A Time-Dependent Density Functional Theory Study of the Impact of Ligand Passivation on the Plasmonic Behavior of Ag Nanoclusters

Other · Wed Feb 15 00:00:00 EST 2017 · Advances in Quantum Chemistry Advances in Quantum Chemistry: Ratner Volume

DOI:https://doi.org/10.1016/bs.aiq.2017.01.001· OSTI ID:1594821

Ashwell, Adam P. ^[1]; Ratner, Mark A. ^[1]; Schatz, George C. ^[1]

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1. Northwestern Univ., Evanston, IL (United States)

We present a detailed study of the impact of ligand passivation on the electronic structures and optical properties of plasmonic Ag nanoclusters using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The clusters studied are ${{\mathrm{A}\mathrm{g}}_{13}}^{5+}$, ${\mathrm{A}\mathrm{g}}_{25}{{\left(\mathrm{S}\mathrm{H}\right)}_{18}}^{-}$, ${\mathrm{A}\mathrm{g}}_{25}{{\left({\mathrm{N}\mathrm{H}}_2\right)}_{18}}^{-}$, ${{\mathrm{A}\mathrm{g}}_{32}}^{14+}$, and ${\mathrm{A}\mathrm{g}}_{44}{{\left(\mathrm{S}\mathrm{H}\right)}_{30}}^{4-}$. We find that the highest occupied ligand orbitals from S (3p) and N (2p) appear just above the conduction band, and this leads to significant ligand-to-metal charge transfer transitions at high energies. Dielectric screening associated with ligand passivation results in reduced HOMO–LUMO gaps and in an increased gap between the HOMO and the valence band associated with the Ag 4d orbitals. Ligand field effects result in splitting of plasmonic peaks, leading to reduced mixing between nearby single-particle excitations. The magnitude of these effects is found to decrease when thiolate ligands are replaced with amine ligands. We also find that, in the case of the ${\mathrm{A}\mathrm{g}}_{44}{{\left(\mathrm{S}\mathrm{H}\right)}_{30}}^{4-}$ cluster, the ligands localize plasmonic excitations into the core of the cluster.

• Research Organization: Northwestern Univ., Evanston, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division
• DOE Contract Number: SC0004752
• OSTI ID: 1594821
• Journal Information: Advances in Quantum Chemistry Advances in Quantum Chemistry: Ratner Volume, Vol. 75; ISSN 0065-3276
• Country of Publication: United States
• Language: English

Related Subjects

77 NANOSCIENCE AND NANOTECHNOLOGY
TDDFT
silver cluster
plasmonic
ligand‐passivation