Computational Study of the Resonance Enhancement of Raman Signals of Ligands Adsorbed to CdSe Clusters through Photoexcitation of the Cluster

Nathaniel K. Swenson, Mark A Ratner, Emily A Weiss

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11 Citations (Scopus)

Abstract

This paper describes density-functional-theory-based computations of resonance Raman (RR) spectra of ligand molecules adsorbed to the surface of a Cd16Se13 cluster. Signals from asymmetric vibrational modes of ligand binding groups, such as the asymmetric O-C-O stretching modes of carboxylates, are enhanced relative to the symmetric vibrational modes when the excitation energy is on-resonance with the excitonic energy of the cluster. Certain ligand molecules have frontier orbitals with the correct energies and symmetries to mix with the orbitals of the CdSe cluster, and as a result, the wave functions of the electron and the hole delocalize from the cluster onto the ligand molecules; experimentally, this delocalization results in a bathochromic shift of the band edge excitonic absorption. Increased excitonic delocalization results in greater vibronic coupling between the exciton and the ligand vibrations and, on average, preferential enhancements in the RR signals of those vibrations. This work suggests that the use of exciton-delocalizing ligands to optimize electronic coupling between neighboring CdSe nanoparticles may, at the same time, enhance the rates of nonradiative exciton decay by coupling the exciton and ligand vibrational modes.

Original languageEnglish
Pages (from-to)20954-20960
Number of pages7
JournalJournal of Physical Chemistry C
Volume120
Issue number37
DOIs
Publication statusPublished - Sep 22 2016

Fingerprint

Photoexcitation
photoexcitation
Ligands
ligands
augmentation
Excitons
excitons
vibration mode
Molecules
molecules
orbitals
vibration
Excitation energy
Wave functions
carboxylates
Vibrations (mechanical)
Stretching
Density functional theory
energy
Raman scattering

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Surfaces, Coatings and Films
  • Physical and Theoretical Chemistry

Cite this

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title = "Computational Study of the Resonance Enhancement of Raman Signals of Ligands Adsorbed to CdSe Clusters through Photoexcitation of the Cluster",
abstract = "This paper describes density-functional-theory-based computations of resonance Raman (RR) spectra of ligand molecules adsorbed to the surface of a Cd16Se13 cluster. Signals from asymmetric vibrational modes of ligand binding groups, such as the asymmetric O-C-O stretching modes of carboxylates, are enhanced relative to the symmetric vibrational modes when the excitation energy is on-resonance with the excitonic energy of the cluster. Certain ligand molecules have frontier orbitals with the correct energies and symmetries to mix with the orbitals of the CdSe cluster, and as a result, the wave functions of the electron and the hole delocalize from the cluster onto the ligand molecules; experimentally, this delocalization results in a bathochromic shift of the band edge excitonic absorption. Increased excitonic delocalization results in greater vibronic coupling between the exciton and the ligand vibrations and, on average, preferential enhancements in the RR signals of those vibrations. This work suggests that the use of exciton-delocalizing ligands to optimize electronic coupling between neighboring CdSe nanoparticles may, at the same time, enhance the rates of nonradiative exciton decay by coupling the exciton and ligand vibrational modes.",
author = "Swenson, {Nathaniel K.} and Ratner, {Mark A} and Weiss, {Emily A}",
year = "2016",
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T1 - Computational Study of the Resonance Enhancement of Raman Signals of Ligands Adsorbed to CdSe Clusters through Photoexcitation of the Cluster

AU - Swenson, Nathaniel K.

AU - Ratner, Mark A

AU - Weiss, Emily A

PY - 2016/9/22

Y1 - 2016/9/22

N2 - This paper describes density-functional-theory-based computations of resonance Raman (RR) spectra of ligand molecules adsorbed to the surface of a Cd16Se13 cluster. Signals from asymmetric vibrational modes of ligand binding groups, such as the asymmetric O-C-O stretching modes of carboxylates, are enhanced relative to the symmetric vibrational modes when the excitation energy is on-resonance with the excitonic energy of the cluster. Certain ligand molecules have frontier orbitals with the correct energies and symmetries to mix with the orbitals of the CdSe cluster, and as a result, the wave functions of the electron and the hole delocalize from the cluster onto the ligand molecules; experimentally, this delocalization results in a bathochromic shift of the band edge excitonic absorption. Increased excitonic delocalization results in greater vibronic coupling between the exciton and the ligand vibrations and, on average, preferential enhancements in the RR signals of those vibrations. This work suggests that the use of exciton-delocalizing ligands to optimize electronic coupling between neighboring CdSe nanoparticles may, at the same time, enhance the rates of nonradiative exciton decay by coupling the exciton and ligand vibrational modes.

AB - This paper describes density-functional-theory-based computations of resonance Raman (RR) spectra of ligand molecules adsorbed to the surface of a Cd16Se13 cluster. Signals from asymmetric vibrational modes of ligand binding groups, such as the asymmetric O-C-O stretching modes of carboxylates, are enhanced relative to the symmetric vibrational modes when the excitation energy is on-resonance with the excitonic energy of the cluster. Certain ligand molecules have frontier orbitals with the correct energies and symmetries to mix with the orbitals of the CdSe cluster, and as a result, the wave functions of the electron and the hole delocalize from the cluster onto the ligand molecules; experimentally, this delocalization results in a bathochromic shift of the band edge excitonic absorption. Increased excitonic delocalization results in greater vibronic coupling between the exciton and the ligand vibrations and, on average, preferential enhancements in the RR signals of those vibrations. This work suggests that the use of exciton-delocalizing ligands to optimize electronic coupling between neighboring CdSe nanoparticles may, at the same time, enhance the rates of nonradiative exciton decay by coupling the exciton and ligand vibrational modes.

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