Daniel Arenas Esteban

Controlling the interplay between reduction and galvanic processes is critical for tailoring the structure and composition of multimetallic nanocrystals. Here, we report a synthetic strategy to produce anisotropic Au–Pd–Pt nanocrystals with tunable morphologies and elemental distributions. Platinum deposition on single-crystal Au@Pd nanorods (NRs) was modulated by varying the concentration of ascorbic acid, enabling control over the balance between reduction and galvanic-like processes. This approach yields distinct nanostructures, including nanoframes, cloud-like morphologies, and core–shell–shell architectures. Advanced electron microscopy, including high-resolution HAADF STEM imaging, EDX elemental mapping, and electron tomography, reveals intricate elemental distributions, the formation of cavities and tunnels, the apparent preservation of single-crystal characteristics in Au@Pd NRs under the explored conditions, and gold etching induced by the platinum precursor. A preliminary evaluation of catalytic activity suggests enhanced ethanol oxidation performance for nanoframe structures. These findings establish a versatile strategy for engineering anisotropic multimetallic nanocrystals through controlled redox interplay.

Generating hydrogen directly from seawater is an attractive feature for realizing large‐scale solar fuel production. Here, we present an effective photocatalyst design that not only considers solar light activity but also long‐term durability and optimized manufacturing costs. A series of stabilized bimetallic Au–Ag plasmonic “rainbow” nanoparticles were synthesized and grafted at low loadings onto TiO ₂ substrates, yielding strong visible‐light absorption and enhanced photocatalytic activity. To address the intrinsic instability of (plasmonic) metal nanoparticles in saline environments, two encapsulation strategies were investigated: insulating layer‐by‐layer (LbL) polyelectrolyte shells and conductive polyaniline (PANI) shells formed via in situ polymerization. In simulated seawater, a maximum H ₂ evolution rate of 348 ± 108 µmol g ⁻¹ h ⁻¹ was achieved for TiO ₂ + 2 wt% “rainbow” PANI‐stabilized nanoparticles. PANI‐stabilized plasmonic catalysts outperformed both bare and LbL‐coated samples while maintaining full activity even after 1 month of storage in the dark in simulated seawater. These results demonstrate that conductive polymer encapsulation effectively preserves plasmonic activity even in harsh media, offering a prospect toward durable and economically viable solar hydrogen production from simulated seawater.

This work describes the synthesis of ordered 3D siloxane-silsesquioxane reticular materials with silicate D4R cubes (Si₈O₂₀⁸⁻), harvested from a sacrificial tetrabutylammonium cyclosilicate hydrate (TBA-CySH) precursor, interlinked with octyl and dicyclopentyl (Cp₂) hydrocarbon functionalities in a one-step synthesis with organodichlorosilanes. Advanced solid-state NMR spectroscopy allowed us to unravel the molecular order of the nodes and their interconnection by the silicone linkers. In the case of octyl-methyl silicone linkers, changing the silane-to-silicate ratio in the synthesis allowed for tuning the length of the linker between the nodes. With dicyclopentyl linkers, the addition of dimethyldichlorosilane was essential to enable the formation of a reticular network. The resulting materials contained mixed, dimeric silicone linkers, i.e., Si₈-O-Si(Me₂)-O-Si(Cp₂)-O-Si₈.

InP/ZnSe/ZnS core/shell/shell quantum dots are the most investigated quantum dot material for commercial applications involving visible light emission. The inner InP/ZnSe interface is complex since it is not charge balanced, and the InP surface is prone to oxidation. The role of oxidative defects at this interface has remained a topic of debate, with conflicting reports of both detrimental and beneficial effects on the quantum dot properties. In this study we probe the structure of the InP/ZnSe interface at the atomic level using ³¹P, ⁷⁷Se and ¹⁷O ssNMR and HAADF-STEM. We observe clear differences in Se NMR spectra and crystal orientation of core and shell when the InP/ZnSe is oxidized on purpose. High levels of interface oxidation result in an amorphous phosphate layer at the interface, which inhibits epitaxial growth of the ZnSe shell.

Local and high-resolution structural investigation of metal–organic frameworks (MOFs) is essential for understanding the role of defects and incorporated elements. In this paper, we characterize the structure of metalated versions of (Hf)PCN-222(H₂) and locate the position of the additional metal atoms. Transmission electron microscopy (TEM) is a powerful technique for this purpose, but MOFs are highly sensitive to the electron beam. To avoid structural alterations, it is therefore crucial to establish the maximum electron dose that can be applied. In this study, we apply a systematic workflow to measure the critical electron dose, enabling the identification of the optimal technique for extracting reliable information about the local structure of MOFs. We examined the electron beam stability of benchmarked (Zr)NU-1000, (Hf)PCN-222(H₂) and its metalated versions, (Hf)PCN-222(Fe) and (Hf)PCN-222(Pd), and identified factors influencing the stability under the electron beam. After the threshold for electron dose was established, we applied low-dose, four-dimensional scanning transmission electron microscopy (4D-STEM). We then compared annular bright field (ABF), annular dark field (ADF), and real-time integrated center of mass (riCOM) images that could be extracted from the 4D dataset. The riCOM technique successfully revealed the structure of investigated MOFs with minimal beam-induced alterations and provides insights into local features, including organic linkers and additional metalation elements.

Nanoreactors represent a unique strategy to synthesize nanoclusters and nanoparticles with a diverse chemical nature and with a level of tunability that is difficult to achieve with conventional methods. Liquid metals (LMs) have emerged as an intriguing medium for materials synthesis, which hints at opportunities to their use as nanoreactors. Yet, their underdeveloped chemistry at the nanoscale has so far hindered the full exploitation of this research direction. Herein, we advance the chemical knowledge on the synthesis of LM nanoparticles (NPs) and demonstrate their use as a novel type of nanoreactor to access well-defined multi-metallic NPs. We propose a novel approach for the synthesis of colloidal solid-liquid-solid core-shell-shell NPs wherein a solid metal core (i.e. Ag, Au, Cu, Pd) is embedded into a liquid Ga NP surrounded by its native oxide skin. Using state of the art characterization tools, including in-situ electron microscopy and X-Ray absorption spectroscopy, we learn that a dissolution and recrystallization of the solid core within the liquid Ga NP occurs during the synthesis. We leverage this understanding to access unprecedented multi-metallic NPs, exemplified by Ag-Au nanodimers, within the liquid Ga shell. Finally, we demonstrate how the synergistic interactions between the solid metal core, the liquid Ga domain and the oxide skin are promising to explore these materials as a new class of electrocatalysts. The findings of this work deepen our understanding of LM NPs and advance the ability to design these unique nanomaterials with tailored properties for various applications using a novel nanoreactor strategy.