Template-Directed Synthesis of Nanoparticle

The physical and optical properties of the particles can be tuned by the rational design of nanoparticles (NPs)---the ability to select, in advance, desired particle geometry. In particular, template-directed synthesis can define the geometry of NPs with precise control over the size and shape of individual particles over a wide range of dimensions. This dissertation describes different approaches to create geometry-controlled particles. First, we generated multiscale Au NPs spanning multiple length scales (e.g. >100 nm dimensions, >10 nm thin shells/components, and >1 nm sharp features) with different aspect ratios ranging from 1.0 to 7.7 using Si templates. Three dimensional (3D) multiscale Au particles showed that increasing the length of the particles resulted in excitation of a longitudinal mode and two different transverse modes having different multipolar orders. The multipolar orders increased for both longitudinal and transverse modes as the aspect ratio increased. Finite-difference time-domain calculations revealed that the structural asymmetry of the 3D anisotropic particles resulted in two distinct transverse plasmon resonances. When the 3D structural change occurred at the ends of the multiscale particle, however, the optical response showed two resonances in the longitudinal direction and only a single resonance in the transverse direction. Second, we created arsenic trioxide (ATO) nanoparticles using nanowell templates. The different sizes of ATO nanocrystals were generated by controlling the concentration of the precursor materials while keeping the well volume the same. Selected area electron diffraction showed that the nanoparticles are single crystalline. Furthermore, the biological activity of ATO nanocrystals as anticancer drug was tested by investigating their cytotoxicity. We found that ATO nanocrystals have a modestly attenuated activity compared to free ATO. Finally, we synthesized Au nanospheres with size control and functionalized the surface of NPs with different recognition moieties including antibodies and aptamers to target histone proteins in chromatin structures. Au NPs as imaging probes decorated chromatin structures, which were observed using transmission electron microscopy. The NP-labeled chromatin structures can be used to determine the distinctive patterns of higher-order chromatin organization in cancer cells compared to normal cells.