▎ 摘　　要

The aim of this work is to develop a surface-enhanced Raman spectroscopy (SERS)-active platform based on a mixture of graphene/Ag nanocomposite and a silver colloid for biomedical applications and to test it in the case of DNA molecules at low pH. Graphene/silver nanocomposites were synthesized by the reduction process and were characterized by transmission electron microscopy, X-ray powder diffraction patterns, and thermogravimetric analysis. The following graphene/Ag composites were prepared: (a) "thermally reduced graphene oxide" (TRGO), containing about 2-3% silver nanoparticles (AgNPs); (b) TRGO 1 (graphene with crowded AgNPs 20%); and (c) TRGO 2 (graphene with ordered AgNPs 20%). Different mixtures of these systems with a silver colloid were tested not only by ultraviolet-visible spectrophotometry but also by SERS in the presence of the test substance crystal violet. Moreover, the time stability of the mixtures of graphene/AgNPs composite (TRGO 1) with the silver colloid was tested for crystal violet. Based on these results, the platform with the best SERS enhancement properties was selected for DNA analyses at low pH values. Chemical stability under acidic conditions has been found for nucleic acid systems, in the presence of graphene/crowded AgNPs 20% and silver colloid. This chemical stability has been discussed considering a hydracid catalyzed electrophilic hydration reaction mechanism characteristic to the trans-1,3-butadiene-type building moieties from graphene.