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@ARTICLE{Hess:874183,
      author       = {Hess, Melissa and Roeben, Eric and Rochels, Patricia and
                      Zylla, Markus and Webers, Samira and Wende, Heiko and
                      Schmidt, Annette M.},
      title        = {{S}ize effects on rotational particle diffusion in complex
                      fluids as probed by {M}agnetic {P}article {N}anorheology},
      journal      = {Physical chemistry, chemical physics},
      volume       = {21},
      number       = {48},
      issn         = {1463-9084},
      address      = {Cambridge},
      publisher    = {RSC Publ.},
      reportid     = {FZJ-2020-01283},
      pages        = {26525 - 26539},
      year         = {2019},
      abstract     = {Rheological approaches based on micro- or nanoscopic probe
                      objects are of interest due to the low volume requirement,
                      the option of spatially resolved probing, and the
                      minimal-invasive nature often connected to such probes. For
                      the study of microstructured systems or biological
                      environments, such methods show potential for investigating
                      the local, size-dependent diffusivity and particle–matrix
                      interactions. For the latter, the relative length scale of
                      the used probes compared to the size of the structural units
                      of the matrix becomes relevant. In this study, a
                      rotational-dynamic approach based on Magnetic Particle
                      Nanorheology (MPN) is used to extract size- and
                      frequency-dependent nanorheological properties by using an
                      otherwise well-established polymer model system. We use
                      magnetically blocked CoFe2O4 nanoparticles as tracers and
                      systematically vary their hydrodynamic size by coating them
                      with a silica shell. On the polymer side, we employ aqueous
                      solutions of poly(ethylene glycol) (PEG) by varying molar
                      mass M and volume fraction ϕ. The complex Brownian
                      relaxation behavior of the tracer particles in solutions of
                      systematically varied composition is investigated by means
                      of AC susceptometry (ACS), and the results provide access to
                      frequency dependent rheological properties. The
                      size-dependent particle diffusivity is evaluated based on
                      theoretical descriptions and macroscopic measurements. The
                      results allow the classification of the investigated
                      compositions into three regimes, taking into account the
                      probe particle size and the length scales of the polymer
                      solution. While a fuzzy cross-over is indicated between the
                      well-known macroscopic behavior and structurally dominated
                      spectra, where the hydrodynamic radius is equal to the
                      radius of gyration of the polymer (rh ∼ Rg), the
                      frequency-related scaling behavior is dominated by the
                      correlation length ξ respectively by the tube diameter a in
                      entangled solutions for rh < Rg.},
      cin          = {ICS-2 / IHRS-BioSoft},
      ddc          = {540},
      cid          = {I:(DE-Juel1)ICS-2-20110106 /
                      I:(DE-Juel1)IHRS-BioSoft-20161118},
      pnm          = {551 - Functional Macromolecules and Complexes (POF3-551) /
                      IHRS-BioSoft - International Helmholtz Research School of
                      Biophysics and Soft Matter (IHRS-BioSoft-20061101)},
      pid          = {G:(DE-HGF)POF3-551 / G:(DE-Juel1)IHRS-BioSoft-20061101},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:31778132},
      UT           = {WOS:000502767400022},
      doi          = {10.1039/C9CP04083H},
      url          = {https://juser.fz-juelich.de/record/874183},
}