1,721,081 research outputs found
Solar-Driven Hydrogen Generation by Metal Halide Perovskites: Materials, Approaches, and Mechanistic View
No full textSolar-driven photocatalysis by metal halide perovskites (MHPs) is emerging as an exciting and promising field to promote several relevant catalytic reactions taking advantage of the superior optical properties of MHPs. Their electronic structure is suitable to run reduction reactions (H2 generation, CO2 reduction) and even oxidation reactions, in particualr for perovskites with higher band gap values, and further extends their possible use in the field of photochemical organic syntheses. This Mini-Review focuses on the application of MHPs in the solar-driven hydrogen generation with particular emphasis on the materials' design and mechanistic features involved in the catalytic reactions
Pianeta Varda
No full textFotografa, regista, scrittrice, disegnatrice, spettatrice, pensatrice... più semplicemente: artista. Difficile chiudere in una sola definizione il percorso di Agnès Varda (1928-2019), una figura chiave della cultura contemporanea, una narratrice instancabile che ha saputo utilizzare in modo sempre personale e spesso sorprendente tutte le forme della comunicazione audiovisiva, iniziando alla fine degli anni Quaranta con la fotografia per poi inaugurare, superati i settant’anni, una felice carriera di artista visuale. In mezzo, tanto cinema, di finzione e documentario, dagli anni Cinquanta, quando debutta nel lungometraggio con La pointe courte (1955), definito da André Bazin “un vero miracolo”, fino all’anno della sua scomparsa, quando presenta al Festival di Berlino Varda par Agnès (2019), un viaggio personale nella propria avventura di cineasta, ideale chiusura di un percorso autobiografico che occupa l’ultima parte della sua carriera. Il successo “nouvelle vague” di Cleo dalle 5 alle 7 (1961) è solo la prima tappa di un cammino in cui, nel corso di più di sei decenni, Varda ha attraversato stagioni molto diverse tra loro, segnate da importanti cambiamenti tecnologici, culturali e linguistici, sempre intuendo il modo più fecondo di continuare e, insieme, rinnovare il proprio percorso artistico. E, soprattutto, senza mai smarrire quella stupefazione per la vita, la realtà, i luoghi e le persone che segna in modo costante la sua produzione.
Attraverso ventidue parole chiave – da America a Memoria, da Voce a Spiagge, da Cinema a Donne, da Autoritratto a Parigi... – il libro compone un ritratto di Varda, scritto e visivo, il più possibile esauriente e, insieme, aperto, mobile, stratificato: un ritratto in grado di dare conto della costellazione di passioni, curiosità, incontri ed esperimenti attraverso i quali Agnès Varda ha raccontato la realtà e, insieme, se stessa. Un pianeta umanissimo e gioioso, di cui resta ancora molto da esplorare
Physical and chemical vapor deposition methods applied to all-inorganic metal halide perovskites
No full textThis review focuses on the physical and chemical vapor deposition methods applied to the preparation of all-inorganic metal halide perovskites. Particular emphasis is devoted to the specific characteristic of the available approaches explored in the current literature for lead-based and lead-free films with also examples of the preparation of microstructure and nanostructure for applications beyond perovskite solar cells. Main characteristics, device architectures, and pros and cons of exploited vapor deposition methods are highlighted, providing a guide for future research in the field of all-inorganic perovskite growth
Germanium-Based Halide Perovskites: Materials, Properties, and Applications
No full textPerovskites are attracting an increasing interest in the wide community of photovoltaics, optoelectronic, and detection, traditionally relying on lead-based systems. This Minireview provides an overview of the current status of experimental and computational results available on Ge-containing 3D and low-dimensional halide perovskites. While stability issues analogous to those of tin-based materials are present, some strategies to afford this problem in Ge metal halide perovskites (MHPs) for photovoltaics have already been identified and successfully employed, reaching efficiencies of solar devices greater than 7 % at up to 500 h of illumination. Interestingly, some Ge-containing MHPs showed promising nonlinear optical responses as well as quite broad emissions, which are worthy of further investigation starting from the basic materials chemistry perspective, where a large space for properties modulation through compositions/alloying/fnanostructuring is present
Pressure Effects on Lead-Free Metal Halide Perovskites: a Route to Design Optimized Materials for Photovoltaics
No full textMetal halide perovskites have drawn significant attention for their promising physical properties and their possible application in solar cells and light-emitting diodes. Research and technology have made extraordinary progress in this field, but some issues are still to be tackled. In fact, most of the used materials contain lead, which is highly toxic. For this reason, many efforts have been made on substituting lead with other elements to design more environmentally friendly solar cells. However, devices based on lead-free materials still show relatively low efficiencies. Physical properties tuning of such materials, to improve their performance, can be achieved in different ways, and among them pressure can be thought of as a green method for this aim as well as a powerful technique to systematically explore structure–property relationships. The possibility of unveiling and discovering novel and appealing optical and electronic features, resulting from the application of an external pressure, can open an effective route to design more performing materials
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
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