Theoretical Analysis of the Electronic Structure and Optical Properties of DNA-Stabilized Silver Cluster Ag16Cl2 in Aqueous Solvent

DNA-stabilized silver nanoclusters with 10-30silver atomsare by construction ideal candidates for biocompatible bright fluorescentemitters, but their electronic structure is not well understood. Here,using density functional theory (DFT), we analyze the ground-stateelectronic structure and optical absorption of a bright NIR-emittingcluster Ag16Cl2, which is stabilized by twoDNA strands of 9-base sequence 5 & PRIME;-CACCTAGCG-3 & PRIME; and whoseatomic structure was very recently confirmed to have two chloridesbound to the silver core. We are able to (i) unambiguously assignthe charge of this cluster in aqueous solvent, (ii) analyze the detailsof silver-DNA interactions and their effect on the clustercharge, (iii) analyze the character of low-energy optical absorptionpeaks and the involved electron orbitals and make a first assessmenton circular dichroism, and (iv) evaluate the suitability of variousDFT exchange-correlation functionals via benchmarking to experimentaloptical data. This work lays out a baseline for all future theoreticalwork to understand the electronic, chiroptical, and fluorescence propertiesof these fascinating biocompatible nanostructures.