaliaguine, Serge. Laval University; CanadáFil: Kleitz, Freddy. Laval University; Canad
Oxidation stability of nanographite materials
No full textNanographite materials (NGMs), e.g., carbon nanotubes and graphene, have attracted great attention owing to their unique electronic and structural properties which make them promising for applications in Li-ion batteries, [ 1 ] functional composites, [ 2 ] fuel cells, [ 3 ] supercapacitors, [ 4 ] nano-electromechanical systems [ 5 ] and photovoltaic devices. [ 6 ] However, when NGMs are used as supports of catalysts or active components in electrochemical devices (such as fuel cells), their oxidation and corrosion could lead to a severe degradation of the catalyst which eventually affects the whole performance of the electrochemical systems. Therefore, understanding the oxidation stability of NGMs is essential in order to develop new robust nanoscale devices.© 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim.Huaiguang Li, Niancai Cheng, Yao Zheng, Xiao Zhang, Haifeng Lv, Daping He, Mu Pan, Freddy Kleitz, Shi Zhang Qiao and Shichun M
A new synthesis pathway for colloidal silica spheres coated with crystalline titanium oxide and its comparative cyto- and genotoxic study with titanium oxide nanoparticles in rat osteosarcoma (UMR106) cells
Get PDFSpherical particles with an amorphous core of silica and a crystalline shell of titanium oxide (SiO2@TiO2) formed in a three-step procedure, being the last step a mild chemical treatment. SiO2@TiO2 had a shell with pores (micro and mesopores) permeating between TiO2 nanocrystals (anatase) and a solid core of amorphous silica. The spheres had an outstanding specific surface area (300m2g-1). A cyto- and genotoxic study of SiO2@TiO2 and titanium oxide nanoparticles (TiO2-NP) on UMR106 cells with 24h exposure showed that SiO2@TiO2 colloidal particles were less toxic than TiO2-NP.Fil: Di Virgilio, Ana Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica "Dr. Pedro J. Aymonino"; ArgentinaFil: Maisuls, Iván. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); ArgentinaFil: Kleitz, Freddy. Laval University; CanadáFil: Arnal, Pablo Maximiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. CEMIC-CONICET. Centro de Educaciones Médicas e Investigaciones Clínicas "Norberto Quirno". CEMIC-CONICET.; Argentin
Bewertung der magnesiothermen Reduktion von geordnetem mesoporösem SiO2 zu mesoporösem Silizium für Si-Anodenmaterialien
Get PDFRenewable energy sources (RES) are slowly replacing unsustainable sources such as gasoline and coal, to lead us to a more environmentally sound future. The problem RES are facing is that the energy generation is highly weather-dependent, and therefore inconsistent. Energy storage systems are necessary to guarantee an efficient distribution of energy when it’s needed. Battery systems, especially Li-Ion-Batteries (LIBs), are the storage devices of choice currently, due to their outstanding specific and volumetric capacities combined with solid cycle stability and high energy densities. Nevertheless, the demand for LIBs with higher energy densities and capacities is growing from year to year, urging research to look for alternative materials. Silicon has an outstanding theoretical capacity depending on the LixSiy phase, (i.e., 3579 or 4200 mAh.g-1), which is about ten times higher than graphite (372 mAh.g-1). The downside of silicon is that forming an alloy with Li leads to a substantial, irreversible specific and volumetric capacity loss, due to volume expansion (280-400 %) and solid electrolyte interface (SEI) formation during charge/discharge process. In this master’s thesis project, studies on different protocols to synthesize mesoporous Si anode materials with enhanced cycle stability and specific charge values were conducted. Ordered mesoporous silicas (OMS) with different pore structures and particle sizes were used as starting materials for magnesiothermic reduction to silicon anode materials. Mesoporous silicon with high porosity and specific surface areas of 280 m2.g-1 (K1 made from KIT-6) were obtained. Unfortunately, heat accumulation appeared to be a serious problem, melting the ordered pore structures and original particle shape. Nevertheless, the average pore size of samples remained in the range of the starting materials (4-22 nm). An adapted reduction protocol including the use of NaCl as a heat modulator didn’t decrease thermal effects and pore closing during reduction. The electrochemical performance of the materials is better than that of purchasable nanoparticles with 130 nm, for 70-80 cycles. Especially, Si/C electrodes prepared with MCM-48-type MSNs have increased specific charge values (580 mAh.g-1). Furthermore, studies of samples analysed after different etching post-treatments showed that hazardous HF-treatment is not necessary to obtain phase pure silicon with physio-chemical properties equivalent to samples etched with HF, if the ratio of the starting materials is correct
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