@article{MillerWintzheimerPrieschletal.2021,
  author    = {Miller, Franziska and Wintzheimer, Susanne and Prieschl, Johannes and Strauss, Volker and Mandel, Karl},
  title     = {A Supraparticle-Based Five-Level-Identification Tag That Switches Information Upon Readout},
  series = {Advanced Optical Materials},
  volume    = {9},
  journal   = {Advanced Optical Materials},
  number    = {4},
  doi       = {10.1002/adom.202001972},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-224469},
  year      = {2021},
  abstract  = {Product identification tags are of great importance in a globalized world with increasingly complex trading routes and networks. Beyond currently used coding strategies, such as QR codes, higher data density, flexible application as well as miniaturization and readout indication are longed for in the next generation of security tags. In this work, micron-sized supraparticles (SPs) with encoded information (ID) are produced that not only exhibit multiple initially covert identification levels but are also irreversibly marked as "read" upon readout. To achieve this, lanthanide doped CaF\(_{2}\) nanoparticles are assembled in various quantity-weighted ratios via spray-drying in presence of a broad-spectrum stealth fluorophore (StFl), yielding covert spectrally encoded ID-SPs. Using these as pigments, QR codes, initially dominated by the green fluorescence of the StFl, could be generated. Upon thermal energy input, these particle-based tags irreversibly switch to an activated state revealing not only multiple luminescent colors but also spectral IDs. This strategy provides the next generation of material-based security tags with a high data density and security level that switch information upon readout and can be, therefore, used as seal of quality.},
  language  = {en}
}
@article{MuessigKochColladosCuadradoetal.2022,
  author    = {M{\"u}ssig, Stephan and Koch, Vanessa M. and Collados Cuadrado, Carlos and Bachmann, Julien and Thommes, Matthias and Barr, Ma{\"i}ssa K. S. and Mandel, Karl},
  title     = {Spray-Drying and Atomic Layer Deposition: Complementary Tools toward Fully Orthogonal Control of Bulk Composition and Surface Identity of Multifunctional Supraparticles},
  series = {Small Methods},
  volume    = {6},
  journal   = {Small Methods},
  number    = {1},
  doi       = {10.1002/smtd.202101296},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-262521},
  year      = {2022},
  abstract  = {Spray-drying is a scalable process enabling one to assemble freely chosen nanoparticles into supraparticles. Atomic layer deposition (ALD) allows for controlled thin film deposition of a vast variety of materials including exotic ones that can hardly be synthesized by wet chemical methods. The properties of coated supraparticles are defined not only by the nanoparticle material chosen and the nanostructure adjusted during spray-drying but also by surface functionalities modified by ALD, if ALD is capable of modifying not only the outer surfaces but also surfaces buried inside the porous supraparticle. Simultaneously, surface accessibility in the porous supraparticles must be ensured to make use of all functionalized surfaces. In this work, iron oxide supraparticles are utilized as a model substrate as their magnetic properties enable the use of advanced magnetic characterization methods. Detailed information about the structural evolution upon individual ALD cycles of aluminium oxide, zinc oxide and titanium dioxide are thereby revealed and confirmed by gas sorption analyses. This demonstrates a powerful and versatile approach to freely designing the functionality of future materials by combination of spray-drying and ALD.},
  language  = {en}
}