Abstract
Artificial nano-heterostructures (NHs) with controlled morphology, obtained by combining two or more components in several possible architectures, make them suitable for a wide range of applications. Here, we propose an oleate-based solvothermal approach to design silver-spinel ferrite flower-like NHs. Small oleate-coated silver nanoparticles were used as seeds for the growth of magnetic spinel ferrite (cobalt ferrite and spinel iron oxide) nanodomains on their surface. With the aim of producing homogeneous flower-like heterostructures, a careful study of the effect of the concentration of precursors, the reaction temperature, the presence of water, and the chemical nature of the spinel ferrite was carried out. The magnetic and optical properties of the NHs were also investigated. A heterogeneous growth of the spinel ferrite phase on the silver nanoparticles, through a possible defect-assisted mechanism, was suggested in the light of the high concentration of stacking faults (intrinsic and twins) in the silver seeds, revealed by Rietveld refinement of powder X-ray diffraction patterns and High-Resolution electron microscopy.
Highlights
Artificial nano-heterostructures (NHs) with controlled morphology, obtained by combining two or more components in several possible architectures, make them suitable for a wide range of applications
Insoluble in most organic solvents, is soluble in oleic acid at 100 °C, and oleic acid can be used as the solvent, capping, and reducing agent[36]
An oleate-based solvothermal method was employed for the first time for the synthesis of silver-spinel ferrite nanoheterostructures (NHs)
Summary
Artificial nano-heterostructures (NHs) with controlled morphology, obtained by combining two or more components in several possible architectures, make them suitable for a wide range of applications. Electromagnetic enhancement, caused by the construction of “hot-spots” in aggregated NHs, can contribute to optimizing the SERS performances In this context, magnetic-silver NHs represent an excellent material for SERS activity, since spinel ferrite nanoparticles can induce magnetic aggregation. Fe3O4@Ag flower-like NHs have been synthesized by a seedmediated growth approach in organic solvents starting from magnetite NPs with silver nitrate or silver oleate as Ag precursors[25]. The necessity of more eco-friendly strategies that use less amount of toxic organic solvents, less expensive precursors, and lower temperatures, has moved the interest toward alternative synthetic approaches[29] In this context, the solvothermal methods feature several advantages such as the use of low-boiling and inexpensive solvents, the ease of the synthesis, lower temperature and the possibility to monitor it together with the p ressure[30,31,32,33,34]
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