Seeded Growth Synthesis of Au–Fe₃O₄ Heterostructured Nanocrystals: Rational Design and Mechanistic Insights

Abstract

Multifunctional hybrid nanoparticles comprising two or more entities with different functional properties are gaining ample significance in industry and research. Due to its combination of properties, a particularly appealing example is Au-Fe3O4 composite nanoparticles. Here we present an in-depth study of the synthesis of Au-Fe3O4 heterostructured nanocrystals (HNCs) by thermal decomposition of iron precursors in the presence of preformed 10 nm Au seeds. The role of diverse reaction parameters on the HNCs formation was investigated using two different precursors: iron pentacarbonyl (Fe(CO)5) and iron acetylacetonate (Fe(acac)3). The reaction conditions promoting the heterogeneous nucleation of Fe3O4 onto Au seeds were found to significantly differ depending on the precursor chosen, where Fe(acac)3 is considerably more sensitive to the variation of the parameters than Fe(CO)5, and more subject to homogenous nucleation processes with the consequent formation of isolated iron oxide nanocrystals (NCs). The role of the surfactants was also crucial in the formation of welldefined and monodisperse HNCs by regulating the access to the Au surface. Similarly, the variation of the [Fe]:[Au] ratio, temperature and employed solvent were found to act on the mean size and on the morphology of the obtained products. Importantly, while the optical properties are rather sensitive to the final morphology, the magnetic ones are rather similar for the different types of obtained HNCs. The surface functionalization of dimer-like HNCs with silica allows their dispersion in aqueous media, opening the path to their use in biomedical applications.

Strategies to tailor the architecture of dual Ag/Fe-oxide nano-heterocrystals—interfacial and morphology effects on the magnetic behavior

“…According to these results, the pre-edge energy position, the pre-peak features and the EXAFS profiles of both heteroparticles systems are compatible with a structure that combines ferric (Fe 2+ ) and ferrous (Fe 3+ ) ions [14]. [11,12,20,25], and also for other metalmetal oxide combinations, such as FePt/MnO [26]. Flower-like nanoparticles were also produced in highly polar solvents like poly-alcohols [10], supporting the hypothesis that the polarity of the synthesis medium influences the morphology of the heterostructure.…”

Multimodal Magnetic-Plasmonic Nanoparticles for Biomedical Applications

“…Flower-like Au@Fe 3 O 4 nanoparticles were prepared by Fantechi et al using thermal decomposition followed by a seeded growth approach in which the Fe 3 O 4 nanoparticles are grown onto the gold nanoparticles to form heteronanocrystals [41]. Two iron precursors, Fe(acac) 3 and Fe(CO) 5 were used in the presence of pre-formed gold nanoparticles to investigate the effect that different reaction parameters have on the morphology of the hetero-nanocrystals.…”

Citrate Stabilized Au‐FexOy Nanocomposites for Variable Exchange Bias, Catalytic Properties and Reversible Interaction with Doxorubicin

“…In situ preparation of Au‐Fe x O y nanocomposites generally involves reduction of Au(III) on Fe x O y core as the platform . Alternate routes include the use of iron pentacarbonyl or iron‐oleate as iron source at elevated temperature in inert atmosphere along with the gold nanoparticle as core in the composite . Despite there being a handful of literature reports available on the skillful synthetic strategies of Au‐metal oxide nanocomposites, there are no reports on a generalized synthetic methodology that could be utilized for the preparation of Au‐Fe x O y nanocomposites with variable Au:Fe, more so under amicable reaction conditions.…”