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.
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