Extended-Charge-Transfer Excitons in Crystalline Supramolecular Photocatalytic Scaffolds

Nicholas J. Hestand, Roman V. Kazantsev, Adam S. Weingarten, Liam C. Palmer, Samuel I Stupp, Frank C. Spano

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

Coupling among chromophores in molecular assemblies is responsible for phenomena such as resonant energy transfer and intermolecular charge transfer. These processes are central to the fields of organic photovoltaics and photocatalysis, where it is necessary to funnel energy or charge to specific regions within the system. As such, a fundamental understanding of these transport processes is essential for developing new materials for photovoltaic and photocatalytic applications. Recently, photocatalytic systems based on photosensitizing perylene monomimide (PMI) chromophore amphiphiles were found to show variation in hydrogen gas (H2) production as a function of nanostructure crystallinity. The 2D crystalline systems form in aqueous electrolyte solution, which provides a high dielectric environment where the Coulomb potential between charges is mitigated. This results in relatively weakly bound excitons that are ideal for reducing protons. In order to understand how variations in crystalline structure affect H2 generation, two representative PMI systems are investigated theoretically using a modified Holstein Hamiltonian. The Hamiltonian includes both molecular Frenkel excitations (FE) and charge-transfer excitations (CTE) coupled nonadiabatically to local intramolecular vibrations. Signatures of FE/CTE mixing and the extent of electron/hole separation are identified in the optical absorption spectrum and are found to correlate strongly to the observed H2 production rates. The absorption spectral signatures are found to sensitively depend on the relative phase between the electron and hole transfer integrals, as well as the diabatic energy difference between the Frenkel and CT exciton bands. Our analysis provides design rules for artificial photosynthetic systems based on organic chromophore arrays.

Original languageEnglish
Pages (from-to)11762-11774
Number of pages13
JournalJournal of the American Chemical Society
Volume138
Issue number36
DOIs
Publication statusPublished - Sep 14 2016

Fingerprint

Perylene
Chromophores
Scaffolds
Excitons
Charge transfer
Hamiltonians
Electrons
Crystalline materials
Nanostructures
Energy Transfer
Vibration
Electrolytes
Protons
Hydrogen
Amphiphiles
Photocatalysis
Gases
Energy transfer
Light absorption
Absorption spectra

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Extended-Charge-Transfer Excitons in Crystalline Supramolecular Photocatalytic Scaffolds. / Hestand, Nicholas J.; Kazantsev, Roman V.; Weingarten, Adam S.; Palmer, Liam C.; Stupp, Samuel I; Spano, Frank C.

In: Journal of the American Chemical Society, Vol. 138, No. 36, 14.09.2016, p. 11762-11774.

Research output: Contribution to journalArticle

Hestand, Nicholas J. ; Kazantsev, Roman V. ; Weingarten, Adam S. ; Palmer, Liam C. ; Stupp, Samuel I ; Spano, Frank C. / Extended-Charge-Transfer Excitons in Crystalline Supramolecular Photocatalytic Scaffolds. In: Journal of the American Chemical Society. 2016 ; Vol. 138, No. 36. pp. 11762-11774.
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