Multifunctional behavior of molecules comprising stacked cytosine–AgI–cytosine base pairs; towards conducting and photoluminescence silver-DNA nanowires

Abstract

DNA molecules containing a 1D silver array may be applied for nanotechnology applications, but first their conducting and photoluminescence behavior must be enhanced. Here we have synthesized and characterized three new helical compounds based on stacked silver–mediated cytosine base pairs [Ag(mC)₂]X (mC = N1-methylcytosine; X = NO₃ (1), BF₄ (2) and ClO₄ (3)), that contain uninterrupted polymeric Ag^I chains that run through the center of the helixes, comparable to related silver-DNA structures. The exposure of nanostructures of [Ag(mC)₂]BF₄ (2) to cold hydrogen plasma stimulates the reduction of the prearranged Ag^I polymeric chains to metallic silver along the material. This solvent-free reduction strategy leads to the compound [Ag^I(mC)₂]X@Ag⁰ (2H) that contains uniformly well-distributed silver metallic nanostructures that are responsible for the new conducting and photoluminescence properties of the material. The presence of silver nanostructures alongside compound 2H has been evaluated by means of X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, and X-ray powder diffraction (XRPD). The conducting and photoactive properties of 2H were studied by electrostatic force microscopy (EFM) and conducting-AFM (c-AFM), and photoluminescence microscopy (PL), respectively. The results demonstrate that the presence of well-organized metallic silver nanoentities on the material is responsible for the novel conductivity and photoactive properties of the material. This methodology can be employed for the generation of multifunctional silver-DNA related materials with tailored properties.