TY - THES

T1 - Shape retrieval of inorganic nanocrystals from SAXS-data

AU - Burian, Max

N1 - embargoed until null

PY - 2014

Y1 - 2014

N2 - The size and shape of inorganic Nanocrystals (NCs) have a fundamental influence on their unique physical properties. Small angle x-ray scattering (SAXS) is an established technique to obtain not only the mean size but also the mean shape of various colloidal NC systems. The ab-initio program DAMMIN has previously been developed to retrieve a three dimensional shape that best fits an experimental SAXS curve of monodisperse particles such as proteins. The use of this technique for inorganic NCs yields great potential to obtain the real mean shape in sub-nanometer resolution. In order to obtain information on the sensitivity of this technique, numerous scattering curves of known theoretical models were computed and used as input for DAMMIN. To directly interpret the obtained three dimensional structures, several evaluation methods were developed and implemented. E.g., one of them reveals, that the averaging of multiple simulation leads to a three dimensional probability map which now can directly be correlated to the electron density in real space. These developed analysis methods allow to derive quantitative parameters from the retrieved shape. Multiple series of simulations could be performed to reveal the influence of the main fitting parameters. Furthermore the influence of the information content provided from the experimental scattering curve is studied. Additionally, the simulation was performed on systems with distinct size distributions. Finally an error of the values obtained by the developed methods is estimated that confirms DAMMIN as a powerful method for the shape retrieval of inorganic NCs with a polydispersity up to 10 %.

AB - The size and shape of inorganic Nanocrystals (NCs) have a fundamental influence on their unique physical properties. Small angle x-ray scattering (SAXS) is an established technique to obtain not only the mean size but also the mean shape of various colloidal NC systems. The ab-initio program DAMMIN has previously been developed to retrieve a three dimensional shape that best fits an experimental SAXS curve of monodisperse particles such as proteins. The use of this technique for inorganic NCs yields great potential to obtain the real mean shape in sub-nanometer resolution. In order to obtain information on the sensitivity of this technique, numerous scattering curves of known theoretical models were computed and used as input for DAMMIN. To directly interpret the obtained three dimensional structures, several evaluation methods were developed and implemented. E.g., one of them reveals, that the averaging of multiple simulation leads to a three dimensional probability map which now can directly be correlated to the electron density in real space. These developed analysis methods allow to derive quantitative parameters from the retrieved shape. Multiple series of simulations could be performed to reveal the influence of the main fitting parameters. Furthermore the influence of the information content provided from the experimental scattering curve is studied. Additionally, the simulation was performed on systems with distinct size distributions. Finally an error of the values obtained by the developed methods is estimated that confirms DAMMIN as a powerful method for the shape retrieval of inorganic NCs with a polydispersity up to 10 %.

KW - SAXS

KW - nanocrystal

KW - colloids

KW - shape

KW - Röntgenstreuung

KW - Nanokristalle

KW - Kolloide

KW - Form

M3 - Diploma Thesis

ER -