Plasmonic core-shell nanoparticles: From synthesis to photocatalytic applications
18 December 2019
Campus Drie Eiken, O.08 - Universiteitsplein 1 - 2610 Antwerpen-Wilrijk (route: UAntwerpen, Campus Drie Eiken
Organization / co-organization:
Department of Bioscience Engineering
Silvia Lenaerts & Sammy Verbruggen
PhD defence Natan Blommaerts - Faculty of Science, Department of Bioscience Engineering
The use of plasmonic nanoparticles has attracted a great deal of interest in the last 10 years among researchers in various fields of application such as photocatalysis or surface enhanced Raman spectroscopy. However, there is a large limiting factor when using precious metal nanoparticles such as gold and silver, and that is their stability. They tend to oxidize and aggregate easily, certainly in an oxidative environment such as in air. An interesting approach for stabilization of plasmonic nanoparticles is to encapsulate them in a shell, in other words to form a core-shell nanoparticle.
There are many different ways in which core-shell nanoparticles can be synthesized. In the first instance, metal nanoparticles were surrounded by a (thin) TiO2 layer. Depending on the amount of TiO2 precursor, the thickness of the layer could be controlled to a few nanometers thick. The samples were tested for the photocatalytic degradation of a solid layer of stearic acid with the addition of 2 wt% metal @ TiO2 on P25 leading to a significant improvement in degradation efficiency compared to pure P25.
Another way to stabilize metal nanoparticles is to surround them with a polymer shell. In this way, the layer thickness could be controlled with sub-nanometer control, which is a very important factor for the amount of near-field enhancement that can penetrate outside the polymer shell. An XTT test was performed to determine the oxygen activation rate of gold and silver (and gold-silver bimetallic) nanoparticles, whether or not surrounded by a (non-) conductive polymer layer. When the samples were coated with four non-conductive polymer layers, the oxygen activation dropped practically to zero. On the other hand, when gold nanoparticles were surrounded by a conductive shell, there was still oxygen activation, although lower than in the case of gold without a layer.
The final part of this thesis focused more on possible applications in air purification. In this work, a glass tube coated on the inside with (Ag@polymer-modified) TiO2 was spiraled around a UVA lamp. The optimized spiral reactor was then compared to a conventional cylindrical photoreactor, with the same dimensions and total catalyst loading, over a wide range of experimental conditions. The results showed that the spiral reactor exhibited significantly better degradation efficiencies compared to the conventional cylindrical reactor over a large range of flows. An adsorption step in combination with the optimized spiral reactor could lead to a very powerful air purification Technology