Theoretical Investigations on the Plasmon-Mediated Dissociation of Small Molecules in the Presence of Silver Atomic Wires

Abstract

Plasmonic nanoparticles can promote bond activation in adsorbed molecules under relatively benign conditions via excitation of the nanoparticle's plasmon resonance. As the plasmon resonance often falls within the visible light region, plasmonic nanomaterials are a promising class of catalysts. However, the exact mechanisms through which plasmonic nanoparticles activate the bonds of nearby molecules are still unclear. Herein, we evaluate Ag 8 −X 2 (X = N, H) model systems via real-time time-dependent density functional theory (RT-TDDFT), linear response time-dependent density functional theory (LR-TDDFT), and Ehrenfest dynamics in order to better understand the bond activation processes of N 2 and H 2 facilitated by the presence of the atomic silver wire under excitation at the plasmon resonance energies. We find that dissociation is possible for both small molecules at high electric field strength. Activation of each adsorbate is symmetry-and electric field-dependent, and H 2 activates at lower electric field strengths than N 2 . This work serves as a step toward understanding the complex timedependent electron and electron−nuclear dynamics between plasmonic nanowires and adsorbed small molecules.

Recent Advances in Real-Time Time-Dependent Density Functional Theory Simulations of Plasmonic Nanostructures and Plasmonic Photocatalysis

“…The significant overlap of H 2 antibonding orbitals with Ag states allows for the external laser to drive charge to excited states and then couple to the antibonding H 2 state, driving dissociation. In a separate study using the LC-ωPBE functional, H 2 was found to activate readily even with small amounts of charge transfer from linear Ag chains …”

“…In a separate study using the LC-ωPBE functional, H 2 was found to activate readily even with small amounts of charge transfer from linear Ag chains. 71 To gain mechanistic insight into plasmon-mediated N 2 dissociation, RT-TDDFT was used with a variety of longrange corrected and GGA functionals to study the interaction of N 2 with linear Ag chains (n = 4, 6, 8). 13 It was found that N 2 π* hybridization with Ag σ orbitals provided a path for plasmon-mediated charge transfer.…”

Effects of Field Strength and Silver Nanowire Size on Plasmon-Enhanced N2 Dissociation

“…They found that the N 2 molecule gained a greater degree of activation when the longitudinal excitation mode was excited compared to the charge-transfer and transverse excitation modes . Hull and Aikens then compared N 2 and H 2 activation/dissociation when these adsorbates interact with Ag n systems . The orientation of small molecules on the nanowire was compared and the parallel orientation was found to lead to a greater degree of charge transfer between the wire and the N 2 and H 2 molecules, which can aid the dissociation of the adsorbate.…”

“…43 Hull and Aikens then compared N 2 and H 2 activation/dissociation when these adsorbates interact with Ag n systems. 44 The orientation of small molecules on the nanowire was compared and the parallel orientation was found to lead to a greater degree of charge transfer between the wire and the N 2 and H 2 molecules, which can aid the dissociation of the adsorbate. Both adsorbates were found to pick up electron density early in the dissociation process, with N 2 accommodating more additional electrons than H 2 , even though H 2 was found to dissociate more readily than N 2 .…”

Connectivity between Static Field and Continuous Wave Field Effects on Excitation-Induced H2 Activation

“…The electric field is applied along the z axis (Figure ), and the strengths of the fields were chosen to be 0.01 au (3.57 × 10 14 W/cm 2 ), 0.005 au (1.79 × 10 14 W/cm 2 ), and 0.001 au (3.57 × 10 13 W/cm 2 ), respectively. The electric fields were chosen based on a previous work that shows very weak activation of H 2 (coupled with an Ag 8 nanowire) with a CW electric field strength of 0.001 au and slightly stronger activation for 0.01 au . Electric fields were applied in both the positive z ( Z +) and negative z ( Z −) directions, which correspond to the maxima of the CW fields.…”