Fabrication of synthetic nanoparticles for cell manipulation, water purification and plasmonic applications [electronic resource]

A major challenge in nanoparticle synthesis is to achieve monodispersity, excellent shape and composition control and high throughput simultaneously. Here, a new template-based method to fabricate monodisperse, multi-layered, anisotropic nanoparticles is established, which involves nanoimprinting lithography. These particles are so-called synthetic nanoparticles. Particles with different shapes are fabricated using this method at wafer-scale and are explored for different applications. In this dessertation, four different topics are covered. First, high-moment synthetic antiferromagnetic (SAF) nanoparticles are used for cell manipulations. They are covalently bound with streptavidin and therefore ready for specific binding to H1650 lung cancer cells, which are conjugated with biotin. Once coated with particles, these cells can be easily manipulated under external magnetic field and be 'identified' and 'picked-up' using a magnetic sifter when spiked into blood sample. Second, a point-of-use water purification device is proposed based on novel magnetically ultraresponsive nanoscavengers. The nanoscavengers are disk-shaped, with SAF core layers and functional capping layers. Specifically, Ag-capped SAF nanoscavengers are fabricated for water disinfection. These nanoscavengers are very efficient in disinfecting bacteria and can be collected with a permanent magnet within 5 min. A collision based model is established to explain the high disinfection efficiency using Monte-Carlo simulation. The cyclic performance of these nanoscavengers is also demonstrated with a high disinfection efficiency up to 9 cycles. Third, high-density Ag/Au dimer arrays are patterned on a whole wafer using a novel shadow evaporation method. By controlling the deposition angle, dimers with sub-10-nm gaps with universal orientation throughout the wafer are achieved. The plasmon modes of Au-Au and Au-Ag dimers are studied, where dimers are fabricated on 50-nm-thin Si3N4 films for Electron Energy-Loss Spectrum (EELS) measurements. Several resonance peaks are identified for the different dimer structures. Fourth, an orthogonal double exposure method, incorporating both normal photo-lithography and edge photo-lithography, is developed to fabricate templates of nanorod arrays. These templates are then used for making monodisperse nanorods with different aspect ratios. Specifically, novel synthetic magnetic multilayered nanorods are fabricated and the magnetic properties of these novel nanorods are characterized, with anisotropic hysteresis loops when the external magnetic field is applied along different directions. A model is established to explain that both shape anisotropy and interlayer interaction play a role in the magnetic response of these nanorods. The theoretically calculated saturation fields in the transverse direction match well with the experimentally measured values for all different geometries of nanorods.

Keywords: Materials Science and Engineering.
Advisor: Wang Shan
Cui Yi
Sinclair Robert (Materials scientist) advisor. Thesis advisor