Multidimensional analysis of nanoparticulate structures using analytical ultracentrifugation with integrated multiwavelength detection

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Objective of this project is the development of the multiwavelength-detector (MWL-detector) in the analytical ultracentrifuge (AUC) and its application in particle technology as a method for multidimensional particle analysis. Sedimentation and extinction data are obtained simultaneously by means of MWL-AUC. Such data can be used to determine broad multimodal particle size distributions (PSDs) as well as the shape and optical properties of nanoparticles (NPs). The key questions arising from the first funding period will be complemented and completed in the second funding period by the development of new methods. By means of a dynamic rotor speed ramp even very broad multimodal PSDs reaching from a few nanometers to several microns can be analyzed with high resolution. A software package developed in the first funding period (HDR-MULTIFIT) will be extended in such way that complex sedimenting and floating systems can be characterized. An increased dynamic range is accomplished due to a new analysis routine based on direct boundary modelling. Further emphasis will be put on the characterization of semiconductor NPs less than 10 nm in diameter. New algorithms will allow to determine the size and density of ZnO, CuInS2, CdSe and CdS NPs simultaneously and with high resolution. Furthermore, the shape of ZnO- and silver-nanotubes will be investigated. For this purpose, methods developed in the first funding period for graphene oxide will be adapted and extended. The thicknesses and length distributions of the nanotubes can be determined without the necessity of imaging techniques by conducting complementary experiments using a scanning mobility particles sizer. The required correlation of both techniques will first be validated by means of comparative studies using spherical NPs. Besides size and shape of NPs also optical properties become available using strong data evaluation techniques. Implementations in free software packages will be realized in close collaboration with Prof. B. Demeler (U Texas) and Dr. W. F. Stafford (Harvard Medical School). By means of this the size - band gap correlation of semiconductor NPs will become accessible using AUC. For patchy particles the surface coverage of silver or gold on SiO2 or polystyrene NPs can be determined. Moreover, the particle morphology can be correlated with the optical properties. In addition, algorithms will be developed to determine the refractive indices of materials such as pigments by means of MWL-AUC.