Magnetically-controllable hollow multi-shell magnetite spheres as stable and reusable SERS substrates

This study successfully synthesized magnetically-manipulatable and reusable SERS active buoyant substrates, i.e. [email protected]2@Fe3O4 composite hollow spheres. The composites comprised mesoscopic spheres with a Fe3O4 inner shell of 15–30 nm in thickness strong ferromagnetism, which were using spray pyrolysis the subsequent reduction, SiO2 outer to maintain stability Fe3O4, as well Ag nanoparticles on sphere surface providing localized plasmon resonance. coercive field (Hc) bare reached 200 Oe, saturation magnetization (Ms) was 130 emu/g at 300 K, least 30% higher than reported values no matter bulk or nanoscales. Compared solid cores, signal intensity structures 2.6 times greater, could be attributed buoyancy structure contribute more interaction target analytes. Under external magnetic field, these ferromagnetic can concentrated separated easily, resulting augmented effect (about 1.5 those collected without applying field). also demonstrated possibility reuse for measurements.