DNA Duplex\nContaining Ag<sup>+</sup>‑Mediated\nCytosine–Cytosine Base Pairs as a Catalyst Precursor for the\n4‑Nitrophenol Reduction with NaBH<sub>4</sub>

Catalytic applications of DNA duplexes containing Ag<sup>+</sup>-mediated cytosine–cytosine base pairs (C-Ag<sup>+</sup>-C)\nhave not been well investigated. In this study, we demonstrate a novel\napproach for forming highly active DNA-capped Ag nanoparticle (DNA-AgNP)\ncatalysts for the reduction of 4-nitrophenol (4-NP) using sodium borohydride\n(NaBH<sub>4</sub>). This approach is based on the <i>in situ</i> generation of DNA-AgNPs from DNA duplexes containing C-Ag<sup>+</sup>-C (DNA duplex-Ag<sup>+</sup>). UV–vis spectroscopic analysis\nsuggests that the DNA duplex-Ag<sup>+</sup> complex acts as an excellent\ncatalyst precursor for 4-NP reduction with NaBH<sub>4</sub>. Transmission\nelectron microscopy observations of the reaction solution after the\n4-NP reduction reaction using DNA duplex-Ag<sup>+</sup> provided detailed\nexperimental insights into the mechanism of the catalytic activity\nof DNA duplex-Ag<sup>+</sup> for 4-NP reduction. In the reaction solution,\nDNA-AgNPs were initially formed (DNA duplex-Ag<sup>+</sup> + NaBH<sub>4</sub> → DNA-AgNPs) and then served as water-soluble catalysts\nfor 4-NP reduction. Notably, the catalytic properties of the DNA-AgNPs\ngenerated <i>in situ</i> were affected by the DNA strand\nlength and sequence. The properties of DNA duplex-Ag<sup>+</sup> may\nprovide a new application of DNA molecules containing metallobase\npairs as water-soluble catalyst precursors.