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

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 x 10 (-10) to 1 x 10(-5) M and a low detection limit (S/N = 3) of 5.0 x 10(-11) M.