Carbon Dioxide Cycloaddition to Epoxides Promoted by Nicotinamidium Halide Catalysts: A DFT Investigation

The utilization of CO2 as building block for the production of cyclic carbonate is a promising route to simultaneously mitigate the global warming issue and obtain valuable commercial chemicals. In this work, the activity of nicotinamidium halide catalysts towards the CO2 conversion into cyclic carbonate has been explored by means of density functional theory (DFT) calculations. DFT calculations support the ability, suggested experimentally, of the pyridium & alpha;-C-H proton of the catalysts to activate the epoxide ring via a hydrogen bond. Interestingly, DFT calculations underline the involvement of the n-octyl substituent of the pyridyl ring in the epoxide activation, while the hydrogen atom of the amide group N-H is rather involved in the stabilization of the iodide trough electrostatic interactions. Moreover, the replacement of the pyridium & alpha;-C-H proton with the bulkier methyl group leads to a different reaction mechanism. The calculated energy barriers well reproduce the experimental trends of the studied catalysts, and the computed activation barrier of 29.0 kcal/mol, relative to the ring opening step of the most active catalyst, is in line with the experimental working temperature of 80 & DEG;C. Those results shed light on the CO2 fixation reaction contributing to the development of more efficient catalytic systems

Hinter dem Vorhang: Eine Vorzeichnung Johann Heinrich Rambergs für das Titelkupfer zu Goethes ‚Claudine von Villa Bella‘

Der Beitrag befasst sich mit einer 1827 datierten aquarellierten Zeichnung von Johann Heinrich Ramberg (1793‒1840), welche ohne Hinweis auf ihren ursprünglichen Entstehungskontext als Neuerwerbung in die Grafische Sammlung des Deutschen Historischen Museums gelangte. Der Beitrag verfolgt die Entstehung der Zeichnung, die inzwischen in Verbindung zu einem wenig bekannten frühen Schauspiel des jungen Goethe, ‚Claudine von Villa Bella‘ (1776), gesetzt werden konnte. Parallel werden auch andere Fragen thematisiert: die Rolle des Künstlers als Buchillustrator der Goethe-Zeit, seine Tätigkeit für die Bühne sowie der Einfluss der italienischen Reise und des römischen Karnevals sowohl auf das Schauspiel Goethes als auch auf die Darstellung Rambergs

Die Bilderpredigten von Daniel Hopfer und die Rolle der Graphik in der Verbreitung der evangelischen Lehre

Lo studio si concentra su alcune acqueforti dell'artista di Augusta Daniel Hopfer (1471-1536) di soggetto religioso, che illustrano preghiere, proverbi, parabole e altri passi del Vangelo in forma narrativa e che risultano chiaramente influenzate dalle idee riformate. Dopo un approfondimento del contesto storico e culturale e delle opinioni dei maggiori riformatori in merito alla questione delle immagini, le originali opere di Hopfer sono state messe a confronto con gli scritti omiletici e catechetici dei riformatori del tempo, in particolar modo quelli attivi ad Augusta, per rintracciarne i presupposti teologici. Le stampe di Hopfer sono state anche confrontate con le testimonianze figurative precedenti, se presenti, e con i manifesti di satira religiosa di artisti contemporanei, per mettere in luce il rapporto con la tradizione, ma soprattutto il carattere di novità di queste rappresentazioni. Esse contengono spesso messaggi di denuncia dell'ipocrisia religiosa e degli abusi del clero, legittimati dalle citazioni bibliche, che rafforzano il legame testo-immagine e permettono di leggere le stampe-manifesto di Hopfer come prediche figurate.The researches have primarily focused on deepening the historical and cultural environment of the Reformation, especially on the positions of the most important exponents and theologians to the question of the images, the representability of God and the various functions of art at the beginning of the Reformation period. The core pieces of research are some broadsheets by the Augsburg artist Daniel Hopfer (1471-1536), which represent paragraphs of the Bible in a narrative form and are strictly connected to the theological issues of the modernity. In the collections of the Bavarian State Library of Munich, the Herzog August Library in Wolfenbüttel and the Forschungsbibliothek Gotha-Erfurt University I have analyzed the graphic work Hopfer’s in conjunction with the Augsburg Reformation and sermons, treatises and catechetical writings of reformers of the first decades of the XVI century. Moreover the etchings of Hopfer were compared with broadsheets od contemporary artists, who deals with similar subjects. The leitmotifs of the pictures are the juxtaposition between the teachings of Christ and the law of the Pharisees, through which Hopfer refer to the hypocrisy and abuses of the catholic clergy. Moreover, Hopfer added to the illustrated scenes the pieces of the Holy Scripture that justify these theological terms. In this way he uses the same rhetorical principle of the Reformers: a paratactic arrangement of the biblical source, often without other explanation. My argumentation consider this particularly work by Hopfer a pictorial sermon. On one hand, it embodies the spiritual needs of a spontaneous and authentic relationship with the Gospel, on the other hand, especially in the printing of the 30s, it expresses a strong message of social controversy.Das Forschungsprojekt konzentriert sich auf die Einblattdrucke von Daniel Hopfer (1471-1536), die Gebete, Gleichnisse, Salomonische Sprüche und Absätze des Neuen Testaments in szenischer Form darstellen. In seinen graphischen Werken stellt der Augsburger Radierer Hopfer Zusammenhänge zu den theologischen Fragen der Gegenwart her. In meiner Dissertation werden Predigten, Traktate und katechetische Schriften der Reformationszeit, die sich auf das Oeuvre Hopfers auswirken, untersucht. Gleichzeitig werden die Radierungen Hopfers mit anderen ikonographischen Vorbildern der Reformationszeit, wie Titelblättern, Buchillustrationen und Flugblättern, in Verbindung gesetzt. Die textuellen und bildlichen Quellen der Werke Hopfers wurden vor allem in München, bei der Bayerische Staatsbibliothek und dem Zentralinstitut für Kunstgeschichte, in Wolfenbüttel, bei der Herzog August Bibliothek und in Gotha, bei der Forschungsbibliothek, geforscht

Photochemical CO2 conversion on pristine and Mg-doped gallium nitride (GaN): a comprehensive DFT study based on a cluster model approach

The photochemical reduction of carbon dioxide (CO2) into methanol is very appealing since it requires sunlight as the only energy input. However, the development of highly selective and efficient photocatalysts is still very challenging. It has been reported that CO2 can be spontaneously activated on gallium nitride (GaN). Moreover, the photocatalytic activity for CO2 conversion into methanol can be drastically enhanced by incorporating a small amount of Mg dopant. In this work, density functional theory (DFT) based on a cluster model approach has been applied to further explore the photocatalytic activity of bare GaN towards CO2 adsorption and conversion. We extended the investigation of Mg-doping replacing one Ga atom with Mg on three different sites and evaluated the consequent effects on the band gaps and CO2 adsorption energies. Finally, we explore different routes leading to the production of methanol and evaluate the catalytic activity of bare GaN by applying the energetic span model (ESM) in order to identify the rate-determining states which are fundamental for suggesting modifications that can improve the photocatalytic activity of this promising material

Electron-Poor Acridones and Acridiniums as Super Photooxidants in Molecular Photoelectrochemistry by Unusual Mechanisms

Electron-deficient acridones and in situ generated acridinium salts are reported potent, closed-shell photooxidants that undergo surprising mechanisms. When bridging acyclic triarylamine catalysts with a carbonyl group (acridones), this completely diverts their behavior away from open-shell, radical cationic, 'beyond diffusion' photocatalysis to closed-shell, neutral, diffusion-controlled photocatalysis. Brønsted acid activation of acridones dramatically increases excited state oxidation power (by +0.8 V). Upon reduction of protonated acridones, they transform to electron-deficient acridinium salts as even more potent photooxidants (*E1/2 = +2.56-3.05 V vs SCE). These oxidize even electron-deficient arenes where conventional acridinium salt photooxidants have thusfar been limited to electron-rich arenes. Surprisingly, upon photoexcitation these electron-deficient acridinium salts appear to undergo two electron reductive quenching to form spectroscopically-detected acridinide anions. This new behaviour is partly enabled by a substrate assembly with the arene, and contrasts to conventional SET reductive quenching of acridinium salts. Critically, this study illustrates how redox active chromophoric molecules initially considered photocatalysts can transform during the reaction to catalytically active species with completely different redox and spectroscopic properties

d-Glucose Adsorption on the TiO2 Anatase (100) Surface: A Direct Comparison Between Cluster-Based and Periodic Approaches

Titanium dioxide (TiO2) has been extensively studied as a suitable material for a wide range of fields including catalysis and sensing. For example, TiO2-based nanoparticles are active in the catalytic conversion of glucose into value-added chemicals, while the good biocompatibility of titania allows for its application in innovative biosensing devices for glucose detection. A key process for efficient and selective biosensors and catalysts is the interaction and binding mode between the analyte and the sensor/catalyst surface. The relevant features regard both the molecular recognition event and its effects on the nanoparticle electronic structure. In this work, we address both these features by combining two first-principles methods based on periodic boundary conditions and cluster approaches (CAs). While the former allows for the investigation of extended materials and surfaces, CAs focus only on a local region of the surface but allow for using hybrid functionals with low computational cost, leading to a highly accurate description of electronic properties. Moreover, the CA is suitable for the study of reaction mechanisms and charged systems, which can be cumbersome with PBC. Here, a direct and detailed comparison of the two computational methodologies is applied for the investigation of d-glucose on the TiO2 (100) anatase surface. As an alternative to the commonly used PBC calculations, the CA is successfully exploited to characterize the formation of surface and subsurface oxygen vacancies and to determine their decisive role in d-glucose adsorption. The results of such direct comparison allow for the selection of an efficient, finite-size structural model that is suitable for future investigations of biosensor electrocatalytic processes and biomass conversion catalysis.</p

Elucidation of single atom catalysts for energy and sustainable chemical production: Synthesis, characterization and frontier science

The emergence of single atom sites as a frontier research area in catalysis has sparked extensive academic and industrial interest, especially for energy, environmental and chemicals production processes. Single atom catalysts (SACs) have shown remarkable performance in a variety of catalytic reactions, demonstrating high selectivity to the products of interest, long lifespan, high stability and more importantly high atomic metal utilization efficiency. In this review, we unveil in depth insights on development and achievements of SACs, including (a) Chronological progress on SACs development, (b) Recent advances in SACs synthesis, (c) Spatial and temporal SACs characterization techniques, (d) Application of SACs in different energy and chemical production, (e) Environmental and economic aspects of SACs, and (f) Current challenges, promising ideas and future prospects for SACs. On a whole, this review serves to enlighten scientists and engineers in developing fundamental catalytic understanding that can be applied into the future, both for academia or valorizing chemical processes

Prevalenza e profili di antimicrobicoresistenza in Salmonella spp isolata da alimenti nel triennio 2019-2021

Summary Salmonella spp. is among the most frequent causes of foodborne diseases, and the increasing occurrence of MDR strains is an additional cause for concern. In the three-year period 2019-2021, we collected Salmonella spp. strains isolated from different food categories analyzed in the context of Regulation (EC) No 2073/2005, to assess their antibiotic susceptibility profile and ESBLs production. To determine the susceptibility profile and identify MDR strains, we performed the Kirby-Bauer method by testing 17 antibiotics belonging to different classes, moreover the double disc test therefore allowed us to evaluate ESBL production. Phenotypic tests showed that 36/67 strains are MDR and 53% of these are ESBLs producers. Our results confirmed the prevalence of S. Infantis MDR and ESBL producer in chicken meat, and that further studies on the prevalence of food-borne MDR strains are needed, especially from a One Health perspective. Introduzione: Salmonella spp. è comunemente causa di infezioni gastrointestinali e di focolai di origine alimentare nell’uomo. La principale via di infezione è l'ingestione di cibo o acqua contaminati e S. Enteritidis, S. Typhimurium, S. Typhimurium monofasica, S. Infantis e S. Derby rappresentano sono i cinque sierotipi più comunemente coinvolti nelle infezioni umane. Nell'UE, i controlli microbiologici sugli alimenti effettuati nel contesto del regolamento (CE) n. 2073/2005 hanno rilevato le percentuali più elevate di campioni positivi alla salmonella nei prodotti a base di uova, carne di pollame e prodotti a base di pollame, che risultano essere le maggiori fonti di trasmissione di Salmonella spp. per l'uomo [2]. L'uso eccessivo di antibiotici ha contribuito alla selezione di ceppi di Salmonella MDR (Multi Drug Resistant), resistenti a tre o più classi di antibiotici [3]. La diffusione di Salmonella MDR rappresenta un problema sanitario rilevante, in quanto causa ospedalizzazioni più lunghe, malattie prolungate e tassi di mortalità più elevati [7, 5]. Inoltre il meccanismo di resistenza è potenziato dalla presenza di beta-lattamasi a spettro esteso (ESBL), in grado di idrolizzare penicilline e cefalosporine di prima, seconda e terza generazione. Lo scopo di questo studio è stato quello di individuare i sierotipi di Salmonella spp. presenti in diverse matrici alimentari analizzate nel contesto del regolamento (CE) n. 2073/2005 [2] con particolare riguardo alla diffusione di Salmonella MDR produttore di ESBL. Materiali e metodi: Da gennaio 2019 a dicembre 2021 sono stati analizzati 145 carni di pollame, 106 di maiale, 54 di manzo, 109 molluschi bivalvi, 43 uova e 36 semi germogliati, per un totale di 493 matrici alimentari. L’isolamento di Salmonella spp è stato eseguito secondo la norma ISO 6579-1:2017, i ceppi sono stati identificati mediante saggi biochimici- enzimatici e sierotipizzazione, secondo lo schema Kauffmann - White - Le Minor [6]. Il fenotipo di suscettibilità agli antibiotici è stato determinato mediante il metodo Kirby-Bauer, testando 17 antibiotici appartenenti a 6 classi differenti. L'interpretazione delle zone di inibizione e la classificazione degli isolati come sensibili (S), intermedi (I) o resistenti (R) sono state effettuate secondo le linee guida CLSI [1]. Su 36 ceppi è stata testata la produzione di ESBL mediante Double Disk test (DDT), secondo le linee guida EUCAST [4] e su 19 dei ceppi testati è stata effettuata la caratterizzazione molecolare in PCR per la ricerca dei geni beta-lattamasi produttori. Risultati: Nel triennio 2019-2021, sul totale delle matrici alimentari esaminate, sono stati isolati 67 ceppi di Salmonella spp. (15/172 nel 2019, 17/132 nel 2020 e 35/189 nel 2021); inoltre, nel triennio considerato, sono state riscontrate le seguenti percentuali di isolamento (Figura 1): carne di pollame (40%, 52,9% e 71,4%), carne di maiale (20%, 23,5% e 5,7%), carne bovina (2,9% soltanto nel 2021), molluschi bivalvi (26,7% nel 2020 e 8,6% nel 2021), uova (11,8% soltanto nel 2020) e semi germogliati (13,3%, 11,8%, 11,4%). Tra i vari sierotipi isolati, S. Infantis è stato quello predominante (48%), isolato in 32 campioni di carne di pollame; i sierotipi di S. Typhimurium (9%), S. Derby (6%) e S. Enteritidis (3%) hanno mostrato una bassa prevalenza (Figura 2). Riguardo i profili di antimicrobicoresistenza, 43/67 ceppi testati sono risultati resistenti ad almeno un antibiotico, con percentuali del 31,3% alla kanamicina, 43,2% alle sulfonamidi, 47,7% all'acido nalidixico, 49,2% all'ampicillina e 50,7% alla tetraciclina. Pochi ceppi sono risultati resistenti a levofloxacina (5%) e cloramfenicolo (6%); tutti sono risultati sensibili a imipenem, ciprofloxacina ed enrofloxacina. Un profilo MDR è stato trovato in 36/67 ceppi (54%), che hanno mostrato resistenza a tre (n=4), quattro (n=22) e cinque (n=10) classi di antibiotici. I profili MDR più frequenti sono stati: R ad aminoglicosidi, beta-lattamici, chinolonici, sulfamidici e tetracicline (in 8 S. Infantis, 1 S. Salamae e 1 S. Kentucky) e R a beta-lattamici, chinolonici, sulfamidici e tetracicline (in 9 S. Infantis e 1 S. Cerro). Il DDT ha consentito di rilevare la produzione di ESBL in 19/36 ceppi MDR (53 %) (Figura 3). Tale risultato fenotipico è stato confermato rilevando in tutti i ceppi la presenza dei geni beta-lattamasi risultati, con maggiore frequenza, blaSHV (68.4%) e blaCTX- M (47.3%) Conclusioni: I nostri dati evidenziano come sia elevato il rischio di infezione da Salmonella MDR, in particolare produttore di ESBL, per i consumatori; inoltre confermano quanto raccomandato dall’EFSA rispetto alla necessità di un monitoraggio efficace dell’AMR anche negli alimenti, soprattutto in un’ottica One Health, che riconosce la circolarità della salute umana, animale ed ambientale