@phdthesis{FortesMartin2023,
  author    = {Fortes Mart{\´i}n, Rebeca},
  title     = {Water-in-oil microemulsions as soft-templates to mediate nanoparticle interfacial assembly into hybrid nanostructures},
  doi       = {10.25932/publishup-57180},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-571801},
  school      = {Universit{\"a}t Potsdam},
  pages     = {119},
  year      = {2023},
  abstract  = {Hybrid nanomaterials offer the combination of individual properties of different types of nanoparticles. Some strategies for the development of new nanostructures in larger scale rely on the self-assembly of nanoparticles as a bottom-up approach. The use of templates provides ordered assemblies in defined patterns. In a typical soft-template, nanoparticles and other surface-active agents are incorporated into non-miscible liquids. The resulting self-organized dispersions will mediate nanoparticle interactions to control the subsequent self-assembly. Especially interactions between nanoparticles of very different dispersibility and functionality can be directed at a liquid-liquid interface. In this project, water-in-oil microemulsions were formulated from quasi-ternary mixtures with Aerosol-OT as surfactant. Oleyl-capped superparamagnetic iron oxide and/or silver nanoparticles were incorporated in the continuous organic phase, while polyethyleneimine-stabilized gold nanoparticles were confined in the dispersed water droplets. Each type of nanoparticle can modulate the surfactant film and the inter-droplet interactions in diverse ways, and their combination causes synergistic effects. Interfacial assemblies of nanoparticles resulted after phase-separation. On one hand, from a biphasic Winsor type II system at low surfactant concentration, drop-casting of the upper phase afforded thin films of ordered nanoparticles in filament-like networks. Detailed characterization proved that this templated assembly over a surface is based on the controlled clustering of nanoparticles and the elongation of the microemulsion droplets. This process offers versatility to use different nanoparticle compositions by keeping the surface functionalization, in different solvents and over different surfaces. On the other hand, a magnetic heterocoagulate was formed at higher surfactant concentration, whose phase-transfer from oleic acid to water was possible with another auxiliary surfactant in ethanol-water mixture. When the original components were initially mixed under heating, defined oil-in-water, magnetic-responsive nanostructures were obtained, consisting on water-dispersible nanoparticle domains embedded by a matrix-shell of oil-dispersible nanoparticles. Herein, two different approaches were demonstrated to form diverse hybrid nanostructures from reverse microemulsions as self-organized dispersions of the same components. This shows that microemulsions are versatile soft-templates not only for the synthesis of nanoparticles, but also for their self-assembly, which suggest new approaches towards the production of new sophisticated nanomaterials in larger scale.},
  language  = {en}
}
@article{HasinovicBoggsFribergetal.2014,
  author    = {Hasinovic, Hida and Boggs, Cami and Friberg, Stig E. and Kovach, Ildiko and Koetz, Joachim},
  title     = {Janus emulsions from a one-step process; optical microscopy images},
  series = {Journal of dispersion science and technology},
  volume    = {35},
  journal   = {Journal of dispersion science and technology},
  number    = {5},
  publisher = {Taylor \& Francis Group},
  address   = {Philadelphia},
  issn      = {0193-2691},
  doi       = {10.1080/01932691.2013.801019},
  pages     = {613 -- 618},
  year      = {2014},
  abstract  = {The optical microscopy images of an emulsion are commonly distorted when viewed between a cover glass and a planar microscopy slide. An alternative method is to place the sample on a slide with a cavity, which in turn suffers from incomplete information for high internal phase ratio (HIPR) emulsions, due to the inevitable crowding of the drops. This problem is particularly acute for more complex emulsions, such as those with Janus drops, for which a detailed image of the drop is essential. A number of publications have recently described Janus emulsions prepared by a one-step high energy emulsification process with microscopy images obtained by the sample between a planar slide and a cover glass. The correlation to the morphology of emulsions in bulk of these images is critical, but, so far, a potential equivalence has not been established. Since the images are central in order to understand why Janus emulsions should form under such conditions, the need to ascertain any such association is urgent. With this contribution, we compare images from different microscopy methods to those of gently diluted HIPR emulsions. The results reveal that the images of the emulsion samples between a cover glass and a planar microscope slide actually present a realistic representation of the drop topology in bulk emulsions.},
  language  = {en}
}