Impact of Orbital Hybridization at Molecule–Metal Interface on Carrier Dynamics

Abstract

The orientation of a molecule on a metal surface can impact the performance of electronic devices fabricated from organic materials. This orientation effect of physiosorbed or weakly chemisorbed molecules has been widely debated, and its origin remains unknown because methods to investigate the weak interaction at the molecule/inert-metal interface have been limited. Here, it is shown via spectroscopy and density functional calculations that molecule/metal orbital hybridization, which is determined by the molecular orientation, is an identity of the orientation effect dictating the carrier dynamics at the interface. Nanoscale model interfaces, where molecules were weakly chemisorbed on a metal, made it possible to visualize the orientation-dependent shift of the electronic state. The transient absorption spectroscopy and scanning tunneling spectroscopy of porphyrin derivative coordinated on gold nanoparticle demonstrated that the orbital hybridization dictates the interfacial carrier dynamics. This new understanding of the molecule/metal interfaces will enable functional-molecule designs based on the cross-materials orbital hybridization for various devices.

Decoding Chemical and Physical Processes Driving Plasmonic Photocatalysis Using Surface-Enhanced Raman Spectroscopies

“…The transfer of hot carriers between metals and molecules is an exciting prospect for driving important multielectron redox reactions such as carbon dioxide reduction, water splitting, and ammonia synthesis. ,, Charge transfer from a plasmonic substrate can be affected by a number of factors, including charge delocalization, phonon generation, molecular orientation, and metal–molecule hybridization. − In addition, the mechanism of hot electron transfer processes, whether direct or indirect, is highly dependent on the particular plasmonic–molecular system under study. ,,, Because LSPRs decay so quickly and hot electrons are short-lived, unlocking the interplay between hot electrons and molecules requires a method with high time resolution. We have used our ultrafast SERS technique, with picosecond time resolution, ,,, to gain new insights into indirect transfers of hot electrons in the plasmon-driven dimerization of 4-NBT to form dimercaptoazobenzene (DMAB) on silver nanostructures.…”

Plasmon-Mediated Intramolecular Methyl Migration with Nanoscale Spatial Control

“…It is reasonable to assume that some other feature in the local environment, beyond the electric field magnitude, is critical to the observation of this phenomenon. Molecular orientation at metal interfaces can significantly impact carrier dynamics between metals and chemisorbed analytes, so any change that modifies the surface structure or accentuates signal from a region with a particular molecular orientation could have a significant impact on SER spectra. , On focus, the SERS signal originates from the hot spots between the spheres, where it is plausible that the molecules are more sterically hindered, particularly when undergoing intramolecular methyl migration. This would explain our observation that the methyl migration reaction does not occur with any reasonable yield when the sample is held at the laser focus.…”

Adsorchromism: Molecular Nanoarchitectonics at 2D Nanosheets—Old Chemistry for Advanced Chromism

“…[75] The orbital hybridization between porphyrins and gold nanoparticles was studied spectroscopically by Sakamoto et al They concluded that orbital hybridization was depending on the orientation of the porphyrins at the surface of gold nanoparticles, leading the orientation-dependent carrier dynamics, which determines the performances of organic electronics. [76] The mechanism underlying the MLCT redshift (452 to 472 nm) involves destabilization of the ground state of Ru(bpy) 3 2+ upon adsorption. XPS measurements conducted by Thomas et al revealed that Ru 3d 5/2 binding energy was shifted to higher energies (ruthenium has a 3+ valence on the surface), which would raise the d-orbital energy in the complex on the surface.…”

“…They concluded that orbital hybridization was depending on the orientation of the porphyrins at the surface of gold nanoparticles, leading the orientation‐dependent carrier dynamics, which determines the performances of organic electronics. [ 76 ]…”