Syntheses, Characterizations and Applications of Zinc Peroxide Nanoparticles
- Synthesen, Charakterisierungen und Anwendungen von Zinkperoxid-Nanopartikeln
Bergs, Christian; Pich, Andrij (Thesis advisor); Elling, Lothar (Thesis advisor)
Dissertation / PhD Thesis
Dissertation, RWTH Aachen University, 2017
The aim of this work was the synthesis of zinc peroxide nanoparticles via a high pressure impinging-jet reactor and via classical flask reaction. The nanoparticles were in situ stabilized and functionalized with six different stabilizer molecules: BMEP, o-PEA, citrate, glucose-1-phospahte, UDP-glucose and AOT. These molecules interacted with the particle surface via phosphate, carboxylate and sulfonate functions causing nanoparticle stabilization, while their other functional groups (methacrylates, amines, corboxylates, glucose functions) introduced new accessible functionalities. All synthesis approaches resulted in small and uniform nanoparticles with varying diameter between 2.1±0.6 and 14.4±5.2 nm depending on parameter like reaction time, stabilizer type and concentration. Further the investigations revealed that the nanoparticles were capable of releasing oxygen. This release could be triggered through elevated temperatures (T>190.0 °C) or through acidic aqueous environment (pH<7.4). Thereby the amount of released oxygen was dependent on the nanoparticle sizes, the sample compositions and the pH values of the corresponding dispersions.This special property made the nanoparticles suitable for the bleaching or recycled PET or as antibacterial agent against anaerobe bacteria. PET becomes grayer during the recycling process caused through the reduction of catalyst remnants inside the polymer. The oxygen released from zinc peroxide nanoparticles (temperature induced) present during the recycling process can oxidize these catalyst remnants leading to a color change from black to white. Additionally the zinc peroxide nanoparticles were converted to zinc oxide during oxygen release which can act as white pigments increasing the white grade enhancement even further. It could be shown that the color enhancement was dependent on the type of nanoparticle stabilizer, the particle size and the amount of used nanoparticles. Furthermore the antibacterial properties of the biofunctionalized nanoparticles (glucose-1-phospahte, UDP-glucose) could be proven. The antibacterial efficiency against different bacteria like Enterococcus faecalis, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis and Prevotella intermedia was determined and quantified trough the minimal inhibition concentration (MIC). The investigations showed that the antibacterial effect increased with decreasing oxygen tolerance of the bacteria and with increasing nanoparticle concentration.Further the o-PEA and citrate stabilized nanoparticles were incorporated into PVCL/GMA respectively PNIPAm microgels. The ZnO2/o-PEA nanoparticles could be chemisrobed through the formation of covalent bonds, while the ZnO2/citrate nanoparticles were phisisorbed mostly through the formation of hydrogen bonds. The amount of immobilized nanoparticles could be tuned through the initial reactant ratios, which also influenced the hydrodynamic radii of the loaded microgels. This synthesis approach led to the formation of thermoresponsive, oxygen releasing composites.