Magneto-plasmonic nanostructures for SERS: magnetite decorated by silver and gold nanoparticles

Abstract

Surface enhanced Raman spectroscopy (SERS) is a powerful tool for the investigation of low concentration analytes. To improve this method, magnetic nanoparticles were introduced to the system. Magnetic nanoparticles together with plasmonic silver or gold nanoparticles or shells not only enhance the SERS signal but also facilitate to focus the sample and direct it to the place of need. In this work, different chemicals were used for the modification of magnetite in order to improve the attachment of plasmonic nanoparticles on the surface of magnetic nanoparticles. In addition to this, the modification using PEI was chosen for a further decoration procedure with different ratios of AgNPs and AuNPs in various sequences. Composites having silver, gold, and magnetite nanoparticles were obtained and the best modification conditions for optimal SERS signal were evaluated by employing multiwavelength excitation. It was noticed that the order of the decoration makes a difference in the obtained signal enhancement. These composites can improve the adsorption and sensing of different analytes as both silver and gold surfaces are accessible to the solution.