SFB 1214 TP A10 Wittemann "Shape-anisotropic..."

  • Sonderforschungsbereiche
  • SFB 1214 "Anisotropic Particles as Building Blocks"
  • FB Chemie
    Plüisch, Claudia Simone; Bössenecker, Brigitte; Dobler, Lukas; Wittemann, Alexander(2019): Zonal rotor centrifugation revisited : new horizons in sorting nanoparticles RSC Advances ; 9 (2019), 47. - S. 27549-27559. - eISSN 2046-2069

Zonal rotor centrifugation revisited : new horizons in sorting nanoparticles

Density gradient centrifugation is an effective method for the isolation and purification of small particles. Hollow rotors capable of hosting density gradients replace the need for centrifuge tubes and therefore allow separations at large scales. So far, zonal rotors have been used for biological separations ranging from the purification of whole cells down to serum proteins. We demonstrate that the high-resolution separation method opens up exciting perspectives apart from biology, namely in sorting mixtures of synthetic nanoparticles. Loading and unloading, while the rotor is spinning, avoids perturbations during acceleration and deceleration periods, and thus makes a vital contribution to sorting accuracy. Nowadays one can synthesize nanoscale particles in a wide variety of compositions and shapes. A prominent example for this are “colloidal molecules” or, generally speaking, defined assemblies of nanoparticles that can appear in varying aggregation numbers. Fractionation of such multimodal colloids plays an essential role with regard to their organization into hierarchical organized superstructures such as films, mesocrystals and metamaterials. Zonal rotor centrifugation was found to be a scalable method of getting “colloidal molecules” properly sorted. It allows access to pure fractions of particle monomers, dimers, and trimers, just as well as to fractions that are essentially rich in particle tetramers. Separations were evaluated by differential centrifugal sedimentation, which provides high-resolution size distributions of the collected nanoparticle fractions. The performance achieved in relation to resolution, zone widths, sorting efficiencies and recovery rates clearly demonstrate that zonal rotor centrifugation provides an excellent solution to the fractionation of nanoparticle mixtures.

Forschungszusammenhang (Projekte)

  Kalb, Julian; Dorman, James A.; Gerigk, Melanie; Knittel, Vanessa; Plüisch, Claudia S.; Trepka, Bastian; Lehr, Daniela; Wittemann, Alexander; Polarz, Sebastian; Schmidt-Mende, Lukas(2018): Influence of substrates and rutile seed layers on the assembly of hydrothermally grown rutile TiO2 nanorod arrays Journal of Crystal Growth ; 494 (2018). - S. 26-35. - ISSN 0022-0248. - eISSN 1873-5002

Influence of substrates and rutile seed layers on the assembly of hydrothermally grown rutile TiO<sub>2</sub> nanorod arrays

Rutile TiO<sub>2</sub> nanorod arrays (NRAs) are applicable in various prospective technologies. Hydrothermal methods present a simple technique to fabricate such NRAs. In this report, we present the fabrication of seed layers for the hydrothermal growth of rutile TiO<sub>2</sub> nanorods via sputter deposition, electron-beam evaporation, and sol-gel method and study the influence of each on the growth behavior. To satisfy the requirements of numerous applications, p-type silicon, platinum, levitating carbon membranes, a template made of polystyrene spheres, and commercial fluorine tin oxide (FTO) were employed as substrates. We document the structural properties of the TiO<sub>2</sub> seed layers and describe the relationship between the characteristics of the seed crystals, the growth evolution, and the appearance of as-grown nanorods. Various growth stages of rutile TiO<sub>2</sub> nanorods are compared depending on whether they are grown on polycrystalline TiO<sub>2</sub> or FTO seed layers. In both cases, a homogenous TiO<sub>2</sub> bottom layer is formed at the seed layer/substrate interface, which is essential for electronic applications such as hybrid solar cells. Detached NRAs illustrate the effect of rutile FTO and TiO<sub>2</sub> on the porosity of this bottom layer. Further details about the formation process of this layer are obtained from the growth on confined seed layers fabricated by electron-beam lithography.

Forschungszusammenhang (Projekte)

  Plüisch, Claudia Simone; Wittemann, Alexander(2016): Assembly of Nanoparticles into “Colloidal Molecules” : Toward Complex and yet Defined Colloids with Exiting Perspectives Advances in Colloid Science / Rahman, Mohammed Muzibur; Asiri, Abdullah Mohamed (Hrsg.). - Rijeka, Croatia : InTech, 2016. - S. 237-264. - ISBN 978-953-51-2773-4

Assembly of Nanoparticles into “Colloidal Molecules” : Toward Complex and yet Defined Colloids with Exiting Perspectives

In line with atoms being the elementary units of molecules and crystals, colloidal particles can be used as building blocks for organized materials. A major benefit in doing so is that joining colloids in a defined manner comes along with structuring. In view of opening avenues to more complex structural motifs, significant efforts must be geared to colloids with specific shapes and symmetries. A straightforward strategy is joining equal‐sized spherical particles into stable clusters. Such clusters are called “colloidal molecules” because they may exhibit configurations resembling pretty much those of molecules. Their preparation can be based on the agglomeration of particles dispersed in an emulsion. The particles adsorb on the emulsion droplets and coagulate in a defined way during the evaporation of the droplet phase. Using this method originally applied to microscale particles, one can produce clusters with submicronsized global dimensions. Variable parameters such as radii and concentration of cluster constituents provide the framework needed to obtain “colloidal molecules” that differ in size, shape, and physical properties. This opens up exciting perspectives for tailormade colloids as building units for hierarchically organized materials. Moreover, new physical properties such as plasmonic “hotspots” may emerge from packing particles into assemblies of specific configurations.

Forschungszusammenhang (Projekte)

SFB587/16SFB 1214keine Angabe
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Laufzeit: 01.07.2016 – 30.06.2020