---
_id: '13386'
abstract:
- lang: eng
  text: Azobenzenealkanethiols in self-assembled monolayers (SAMs) on Au(111) exhibit
    reversible trans–cis photoisomerization when diluted with alkanethiol spacers.
    Using these mixed SAMs, we show switching of the linear optical and second-harmonic
    response. The effective switching of these surface optical properties relies on
    a reasonably large cross section and a high photoisomerization yield as well as
    a long lifetime of the metastable cis isomer. We quantified the switching process
    by X-ray absorption spectroscopy. The cross sections for the trans–cis and cis–trans
    photoisomerization with 365 and 455 nm light, respectively, are 1 order of magnitude
    smaller than in solution. In vacuum, the 365 nm photostationary state comprises
    50–74% of the molecules in the cis form, limited by their rapid thermal isomerization
    back to the trans state. In contrast, the 455 nm photostationary state contains
    nearly 100% trans-azobenzene. We determined time constants for the thermal cis–trans
    isomerization of only a few minutes in vacuum and in a dry nitrogen atmosphere
    but of more than 1 day in ambient air. Our results suggest that adventitious water
    adsorbed on the surface of the SAM stabilizes the polar cis configuration of azobenzene
    under ambient conditions. The back reaction rate constants differing by 2 orders
    of magnitude underline the huge influence of the environment and, accordingly,
    its importance when comparing various experiments.
article_processing_charge: No
article_type: original
author:
- first_name: Thomas
  full_name: Moldt, Thomas
  last_name: Moldt
- first_name: Daniel
  full_name: Przyrembel, Daniel
  last_name: Przyrembel
- first_name: Michael
  full_name: Schulze, Michael
  last_name: Schulze
- first_name: Wibke
  full_name: Bronsch, Wibke
  last_name: Bronsch
- first_name: Larissa
  full_name: Boie, Larissa
  last_name: Boie
- first_name: Daniel
  full_name: Brete, Daniel
  last_name: Brete
- first_name: Cornelius
  full_name: Gahl, Cornelius
  last_name: Gahl
- first_name: Rafal
  full_name: Klajn, Rafal
  id: 8e84690e-1e48-11ed-a02b-a1e6fb8bb53b
  last_name: Klajn
- first_name: Petra
  full_name: Tegeder, Petra
  last_name: Tegeder
- first_name: Martin
  full_name: Weinelt, Martin
  last_name: Weinelt
citation:
  ama: Moldt T, Przyrembel D, Schulze M, et al. Differing isomerization kinetics of
    azobenzene-functionalized self-assembled monolayers in ambient air and in vacuum.
    <i>Langmuir</i>. 2016;32(42):10795-10801. doi:<a href="https://doi.org/10.1021/acs.langmuir.6b01690">10.1021/acs.langmuir.6b01690</a>
  apa: Moldt, T., Przyrembel, D., Schulze, M., Bronsch, W., Boie, L., Brete, D., …
    Weinelt, M. (2016). Differing isomerization kinetics of azobenzene-functionalized
    self-assembled monolayers in ambient air and in vacuum. <i>Langmuir</i>. American
    Chemical Society. <a href="https://doi.org/10.1021/acs.langmuir.6b01690">https://doi.org/10.1021/acs.langmuir.6b01690</a>
  chicago: Moldt, Thomas, Daniel Przyrembel, Michael Schulze, Wibke Bronsch, Larissa
    Boie, Daniel Brete, Cornelius Gahl, Rafal Klajn, Petra Tegeder, and Martin Weinelt.
    “Differing Isomerization Kinetics of Azobenzene-Functionalized Self-Assembled
    Monolayers in Ambient Air and in Vacuum.” <i>Langmuir</i>. American Chemical Society,
    2016. <a href="https://doi.org/10.1021/acs.langmuir.6b01690">https://doi.org/10.1021/acs.langmuir.6b01690</a>.
  ieee: T. Moldt <i>et al.</i>, “Differing isomerization kinetics of azobenzene-functionalized
    self-assembled monolayers in ambient air and in vacuum,” <i>Langmuir</i>, vol.
    32, no. 42. American Chemical Society, pp. 10795–10801, 2016.
  ista: Moldt T, Przyrembel D, Schulze M, Bronsch W, Boie L, Brete D, Gahl C, Klajn
    R, Tegeder P, Weinelt M. 2016. Differing isomerization kinetics of azobenzene-functionalized
    self-assembled monolayers in ambient air and in vacuum. Langmuir. 32(42), 10795–10801.
  mla: Moldt, Thomas, et al. “Differing Isomerization Kinetics of Azobenzene-Functionalized
    Self-Assembled Monolayers in Ambient Air and in Vacuum.” <i>Langmuir</i>, vol.
    32, no. 42, American Chemical Society, 2016, pp. 10795–801, doi:<a href="https://doi.org/10.1021/acs.langmuir.6b01690">10.1021/acs.langmuir.6b01690</a>.
  short: T. Moldt, D. Przyrembel, M. Schulze, W. Bronsch, L. Boie, D. Brete, C. Gahl,
    R. Klajn, P. Tegeder, M. Weinelt, Langmuir 32 (2016) 10795–10801.
date_created: 2023-08-01T09:42:37Z
date_published: 2016-10-25T00:00:00Z
date_updated: 2023-08-07T12:27:06Z
day: '25'
doi: 10.1021/acs.langmuir.6b01690
extern: '1'
external_id:
  pmid:
  - '27681851'
intvolume: '        32'
issue: '42'
keyword:
- Electrochemistry
- Spectroscopy
- Surfaces and Interfaces
- Condensed Matter Physics
- General Materials Science
language:
- iso: eng
month: '10'
oa_version: None
page: 10795-10801
pmid: 1
publication: Langmuir
publication_identifier:
  eissn:
  - 1520-5827
  issn:
  - 0743-7463
publication_status: published
publisher: American Chemical Society
quality_controlled: '1'
scopus_import: '1'
status: public
title: Differing isomerization kinetics of azobenzene-functionalized self-assembled
  monolayers in ambient air and in vacuum
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 32
year: '2016'
...
---
_id: '13396'
abstract:
- lang: eng
  text: '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.'
article_processing_charge: No
article_type: original
author:
- first_name: Thomas
  full_name: Moldt, Thomas
  last_name: Moldt
- first_name: Daniel
  full_name: Brete, Daniel
  last_name: Brete
- first_name: Daniel
  full_name: Przyrembel, Daniel
  last_name: Przyrembel
- first_name: Sanjib
  full_name: Das, Sanjib
  last_name: Das
- first_name: Joel R.
  full_name: Goldman, Joel R.
  last_name: Goldman
- first_name: Pintu K.
  full_name: Kundu, Pintu K.
  last_name: Kundu
- first_name: Cornelius
  full_name: Gahl, Cornelius
  last_name: Gahl
- first_name: Rafal
  full_name: Klajn, Rafal
  id: 8e84690e-1e48-11ed-a02b-a1e6fb8bb53b
  last_name: Klajn
- first_name: Martin
  full_name: Weinelt, Martin
  last_name: Weinelt
citation:
  ama: Moldt T, Brete D, Przyrembel D, et al. Tailoring the properties of surface-immobilized
    azobenzenes by monolayer dilution and surface curvature. <i>Langmuir</i>. 2015;31(3):1048-1057.
    doi:<a href="https://doi.org/10.1021/la504291n">10.1021/la504291n</a>
  apa: 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. <i>Langmuir</i>. American Chemical
    Society. <a href="https://doi.org/10.1021/la504291n">https://doi.org/10.1021/la504291n</a>
  chicago: Moldt, Thomas, Daniel Brete, Daniel Przyrembel, Sanjib Das, Joel R. Goldman,
    Pintu K. Kundu, Cornelius Gahl, Rafal Klajn, and Martin Weinelt. “Tailoring the
    Properties of Surface-Immobilized Azobenzenes by Monolayer Dilution and Surface
    Curvature.” <i>Langmuir</i>. American Chemical Society, 2015. <a href="https://doi.org/10.1021/la504291n">https://doi.org/10.1021/la504291n</a>.
  ieee: T. Moldt <i>et al.</i>, “Tailoring the properties of surface-immobilized azobenzenes
    by monolayer dilution and surface curvature,” <i>Langmuir</i>, vol. 31, no. 3.
    American Chemical Society, pp. 1048–1057, 2015.
  ista: 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. 31(3), 1048–1057.
  mla: Moldt, Thomas, et al. “Tailoring the Properties of Surface-Immobilized Azobenzenes
    by Monolayer Dilution and Surface Curvature.” <i>Langmuir</i>, vol. 31, no. 3,
    American Chemical Society, 2015, pp. 1048–57, doi:<a href="https://doi.org/10.1021/la504291n">10.1021/la504291n</a>.
  short: T. Moldt, D. Brete, D. Przyrembel, S. Das, J.R. Goldman, P.K. Kundu, C. Gahl,
    R. Klajn, M. Weinelt, Langmuir 31 (2015) 1048–1057.
date_created: 2023-08-01T09:45:02Z
date_published: 2015-01-27T00:00:00Z
date_updated: 2023-08-07T13:05:04Z
day: '27'
doi: 10.1021/la504291n
extern: '1'
external_id:
  pmid:
  - '25544061'
intvolume: '        31'
issue: '3'
keyword:
- Electrochemistry
- Spectroscopy
- Surfaces and Interfaces
- Condensed Matter Physics
- General Materials Science
language:
- iso: eng
month: '01'
oa_version: None
page: 1048-1057
pmid: 1
publication: Langmuir
publication_identifier:
  eissn:
  - 1520-5827
  issn:
  - 0743-7463
publication_status: published
publisher: American Chemical Society
quality_controlled: '1'
scopus_import: '1'
status: public
title: Tailoring the properties of surface-immobilized azobenzenes by monolayer dilution
  and surface curvature
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 31
year: '2015'
...
---
_id: '13426'
abstract:
- lang: eng
  text: Photoswelling of thin films of dichromated gelatin provides a basis for fabrication
    of multilevel surface reliefs via sequential UV illumination through different
    photomasks. The remarkable feature of this simple, benchtop technique is that
    by adjusting irradiation times, film thickness, or its hydration state the heights
    of the developed features can be varied from few nanometers to tens of microns.
    After UV exposure, the surface structures can be replicated faithfully into either
    soft or hard PDMS stamps.
article_processing_charge: No
article_type: original
author:
- first_name: Maciej
  full_name: Paszewski, Maciej
  last_name: Paszewski
- first_name: Stoyan K.
  full_name: Smoukov, Stoyan K.
  last_name: Smoukov
- first_name: Rafal
  full_name: Klajn, Rafal
  id: 8e84690e-1e48-11ed-a02b-a1e6fb8bb53b
  last_name: Klajn
- first_name: Bartosz A.
  full_name: Grzybowski, Bartosz A.
  last_name: Grzybowski
citation:
  ama: Paszewski M, Smoukov SK, Klajn R, Grzybowski BA. Multilevel surface nano- and
    microstructuring via sequential photoswelling of dichromated gelatin. <i>Langmuir</i>.
    2007;23(10):5419-5422. doi:<a href="https://doi.org/10.1021/la062982c">10.1021/la062982c</a>
  apa: Paszewski, M., Smoukov, S. K., Klajn, R., &#38; Grzybowski, B. A. (2007). Multilevel
    surface nano- and microstructuring via sequential photoswelling of dichromated
    gelatin. <i>Langmuir</i>. American Chemical Society. <a href="https://doi.org/10.1021/la062982c">https://doi.org/10.1021/la062982c</a>
  chicago: Paszewski, Maciej, Stoyan K. Smoukov, Rafal Klajn, and Bartosz A. Grzybowski.
    “Multilevel Surface Nano- and Microstructuring via Sequential Photoswelling of
    Dichromated Gelatin.” <i>Langmuir</i>. American Chemical Society, 2007. <a href="https://doi.org/10.1021/la062982c">https://doi.org/10.1021/la062982c</a>.
  ieee: M. Paszewski, S. K. Smoukov, R. Klajn, and B. A. Grzybowski, “Multilevel surface
    nano- and microstructuring via sequential photoswelling of dichromated gelatin,”
    <i>Langmuir</i>, vol. 23, no. 10. American Chemical Society, pp. 5419–5422, 2007.
  ista: Paszewski M, Smoukov SK, Klajn R, Grzybowski BA. 2007. Multilevel surface
    nano- and microstructuring via sequential photoswelling of dichromated gelatin.
    Langmuir. 23(10), 5419–5422.
  mla: Paszewski, Maciej, et al. “Multilevel Surface Nano- and Microstructuring via
    Sequential Photoswelling of Dichromated Gelatin.” <i>Langmuir</i>, vol. 23, no.
    10, American Chemical Society, 2007, pp. 5419–22, doi:<a href="https://doi.org/10.1021/la062982c">10.1021/la062982c</a>.
  short: M. Paszewski, S.K. Smoukov, R. Klajn, B.A. Grzybowski, Langmuir 23 (2007)
    5419–5422.
date_created: 2023-08-01T10:31:33Z
date_published: 2007-04-11T00:00:00Z
date_updated: 2023-08-08T11:26:24Z
day: '11'
doi: 10.1021/la062982c
extern: '1'
external_id:
  pmid:
  - '17425340'
intvolume: '        23'
issue: '10'
keyword:
- Electrochemistry
- Spectroscopy
- Surfaces and Interfaces
- Condensed Matter Physics
- General Materials Science
language:
- iso: eng
month: '04'
oa_version: None
page: 5419-5422
pmid: 1
publication: Langmuir
publication_identifier:
  eissn:
  - 1520-5827
  issn:
  - 0743-7463
publication_status: published
publisher: American Chemical Society
quality_controlled: '1'
scopus_import: '1'
status: public
title: Multilevel surface nano- and microstructuring via sequential photoswelling
  of dichromated gelatin
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 23
year: '2007'
...
---
_id: '13432'
abstract:
- lang: eng
  text: A new experimental technique is described that uses reaction−diffusion phenomena
    as a means of one-step microfabrication of complex, multilevel surface reliefs.
    Thin films of dry gelatin doped with potassium hexacyanoferrate are chemically
    micropatterned with a solution of silver nitrate delivered from an agarose stamp.
    Precipitation reaction between the two salts causes the surface to deform. The
    mechanism of surface deformation is shown to involve a sequence of reactions,
    diffusion, and gel swelling/contraction. This mechanism is established experimentally
    and provides a basis of a theoretical lattice-gas model that allows prediction
    surface topographies emerging from arbitrary geometries of the stamped features.
    The usefulness of the technique is demonstrated by using it to rapidly prepare
    two types of mold for passive microfluidic mixers.
article_processing_charge: No
article_type: original
author:
- first_name: Christopher J.
  full_name: Campbell, Christopher J.
  last_name: Campbell
- first_name: Rafal
  full_name: Klajn, Rafal
  id: 8e84690e-1e48-11ed-a02b-a1e6fb8bb53b
  last_name: Klajn
- first_name: Marcin
  full_name: Fialkowski, Marcin
  last_name: Fialkowski
- first_name: Bartosz A.
  full_name: Grzybowski, Bartosz A.
  last_name: Grzybowski
citation:
  ama: Campbell CJ, Klajn R, Fialkowski M, Grzybowski BA. One-step multilevel microfabrication
    by reaction−diffusion. <i>Langmuir</i>. 2005;21(1):418-423. doi:<a href="https://doi.org/10.1021/la0487747">10.1021/la0487747</a>
  apa: Campbell, C. J., Klajn, R., Fialkowski, M., &#38; Grzybowski, B. A. (2005).
    One-step multilevel microfabrication by reaction−diffusion. <i>Langmuir</i>. American
    Chemical Society. <a href="https://doi.org/10.1021/la0487747">https://doi.org/10.1021/la0487747</a>
  chicago: Campbell, Christopher J., Rafal Klajn, Marcin Fialkowski, and Bartosz A.
    Grzybowski. “One-Step Multilevel Microfabrication by Reaction−diffusion.” <i>Langmuir</i>.
    American Chemical Society, 2005. <a href="https://doi.org/10.1021/la0487747">https://doi.org/10.1021/la0487747</a>.
  ieee: C. J. Campbell, R. Klajn, M. Fialkowski, and B. A. Grzybowski, “One-step multilevel
    microfabrication by reaction−diffusion,” <i>Langmuir</i>, vol. 21, no. 1. American
    Chemical Society, pp. 418–423, 2005.
  ista: Campbell CJ, Klajn R, Fialkowski M, Grzybowski BA. 2005. One-step multilevel
    microfabrication by reaction−diffusion. Langmuir. 21(1), 418–423.
  mla: Campbell, Christopher J., et al. “One-Step Multilevel Microfabrication by Reaction−diffusion.”
    <i>Langmuir</i>, vol. 21, no. 1, American Chemical Society, 2005, pp. 418–23,
    doi:<a href="https://doi.org/10.1021/la0487747">10.1021/la0487747</a>.
  short: C.J. Campbell, R. Klajn, M. Fialkowski, B.A. Grzybowski, Langmuir 21 (2005)
    418–423.
date_created: 2023-08-01T10:38:29Z
date_published: 2005-01-21T00:00:00Z
date_updated: 2023-08-08T12:15:48Z
day: '21'
doi: 10.1021/la0487747
extern: '1'
external_id:
  pmid:
  - '15620333'
intvolume: '        21'
issue: '1'
keyword:
- Electrochemistry
- Spectroscopy
- Surfaces and Interfaces
- Condensed Matter Physics
- General Materials Science
language:
- iso: eng
month: '01'
oa_version: None
page: 418-423
pmid: 1
publication: Langmuir
publication_identifier:
  eissn:
  - 1520-5827
  issn:
  - 0743-7463
publication_status: published
publisher: American Chemical Society
quality_controlled: '1'
scopus_import: '1'
status: public
title: One-step multilevel microfabrication by reaction−diffusion
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 21
year: '2005'
...