Dynamic Light Scattering on Nanoparticles in Microgravity in a Drop Tower

Abstract

Gravity affects colloidal dispersions via sedimentation and convection. We used dynamic light scattering (DLS) to quantify the mobility of nanoparticles on ground and in microgravity. A DLS instrument was adapted to withstand the accelerations in a drop tower, and a liquid handling set-up was connected in order to stabilize the liquid temperature and enable rapid cooling or heating. Light scattering experiments were performed in the drop tower at ZARM (Bremen, Germany) during a microgravity interval of 9.1 s and compared to measurements on ground. Particle dynamics were analyzed at constant temperature and after a rapid temperature drop using a series of DLS measurements with 1 s integration time. We observed nanoparticles with average gold core diameters of 7.8 nm and non-polar oleylamine shells that were dispersed in tetradecane and had an average hydrodynamic diameter of 21 nm. The particles did not change their diameter in the observed temperature range. The particle dynamics inferred from DLS on ground and in microgravity were in good agreement, demonstrating the possibility to perform reliable DLS measurements in a drop tower.

Microgravity Removes Reaction Limits from Nonpolar Nanoparticle Agglomeration

“…[25] We studied the agglomeration of rapidly cooled particles in a microgravity-compatible DLS set-up that we describe in detail in an earlier publication. [33] Agglomeration was initiated by injecting the hot particle dispersion (70 °C) into the precooled measurement cell (10 °C). We repeated identical experiments on ground and in microgravity multiple times and compared the results.…”

“…The temperature inside the scattering volume while cooling the sample from 70 to 10 °C was determined by following an approach developed previously. [33] It is based on the temperaturedependent dynamics of nonagglomerating reference particles Small 2022, 18, 2204621 that we quantified by dynamic light scattering. These particles are coated with oleylamine that suppresses agglomeration in the entire temperature range and makes them suitable as thermometers.…”

“…According to these reference investigations, within the first seconds after sample injection, the temperature in the scattering volume drops below 60 °C, i.e., agglomeration temperature of the samples investigated in this study. [33] We initiated agglomeration on ground and in the drop tower by injecting the temperature-sensitive particles with hexadecanethiol shells so that they were rapidly cooled to below 60 °C. Autocorrelation curves with 1 s measurement time were then continuously recorded from DLS on the agglomerating particle system.…”

“…We used previously published results on temperature measurements in the dispersion during microgravity to evaluate the size change due to agglomeration. [33] This manuscript is organized as follows: we first report on the agglomeration of the nanoparticles on ground at two different concentrations and the evolution of their average hydrodynamic diameters. Experiments in microgravity with catapult launches under the same conditions at two concentrations are followed by the results for one concentration in a drop experiment to assess the possible effects of the catapult.…”

Recent Trends in the Preparation of Nano-Starch Particles

“…DLS concurrently measures the scattering at a unique set of scattering angles using a variety of detectors that act as a base for the simultaneous dLS detecting concept and systems for scattering commercial light [ 104 ]. Pyttlik et al [ 105 ] clarified that hydrodynamic particle sizes between nanometers and micrometers can be measured using dynamic light scattering. The relevant specific mean residence times can be resolved with a 1 s integration time.…”