Spectroscopic Evidence of Charge Transfer at the Noble Metal Nanostructure-Organic Ligand Hybrid Nanoconjugate Interface

Thursday, March 11, 2021: 3:45 PM - 4:05 PM

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Description

Ligand-controlled tuning of localized surface plasmon resonance (LSPR) properties of noble metal nanostructures is fundamentally important for various optoelectronic applications such as photocatalysis, photovoltaics, and sensing. To obtain the highest efficiency for these applications, it is extremely important that the Fermi level and work function of noble metal nanostructures suitably align with their surrounding environment such as passivating ligands and/or solid heterojunction supports. Until now, research has not been systematically conducted to determine how surface passivating ligands control the work function of plasmonic, noble metal nanostructures. Herein, we present the first spectroscopic evidence that the appropriate passivation of the surface of chemically-synthesized plasmonic gold triangular nanoprisms (Au TNPs) with para-substituted thiophenolate (from electron withdrawing to donating functional groups) results in an ~1.9 eV change in the work function of Au that was determined by an ultraviolet photoelectron spectroscopy analysis. Importantly, from the steady-state spectroscopic measurement, we calculated that the electron density of Au TNPs can be tuned up to 12% upon functionalization of their surface with para-substituted thiophenolate ligands that resulted in an unprecedentedly large, 50 nm LSPR response. Utilizing density functional theory calculations, we developed frontier molecular orbital (MO) diagrams of Au-thiophenolate interactions in the solid-state to delineate the observed spectral responses. Based on the experimental data, and calculations we proposed that the delocalization of photoexcited electron wave functions controls the optoelectronic properties of Au TNPs rather than simple electronic properties (inductive and/or resonance effects) of thiophenolate.

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Additional Info

Keywords: Please select up to 4 keywords ONLY:
Materials Characterization,Surface Enhanced Raman Spectroscopy,Spectroscopy,Surface Analysis