@misc{PavlenkoSanderMitzscherlingetal.2016, author = {Pavlenko, Elena S. and Sander, Mathias and Mitzscherling, Steffen and Pudell, Jan-Etienne and Zamponi, Flavio and R{\"o}ssle, Matthias and Bojahr, Andre and Bargheer, Matias}, title = {Azobenzene - functionalized polyelectrolyte nanolayers as ultrafast optoacoustic transducers}, volume = {8}, doi = {10.1039/C6NR01448H}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-101996}, 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 ε ∼ 5 × 10-4 is calibrated by ultrafast X-ray diffraction.}, language = {en} } @article{BojahrHerzogMitzscherlingetal.2013, author = {Bojahr, Andre and Herzog, Marc and Mitzscherling, Steffen and Maerten, Lena and Schick, Daniel and Goldshteyn, J. and Leitenberger, Wolfram and Shayduk, R. and Gaal, P. and Bargheer, Matias}, title = {Brillouin scattering of visible and hard X-ray photons from optically synthesized phonon wavepackets}, series = {Optics express : the international electronic journal of optics}, volume = {21}, journal = {Optics express : the international electronic journal of optics}, number = {18}, publisher = {Optical Society of America}, address = {Washington}, issn = {1094-4087}, doi = {10.1364/OE.21.021188}, pages = {21188 -- 21197}, year = {2013}, abstract = {We monitor how destructive interference of undesired phonon frequency components shapes a quasi-monochromatic hypersound wavepacket spectrum during its local real-time preparation by a nanometric transducer and follow the subsequent decay by nonlinear coupling. We prove each frequency component of an optical supercontinuum probe to be sensitive to one particular phonon wavevector in bulk material and cross-check this by ultrafast x-ray diffraction experiments with direct access to the lattice dynamics. Establishing reliable experimental techniques with direct access to the transient spectrum of the excitation is crucial for the interpretation in strongly nonlinear regimes, such as soliton formation.}, language = {en} } @article{MitzscherlingCuiKoopmanetal.2015, author = {Mitzscherling, Steffen and Cui, Q. and Koopman, Wouter-Willem Adriaan and Bargheer, Matias}, title = {Dielectric function of two-phase colloid-polymer nanocomposite}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {17}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, number = {44}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c5cp04326c}, pages = {29465 -- 29474}, year = {2015}, abstract = {The plasmon resonance of metal nanoparticles determines their optical response in the visible spectral range. Many details such as the electronic properties of gold near the particle surface and the local environment of the particles influence the spectra. We show how the cheap but highly precise fabrication of composite nanolayers by spin-assisted layer-by-layer deposition of polyelectrolytes can be used to investigate the spectral response of gold nanospheres (GNS) and gold nanorods (GNR) in a self-consistent way, using the established Maxwell-Garnett effective medium (MGEM) theory beyond the limit of homogeneous media. We show that the dielectric function of gold nanoparticles differs from the bulk value and experimentally characterize the shape and the surrounding of the particles thoroughly by SEM, AFM and ellipsometry. Averaging the dielectric functions of the layered surrounding by an appropriate weighting with the electric field intensity yields excellent agreement for the spectra of several nanoparticles and nanorods with various cover-layer thicknesses.}, language = {en} } @misc{MitzscherlingCuiKoopmanetal.2015, author = {Mitzscherling, Steffen and Cui, Qianling and Koopman, Wouter-Willem Adriaan and Bargheer, Matias}, title = {Dielectric function of two-phase colloid-polymer nanocomposite}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-102695}, pages = {29465 -- 29474}, year = {2015}, abstract = {The plasmon resonance of metal nanoparticles determines their optical response in the visible spectral range. Many details such as the electronic properties of gold near the particle surface and the local environment of the particles influence the spectra. We show how the cheap but highly precise fabrication of composite nanolayers by spin-assisted layer-by-layer deposition of polyelectrolytes can be used to investigate the spectral response of gold nanospheres (GNS) and gold nanorods (GNR) in a self-consistent way, using the established Maxwell-Garnett effective medium (MGEM) theory beyond the limit of homogeneous media. We show that the dielectric function of gold nanoparticles differs from the bulk value and experimentally characterize the shape and the surrounding of the particles thoroughly by SEM, AFM and ellipsometry. Averaging the dielectric functions of the layered surrounding by an appropriate weighting with the electric field intensity yields excellent agreement for the spectra of several nanoparticles and nanorods with various cover-layer thicknesses.}, language = {en} } @article{KielKloetzerMitzscherlingetal.2012, author = {Kiel, Mareike and Kloetzer, Madlen and Mitzscherling, Steffen and Bargheer, Matias}, title = {Measuring the Range of Plasmonic Interaction}, series = {Langmuir}, volume = {28}, journal = {Langmuir}, number = {10}, publisher = {American Chemical Society}, address = {Washington}, issn = {0743-7463}, doi = {10.1021/la204577m}, pages = {4800 -- 4804}, year = {2012}, abstract = {When gold nanoparticles are covered with nanometric layers of transparent polyelectrolytes, the plasmon absorption spectrum A(lambda) increases by a factor of approximately three and shifts to the red. These modifications of dissipative experimental observables stop when the cover layer thickness approaches the particle diameter. Spectral modifications of dispersive parameters like the reflection R, however, keep changing with increasing cover layer thickness. The shift of the plasmon resonance caused by two interacting particle layers is studied as a function of the separating distance between the two layers. We discuss these observations in the context of an effective medium theory and conclude that it can only be applied for a layer thickness on the order of the particle diameter.}, language = {en} } @phdthesis{Mitzscherling2015, author = {Mitzscherling, Steffen}, title = {Polyelectrolyte multilayers for plasmonics and picosecond ultrasonics}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-80833}, school = {Universit{\"a}t Potsdam}, pages = {93}, year = {2015}, abstract = {This thesis investigates the application of polyelectrolyte multilayers in plasmonics and picosecond acoustics. The observed samples were fabricated by the spin-assisted layer-by-layer deposition technique that allowed a precise tuning of layer thickness in the range of few nanometers. The first field of interest deals with the interaction of light-induced localized surface plasmons (LSP) of rod-shaped gold nanoparticles with the particles' environment. The environment consists of an air phase and a phase of polyelectrolytes, whose ratio affects the spectral position of the LSP resonance. Measured UV-VIS spectra showed the shift of the LSP absorption peak as a function of the cover layer thickness of the particles. The data are modeled using an average dielectric function instead of the dielectric functions of air and polyelectrolytes. In addition using a measured dielectric function of the gold nanoparticles, the position of the LSP absorption peak could be simulated with good agreement to the data. The analytic model helps to understand the optical properties of metal nanoparticles in an inhomogeneous environment. The second part of this work discusses the applicability of PAzo/PAH and dye-doped PSS/PAH polyelectrolyte multilayers as transducers to generate hypersound pulses. The generated strain pulses were detected by time-domain Brillouin scattering (TDBS) using a pump-probe laser setup. Transducer layers made of polyelectrolytes were compared qualitatively to common aluminum transducers in terms of measured TDBS signal amplitude, degradation due to laser excitation, and sample preparation. The measurements proved that fast and easy prepared polyelectrolyte transducers provided stronger TDBS signals than the aluminum transducer. AFM topography measurements showed a degradation of the polyelectrolyte structures, especially for the PAzo/PAH sample. To quantify the induced strain, optical barriers were introduced to separate the transducer material from the medium of the hypersound propagation. Difficulties in the sample preparation prohibited a reliable quantification. But the experiments showed that a coating with transparent polyelectrolytes increases the efficiency of aluminum transducers and modifies the excited phonon distribution. The adoption of polyelectrolytes to the scientific field of picosecond acoustics enables a cheap and fast fabrication of transducer layers on most surfaces. In contrast to aluminum layers the polyelectrolytes are transparent over a wide spectral range. Thus, the strain modulation can be probed from surface and back.}, language = {en} } @article{CuiXiaMitzscherlingetal.2015, author = {Cui, Qianling and Xia, Bihua and Mitzscherling, Steffen and Masic, Admir and Li, Lidong and Bargheer, Matias and Moehwald, Helmuth}, title = {Preparation of gold nanostars and their study in selective catalytic reactions}, series = {Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects}, volume = {465}, journal = {Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0927-7757}, doi = {10.1016/j.colsurfa.2014.10.028}, pages = {20 -- 25}, year = {2015}, abstract = {In this work, gold nanostars (AuNSs) with size around 90 nm were prepared through an easy one-step method. They show excellent catalytic activity and large surface-enhanced Raman scattering (SERS) activity at the same time. Surprisingly, they exhibited different catalytic performance on the reduction of aromatic nitro compounds with different substituents on the para position. To understand such a difference, the SERS spectra were recorded, showing that the molecular orientation of reactants on the gold surface were different. We anticipate that this research will help to understand the relationship of the molecular orientation with the catalytic activity of gold nanoparticles.}, language = {en} }