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@ARTICLE{Hardt:1024739,
      author       = {Hardt, Michael and Busse, Franziska and Raschke, Simon and
                      Honnigfort, Christian and Carrascosa-Tejedor, Javier and
                      Wenk, Paul and Gutfreund, Philipp and Campbell, Richard A.
                      and Heuer, Andreas and Braunschweig, Björn},
      title        = {{P}hoto-{R}esponsive {C}ontrol of {A}dsorption and
                      {S}tructure {F}ormation at the {A}ir–{W}ater {I}nterface
                      with {A}rylazopyrazoles},
      journal      = {Langmuir},
      volume       = {39},
      number       = {16},
      issn         = {0743-7463},
      address      = {Washington, DC},
      publisher    = {ACS Publ.},
      reportid     = {FZJ-2024-02405},
      pages        = {5861 - 5871},
      year         = {2023},
      abstract     = {Smart interfaces that are responsive to external triggers
                      such as light are of great interest for the development of
                      responsive or adaptive materials and interfaces. Using
                      alkyl-arylazopyrazole butyl sulfonate surfactants
                      (alkyl-AAP) that can undergo E/Z photoisomerization when
                      irradiated with green (E) and UV (Z) lights, we demonstrate
                      through a combination of experiments and computer
                      simulations that there can be surprisingly large changes in
                      surface tension and in the molecular structure and order at
                      air–water interfaces. Surface tensiometry, vibrational
                      sum-frequency generation (SFG) spectroscopy, and neutron
                      reflectometry (NR) are applied to the study of
                      custom-synthesized AAP surfactants with octyl- and
                      H-terminal groups at air–water interfaces as a function of
                      their bulk concentration and E/Z configuration. Upon
                      photoswitching, a drastic influence of the alkyl chain on
                      both the surface activity and the responsiveness of
                      interfacial surfactants is revealed from changes in the
                      surface tension, γ, where the largest changes in γ are
                      observed for octyl-AAP (Δγ ∼ 23 mN/m) in contrast to
                      H-AAP with Δγ < 10 mN/m. Results from vibrational SFG
                      spectroscopy and NR show that the interfacial composition
                      and the molecular order of the surfactants drastically
                      change with E/Z photoisomerization and surface coverage.
                      Indeed, from analysis of the S–O (head group) and C–H
                      vibrational bands (hydrophobic tail), a qualitative analysis
                      of orientational and structural changes of interfacial AAP
                      surfactants is provided. The experiments are complemented by
                      resolution of thermodynamic parameters such as equilibrium
                      constants from ultra-coarse-grained simulations, which also
                      capture details like island formation and interaction
                      parameters of interfacial molecules. Here, the interparticle
                      interaction (“stickiness”) and the interaction with the
                      surface are adjusted, closely reflecting experimental
                      conditions.},
      cin          = {IEK-12},
      ddc          = {540},
      cid          = {I:(DE-Juel1)IEK-12-20141217},
      pnm          = {1221 - Fundamentals and Materials (POF4-122) / DFG project
                      G:(GEPRIS)433682494 - SFB 1459: Intelligente Materie – Von
                      responsiven zu adaptiven Nanosystemen (433682494)},
      pid          = {G:(DE-HGF)POF4-1221 / G:(GEPRIS)433682494},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {37058525},
      UT           = {WOS:000974305400001},
      doi          = {10.1021/acs.langmuir.3c00294},
      url          = {https://juser.fz-juelich.de/record/1024739},
}