Abstract
Bare and guanine-complexed silver clusters Agnz (n = 2-6; z = 0-2) are examined using density functional theory to elucidate the geometries and binding motifs that are present experimentally. Whereas the neutral systems remain planar in this size range, a 2D-3D transition occurs at Ag5+ for the cationic system and at Ag42+ for the dicationic system. Neutral silver clusters can bind with nitrogen 3 or with the pi system of the base. However, positively charged clusters interact with nitrogen 7 and the neighboring carbonyl group. Thus, the cationic silver-DNA clusters present experimentally may preferentially interact at these sites.
Highlights
Over the years, gold and silver nanoparticles have demonstrated fascinating optical and chemical properties that depend on the size of the particle.[1,2,3] Small sized metal nanoclusters are considered to be brighter and more photostable fluorophores[4,5,6,7,8,9,10,11] compared to existing organic dyes as well as smaller and less toxic compared to quantum dots.[12]
The Becke Perdew (BP86)[51,52] exchange-correlation functional with a triple zeta with polarization (TZP) basis set was used for all molecules
The isomers and relative energies of these systems are summarized in the most favorable isomers (Table I), and the coordinates of optimized systems are provided in the supplementary material
Summary
Gold and silver nanoparticles have demonstrated fascinating optical and chemical properties that depend on the size of the particle.[1,2,3] Small sized metal nanoclusters (with diameters up to around 2 nm) are considered to be brighter and more photostable fluorophores[4,5,6,7,8,9,10,11] compared to existing organic dyes as well as smaller and less toxic compared to quantum dots.[12] In particular, silver nanoclusters (AgNCs) are of interest, and these systems involve stabilizing ligands to prevent them from oxidation and aggregation.[13] Dendrimers, synthetic polymers, biopolymers, thiol ligands, and inorganic matrices have been used as the stabilizing ligands for AgNCs.[6,11,14,15,16,17] In 2004, Dickson and coworkers first discovered the formation of DNA-templated Ag nanoclusters (DNA-AgNCs) where they showed that DNA acts as a template for the time-dependent and size-specific formation of nanoclusters.[18] Since DNA-AgNCs have become a research field of growing interest
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