Pubblicazioni recenti in evidenza

Cesare Benedetti, Alessandro Cazzolaro, Mauro Carraro, Robert Graf, Katharina Landfester, Silvia Gross*, and Rafael Muñoz-Espí*

Journal: ACS Applied Materials & Interfaces IF: 7.145

DOI: 10.1021/acsami.6b07023

Accepted 9 September 2016

Organic–inorganic hybrid nanoparticles are prepared by free-radical copolymerization of methyl methacrylate (MMA) with the structurally well-defined methacrylate-functionalized zirconium oxocluster Zr4O2(methacrylate)12. The polymerization process occurs in the confined space of miniemulsion droplets. The formation of covalent chemical bonds between the organic and the inorganic counterparts improves the distribution of the guest species (oxoclusters) in the polymer particles, overcoming problems related to migration, leaching and stability. Because of the presence of a high number of double bonds (12 per oxocluster), the oxoclusters act as efficient cross-linking units for the resulting polymer matrix, thus ruling its swelling behavior in organic solvents. The synthesized hybrid nanostructures are applied as heterogeneous systems in the catalytic oxidation of an organic sulfide to the corresponding sulfoxide and sulfone by hydrogen peroxide, displaying quantitative sulfide conversion in 4-24 h with more than 2000 catalytic cycles.

A. Politano, M. Cattelan, D.W. Boukhvalov, D. Campi, A. Cupolillo, S. Agnoli, N.G. Apostol, P. Lacovig, S. Lizzit, D. Farías, G. Chiarello, G. Granozzi, and R. Larciprete 

ACS Nano (IF: 12.881)

DOI: 10.1021/acsnano.6b00554

By means of a combination of surface-science spectroscopies and theory, we have investigated the mechanisms ruling the catalytic role of epitaxial graphene (Gr) grown on transition-metal substrates for the production of hydrogen from water. Water decomposition at the Gr/metal interface at room temperature provides a hydrogenated Gr sheet, which is buckled and decoupled from the metal substrate. We evaluated the performance of Gr/metal interface as a hydrogen storage medium, with a storage density in the Gr sheet comparable with state-of-the-art materials (1.42 wt.%). Moreover, thermal programmed reaction experiments showed that molecular hydrogen can be released upon heating the water-exposed Gr/metal interface above 400 K. The Gr hydro/dehydrogenation process might be exploited for an effective and eco-friendly device to produce (and store) hydrogen from water, i.e. starting from an almost unlimited source.

Sven Urban, Paolo Dolcet, Maren Möller, Limei Chen, Peter J. Klar, Igor Djerdj, Silvia Gross, Bernd Smarsly, Herbert Over

Applied Catalysis B: Environmental

I. F.: 7.435

It is known that the k-Ce2Zr2O8 phase is an active oxidation catalyst with an extraordinarily high oxygen storage capacity. The k-Ce2Zr2O8 phase is synthesized starting from t-Ce0.5Zr0.5O2 solid solution which is reduced by hydrogen at high temperatures to form the pyrochlore Ce2Zr2O7 phase (pyr-Ce2Zr2O7) with high degree of ordering of the cationic sublattice. The final step in the synthesis of the k-Ce2Zr2O8 phase includes a mild re-oxidation of pyr-Ce2Zr2O7 at around 600 °C under atmospheric conditions. Yet, the optimum synthesis of the k-Ce2Zr2O8 phase is still not settled since most of the previous studies used reduction temperatures of 1300 °C and below. We show in contribution that 1300 °C is not sufficient to warrant the preparation of phase-pure pyr-Ce2Zr2O7 and k-Ce2Zr2O8, but rather that temperatures as high as 1500 °C are required to assure phase purity. This conclusion is drawn from extended X-ray diffraction and X-ray absorption spectroscopy analysis together with Raman spectroscopy, providing in-depth details of the structure on the level of both, the evolution of the special periodic structure and the coordination of the metal atoms. 

 

Annalisa Dalzini, Christian Bergamini, Barbara BiondiMarta De ZottiGiacomo Panighel, Romana Fato, Cristina PeggionMarco Bortolus & Anna Lisa Maniero

Scintific Reports

doi:10.1038/srep24000

IF: 5.578

Peptaibols are peculiar peptides produced by fungi as weapons against other microorganisms. Previous studies showed that peptaibols are promising peptide-based drugs because they act against cell membranes rather than a specific target, thus lowering the possibility of the onset of multi-drug resistance, and they possess non-coded α-amino acid residues that confer proteolytic resistance. Trichogin GA IV (TG) is a short peptaibol displaying antimicrobial and cytotoxic activity. In the present work, we studied thirteen TG analogues, adopting a multidisciplinary approach. We showed that the cytotoxicity is tuneable by single amino-acids substitutions. Many analogues maintain the same level of non-selective cytotoxicity of TG and three analogues are completely non-toxic. Two promising lead compounds, characterized by the introduction of a positively charged unnatural amino-acid in the hydrophobic face of the helix, selectively kill T67 cancer cells without affecting healthy cells. To explain the determinants of the cytotoxicity, we investigated the structural parameters of the peptides, their cell-binding properties, cell localization, and dynamics in the membrane, as well as the cell membrane composition. We show that, while cytotoxicity is governed by the fine balance between the amphipathicity and hydrophobicity, the selectivity depends also on the expression of negatively charged phospholipids on the cell surface.

Yun Luo, Luis Alberto Estudillo-Wong, Laura Calvillo, Gaetano Granozzi, Nicolas Alonso-Vante 

Journal of Catalysis 2016

DOI:10.1016/j.jcat.2016.03.001

IF: 6.921

Carbon supported PdCu alloy (PdCu/C-1) with surface atomic Pd/Cu ratio of 0.8/1 was successfully synthesized via an easy and cheap chemical route, using a Cu-MOF precursor (HKUST-1). This material shows nanorod-like morphology. The addition of Cu results in a lattice contraction (afcc = 0.3869 nm), and an increase of micro-strain (ε = 0.71 %) and stacking fault (α = 5.20 %) with respect to Pd/C NPs (afcc = 0.3889 nm, ε = 0.37 %, α = 1.98 %) prepared via the same chemical route. When using the CuCl2 precursor (PdCu/C-2), the micro-strain (ε = 0.47 %) and stacking-fault (α = 4.10 %) values also increases with respect to Pd/C NPs. The XPS characterization demonstrates the predominant metallic character of Cu and the formation of a PdCu alloy with a stoichiometry close to 1:1 in the near surface region. The use of a sacrificial HKUST-1 precursor is crucial for the formation of PdCu alloy. The electrochemical behavior of the MOF-derived PdCu/C sample is rather different from the other reference catalysts. Based on the results of CO-stripping, the CO-oxidation potential could be related to both micro-strain and stacking-fault. This fact reveals that the electrochemistry of this sample is associated with surface defects induced by Cu atoms in the PdCu alloy. Moreover, the ORR activity is improved on the MOF-derived PdCu/C sample with respect to other Pd-based catalysts, demonstrating a positive effect of the surface defects induced by alloyed PdCu NPs prepared from HKUST-1. Compared with commercial Pt/C (JM) catalyst, the ORR mass activity of PdCu/C-1 was lower in acid medium, whereas it was around 3-fold higher in alkaline solution. Therefore, the synthesis of PdCu nanoalloyed NPs, using HKUST-1 precursors, not only extends the application of MOF in the field of electrocatalysis, but also brings a new methodology in advanced non-Pt active centers for the ORR.

Yun Luo, Laura Calvillo, Carole Daiguebonne, Maria K. Daletou, Gaetano Granozzi, Nicolas Alonso-Vante

Applied Catalysis B: Environmental 2016 (IF=7.435)

DOI: 10.1016/j.apcatb.2016.02.028

Advanced Pt/CeOx/C nanocomposite, where C = porous carbon and multi-walled carbon nanotube (MWCNT), was synthesized using a precursor based on Ce-containing metal organic framework (MOF), via carbonyl chemical route, followed by heat-treatment at 900 °C under argon atmosphere. The use of MOF lead to the formation of CeOx intimately contacted to Pt surface that protects Pt NPs against agglomeration. CeOx, derived from MOF(Ce), interacts with Pt NPs, stabilizing Pt0 and Ce3+ state in the nanocomposite. The surface electrochemistry of Pt/CeOx/C nanocomposite showed the promotion of H and CO adsorption, thus higher Pt active surface area with respect to the samples prepared at lower temperatures and commercial Pt/C (JM) catalyst. The ORR activity and stability was highly enhanced, outperforming DOE 2015/2017 target in half-cell. Finally, such an innovative composite was validated as cathode catalyst in a H2/O2 μLFFC system. Compared with other homemade and Pt/C (JM) cathodic catalysts, the cell power density was enhanced by a factor of ca. 1.2 – 1.7. All these facts assess the significant role of CeOx, based on MOF(Ce) precursor, in the formation of Pt/CeOx/C nanocomposite, leading to a modified Pt surface and resulting enhanced ORR kinetic and stability. This work has also demonstrated that the novel Pt/CeOx/C nanocomposite can be in-situ prepared at high temperature (900 °C under inert gas) where both MWCNTs and porous carbon are key ingredients. Our study, indeed, extends the application of MOF materials in preparation of Pt-based nanomaterials for energy conversion.