Tailoring the properties of surface-immobilized azobenzenes by monolayer dilution and surface curvature

Thomas Moldt, Daniel Brete, Daniel Przyrembel, Sanjib Das, Joel R. Goldman, Pintu K. Kundu, Cornelius Gahl, Rafal Klajn, Martin Weinelt

Research output: Contribution to journalArticle

38 Citations (Scopus)

Abstract

Photoswitching in densely packed azobenzene self-assembled monolayers (SAMs) is strongly affected by steric constraints and excitonic coupling between neighboring chromophores. Therefore, control of the chromophore density is essential for enhancing and manipulating the photoisomerization yield. We systematically compare two methods to achieve this goal: First, we assemble monocomponent azobenzene-alkanethiolate SAMs on gold nanoparticles of varying size. Second, we form mixed SAMs of azobenzene-alkanethiolates and "dummy" alkanethiolates on planar substrates. Both methods lead to a gradual decrease of the chromophore density and enable efficient photoswitching with low-power light sources. X-ray spectroscopy reveals that coadsorption from solution yields mixtures with tunable composition. The orientation of the chromophores with respect to the surface normal changes from a tilted to an upright position with increasing azobenzene density. For both systems, optical spectroscopy reveals a pronounced excitonic shift that increases with the chromophore density. In spite of exciting the optical transition of the monomer, the main spectral change in mixed SAMs occurs in the excitonic band. In addition, the photoisomerization yield decreases only slightly by increasing the azobenzene-alkanethiolate density, and we observed photoswitching even with minor dilutions. Unlike in solution, azobenzene in the planar SAM can be switched back almost completely by optical excitation from the cis to the original trans state within a short time scale. These observations indicate cooperativity in the photoswitching process of mixed SAMs.

Original languageEnglish
Pages (from-to)1048-1057
Number of pages10
JournalLangmuir
Volume31
Issue number3
DOIs
Publication statusPublished - Jan 27 2015

Fingerprint

Azobenzene
Self assembled monolayers
chromophores
Dilution
dilution
Chromophores
Monolayers
curvature
Photoisomerization
dummies
Optical transitions
optical transition
Photoexcitation
spectroscopy
X ray spectroscopy
light sources
Gold
monomers
Light sources
azobenzene

ASJC Scopus subject areas

  • Electrochemistry
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Materials Science(all)
  • Spectroscopy

Cite this

Moldt, T., Brete, D., Przyrembel, D., Das, S., Goldman, J. R., Kundu, P. K., ... Weinelt, M. (2015). Tailoring the properties of surface-immobilized azobenzenes by monolayer dilution and surface curvature. Langmuir, 31(3), 1048-1057. https://doi.org/10.1021/la504291n

Tailoring the properties of surface-immobilized azobenzenes by monolayer dilution and surface curvature. / Moldt, Thomas; Brete, Daniel; Przyrembel, Daniel; Das, Sanjib; Goldman, Joel R.; Kundu, Pintu K.; Gahl, Cornelius; Klajn, Rafal; Weinelt, Martin.

In: Langmuir, Vol. 31, No. 3, 27.01.2015, p. 1048-1057.

Research output: Contribution to journalArticle

Moldt, T, Brete, D, Przyrembel, D, Das, S, Goldman, JR, Kundu, PK, Gahl, C, Klajn, R & Weinelt, M 2015, 'Tailoring the properties of surface-immobilized azobenzenes by monolayer dilution and surface curvature', Langmuir, vol. 31, no. 3, pp. 1048-1057. https://doi.org/10.1021/la504291n
Moldt T, Brete D, Przyrembel D, Das S, Goldman JR, Kundu PK et al. Tailoring the properties of surface-immobilized azobenzenes by monolayer dilution and surface curvature. Langmuir. 2015 Jan 27;31(3):1048-1057. https://doi.org/10.1021/la504291n
Moldt, Thomas ; Brete, Daniel ; Przyrembel, Daniel ; Das, Sanjib ; Goldman, Joel R. ; Kundu, Pintu K. ; Gahl, Cornelius ; Klajn, Rafal ; Weinelt, Martin. / Tailoring the properties of surface-immobilized azobenzenes by monolayer dilution and surface curvature. In: Langmuir. 2015 ; Vol. 31, No. 3. pp. 1048-1057.
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