title: Fluorescence-based high-resolution tracking of nanoparticles
Creators: name: Zalami, Daniel
Publisher: name: University of Bayreuth
Year: 2021
Subjects: subject: Fluoreszenzmikroskopie
subject: Trajektorien
subject: Diffusion
subject: Single-particle tracking
subject: Filtration
subject: Nanopartikel
subject: Polymermembranen
subject: Feedback
subject: Lineare zeitinvariante Systeme
subject: Kontrollproblem
subject: 500

description: High-precision tracking of nanoparticles via fluorescence-optical methods is a current research area with many applications. While optical methods are usually characterized by causing minimal damage to the sample, their ability to resolve the sample spatially is limited. Therefore, many modern measurement methods make use of tricks to circumvent the diffraction limit and to obtain information at the nanometer scale. In this dissertation, a fluorescence optical method for tracking single nanoparticles, called single-particle orbit tracking (SPOT), is further developed, investigated, and applied. One focus of those new developments was to update the existing experimental setup so that three-dimensional localization can take place instead of only two-dimensional tracking. Another important point of improvement was the extension of the control logic to include additional parameters and signals. The required technical modifications demanded a renewed mathematical modeling of the method, as well as analysis of the measurement errors and setup performance. While the temporal resolution of the experimental setup could be improved, an axial localization of the particles was only achievable at the expense of the accuracy in the lateral direction. Reference samples were used to experimentally validate the upgraded technique and to point out existing issues. A major problem in the application of SPOT lies in measurement artifacts, which can, for example, mask existing anomalies in the diffusion behavior of the tracked nanoparticles and would lead to misinterpretations in unknown systems. Parameter studies with variation of easily accessible quantities, such as the solvent viscosity, the particle, size or the considered time scales, offer possible remedies and concurrently show the importance of reference systems. A new field of research is the investigation of the diffusion behavior of nanoparticles in complex filter materials. In this work, SPOT was used to study nanoparticles in a nanoporous triblock terpolymer-based membrane. Using conventional methods, the non-destructive characterization of such a system at room-temperature and in a liquid-filled state, is a great challenge. With SPOT, however, the size distribution of the voids could be determined non-invasively. For this purpose, nanometer-sized polymer particles were tracked during their thermal movement through the pore structure of the filter material. At the same time, indications of a suitable statistical model for the description of the particle motion were collected. Theoretical parameters for normal and anomalous diffusion in harmonic potentials were explicitly compared with experimentally determined values. It was shown that the particle motion can be described mainly by confined Brownian motion, but there exists a weak influence of anomalous diffusion components, which can be best described by the so-called fractional Langevin equation.