@article{PavlenkoSanderMitzscherlingetal.2016,
  author    = {Pavlenko, Elena S. and Sander, Mathias and Mitzscherling, S. and Pudell, Jan-Etienne and Zamponi, Flavio and Roessle, M. and Bojahr, Andre and Bargheer, Matias},
  title     = {Azobenzene - functionalized polyelectrolyte nanolayers as ultrafast optoacoustic transducers},
  series = {Nanoscale},
  volume    = {8},
  journal   = {Nanoscale},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {2040-3364},
  doi       = {10.1039/c6nr01448h},
  pages     = {13297 -- 13302},
  year      = {2016},
  abstract  = {We introduce azobenzene-functionalized polyelectrolyte multilayers as efficient, inexpensive optoacoustic transducers for hyper-sound strain waves in the GHz range. By picosecond transient reflectivity measurements we study the creation of nanoscale strain waves, their reflection from interfaces, damping by scattering from nanoparticles and propagation in soft and hard adjacent materials like polymer layers, quartz and mica. The amplitude of the generated strain epsilon similar to 5 x 10(-4) is calibrated by ultrafast X-ray diffraction.},
  language  = {en}
}
@article{PavlenkoSanderCuietal.2016,
  author    = {Pavlenko, Elena S. and Sander, Mathias and Cui, Q. and Bargheer, Matias},
  title     = {Gold Nanorods Sense the Ultrafast Viscoelastic Deformation of Polymers upon Molecular Strain Actuation},
  series = {The journal of physical chemistry : C, Nanomaterials and interfaces},
  volume    = {120},
  journal   = {The journal of physical chemistry : C, Nanomaterials and interfaces},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1932-7447},
  doi       = {10.1021/acs.jpcc.6b06915},
  pages     = {24957 -- 24964},
  year      = {2016},
  abstract  = {On the basis of the layer-by-layer deposition of polyelectrolytes, we have designed hybrid nanolayer composites for integrated optoacoustic experiments. The femtosecond-laser-excitation of an Azo functionalized film launches nanoscale strain waves at GHz frequencies into a transparent polymer layer. Gold nanorods deposited on the surface sense the arrival of these hyper-sound-waves on the picosecond time scale via a modification of their longitudinal plasmon resonance. We simulated the strain waves using a simple linear masses-and-springs model, which yields good agreement with the observed time scales associated with the nanolayer thicknesses of the constituent materials. From systematic experiments with calibrated strain amplitudes we conclude that reversible viscoelastic deformations of the polyelectrolyte multilayers are triggered by ultrashort pressure transients of about 4 MPa. Our experiments show that strain-mediated interactions in nanoarchitectures composed of molecular photoswitches and plasmonic particles may be used to design new functionalities. The approach combines the highly flexible and cost-effective preparation of polyelectrolyte multilayers with ultrafast molecular strain actuation and plasmonic sensing. Although we use simple flat layered structures for demonstration, this new concept can be used for three-dimensional nanoassemblies with different functionalities. The ultrafast and reversible nature of the response is highly desirable, and the short wavelength associated with the high frequency of the hyper-sound-waves connecting photoactive molecules and nanoparticles inherently gives spectroscopic access to the nanoscale. High-frequency elastic moduli are derived from the ultrafast spectroscopy of the hypersonic response in polyelectrolyte multilayers.},
  language  = {en}
}