Improved mechanical stability of HKUST-1 in confined nanospace.

One of the main concerns in the technological application of several metal-organic frameworks (MOFs) relates to their structural instability under pressure (after a conforming step). Here we report for the first time that mechanical instability can be highly improved via nucleation and growth of MOF nanocrystals in the confined nanospace of activated carbons.

Use of eutectic mixtures for preparation of monolithic carbons with CO2-adsorption and gas-separation capabilities.

With global warming becoming one of the main problems our society is facing nowadays, there is an urgent demand to develop materials suitable for CO2 storage as well as for gas separation. Within this context, hierarchical porous structures are of great interest for in-flow applications because of the desirable combination of an extensive internal reactive surface along narrow nanopores with facile molecular transport through broad "highways" leading to and from these pores. Deep eutectic solvents (DESs) have been recently used in the synthesis of carbon monoliths exhibiting a bicontinuous porous structure composed of continuous macroporous channels and a continuous carbon network that contains a certain microporosity and provides considerable surface area. In this work, we have prepared two DESs for the preparation of two hierarchical carbon monoliths with different compositions (e.g., either nitrogen-doped or not) and structure. It is worth noting that DESs played a capital role in the synthesis of hierarchical carbon monoliths not only promoting the spinodal decomposition that governs the formation of the bicontinuous porous structure but also providing the precursors required to tailor the composition and the molecular sieve structure of the resulting carbons. We have studied the performance of these two carbons for CO2, N2, and CH4 adsorption in both monolithic and powdered form. We have also studied the selective adsorption of CO2 versus CH4 in equilibrium and dynamic conditions. We found that these materials combined a high CO2-sorption capacity besides an excellent CO2/N2 and CO2/CH4 selectivity and, interestingly, this performance was preserved when processed in both monolithic and powdered form.

Ethanol steam reforming on Ni/Al2O3 catalysts: effect of the addition of Zn and Pt.

Ni-based catalysts supported on Zn-modified alumina were investigated in the ethanol steam reforming reaction. A commercial γ-alumina was impregnated with different amounts of zinc nitrate (0, 2, 5, 10, 15, 20 wt.% on Zn basis), calcined, and then impregnated with nickel nitrate aqueous solutions. The samples were characterized by a number of techniques: N(2) adsorption at 77 K, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray fluorescence (XRF), and temperature-programmed reduction (TPR). Their catalytic behavior in the ethanol steam reforming reaction was studied at 873 K, with a H(2)O/ethanol ratio of 5:1. Two effects of the presence of Zn were detected. On the one hand, zinc modifies the surface structure and the surface chemistry of the catalysts by formation of zinc aluminates, and on the other hand, zinc oxide can be reduced to metallic zinc under reaction conditions, thus modifying the catalytic properties of the active phase. The presence of Zn increases the ethanol conversion to gaseous compounds as compared with the catalyst supported on the Zn-free commercial alumina. The addition of a small amount of Pt (1 wt.%) causes a beneficial effect in the reaction. When Ni catalysts were used without a previous reduction treatment, ethylene was formed in high amounts; however, the Pt-Ni catalysts need no reduction pre-treatment to achieve high H(2) yields (close to 70%) and showed a high stability versus time on stream because of the control of the production of ethylene, a coke precursor.

Comparison of nanostructured titania matrices obtained by carbon template and sol-gel methods for controlled release of fluoxetine.

Two types of titania matrix were investigated as a support for the prolonged drug delivery of the antidepressant fluoxetine. Sample MT was synthesized using carbon template and consisted of titania microtubes on which then fluoxetine was adsorbed. Sample SG was synthesized by the sol-gel method when the drug was added during the reaction. The morphology of the powder surfaces was found to be different: nanotubes versus almost spherical particles with much larger surface area of SG and smaller pores. The relative degrees of hydroxyl coverage of the surface were studied by FTIR-spectroscopy and were found to be much larger for the sol-gel complex. Theoretical modeling was applied to consider possible interactions between the drug and the matrices. The liberation of the drug was proved to be faster from complex MT and was attributed to weaker drug-matrix interactions in combination with larger pore size.

Influence of water/alkoxide ratio in the synthesis of nanosized sol-gel titania on the release of phenytoin.

The sol-gel method was used to synthesize inorganic reservoirs with encapsulated antiepileptic drug phenytoin. The drug release profile was shown to depend on the morphology and surface properties of the matrix. A parameter of the synthesis such as water/alkoxide ratio r(w) was varied in order to investigate its influence on the matrix properties and as a result on the drug release profile. It was found that the specific surface area and crystallization degree decrease with an increase of r(w), whereas the hydroxyl group coverage increases with an increase of r(w). Drug release kinetics studies revealed that the initial release rate increases with an increase of water content in the reaction, whereas the long time release rate first slightly increases with an increase of water content from 4 to 8 and then decreases for r(w) = 16. The interplay of different parameters of the matrix is shown to be responsible for such a dependence and is discussed in the Article.

A site energy distribution function from Toth isotherm for adsorption of gases on heterogeneous surfaces.

A site energy distribution function based on a condensation approximation method is proposed for gas-phase adsorption systems following the Toth isotherm. The proposed model is successfully applied to estimate the site energy distribution of three pitch-based activated carbons (PA, PFeA and PBA) developed in our laboratory and also for other common adsorbent materials for different gas molecules. According to the proposed model the site energy distribution curves of the activated carbons are found to be exponential for hydrogen at 77 K. The site energy distribution of some of the activated carbon fibers, ambersorb, Dowex optipore, 13X Zeolite for different adsorbate molecules represents a quasi-Gaussian curve with a widened left hand side, indicating that most sites have adsorption energies lower than a statistical mean value.

Catalytic nanomedicine: a new field in antitumor treatment using supported platinum nanoparticles. In vitro DNA degradation and in vivo tests with C6 animal model on Wistar rats.

Novel nanostructured TiO2 and SiO2 based biocatalysts, with 3-4 wt. % of Pt have been developed. The obtained materials exhibit a high surface area together with a broad pore size distribution. The method of synthesis allowed obtaining high dispersed platinum metal nanoparticles. In vitro DNA reactivity test of the biocatalysts were carried out by electrophoresis and formation of DNA adducts was observed. The most active biocatalyst was H2PtCl6/SiO2. These biocatalysts were also tested in an experimental model of C6 brain tumours in Wistar rats. Administration of the material was made by stereotactic brain surgery to place it directly in the malignant tissue. A significant decrease in tumour size and weight as well as morphologic changes in cancer cells were observed.

Spectroscopic and microcalorimetric study of a TiO(2)-supported platinum catalyst.

This paper reports a CO adsorption study on a Pt/TiO(2) catalyst reduced at two different temperatures, 473 and 773 K, followed by in situ infrared spectroscopy and adsorption microcalorimetry. The study is complemented with XPS characterization of the reduced catalysts.

Is there any microporosity in ordered mesoporous silicas?

The porous structure of nanostructured silicas MCM-41 and SBA-15 has been characterized using N2 adsorption at 77 K, before and after n-nonane preadsorption, together with immersion calorimetry into liquids of different molecular dimensions. Selective blocking of the microporosity with n-nonane proves experimentally that MCM-41 is exclusively mesoporous while SBA-15 exhibits both micro- and mesopores. Additionally, N2 adsorption experiments on the preadsorbed samples show that the microporosity on SBA-15 is located in intrawall positions, the micropore volume accounting for only approximately 7-8 % of the total pore volume. Calorimetric measurements into n-hexane (0.43 nm), 2-methylpentane (0.49 nm), and 2,2-dimethylbutane (0.56 nm) estimate the size of these micropores to be < or = 0.56 nm.

Nearly space-filling fractal networks of carbon nanopores.

Small-angle x-ray scattering, nitrogen adsorption, and scanning tunneling microscopy show that a series of activated carbons host an extended fractal network of channels with dimension D(p) = 2.8-3.0 (pore fractal), channel width 15-20 A (lower end of scaling), network diameter 3000-3400 A (upper end of scaling), and porosity of 0.3-0.6. We interpret the network as a stack of quasiplanar invasion percolation clusters, formed by oxidative removal of walls between closed voids of diameter of approximately 10 A and held in registry by fibrils of the biological precursor, and point out unique applications.