Preparation of surface-enhanced raman scattering-active Au/Al ₂O₃ colloids by sonoelectrochemical methods

As shown in the literature, surface-enhanced Raman scattering (SERS)-active Au or Ag nanoparticle films in agglomerated states on substrates were generally prepared by salting-out the colloidal solutions with NaClO₄ or NaCl. In this work, we report a new pathway to prepare SERS-active Au/Al ₂O₃ colloids by sonoelectrochemical methods. The prepared colloids demonstrate strong SERS effects on substrates without an additional salting-out procedure. The particle size of prepared Au nanoparticles (NPs) coated on Al₂O₃ NPs is ca. 20 nm in diameter. Experimental results indicate that the synthesized SERS-active Au/Al₂O ₃ colloids demonstrate a large Raman scattering enhancement for Rhodamine 6G with a detection limit of 2 × 10^-10 M, which is lower than most of those shown in the literature based on Au NPs.