Fig. 3

DNA-based Ag⁺ detection method for label-free (A) and labeled AuNPs colorimetric sensor (B) (reproduced with permission from Ref. [25],© Analytica Chimica Acta 2009); (C) Schematic diagram of Ag⁺ fluorescent sensor based on the targeted-induced conformational changes of silver-specific cytosine-rich oligonucleotides (SSO) and the interaction of fluorescent probes with graphene oxide. SSO: FAM-labeled silver-specific nucleotide probe(reproduced with permission from Ref. [26],© Journal of Luminescence 2010)