Carbon based dot capped silver nanoparticles for efficient surface-enhanced Raman scattering

Abstract

A simple method has been developed for the preparation of silver nanoparticles/carbon based quantum dot nano-hybrids (AgNPs@CDs). First, the small-sized CDs with abundant oxygen-containing functional groups adsorbed Ag⁺ ions through ion exchange or coordination reactions. Then, during the reaction with NaBH₄, the Ag⁺ ions were reduced to AgNPs while the oxygen-containing functional groups were partially removed from the CDs. Thus, CDs were coated on the surfaces of the resultant AgNPs, leading to the formation of AgNPs@CDs. The residual oxygen-containing groups on the CDs made the obtained AgNPs@CDs possess excellent dispersivity and long-term stability in water. The synthesized AgNPs@CDs showed high surface-enhanced Raman scattering (SERS) activity and provided a sensitive SERS sensing ability for 4-aminothiophenol, with a wide dynamic range from 1 × 10⁻¹⁰ to 1 × 10⁻⁵ M and a low detection limit (S/N = 3) of 5.0 × 10⁻¹¹ M.