Agnanostructures assembled on magnetic particles for ready SERS-based detection of dissolved chemical species

Abstract

In this investigation, a novel one-step fabrication of Ag-deposited Fe₂O₃ particles and their application as surface-enhanced Raman scattering (SERS) substrates in chemical analyses are demonstrated. To deposit Ag onto them, Fe₂O₃ particles were dispersed in a reaction mixture consisting of ethanolic AgNO₃ and butylamine, and then the reaction mixture was incubated and shaken for 40 min at 50 °C. The Ag-deposited Fe₂O₃ particles are found to be efficient SERS substrates for the vibrational spectroscopic characterization of molecular adsorbates prepared in a similar way on silver surfaces; the enhancement factor of benzenethiol adsorbed on Ag-deposited Fe₂O₃ was estimated to be about 3 × 10⁶. Since the magnetic particles are readily recovered from the solution phase without centrifugation and/or filtering, the SERS-active magnetic particles are useful especially in the Raman spectroscopic analysis of dissolved organic species. We evaluate their performance as SERS substrates using benzenethiol, adenine, riboflavin, and naphthalene as model compounds; thereby, for instance, adenine could be detected down to 10 nM concentrations, and naphthalene was also able to be detected down to 200 nM by using pentachlorobenzenethiol-adsorbed Ag-deposited Fe₂O₃ particles as the adsorbent.