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Introduction of the SPP 2045 subproject “Fractionation of Nanoparticles by Preparative Gel Electrophoresis“

Project Team: Matthäus Barasinski, Prof. Georg Garnweitner (TU Braunschweig, iPAT)

Monodisperse nanoparticles with completely uniform properties regarding size and morphology are essential already today for optical (plasmonic) applications. In the future, such particles will be necessary for many further areas. For example, in the field of medicine or for self-assembly processes these uniform nanoparticles promise a high-precision mode of action and structures with highest precision, respectively.
Since the required narrow particle size distribution or monodispersity is not reached with conventional methods, this subproject shall investigate the fractionation of these synthesized particles with preparative gel electrophoresis. Thereby, the nanoparticles are separated spatially in an appropriate gel due to their different electrophoretic mobilities (µ_E). In principle it is possible to calculate this mobility by the measurement of zeta potential and utilization of the Henry formula (s. eq. 1).

In biochemistry this method is known for the separation of macromolecules (DNA-, protein purification). Here this know-how shall be transferred for the separation of metal oxide nanoparticles. As model systems, SiO2 and ZnO nanoparticles shall be applied with a size range from 10 to 200 nm. The gel can consist of agarose or polyamide, which allows specific adjustment of the pore size by variation of concentration. An important aspect is to obtain constantly highly defined and reproducible pore structures.
Figure 1 shows exemplarily the migration of SiO2 nanoparticles with a mean volumetric diameter of 25 nm in an agarose gel (1D-gel electrophoresis) depending on time.

Figure 1: Migration distance of SiO2 nanoparticles in dependence of time

Modification of the particle surfaces by ligand binding are planned, in order to influence the migration of the particles. Furthermore, the gel shall be varied by passivation or a pH-gradient.
In the later stages of the project, a two dimensional gel electrophoresis chamber will be designed (s. Figure 2), allowing a separation of nanoparticles with regard to size and morphology. Due to this apparatus a preparative separation of a large quantity of particle fractions in short time is possible, which means that separated particles will be retrieved as fractions of dispersions. That aspect makes this process interesting for future applications in large scale. The apparatus will be complemented by a camera and an in-situ UV/Vis-measurement. For this purpose, the multiplexing method will be used. This allows an almost simultaneous measurement at different measurement points with only one photometer. By the assumption of defined morphology and a previous calibration, the particle sizes of the already separated nanoparticles can be calculated.

Figure 2: 2-D gel electrophoresis for separation of nanoparticles

The success of separation will be monitored by the above mentioned UV/Vis-measurement, whereas for the ZnO nanoparticles an online-measurement of the particle size and morphology shall be achieved. Further important methods for tracing the separation are the dynamic light scattering (DLS) and the small-angle X-ray scattering (SAXS). The method of electron microscopy (TEM and Cryo-SEM) will be used for select samples, however requiring the isolation of the nanoparticles from the gel.
Finally, the migration behavior of the nanoparticles inside the gel by a complex electric field has to be modelled and simulated. Such a model would enable the rational determination of the properties of the needed gel and the parameters to separate a certain particle system.


Team Members

Current Projects
Synthesis and processing of tailored AZO nanocrystals more

Fractionation of Nanoparticles by Preparative Gel Electrophoresis more

Thin nanoparticle films for cathode composites in all solid state batteries more

ElektroBak – Innovative Materials and Concepts for Microbial Electrochemical Systems more

Preparation of multifunctional nanocomposite thin films made of nanosized building blocks more

Characteristics of a nanoparticulate coating based on the process chain more

Finished Projects
Process technology of the synthesis of metal oxide nanoparticles by nonaqueous sol gel methods more

Biocompatible iron-oxide nanoparticles for the in-situ magnetic separation of bioproducts more

Small-Molecule Stabilization of ITO Nanoparticles more

AiF – CleanCoat: Development of transparent, photocatalytically active coatings on polymer substrates with long-term stability more

Protein purification with functionalized magnetic nanoparticles more