University Honors

Metal nanoparticles have intriguing interactions with light, making them importantoptical materials with promising potential applications. In particular, silver (Ag) nanoparticlesare often used as sensors and detectors because light-induced electron oscillation can becontrolled by particle size and shape, as well as the surrounding environment (Cobley et al.,2009). The electron motion dictates whether the light at a certain frequency is able to passthrough or be reflected. This is measured through the absorption spectrum. Previous research hasexplored the redox-buffering effect, through which iron oxide (Fe3O4) nanoparticles can migratethrough a silica (SiO2) shell to leave a hollow core, changing the morphology of the nanoparticle(Wang et al., 2018). This project utilizes the redox-buffering effect to control the nanostructure ofmetal nanoparticles by changing the local surrounding refractive index of Ag nanoparticles toresult in a change of optical properties. First, Ag@Fe3O4 core-shell nanoparticles are synthesizedvia a solvothermal process, with the Ag nanoparticle as the core and Fe3O4 as the shell. Thesenanoparticles are then coated with a SiO2 shell using a sol-gel process. The thickness of the SiO2shell is manipulated to examine its effect on the amount of Fe3O4 that can react. The redox-buffering effect is observed by treating the nanoparticles in forming gas and N2 atmospheres athigh temperatures. Finally, transmission electron microscope (TEM) images of the samples andUV-vis spectroscopy are carried out to characterize the samples.