Simone Meloni

Scalable processing of lead‐free perovskite‐inspired absorbers is often constrained by a fundamental trade‐off: the structural reconstruction needed to improve electronic dimensionality can simultaneously introduce anisotropic textures that hinder vertical charge extraction. Here we show that this trade‐off can be overcome in vacancy‐ordered antimony halides by coupling ultrasonic spray deposition with solvent‐ and halide‐mediated crystallization control. Using Cs ₃ Sb ₂ I ₉ –xCl _x as a model system, we developed an ambient‐air deposition process followed by annealing under an N ₂ /SbI ₃ atmosphere route based on an amide‐free 2‐methoxyethanol/butanol solvent mixture that yields compact, pinhole‐free films without high‐boiling amide solvents. Chloride incorporation directs annealing‐induced reconstruction from a zero‐dimensional dimeric phase to a layered polymorph, while grazing‐incidence wide‐angle X‐ray scattering reveals that this transformation occurs without generating a strongly detrimental crystallographic texture. Transient absorption spectroscopy further shows suppressed self‐trapping and longer‐lived band‐edge carriers after dimensional reconstruction. As a result, the layered absorber retains an effective out‐of‐plane transport component and enables indoor photovoltaic (iPV) efficiencies up to 6.9% at 1000 lux (6500 K). Our results identify a general route by which scalable spray processing can be used not only to deposit lead‐free absorbers, but also to engineer phase evolution and transport‐relevant texture for efficient vertical optoelectronic operation.

Solid–liquid triboelectric generation is a widespread phenomenon relevant for many natural and technological processes. In particular, solid–liquid triboelectric nanogenerators (TENGs) are an emerging approach for sensing and harvesting dispersed mechanical energy and converting it into electrical power. Triboelectric energy generation relies on charge transfer during contact and separation of different materials, combined with electrostatic induction. Compared with conventional sliding, immersion, or pressing modes, the intrusion–extrusion of liquids into and out of hydrophobic nanopores offers promising advantages, including an enlarged effective contact area and the potential for device miniaturization. However, when water is used as the working liquid, limited charge mobility and weak polarization result in low electrical output. To address these limitations, nanofluids represent a promising alternative. In this work, we investigate how minor concentrations of gold nanoparticles affect triboelectrification during water intrusion–extrusion into-from hydrophobic nanoporous silica. The introduction of gold nanoparticles leads to enhanced triboelectrification and an unexpected reversal of the triboelectric peak polarity. The experimental results indicate that nanoparticle size plays a significant role in determining the electrical response. This approach highlights new opportunities for tuning intrusion–extrusion TENG (IE-TENG) performance and may contribute to the development of advanced sensing and energy-harvesting devices.

Solid–liquid contact electrification is widely studied using diverse experimental geometries that are often implicitly assumed to probe equivalent interfacial processes. Here, we directly test this assumption by comparing immersion–emersion, droplet-based contact, and pressure-driven intrusion–extrusion electrification using the same hydrophobic nanoporous silicon monolith and isotopically substituted liquids (H2O and D2O). Despite identical surface chemistry, isotopic substitution produces qualitatively different electrical responses depending on the wetting regime. Immersion–emersion experiments show polarity inversion between H2O and D2O, while droplet measurements reveal distinct charge evolution and periodic opposite-polarity events. In contrast, forced nanopore intrusion preserves polarity but strongly enhances electrical output for D2O. These results demonstrate that wetting of surface nanoroughness during droplet, vs immersion–emersion, vs complete nanopores wetting upon intrusion–extrusion correspond to fundamentally different electrification states. By using isotope substitution as a controlled probe, this work establishes a general framework for disentangling protocol-dependent effects in solid–liquid contact electrification and triboelectric energy conversion.

Metal–organic frameworks have been intensively investigated for their ability to effectively control the growth and surface chemistry of nanosized guests, with their pores acting as templates and potentially providing anchoring sites. Since the speciation, as determined by the geometry and surface chemistry of hydride-forming metals, such as Pd, under particular conditions (T, p), is controlled by their size at and beyond the nanoscale, metal–organic frameworks are a prospective matrix for speciation or phase selection. This is of relevance because the role and characteristics of the phases in hydrogenation reactions involving hydride-forming Pd catalysts are open questions. In particular, it is a matter of debate which palladium phase is the most active and most selective, as they often occur simultaneously under catalytic conditions. For the first time, our thorough investigation, including operando XAFS and computer simulations, demonstrates that by embedding Pd nanoclusters, ≤1 nm in diameter, in the pores of the NH₂–UiO-66 metal–organic framework, the speciation of subnanometric Pd particles can be controlled, such that the active particles only exist in their metallic state under reaction conditions; in fact, the Pd–H₂ mixture only affords surface-bound hydrogen atoms. This control of Pd speciation consequently enables the direct probing of the phase activity and selectivity in the model reaction of 1,3-butadiene hydrogenation to butenes, wherein it showed no deactivation and improved selectivity compared to conventionally prepared catalytic systems. This result shows that the metallic phase can be stabilized through subnanometric size control and that it is more selective and less prone to overhydrogenating the butadiene reactant to butane, resulting in a purer product.

Solid–liquid–gas three-phase systems are central to chemistry, biology, physics, engineering, and even botany. Representative examples range from gas-evolving reactions at (photo)electrodes to hydrophobic interactions between proteins. Although these processes occur on the nanoscale, they are often interpreted using empirical principles extrapolated from macroscopic laws. Here we show, by means of atomistic simulations, that regularly distributed atomic- or molecular-scale chemical heterogeneities can give rise to counterintuitive behavior: the contact angle of an heterogeneous hydrophobic surface is maximized when the surface is decorated with a ∼20% atomic-level hydrophilic particle (with fixed interaction force). Similarly, a maximum in the contact angle is observed, at fixed hydrophilic particles geometry, when the difference in interaction force between the hydrophobic and hydrophilic spots is Δ ∼ 40%. We demonstrate that such atomistic-level heterogeneities can pin the solid–liquid–gas contact line. These findings have several implications. First, they rationalize the high hydrophobicity of materials that nonetheless contain a significant fraction of hydrophilic sites, Cu₂(tebpz), a metal–organic framework whose pores host Cu nodes, being a notable example. Second, if our results are experimentally confirmed for more general, nonregularly patterned surfaces, they will add a new evidence for the need of overcome the asymptotic homogenization, widely used for describe heterogeneous surfaces from individual component, such as protein surfaces with amino-acid hydrophobicity scales or nanoporous materials.

The wetting behavior of hydrophobic nanoporous materials plays a pivotal role in advanced technologies such as energy storage, molecular separations, catalysis, and biomimetic systems. A central challenge in employing these materials is the precise control of wetting (intrusion) and dewetting (extrusion) pressures. To address this, we investigated how varying the concentration of organic linkers in ZIF-7-8 (composed of Zn-methylimidazole and benzimidazole) influences the intrusion-extrusion behavior of water within its micropores. Remarkably, we noticed that even a minor substitution of organic linkers (below 3%) led to significant and systematic changes in the wetting properties. Owing to the small fraction of substituted linkers, such effect could not be explained by classical models that consider individual cages. To elucidate this phenomenon, we combined experiments with molecular dynamics simulations and stochastic modeling of the crystallites. Our results reveal that the introduction of alien linkers perturbs the hydrogen-bond network, thereby disrupting the cooperative effects fundamental to the intrusion-extrusion process.

The mesoscopic‐level formation mechanism of carbon nanotube growth, particularly the transition from a graphene patch to a tube, remains unclear. Recent studies have focused on finding a complete description of this phenomenon to understand its origin and to have total control over the formation of carbon nanotubes. In this study, a thermodynamic model is proposed that follows the sharp interface model approach, in which all energy contributions to the total energy of the nanotube are identified as bulk or surface terms. This study proposes an additive model to calculate the total energy of these structures and identify the dominant energy contributions that determine whether the adsorbed carbon atoms form a growing cap on the catalyst nanoparticle or initiate a new carbon nanotube perpendicular to the surface. By comparing the total energy of these two mechanisms, the research aims to elucidate the energetic driving force behind each pathway for optimizing future nanotube growth processes. We also discuss the generality of the model introduced in this article, showing how it can incorporate temperature and disorder effects, thereby enabling the description of both vapor‐solid‐solid and vapor‐liquid‐solid mechanisms of carbon nanotube formation at relevant operating conditions. Finally, we outline a strategy for a genuine multiscale framework that combines the microscopic, atomistic picture of carbon nanotube formation with a meso/macroscopic nucleation and growth representation based on a sharp‐interface model.

This roadmap provides a comprehensive overview of the latest advancements in lead-free perovskite materials for photovoltaic and photoelectrochemical /photocatalytic applications. It highlights the urgent need for sustainable energy solutions, emphasizing the role of lead-free perovskites in addressing challenges related to toxicity, scalability, and efficiency. The roadmap is designed to guide the reader from application-driven perspectives to fundamental materials insights, characterization techniques, fabrication strategies and overreaching sustainability considerations. The document explores key material families, including tin-, bismuth-, antimony-, and copper-based perovskites, detailing their optoelectronic properties, fabrication techniques, and application potential. Special attention is given to advanced characterization methods, green processing strategies, the integration of artificial intelligence and machine learning for material design and optimization and lifecycle impact assessments to ensure environmental sustainability. By bringing together insights from global research communities, this roadmap serves as a strategic guide for advancing lead-free perovskite technology, fostering interdisciplinary collaboration, and accelerating the transition to next-generation solar energy solutions.

The wetting–dewetting of liquids in nanoporous solids is central to nanofluidics, separation, and energy storage, yet its temperature dependence under extreme conditions remains poorly understood. Here, we investigate water intrusion–extrusion in ordered mesoporous silica (SBA-15) functionalized with octyl groups (SBA-15-C8) across 25–250 °C and compare it with hydrophobized silica of disordered porosity. Intrusion pressures in both systems follow the expected negative temperature dependence described by classical capillarity. In contrast, extrusion pressures reveal a striking topology-temperature interplay. Up to 175 °C, SBA-15-C8 releases water at near-ambient pressure, unlike its disordered counterpart. Above 200 °C, however, extrusion from ordered pores converges to the high-pressure behavior of disordered silica, indicating a loss of topological distinction. Atomistic simulations suggest that this transition originates from thermally induced restructuring of the grafted layer: chain stretching effectively narrows the pores and may induce a Cassie–Baxter-like state, enhancing hydrophobicity and facilitating vapor nucleation. These findings demonstrate that pore topology ceases to govern extrusion at elevated temperatures, instead being dictated by a temperature-driven surface reconfiguration. The results contribute to a fundamental understanding of capillarity under extreme confinement and open opportunities for exploiting high-temperature wetting/dewetting in energy conversion, damping, and thermal management technologies.