Superparamagnetic plasmonic nanocomposites: Synthesis and characterization studies

• Long mixing time leads to agglomeration of modified magnetite particles.
• The intensity of XRD peaks depends on gold mass ratio in nanostructures.
• Diamagnetic gold shell causes reduction in magnetic saturation of nanocomposites.
• SPR peak shows a red shift to longer wavelengths upon forming magnetic shell.
• Attachment of magnetite particles to APTES-modified nanoshells forms smooth shell.

Bifunctional magneto-optical nanocomposites have recently received significant attention because of their simultaneous magnetic and optical properties, and they can be considered as one of the most promising candidates for future medical diagnosis and therapy. In this paper, multilayer magnetic gold nanoshells were prepared by coating a magnetic shell around outer surface of silica-gold nanoshells (GNs) via using three procedures based on surface modification of gold nanoshells or magnetite nanoparticles (MNs) in order to increase the affinity between these nanostructures. The procedures used in this work include attachment of MNs onto the surface of 3-aminopropyltriethoxysilane (APTES) modified GNs (P1), attachment of APTES-modified MNs onto the surface of GNs (P2) and attachment of APTES-modified MNs onto the surface of 3-mercaptopropionic acid (MPA) modified GNs (P3). From the microscopic characterizations, it is inferred that the surface of the nanocomposites obtained from P1 is smooth. So, P1 is more preferable to produce spherical smooth SiO2@Au@Fe3O4 nanostructures. Besides, the spectroscopic and magnetization data of obtained nanocomposites reveal that all the synthesized nanocomposites have superparamagnetic plasmonic nature. Therefore, they can be considered as possible options for multimodal applications requiring bifunctional magnetic plasmonic structures such as simultaneous MRI imaging and photothermal therapy.

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