FABRICATION OF CRYSTALLINE COLLOIDAL ARRAY PHOTONIC CRYSTALS AND APPLICATIONSWang, Luling (2012) FABRICATION OF CRYSTALLINE COLLOIDAL ARRAY PHOTONIC CRYSTALS AND APPLICATIONS. Doctoral Dissertation, University of Pittsburgh. (Unpublished)
AbstractCrystalline colloidal array (CCA) photonic crystals (PCs) are periodic structures formed by the self-assembly of monodisperse, highly-charged particles in low ionic strength aqueous solutions. Similar to an atomic crystal but with much larger lattice spacings, the CCA can efficiently diffract light in the UV, visible and near-IR spectral regions. This thesis reports the development of new CCA materials, novel CCA Bragg diffraction devices, and utilization of CCA PC templates for new nanostructure and nanomaterial fabrication. We use CCA for development of a CCA deep UV narrow band filter that acts as a Rayleigh rejection filter for UV Raman spectroscopy and for templates for solid-state UV Raman cross section determinations. We developed novel CCA PC deep UV Bragg diffraction devices. We synthesized small, monodisperse, highly surface-charged silica particles and prepared novel silica CCA through the self-assembly of these particles. The silica CCA efficiently Bragg diffract light in the deep UV. The diffracted wavelength was varied by tilting the CCA orientation to the incident beam. We demonstrated the utility of the silica CCA filter as a Rayleigh rejection filter in Teflon UV Raman measurements. We conducted the first resonance Raman cross-section measurements of solids that avoids self-absorption bias by using PC templates. We fabricated complex stoichiometrically defined nanoparticles (NaNO3/Na2SO4 nanoparticles) by utilizing the defined interstitial volume of close-packed PCs. We successfully determined the solid-state NaNO3 UV resonance Raman cross-sections by using solid Na2SO4 as an internal standard. We also developed a refractive-index matching method to measure solid-state Na2SO4 UV Raman cross sections that avoids the effect of the local field and avoids interface scattering of the incident light. We developed a facile method to fabricate silica shell PCs through the use of flexible poly(N-isopropylacrylamide) (PNIPAm) core templates. We synthesized monodisperse PNIPAm-silica core-shell particles and demonstrated their reversible swelling and shrinking as the temperature is cycled. We fabricated close-packed PCs of PNIPAm-silica core-shell particles and further fabricated hollow silica shell PCs by removing the PNIPAm cores by calcination. Share
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