Authors: Rebecca Momper
Source: Gutenberg Open Science (article, 2021-01-01)
Field: Chemistry — Spectroscopy

From the colloidal dispersion to the solid state: Controlling properties by inter-particle distance and orientation Nanoparticles can be synthesized with size-tunable properties.To further explore, the correlation between inter-particle interaction and the generation of new properties for novel applications, like enhanced or polarized photoluminescence or photoconductivity, the nanoparticles have to be transferred from the colloidal dispersion to the solid-state.One of the challenges is to inhibit uncontrolled agglomeration in the solid-state in order to preserve their original colloidal properties.Therefore, the main focus of the thesis is to control the interaction potential between nanoparticles.To approach the transfer of nanoparticles, assembling into superstructures or dispersing into a solid host material are applied.In this work, existing methods are expanded and new strategies are developed to transfer nanoparticles from the dispersion to the solid-state.First, the interactions between two colloids in dispersion are investigated.Through the interaction between carbon dots and polystyrene nanoparticles, the photoluminescence can be strongly enhanced.Next, the interactions between CdSe nanoplatelets are controlled in order to investigate their collective orientation in thin films.The controlled collective orientation is required, to access, to study and to modify the anisotropic properties of the nanoplatelets.The orientation is controlled by the exploitation of kinetic effects through adjusting the evaporation rate in self-assembly experiments at liquidliquid interfaces.Controlled particle interactions are not only important to alter particle orientation and properties, they also play a crucial role when transferring the nanoparticles into a different medium.To avoid agglomeration, nanoparticles are functionalized with photoresinlike polymers for the dispersion in stereolithographic photoresins.3D printing is a promising technology for the manufacturing of highly complex structures, which are not or hardly accessible with traditional manufacturing methods.Stereolithographic 3D printing applies a laser to polymerize and cure the photoresin.However, interactions of nanoparticles with the laser or photogenerated radicals can occur.Understanding the interactions of nanoparticles in the 3D printing process is of utmost importance in order to combine the properties of nanoparticles, like photoluminescence, magnetism or conductivity, with the 3D printing technology, in order to realize highly complex structures with adjustable properties, like fluorescence.Furthermore, nanoplatelets are promising candidates for novel fluorophores in microscopy or in light-emitting diodes.However, interactions have to be carefully adjusted for such applications. Dispersion (optics) ; Orientation (vector space) ; Particle (ecology) ; Colloidal particle ; Colloid ; Solid-state ; Materials science ; Optics ; Physics ; Mathematics ; Chemical engineering ; Engineering physics ; Engineering ; Geometry ; Geology Adsorption, diffusion, and thermodynamic properties of materials