Félix Gregorio Requejo

The role of ligand–metal complexes in directing nanostructure growth is widely documented for thiolates. By contrast, the importance of Au‐amine intermediate complexes remains less systematically investigated despite the widespread use of amines, particularly oleylamine (OAm), in nanowire synthesis. Combining SAXS, XAS, and photoluminescence analysis, we demonstrate the early formation of gold complexes featuring an Au(III) center coordinated by four N atoms from OAm which rapidly assemble into disc‐shaped gold supramolecular clusters (Au SCs) (∼3 nm in diameter) with long‐range Au···Au correlations, stable for at least 48 h in the absence of a reducing agent. As Au(III) is progressively reduced to Au(I), the gold centers form linear complexes coordinated by two N atoms and the clusters become strongly luminescent, consistent with the development of aurophilic interactions. Adding triisopropylsilane accelerates reduction to Au(0) and reinforces anisotropic interactions, promoting the directional stacking of the disc‐shaped supramolecular clusters into ultrathin gold nanowires (∼1.6 nm in diameter). This framework establishes a distinct pathway from the thiolate archetype, highlighting the critical role of amine ligation in governing precursor persistence and wire‐like morphology. Beyond their mechanistic significance, the luminescent properties of these Au SCs suggest their use as functional materials in their own right.

In this study, we report the development of an efficient electrochemical synthesis route for Cu clusters that significantly reduces the formation of deleterious Cu ions during preparation. This breakthrough enabled the controlled production of five‐atom copper clusters (Cu ₅ ), which, when supported on TiO ₂ , exhibit superior catalytic activity compared to previously reported Cu‐based catalysts. Notably, Cu ₅ /TiO ₂ achieves 100% selectivity toward CH ₄ at temperatures as low as 300 °C, with a remarkably low activation energy of 19 kJ·mol ⁻¹ . Operando X‐ray absorption spectroscopy revealed that the reduction in the copper oxidation state during the reaction is due to reversible interactions with hydrogen molecules and CO ₂ in a 4:1 ratio. These results are consistent with DFT calculations of the intrinsic activity of the Cu ₅ cluster, which indicate that CO ₂ methanation may proceed through both methoxide‐ and methylene‐mediated pathways. However, the methoxide route is predicted to be significantly more stable and energetically more favorable than the methylene route, suggesting a mechanistic preference for methoxide‐mediated CH ₄ formation. These insights account for the outstanding catalytic performance of Cu ₅ /TiO ₂ and, combined with the high thermal stability previously reported for Cu ₅ clusters, highlight their great potential as efficient catalysts for industrial CO ₂ ‐to‐CH ₄ conversion.

Graphene oxide has been widely deployed in electricalsensors formonitoring physical, chemical, and biological processes. The presenceof abundant oxygen functional groups makes it an ideal substrate forintegrating biological functional units to assemblies. However, theintroduction of this type of defects on the surface of graphene hasa deleterious effect on its electrical properties. Therefore, adjustingthe surface chemistry of graphene oxide is of utmost relevance foraddressing the immobilization of biomolecules, while preserving itselectrochemical integrity. Herein, we describe the direct immobilizationof glucose oxidase onto graphene oxide-based electrodes prepared byLangmuir-Blodgett assembly. Electrochemical reduction of grapheneoxide allowed to control its surface chemistry and, by this, regulatethe nature and density of binding sites for the enzyme and the overallresponsiveness of the Langmuir-Blodgett biofilm. X-ray photoelectronspectroscopy, surface plasmon resonance, and electrochemical measurementswere used to characterize the compositional and functional featuresof these biointerfaces. Covalent binding between amine groups on glucoseoxidase and epoxy and carbonyl groups on the surface of graphene oxidewas successfully used to build up stable and active enzymatic assemblies.This approach constitutes a simple, quick, and efficient route tolocally address functional proteins at interfaces without the needfor additives or complex modifiers to direct the adsorption process.

Sub‐nanometer metal clusters have special physical and chemical properties, significantly different from those of nanoparticles. However, there is a major concern about their thermal stability and susceptibility to oxidation. In situ X‐ray Absorption spectroscopy and Near Ambient Pressure X‐ray Photoelectron spectroscopy results reveal that supported Cu₅ clusters are resistant to irreversible oxidation at least up to 773 K, even in the presence of 0.15 mbar of oxygen. These experimental findings can be formally described by a theoretical model which combines dispersion‐corrected DFT and first principles thermochemistry revealing that most of the adsorbed O₂ molecules are transformed into superoxo and peroxo species by an interplay of collective charge transfer within the network of Cu atoms and large amplitude “breathing” motions. A chemical phase diagram for Cu oxidation states of the Cu₅‐oxygen system is presented, clearly different from the already known bulk and nano‐structured chemistry of Cu.

Subnanometer-sized metal clusters often feature a molecule-like electronic structure, which makes their physical and chemical properties significantly different from those of nanoparticles and bulk material. Considering potential applications, there is a major concern about their thermal stability and susceptibility towards oxidation. Cu clusters of only 5 atoms (Cu5 clusters) are first synthesized in high concentration using a new-generation wet chemical method. Next, it is shown that, contrary to what is currently assumed, Cu5 clusters display nobility, beyond resistance to irreversible oxidation, at a broad range of temperatures and oxygen pressures. The outstanding nobility arises from an unusual reversible oxidation which is observed by in situ X-ray Absorption Spectroscopy and X-ray Photoelectron Spectroscopy on Cu5 clusters deposited onto highly oriented pyrolitic graphite at different oxygen pressures and up to 773 K. This atypical property is explained by a theoretical approach combining different state-of-the-art first principles theories. It reveals the essential role of collective quantum effects in the physical mechanism responsible for the nobility of Cu5 clusters, encompassing a structural ‘breathing’ through concerted Cu–Cu elongations/contractions upon O2 uptake/release, and collective charge transfer as well. A predictive phase diagram of their reversible oxidation states is also delivered, agreeing with the experimental observations. The collective quantum effects responsible of the observed nobility are expected to be general in subnanometer-sized metal clusters, pushing this new generation of materials to an upper level.

Co‐ and Ni‐based layered hydroxides constitute a unique class of two‐dimensional inorganic materials with exceptional chemical diversity, physicochemical properties and outstanding performance as supercapacitors and overall water splitting catalysts. Recently, the occurrence of Co(III) in these phases has been proposed as a key factor that enhance their electrochemical performance. However, the origin of this centers and control over its contents remains as an open question. We employed the Epoxide Route to synthesize a whole set of α‐NiCo layered hydroxides. The PXRD and XAS characterization alert about the occurrence of Co(III) as a consequence of the increment in the Ni content. DFT+U simulation suggest that the shortening of the Co−O distance promotes a structural distortion in the Co environments, resulting in a double degeneration in the octahedral Co 3d orbitals. Hence, a strong modification of the electronic properties leaves the system prone to oxidation, by the appearance of Co localized electronic states on the Fermi level. This work combines a microscopic interpretation supported by a multiscale crystallochemical analysis, regarding the so‐called synergistic redox behavior of Co and Ni, offering fundamental tools for the controllable design of highly efficient electroactive materials. To the best of our knowledge, this is the first computational–experimental investigation of the electronic and structural details of α‐NiCo hydroxides, laying the foundation for the fine tuning of electronic properties in layered hydroxides.

Ag₅-induced formation of surface polarons at the Ag₅–TiO₂ interface enables to reveal a general polarization phenomenon.