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328 results on '"Melchionna, Michele"'

1. Design of dye-sensitized TiO$_2$ materials for photocatalytic hydrogen production: light and shadow

Author

Zani, Lorenzo, Melchionna, Michele, Montini, Tiziano, and Fornasiero, Paolo

Subjects
Physics - Chemical Physics, Condensed Matter - Materials Science
Abstract

Visible light-driven production of fuels and value-added chemicals is currently one of the most intensely investigated research topics across various scientific disciplines, due to its potential to ease the World s dependence on fossil fuels. In this perspective, we recapitulate some of the main features of dye-sensitized photocatalytic systems aimed at solar H$_2$ production, focusing in particular on TiO$_2$-based three-component assemblies with organic sensitizers. Relevant aspects include the structural and electronic properties of the sensitizers, the nature of the semiconductor and the hydrogen evolution catalysts, the role of the sacrificial donor and the effect of the reaction parameters on H$_2$ production rate and stability. Besides presenting the most significant recent developments of the field, we also analyse some of its common practices in terms of experimental design, laboratory procedures and data presentation, trying to highlight their weaknesses and suggesting possible improvements. We then conclude with a short paragraph discussing the possible future development of this exciting research area.

Published
2022
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2. Electrocatalytic CO$_2$ Reduction: Role of the Cross-Talk at Organic-Inorganic Interfaces

Author

Melchionna, Michele, Fornasiero, Paolo, Prato, Maurizio, and Bonchio, Marcella

Subjects
Condensed Matter - Materials Science, Physics - Chemical Physics
Abstract

Electrocatalytic CO$_2$RR is an interfacial process, involving a minimum of three phases at the contact point of gaseous CO$_2$ with the electrodic surface and the liquid electrolyte. As a consequence, surface chemistry at composite interfaces plays a central role for CO$_2$RR selectivity and catalysis. Each interface defines a functional boundary, where active sites are exposed to a unique environment with respect to distal sites in the bulk or organic and inorganic materials. While the individual role of each component-type is hardly predictable a-solo, the interface ensemble works via a strategic interplay of individual effects, including: (i) enhanced electrical conductivity, (ii) high surface area and exposure of the interfacial catalytic sites, (iii) favorable transport and feeding of reactants, (iv) complementary interactions for the on/off stabilization of cascade intermediates, (v) a secondary sphere assistance to lower the activation energy of bottleneck steps, (vi) a reinforced robustness and long-term operation stability by mutual protection and/or healing mechanisms. Selected CO$_2$RR case studies are compared and contrasted to highlight how the organic domains of carbon nanostructures merge with metal and metal-oxide active sites to separate tasks but also to turn them into a cooperative asset of mutual interactions, thus going beyond the classic Divide et Impera rule.

Published
2022
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6. A water playground for peptide re-assembly from fibrils to plates.

Author

Adorinni, Simone, Kurbasic, Marina, Garcia, Ana M., Kralj, Slavko, Bellotto, Ottavia, Scarel, Erica, Pengo, Paolo, De Zorzi, Rita, Melchionna, Michele, Vargiu, Attilivio V., and Marchesan, Silvia

Abstract

Short-peptide amyloid assembly and disassembly play crucial roles in various research fields, which range from addressing pathologies that lack therapeutic solutions to the development of innovative soft (bio)materials. Hydrogels from short peptides typically show thermo-reversible gel-to-sol transition, whereby fibrils disassemble upon heating, and re-assemble upon cooling down to room temperature (rt). Despite ongoing intense research studies in this area, the majority focus on peptide–peptide interaction and neglect the structuring role of water in peptide supramolecular behavior. This study describes an unprotected tetrapeptide gelator that forms highly stable fibrils which, upon heating, re-organize into plates that persist upon cooling to rt. All-atom molecular dynamics (MD) simulations and experimental methods reveal water as a key player in the thermodynamics that accompany this irreversible morphological transition, and advance our understanding of supramolecular structures. [ABSTRACT FROM AUTHOR]

Published
2024
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14. Contributors

Author

Andreescu, Silvana, primary, Aneggi, Eleonora, additional, Bellardita, Marianna, additional, Boaro, Marta, additional, Castano, Carlos E., additional, de Leitenburg, Carla, additional, Esposito, Vincenzo, additional, Fahrenholtz, William G., additional, Finny, Abraham Samuel, additional, Fiorenza, Roberto, additional, Fornasiero, Paolo, additional, Ivanov, Vladimir K., additional, Kabir, Ahsanul, additional, Loddo, Vittorio, additional, Melchionna, Michele, additional, O’Keefe, Matthew J., additional, Othman, Ali, additional, Palmisano, Leonardo, additional, Parrino, Francesco, additional, Scirè, Salvatore, additional, Shcherbakov, Alexander B., additional, Trovarelli, Alessandro, additional, Yurdakal, Sedat, additional, Zhang, Haiwu, additional, and Zholobak, Nadezhda M., additional

Published
2020
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19. Synthesis and study of novel zwitterionic transition metal complexes and their application as olefin polymerisation catalysts

Author

Melchionna, Michele, Bailey, Philip, and Robertson, Neil

Subjects
541.39, neutral zwitterionic complexes., palladium atom
Abstract

The synthesis, characterization and coordination chemistry of novel zwitterionic late transition metal complexes has been carried out, and an investigation of their ability to act as olefin polymerisation catalysts has been conducted. These systems are based on 6- aminofulvene-2-aldiminate ligands (R2AFA¯) which are capable of binding metal centres via two nitrogen donors, delocalising the negative charge into their cyclopentadienyl moiety, thus resulting in the formation of neutral zwitterionic complexes. Preparation and characterisation of mono- and di-substituted complexes such as Ph2AFACuPPh3, (Ph2AFA)2Zn, (Ph2AFA)2Co, (Ph2AFA)2Ni and (Ph2AFA)2Pd have revealed that this type of ligand has enough flexibility to distort upon coordination to the metal depending on geometrical or steric restrictions. As a result, when the ligand coordination involves narrow binding angle of the metal chelate, as it happens in the square-planar species, a severe loss of planarity of the ligand framework is observed, in contrast with the tetrahedral structures where such binding angles are wider. Although the coordination of the ligand primarily occurs through the nitrogen donors, once they have been occupied by the metal centre, it is possible to exploit the aromatic Cp ring for coordination to a Cp*Ru+ unit. In this way, the synthesis and characterisation of two- and tri-metallic complexes [(Cp*Ru)(Ph’2AFA)Pd(η3-C3H5)][BF4] (where Ph’= 2,4,6-trimethylphenyl) and [(Cp*Ru)2(Ph2AFA)2Pd][BF4]2 has been achieved, featuring the R2AFA¯ molecule acting as an ambidentate ligand, binding the palladium atom in a diimine fashion and the ruthenium centres by means of the C5 ring. The synthesis of the complex Cp*RuPh2AFA where the two N atoms are vacant was also achieved and it was found that this compound acts as a proton sponge in the presence of protic solvents. In an effort to prepare AFA-metal complexes which could be of potential use in olefin polymerisation catalysis, two novel species, [(Ph2AFA)Pd(Me)PPh3] and [(Ph’2AFA)Pd(C3H5)] (where Ph’= 2,4,6-trimethylphenyl) have been synthesised and characterised, and polymerisation tests with ethylene have been carried out. Some preliminary screening of other molecules as monomers for polymerisation catalysis has also been conducted.

Published
2007

24. Carbon Vacancies Steer the Activity in Dual Ni Carbon Nitride Photocatalysis

Author

Marchi, Miriam, primary, Raciti, Edoardo, additional, Gali, Sai Manoj, additional, Piccirilli, Federica, additional, Vondracek, Hendrik, additional, Actis, Arianna, additional, Salvadori, Enrico, additional, Rosso, Cristian, additional, Criado, Alejandro, additional, D'Agostino, Carmine, additional, Forster, Luke, additional, Lee, Daniel, additional, Foucher, Alexandre C., additional, Rai, Rajeev Kumar, additional, Beljonne, David, additional, Stach, Eric A., additional, Chiesa, Mario, additional, Lazzaroni, Roberto, additional, Filippini, Giacomo, additional, Prato, Maurizio, additional, Melchionna, Michele, additional, and Fornasiero, Paolo, additional

Published
2023
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28. Carbon Vacancies Steer the Activity in Dual Ni Carbon Nitride Photocatalysis

Author

Marchi, Miriam, Criado, Alejandro, Filippini, Giacomo, Prato, Maurizio, Melchionna, Michele, Fornasiero, Paolo, Marchi, Miriam, Criado, Alejandro, Filippini, Giacomo, Prato, Maurizio, Melchionna, Michele, and Fornasiero, Paolo

Abstract

[Abstract]: The manipulation of carbon nitride (CN) structures is one main avenue to enhance the activity of CN-based photocatalysts. Increasing the efficiency of photocatalytic heterogeneous materials is a critical step toward the realistic implementation of sustainable schemes for organic synthesis. However, limited knowledge of the structure/activity relationship in relation to subtle structural variations prevents a fully rational design of new photocatalytic materials, limiting practical applications. Here, the CN structure is engineered by means of a microwave treatment, and the structure of the material is shaped around its suitable functionality for Ni dual photocatalysis, with a resulting boosting of the reaction efficiency toward many CX (X = N, S, O) couplings. The combination of advanced characterization techniques and first-principle simulations reveals that this enhanced reactivity is due to the formation of carbon vacancies that evolve into triazole and imine N species able to suitably bind Ni complexes and harness highly efficient dual catalysis. The cost-effective microwave treatment proposed here appears as a versatile and sustainable approach to the design of CN-based photocatalysts for a wide range of industrially relevant organic synthetic reactions.

Published
2023

31. Catalysis-Material Crosstalk at Tailored Nano-Carbon Interfaces

Author

Melchionna, Michele, Bonchio, Marcella, Paolucci, Francesco, Prato, Maurizio, Fornasiero, Paolo, Houk, Kendall N., Series editor, Hunter, Christopher A., Series editor, Ley, S.V., Series editor, Krische, Michael J, Series editor, Lehn, Jean-Marie, Series editor, Olivucci, Massimo, Series editor, Thiem, Joachim, Series editor, Venturi, Margherita, Series editor, Wong, Chi-Huey, Series editor, Wong, Henry N.C., Series editor, Marcaccio, Massimo, editor, and Paolucci, Francesco, editor

Published
2014
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33. DoE‐Assisted Development of a 2H−MoS2‐Catalyzed Approach for the Production of Indole Derivatives.

Author

Gentile, Giuseppe, Morant‐Giner, Marc, Cardo, Lucia, Melchionna, Michele, Fornasiero, Paolo, Prato, Maurizio, and Filippini, Giacomo

Subjects
INDOLE derivatives, METHANE derivatives, ORGANIC synthesis, INDOLE, CATALYTIC activity, ORGANIC compounds, BENZALDEHYDE
Abstract

2H−MoS2 is an appealing semiconductor because of its Earth‐abundant nature, cheapness, and low toxicity. This material has shown promising catalytic activity for various energy‐related processes, but its use in catalysis for C−C bond forming reactions towards useful organic compounds is still largely unexplored. The lack of examples in organic synthesis is mainly due to the intrinsic difficulties of using bulk 2H−MoS2 (e. g., low surface area), which implies the reliance on high catalytic loadings for obtaining acceptable yields. This makes the optimization process more expensive and tedious. Here, we report the development of a 2H−MoS2‐mediated synthesis of valuable bis(indolyl)methane derivatives, using indoles and benzaldehydes as starting materials. Exploiting the Design of Experiments (DoE) method, we identified the critical parameters affecting the catalytic performance of commercial 2H−MoS2 powder and optimized the reaction conditions. Lastly, we demonstrated that the catalytic system has versatility and good tolerance towards functional group variations of the reagents. [ABSTRACT FROM AUTHOR]

Published
2023
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34. Nanotubular TiOxNy-Supported Ir Single Atoms and Clusters as Thin-Film Electrocatalysts for Oxygen Evolution in Acid Media

Author

Suhadolnik, Luka, primary, Bele, Marjan, additional, Čekada, Miha, additional, Jovanovič, Primož, additional, Maselj, Nik, additional, Lončar, Anja, additional, Dražić, Goran, additional, Šala, Martin, additional, Hodnik, Nejc, additional, Kovač, Janez, additional, Montini, Tiziano, additional, Melchionna, Michele, additional, and Fornasiero, Paolo, additional

Published
2023
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37. Driving up the Electrocatalytic Performance for Carbon Dioxide Conversion through Interface Tuning in Graphene Oxide–Bismuth Oxide Nanocomposites

Author

Melchionna, Michele, primary, Moro, Miriam, additional, Adorinni, Simone, additional, Nasi, Lucia, additional, Colussi, Sara, additional, Poggini, Lorenzo, additional, Marchesan, Silvia, additional, Valenti, Giovanni, additional, Paolucci, Francesco, additional, Prato, Maurizio, additional, and Fornasiero, Paolo, additional

Published
2022
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