Hybrid nanoparticles based on gold and bimetallic cyanide complexes for magnetism, catalysis, and biomedicine

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). This work contributes to the growing field of hybrid nanomaterials by offering a versatile platform for exploring and exploiting the synergistic properties of noble metal-PBA systems.