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One-pot three-component regioselective azide-alkyne cycloadditions are central reactions for synthesizing pharmaceuticals and fine chemicals and are also applied for in vivo metabolic labeling biotechnology. Homogeneous catalysts based on copper species coordinated with ancillary ligands are regularly used to perform this reaction, offering superior catalytic activity and selectivity compared to conventional heterogeneous counterparts based on supported copper nanoparticles. However, the challenge of catalyst recovery limits the use of these homogeneous compounds in many large-scale applications. In this work, we report the high catalytic performance of a family of Cu-based single-atom catalysts for triazole synthesis, with an emphasis on the fundamental understanding of the structure and function of the catalyst. The catalysts were prepared via tricyanomethanide polymerization to create a joint electronic structure where the mesoporous graphitic carbon nitride carrier acts as a ligand for the atomically dispersed copper species. The material properties and the precise metal location/coordination (i.e., deposited in the heptazine pore of carbon nitride, substituted in the framework of carbon nitride, hosted in a vacancy, or entrapped in sandwich-like arrangement) were characterized through a battery of spectroscopic and theoretical methods. The catalysts were employed in the synthesis of 1,2,3-triazoles employing azide-alkyne click reaction under base-free conditions. The single-atom Cu catalysts demonstrated improved activity and selectivity compared to the homogeneous reference catalyst. Density functional theory calculations corroborated the results and showed that the reaction proceeds through a barrier given by the activation of the acetylenic moiety on Cu1. The activity of this step was primarily affected by the coordination of the metal with the support. Therefore, understanding the metal coordination in single-atom catalysts is critical to further optimizing

Unraveling structure–activity relationships is a key objective of catalysis. Unfortunately, the intrinsic complexity and structural heterogeneity of materials stand in the way of this goal, mainly because the activity measurements are area-averaged and therefore contain information coming from different surface sites. This limitation can be surpassed by the analysis of the noise in the current of electrochemical scanning tunneling microscopy (EC-STM). Herein, we apply this strategy to investigate the catalytic activity toward the hydrogen evolution reaction of monolayer films of MoSe₂. Thanks to atomically resolved potentiodynamic experiments, we can evaluate individually the catalytic activity of the MoSe₂ basal plane, selenium vacancies, and different point defects produced by the intersections of metallic twin boundaries. The activity trend deduced by EC-STM is independently confirmed by density functional theory calculations, which also indicate that, on the metallic twin boundary crossings, the hydrogen adsorption energy is almost thermoneutral. The micro- and macroscopic measurements are combined to extract the turnover frequency of different sites, obtaining for the most active ones a value of 30 s⁻¹ at −136 mV vs RHE.

The development of catalysts for the hydrogen evolution reaction is pivotal for the hydrogen economy. Thin iron films covered with monolayer graphene exhibit outstanding catalytic activity, surpassing even that of platinum, as demonstrated by a method based on evaluating the noise in the tunnelling current of electrochemical scanning tunnelling microscopy. Using this approach, we mapped with atomic-scale precision the electrochemical activity of the graphene–iron interface, and determined that single iron atoms trapped within carbon vacancies and curved graphene areas on step edges are exceptionally active. Density functional theory calculations confirmed the sequence of activity obtained experimentally. This work exemplifies the potential of electrochemical scanning tunnelling microscopy as the only technique able to determine both the atomic structure and relative catalytic performance of atomically well-defined sites in electrochemical operando conditions and provides a detailed rationale for the design of novel catalysts based on cheap and abundant metals such as iron. [Figure not available: see fulltext.].

Mixed solid system involving cerium and zirconium titanate (ZrTiO4) have been prepared using the sol-gel technique. Both X-ray diffraction and DFT calculations firmly indicate that, till a doping level of 10 mol%, cerium ions are dissolved in the titanate matrix (which has the scrutynite structure, analogous to those of the main TiO2 polymorphs) occupying the cationic sites and progressively altering its cell parameters. Cerium is hosted in the matrix both in the form of Ce4+ and Ce3+ ions (XPS results). The trivalent state seems to be favoured even though the state of the dopant depends on the treatment undergone by the material. DFT calculations describe the intra-band gap states formed in both cases and the strong localisation of the single electron in the case of Ce3+ (4f1). Differently from the case of Ce doped ZrO2, that shows photoactivity in the visible light because of the presence of cerium, the doped titanate is inactive in the same conditions. Under UV–vis illumination charge separation occurs (EPR results) and the low-loading doped systems (0.5%, 1%) form OH radicals, detected by spin trapping, more efficiently than the pristine matrix. The absence of photoactivity in the visible range is interpreted in terms of the detrimental role (charge recombination) played by both the occupied intra-band gap states associated to Ce3+ and the corresponding oxygen vacancies formed in the lattice by charge compensation.

Graphene-h-BN hybrid nanostructures are grown in one step on the Pt(111) surface by ultra-high vacuum chemical vapor deposition using a single precursor, the dimethylamino borane complex. By varying the deposition conditions, different nanostructures ranging from a fully continuous hybrid monolayer to well-separated Janus nanodots can be obtained. The growth starts with heterogeneous nucleation on morphological defects such as Pt step edges and proceeds by the addition of small clusters formed by the decomposition of the dimethylamino borane complex. Scanning tunneling microscopy measurements indicate that a sharp zigzag in-plane boundary is formed when graphene grows aligned with the Pt substrate and consequently with the h-BN layer as well. When graphene is rotated by 30°, the graphene armchair edges are seamlessly connected to h-BN zigzag edges. This is confirmed by a thorough density functional theory (DFT) study. Angle resolved photoemission spectroscopy (ARPES) data suggests that both h-BN and graphene present the typical electronic structure of self-standing non-interacting materials.[Figure not available: see fulltext.].

Il benessere psicologico è un costrutto multidimensionale che secondo il modello di Ryff è composto dalle seguenti componenti: autoaccettazione, relazioni interpersonali positive, autonomia, controllo ambientale, crescita personale e scopo nella vita. Sono molti gli studi che in letteratura hanno studiato il benessere in soggetti anziani; tuttavia, non sono molti quelli che lo hanno messo in relazione esplicitamente con variabili cognitive e con i livelli di riserva cognitiva. Il presente contributo vuole quindi esporre i risultati preliminari di una ricerca correlazionale multicentrica, che ha avuto come scopo principale quello di indagare le possibili relazioni tra queste variabili, in un campione di 59 soggetti anziani (età: M = 72,8 ± 7, scolarità M = 9,86 ± 4,42). I risultati preliminari hanno messo in evidenza come livelli più elevati di abilità cognitive globali (MoCA, Montreal Cognitive Assessment) e di abilità attentivo-esecutive (Trail Making Test, Stroop Test), correlano con più elevati punteggi alla scala di crescita personale (PWB, Psychological Wellbeing Scale). Inoltre, è interessante notare come diverse sottoscale della PWB (i.e. crescita personale, scopo nella vita e crescita personale) siano positivamente correlate in modo specifico con la sottoscala di tempo libero del test di riserva cognitiva. Questi dati sembrano suggerire come, sia l’efficienza cognitiva, che la riserva cognitiva, soprattutto nelle sue componenti “modificabili” di tempo libero, possano avere un significativo ruolo sul benessere percepito dai soggetti anziani. Questo potrebbe avere importanti implicazioni pratiche soprattutto per quanto riguarda la progettazione di interventi di promozione di un invecchiamento attivo e di successo.

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We have investigated the electronic response of single crystals of indium selenide by means of angle-resolved photoemission spectroscopy, electron energy loss spectroscopy and density functional theory. The loss spectrum of indium selenide shows the direct free exciton at ~1.3 eV and several other peaks, which do not exhibit dispersion with the momentum. The joint analysis of the experimental band structure and the density of states indicates that spectral features in the loss function are strictly related to single-particle transitions. These excitations cannot be considered as fully coherent plasmons and they are damped even in the optical limit, i.e. for small momenta. The comparison of the calculated symmetry-projected density of states with electron energy loss spectra enables the assignment of the spectral features to transitions between specific electronic states. Furthermore, the effects of ambient gases on the band structure and on the loss function have been probed.

By means of a combination of surface-science spectroscopies and theory, we investigate 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 evaluate 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 show 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.

Dibromotetracene molecules are deposited on the Cu(110) surface at room temperature. The complex evolution of this system has been monitored at different temperatures (i.e., 298, 523, 673, and 723 K) by means of a variety of complementary techniques that range from STM and temperature-programmed desorption (TPD) to high-resolution X-ray spectroscopy (XPS) and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). State-of-the-art density-functional calculations were used to determine the chemical processes that take place on the surface. After deposition at room temperature, the organic molecules are transformed into organometallic monomers through debromination and carbon-radical binding to copper adatoms. Organometallic dimers, trimers, or small oligomers, which present copper-bridged molecules, are formed by increasing the temperature. Surprisingly, further heating to 673 K causes the formation of elongated chains along the Cu(110) close-packed rows as a consequence of radical-site migration to the thermodynamically more stable molecule heads. Finally, massive dehydrogenation occurs at the highest temperature followed by ring condensation to nanographenic patches. This study is a paradigmatic example of how intermolecular coupling can be modulated by the stepwise control of a simple parameter, such as temperature, through a sequence of domino reactions.

Graphene and h-BN are grown by chemical vapor deposition in ultra high vacuum conditions on the Pt(110) surface. Scanning tunneling microscopy measurements and low-energy electron diffraction data indicate that graphene forms a variety of differently oriented incommensurate domains although with a strong preference to align its [1120] direction with the [001] direction of Pt. Meanwhile, h-BN exhibits a c(8 × 10) commensurate superstructure, which presents a high level of defectivity that implies local variation of the periodicity (i.e. mixed c(8 × 10) and c(8 × 12) patches) and the introduction of local defects. The combination of advanced photoemission spectroscopy data (angle-resolved photoemission spectroscopy from the valence band) and ab initio calculations indicates that both 2D materials interact weakly with the substrate: graphene exhibits neutral doping and is morphologically flat, even if it nucleates on the relatively highly corrugated rectangular (110) surface. In the case of h-BN, the interaction is slightly stronger and is characterized by a small electron transfer from surface Pt atoms to nitrogen atoms. The (110) termination of Pt is therefore a quite interesting surface for the growth of 2D materials because given its low symmetry, it may favor the growth of selectively oriented domains but does not affect their pristine electronic properties.