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Abstract: Coordination nanosheets (CONASHs) or conjugated metal organic frameworks (MOFs) with distinctive metal-organic bonding structures exhibit promise for electronics, sensing, and energy storage. Porous Nickel-Benzene hexathiol complex (Ni-BHT) with noteworthy conductivity was first reported a decade ago, and recent synthetic modifications produced non-porous Ni-BHT with enhanced conductivity (≈50 S cm−1). Here the charge transport physics of such non-porous Ni-BHT films are studied with even higher conductivity (≈112 S cm−1). In contrast to the thermally activated electrical conductivity, thermoelectric measurements suggest an intrinsic metallic nature of Ni-BHT. It is shown that it is possible to tune the Fermi level and carrier polarity in Ni-BHT by electrolyte gating; gating is initially governed by the formation of an interfacial, electric double layer and then evolves into an electrochemical (de)doping process. These findings not only contribute to a deeper understanding of charge transport in CONASHs, but also show that Fermi level tuning is an effective approach for enhancing the thermoelectric performance of CONASHs.

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Abstract: Catastrophic failure is the end result of progressive localisation of damage creating brittle failure on a variety of system scales in the Earth. However, the factors controlling this evolution, and the relationship between deformation and the resulting earthquake hazard, are not well constrained. Here we address the question of how to adapt operational controls in a strain-inducing laboratory experiment so as to minimize associated microseismicity. We simultaneously image the induced damage using x-rays at a synchrotron, and detect acoustic emissions which can be fed back to change operational controls on the experiment. We confirm that using continuous servo-control based on acoustic emission event rate not only slows down deformation compared to standard constant strain rate loading, but also suppresses events of all sizes, including extreme events. We develop a new model that explains this observation, based on the observed evolution of microstructural damage and the fracture mechanics of subcritical crack growth. The model is independently consistent with the observed stress history and acoustic emission statistics. Our results imply that including seismic event rate control may improve risk management of induced seismicity over a range of event magnitudes, if similar processes are relevant at larger scales.

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Abstract: This study reports the preparation and characterization of zeolitic imidazolate framework-67 (ZIF-67) through the recycling of spent synthesis liquor containing unreacted 2-methylimidazole. The recycling enhances the yield of ZIF-67 while maintaining the dodecahedral rhombic morphology of the particles. In the first synthesis, a molar ratio of 1:26 (Co2:2-methylimidazole) results in particles with an average diameter of 230 nm and a surface area of 1374 m2 g−1. The first recycling step produces ZIF-67 particles that doubl in diameter and surface area, reaching 520 nm and 1690 m2 g−1, respectively. In the second recycling step, the particles further increase to 1040 nm in diameter and 1806 m2 g−1 in surface area. This increase in diameter is attributed to changes in the metal-to-ligand ratio, which affects the nucleation and growth rates. Increased surface area is linked to a reduction in the average micropore diameter, which decreases from 1.42 nm (first synthesis) to 1.37 nm (second recycling step). There is a 6 m2 g−1 increase in surface area for every 0.001 cm3 g−1 increase in the volume of micropores. This indicates that the spent liquor can be utilized in consecutive batches to produce ZIF-67, minimizing reagent waste.

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Abstract: Over the past decade, hybrid nanomaterials have emerged as a key area of research due to their ability to combine multiple functionalities within a single nanoscale system. Among these, core@shell heterostructures, especially those integrating noble metals with functional coordination polymers, offer promising properties and synergistic effects for applications in catalysis, magnetism, and biomedicine. This doctoral thesis focuses on the development of hybrid nanoparticles consisting of a gold (Au) core and a Prussian Blue Analogue (PBA) shell, aiming to investigate the synergistic properties arising from their unique hybrid structure. PBAs are coordination polymers with a cubic lattice and a highly tunable structure. Their open lattice structure allows modifications in the chemical composition, enabling the fine-tuning of their magnetic, catalytic, and electrochemical properties. Additionally, their ability to host ions and molecules makes them particularly attractive for biomedical applications. To improve the efficiency of PBAs in specific fields, it is often necessary to enhance their intrinsic properties or introduce new functionalities. In this regard, combining PBAs with Au nanoparticles has proven to be a highly effective strategy. Gold nanoparticles offer excellent chemical stability, unique optical behavior, precise control over size and shape, and broad application potential. Their integration with PBAs not only improves thermal and electrical conductivity but also introduces additional optical effects through localized surface plasmon resonance (LSPR), expanding their functional scope. However, synthesizing Au@PBA nanostructures poses significant challenges due to the reactivity of gold with cyanide, a key component in PBA formation. To overcome this, the thesis presents an optimized protocol based on colloidal chemistry that permits the stable obtention of Au@PBA nanoparticles. The work is organized into four chapters. Chapter 1 introduces the fundamental concepts of PBAs and Au nanoparticles, with an emphasis on their role in advanced hybrid nanomaterials and the advantages of core@shell. Chapter 2 outlines the synthesis and characterization of Au@CsNiFe nanoparticles, developed using Au nanoparticles functionalized with 4-mercaptopyridine (4-MPy) to guide the controlled growth of the PBA shell. These hybrid particles show enhanced electrocatalytic activity in the oxygen evolution reaction (OER), which is directly influenced by the shape architectures (spheres, rods and stars) and size of the gold core. Chapter 3 investigates the photomagnetic behavior of Au@CsCoFe nanoparticles. By varying the PBA shell thickness, it is shown that photomagnetic activity increases due to a higher concentration of photo-responsive species. Furthermore, the removal of the Au core yields hollow nanostructures with altered magnetic properties, underscoring the significant role of chemical morphology in determining functionality. Chapter 4 explores the biomedical application of Au@CsMnFe nanoparticles. These nanoparticles demonstrate high colloidal stability in physiological media and are capable of controlled drug release. The introduction of an internal cavity (yolk@shell configuration) significantly improves drug loading and release efficiency. Furthermore, under near-infrared (NIR) irradiation, the nanoparticles exhibit a strong photothermal response, making them suitable candidates for photothermal therapy (PTT). In conclusion, this thesis establishes effective synthesis methods for fabricating multifunctional Au@PBAcore@shell nanostructures, paving the way for application-specific nanoplatforms. The developed materials demonstrate tunable performance across three domains: catalytic activity (CsNiFe), photomagnetic behavior (CsCoFe), and therapeutic efficiency (CsMnFe).

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Abstract: Lead halide perovskites have emerged as promising materials for solar energy conversion and X-ray detection owing to their remarkable optoelectronic properties. However, the microscopic origins of their superior performance remain unclear. Here we show that low-symmetry dynamic nanodomains present in the high-symmetry average cubic phases, whose characteristics are dictated by the A-site cation, govern the macroscopic behaviour. We combine X-ray diffuse scattering, inelastic neutron spectroscopy, hyperspectral photoluminescence microscopy and machine-learning-assisted molecular dynamics simulations to directly correlate local nanoscale dynamics with macroscopic optoelectronic response. Our approach reveals that methylammonium-based perovskites form densely packed, anisotropic dynamic nanodomains with out-of-phase octahedral tilting, whereas formamidinium-based systems develop sparse, isotropic, spherical nanodomains with in-phase tilting, even when crystallography reveals cubic symmetry on average. We demonstrate that these sparsely distributed isotropic nanodomains present in formamidinium-based systems reduce electronic dynamic disorder, resulting in a beneficial optoelectronic response, thereby enhancing the performance of formamidinium-based lead halide perovskite devices. By elucidating the influence of the A-site cation on local dynamic nanodomains, and consequently, on the macroscopic properties, we propose leveraging this relationship to engineer the optoelectronic response of these materials, propelling further advancements in perovskite-based photovoltaics, optoelectronics and X-ray imaging.