TY  - JOUR
A1  - Pavlenko, Elena S.
A1  - Sander, Mathias
A1  - Cui, Q.
A1  - Bargheer, Matias
T1  - Gold Nanorods Sense the Ultrafast Viscoelastic Deformation of Polymers upon Molecular Strain Actuation
JF  - The journal of physical chemistry : C, Nanomaterials and interfaces
N2  - 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.
Y1  - 2016
U6  - https://doi.org/10.1021/acs.jpcc.6b06915
SN  - 1932-7447
VL  - 120
SP  - 24957
EP  - 24964
PB  - American Chemical Society
CY  - Washington
ER  -