1,721,267 research outputs found
Optimizing the electrodeposition protocol of enantioselective inherently chiral electrode surfaces: a multi-technique investigation
No full textWe have recently introduced "inherently chiral" enantiopure electrode surfaces of outstanding chirality manifestations, including circularly polarized luminescence, reversibly potential-driven circular dichroism, and large potential differences for the enantiomers of chiral probes in voltammetry experiments performed on such surfaces. [1-3]
The outstandingly powerful “inherent chirality” concept implies a molecular structure where the stereogenic element does not consist in an isolated stereocentre or an external chirality source, but originates from a tailored torsion in the whole main backbone endowing the molecule with its key functional property (here electroactivity).
A key issue is now to investigate the enantioselection mechanism and to optimize the experimental protocols for the deposition of our inherently chiral surfaces. For both aims it is important to study the thickness and regularity of the chiral oligomer films as a function of the experimental conditions. We started a systematic profilometry study correlated to electrochemical impedance spectroscopy measurements of the oligomer films obtained by carefully controlled electrodeposition, varying one by one different experimental parameters. The study is also important to properly compare enantioselection by films prepared from different inherently chiral monomers, including e.g. bisindole and tetrathiahelicene ones.
[1] S. Arnaboldi, S. Grecchi, M. Magni, P. Mussini, Electroactive chiral oligo- and polymer layers for electrochemical enantiorecognition, Current Opinion in Electrochemistry, 7 (2018) 188-199.
[2] S. Arnaboldi, M. Magni, P. R. Mussini, Enantioselective selectors for chiral electrochemistry and electroanalysis: Stereogenic elements and enantioselection performance, Current Opinion in Electrochemistry, 8 (2018) 60-72.
[3] S. Arnaboldi, T. Benincori, R. Cirilli, S. Grecchi, L. Santagostini, F. Sannicolò, P.R. Mussini, “Inherently chiral” thiophene-based electrodes at work: a screening of enantioselection ability toward a series of pharmaceutically relevant phenolic or catecholic amino acids, amino esters, and amine, Analytical and Bioanalytical Chemistry, 408 (2016) 7243-7254
Electroactive Inherently Chiral Surfaces at Work: Clues Toward the Elucidation of the Enantioselection Mechanism
Full text linkChirality is a concept strictly related to life and to its evolution. Capability to discriminate antipodes and/or produce enantiopure chiral chemicals through cheap and efficient protocols is a crucial task for our modern civilization. So identification of increasingly effective and robust chiral selectors is a challenging task also for the electrochemical community [1,2].
In this frame our research group is working on the so called “inherently chiral functional molecular materials”, ICFMMs; the idea is simple: make the stereogenic element responsible for chirality coincident with the functional group responsible for the material specific property (Figure, left). This approach has constituted an actual breakthrough in chiral electrochemistry, resulting in the preparation of efficient chiral electroactive surfaces [3,4,5] (and chiral additives/media, too [6]) invariably characterized by outstanding enantiodiscrimination ability in quite different working conditions and with chemically different chiral electroactive analytes. Notwithstanding plenty of proofs pointing to a general validity of the ICFMMs concept, a clear rationalization of the enantiodiscrimination mechanism still lacks.
To fill the gap a deeper knowledge of the behavior of our electrodeposited chiral films is mandatory. As a first step some of the most important experimental parameters governing the growth of the conductive coatings have been changed, one by one, to evaluate their impact on the morphological, optical and electronic properties of the final deposit. Results of the multi-technique characterization will be discussed, including profilometry, electrochemical impedance spectroscopy (Figure, right) and spectroelectrochemistry data, all aimed to collect clues useful to rationalize the way in which ICFMMs work.
The support of Fondazione Cariplo/Regione Lombardia (Project 2016-0923) and SmartMatLab are gratefully acknowledged.
References:
[1] S. Arnaboldi, M. Magni, P. Mussini, Curr. Opin. Electrochem., 2018, 8, 60.
[2] S. Arnaboldi, S. Grecchi, M. Magni, P. Mussini, Curr. Opin. Electrochem., 2018, 7, 188.
[3] F. Sannicolò, P.R. Mussini, T. Benincori, R. Martinazzo, S. Arnaboldi, G. Appoloni, M. Panigati, E. Quartapelle Procopio, V. Marino, R. Cirilli, S. Casolo, W. Kutner, K. Noworyta, A. Pietrzyk-Le, Z. Iskierko, K. Bartold, Chem. Eur. J., 2016, 22, 10839.
[4] S. Arnaboldi, P.R. Mussini, M. Magni, F. Sannicolò, T. Benincori, R. Cirilli, K. Noworyta, W. Kutner, Chem. Sci., 2015, 6, 1706.
[5] F. Sannicolò, S. Arnaboldi, T. Benincori, V. Bonometti, R. Cirilli, L. Dunsch, W. Kutner, G. Longhi, P.R. Mussini, M. Panigati, M. Pierini, S. Rizzo, Angew. Chem. Int. Ed., 2014, 53, 2623.
[6] S. Rizzo S. Arnaboldi, V. Mihali, R. Cirilli, A. Forni, A. Gennaro, A.A. Isse, M. Pierini, P.R. Mussini, F. Sannicolò, Angew. Chem. Int. Ed., 2017, 56, 2079
ReZinCo: Innovazione nel Riciclo Polveri FEA
No full textIl progetto ReZinCo, acronimo inglese di “Riciclo di Zinco come Coating”, punta a valorizzare un rifiuto pericoloso, ricco in Zn, derivante dai forni elettrici ad arco (FEA) impiegati nelle acciaierie, proponendo un’innovazione tecnologica e di prodotto nel campo della galvanica. In quest’ottica, il progetto prevede un ciclo integrato che partendo da rottami di acciaio galvanizzato produce direttamente nuovo acciaio galvanizzato (economia rigenerativa).The project ReZinCo, standing for “Recycling of Zinc as Coating”, aims to enhance a hazardous Zn-rich waste resulting by electric arc furnaces (EAFs) of steel making industry by proposing a technological and product innovation in galvanizing. In doing so, the project provides an integrated cycle that, fed with galvanized scrap, produces directly new finished galvanized steel products (complying with regenerative economy)
Ingenious Electroactive Molecules, Surfaces and Devices at SmartMatLab
Full text linkThe SmartMatLab Centre is a recently acquired facility at the Department of Chemistry of the University of Milan (UniMi), which has been jointly funded by Regione Lombardia, Fondazione Cariplo, Università degli Studi di Milano, Dipartimento di Chimica and CNR ISTM (Institute of Molecular Sciences and Technologies).
It is conceived as an advanced R&D infrastructure including a laboratory for the preparation of thin smart materials by different techniques and for their functionalization, and a laboratory for the characterization and testing of the so-developed advanced and smart functional materials in pre-applicative device mode, employing up-to-date instrumentation. The SmartMatLab Centre also offers training activities in advanced material science. SmartMatLab, run by a Centre Management committee, is hosted by the Department of chemistry of UniMi and involves more than 60 affiliated researchers from both UniMi and CNR, operating in several advanced research fields. An overview of the instrumentation available at SmartMatLab will be presented, together with a series of examples of the electroactive molecules, surfaces and devices which are currently under investigation and development. SmartMatLab is eagerly looking for both scientific partnerships and industrial collaborations!
Acknowledgments The Regione Lombardia – Fondazione Cariplo joint SmartMatLab Project (Fondazione Cariplo grant 2013-1766) is gratefully acknowledged
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Enantioselective voltammetry on achiral electrodes
Full text linkAn attractive target in electroanalysis is the availability of chiral media affording enantioselection in terms of significant peak potential difference between the antipodes of chiral probes in voltammetry experiments on achiral electrodes.
Previous literature attempts pointed to enantioselectivity increasing with the structural order of the chiral medium; on the other hand, outstanding enantioselection performance has been recently observed working on electrode surfaces consisting in "inherently chiral" oligomer films [1-2].
Combining both strategies, we have recently developed two inherently chiral ionic liquids, ICILs, consisting of dialkylated bicollidinium salts, with an atropoisomeric bipyridinium cation featuring at least one octyl chain and bistrifilimide counteranions. They showed high enantioselectivity when tested even as low concentration additives in commercial achiral ionic liquid media [3] and also as chiral bulk media.
Importantly, similar ability was also shown by other terms of the same family,
having shorter alkyl chains and/or different counteranions, solid at room temperature but of easier synthesis. As a first tentative explanation we are considering the high supramolecular order of even simple ionic liquids at the interphase with a charged surface. A chiral additive could result in chiral reorganization of this peculiar interphase, as in the case of nematic-to-cholesteric transitions induced by chiral dopants in liquid crystals.
This allowed us to include in our chiral voltammetry experiments a quite larger number of inherently chiral selectors based on different stereogenic elements, i.e., the bicollidine and bibenzimidazole atropoisomeric scaffolds and the tetrathielicene helicoidal scaffold. They all proved successful.
The support of Fondazione Cariplo/Regione Lombardia "Avviso congiunto per l’incremento dell’attrattività del sistema di ricerca lombardo e della competitività dei ricercatori candidati su strumenti ERC - edizione 2016” (Project 2016-0923) is gratefully acknowledged.
[1] F. Sannicolò, S. Arnaboldi, T. Benincori, V. Bonometti, R. Cirilli, L. Dunsch, W. Kutner, G. Longhi, P. R. Mussini, M. Panigati, M. Pierini, S. Rizzo, Angew. Chem. Int. Ed. 53 (2014) 2623
[2] S. Arnaboldi, P. Mussini, M. Magni, F. Sannicolò, T. Benincori, R. Cirilli, K. Noworyta, W. Kutner, Chem. Sci. 6 (2015) 1706
[3] S. Rizzo, S. Arnaboldi, V. Mihali, R. Cirilli, A. Forni, A. Gennaro, A. A. Isse, M. Pierini, P. R. Mussini, F. Sannicolò, Angew. Chem. Int. Ed 56 (2017) 207
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Spettroscopia di Impedenza Elettrochimica & Film Polimerici Conduttori: il Caso del 4H-CicloPenta[3,2-b]DiTiofene
No full textI polimeri organici conduttori rivestono un posto di rilievo nel panorama scientifico internazionale, grazie alla loro peculiare natura molecolare ed elettronica che permette la convivenza, nello stesso materiale, delle proprietà meccaniche e duttili proprie dei polimeri tradizionali (es. le plastiche) con quelle elettroniche caratteristiche, invece, dei metalli.
Il nostro gruppo di ricerca è impegnato da anni nella sintesi e nella caratterizzazione di monomeri a base tiofenica e dei relativi oligomeri/polimeri ottenuti, principalmente, mediante deposizione elettroossidativa. L’impiego della spettroscopia di impedenza elettrochimica (EIS), in combinazione con la voltammetria ciclica, permette una caratterizzazione approfondita di questi film elettroattivi, elucidandone anche le proprietà di conduzione elettronica.
In questo contesto abbiamo effettuato un’investigazione sistematica su un sistema modello rivolta ad evidenziare la dipendenza delle proprietà conduttive dei film da vari parametri sperimentali. La scelta del monomero modello è ricaduta sul 4H-ciclopenta[3,2-b]ditiofene (CPDT), in quanto: i) è un sistema perfettamente planare e, conseguentemente, è caratterizzato da un’elevata coniugazione elettronica efficace (maggiore dell’analogo 2,2’-ditiofene) e ii) è un monomero avente due posizioni elettroattive omotopiche (posizioni alfa tiofeniche), conseguenza dell’elevata simmetrica molecolare, mantenuta anche a livello delle catene oligo- polimeriche, garantendo quindi una perfetta regioregolarità del materiale risultante dall’elettroossidazione.
La presentazione si focalizzerà sui risultati impedenzistici effettuati sui film di poli-CPDT, considerando in particolare l’influenza dello spessore del materiale elettrodeposto e del potenziale elettrico applicato. Verrà, inoltre, discusso il loro comportamento in presenza di specie elettroattive in soluzione, quali ferrocene e decametilferrocene
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