This thesis is a collection of experimental attempts to enhance photoluminescence of fluorescent molecules and quantum dots with single gold nanorods (GNRs) and relevant applications. Special... Show moreThis thesis is a collection of experimental attempts to enhance photoluminescence of fluorescent molecules and quantum dots with single gold nanorods (GNRs) and relevant applications. Special attention is focused on the interactions between single emitters and GNRs. The idea is to increase the emission of weak emitters by the excellent optical properties of GNRs so that weak light emitters will then be bright enough to be detected and studied individually. We can thus generalize single-molecule fluorescence spectroscopy to weakly emitting species which are currently undetectable by conventional single-molecule spectroscopy. The research is important for extending the scope of single-molecule spectroscopy, which is a powerful technique for understanding the dynamic behaviors at the nanometer scale in biological systems and other materials. Show less
Gold nanorods are biocompatible nanoparticles that present an excellent two-photon signal that can be used to get high spatial resolution inside living cells. Gold nanorods are photostable and... Show moreGold nanorods are biocompatible nanoparticles that present an excellent two-photon signal that can be used to get high spatial resolution inside living cells. Gold nanorods are photostable and therefore can be followed inside cells for long time, with possible applications as trackers in live cells. We explored the use of gold nanorods as labels for single-particle tracking in live cells, both not functionalized and functionalized with nuclear localization signal for nuclear targeting. For single-particle tracking we used mean square displacement analysis, after characterizing the limitations of this analysis with simulations. We also tested the acquisition of excitation spectra of single gold nanorods for sensing applications. Show less
We study the dynamics of single molecules and individual gold nanorods in glycerol at variable temperatures. We demonstrate temperature-cycle microscopy on FRET-labeled polyproline and double... Show moreWe study the dynamics of single molecules and individual gold nanorods in glycerol at variable temperatures. We demonstrate temperature-cycle microscopy on FRET-labeled polyproline and double-stranded DNA molecules to access micro-second dynamics of single molecules, and reveal the influences of dye-dye interaction at short interdye distances on the observed FRET values. We use neutron-scattering techniques to examine the origin of solid-like structures suggested in previous reports and the influence of the thermal history. We find that crystal nucleation takes place in glycerol at temperatures very close to the glass transition temperature. This observation suggests that the thermal history of the glycerol sample needs to be controlled for studying dynamical heterogeneity in supercooled liquids. For the first time, we demonstrate gold nanorods as local viscosity reporter to study heterogeneity in supercooled liquids. Following rotational dynamics of individual gold nanorods in glycerol upon cooling below 226K, we start to observe deviations of local viscosity from the bulk viscosity of glycerol. Our observation suggests heterogeneity on relatively large length scale exists at surprisingly high temperatures. In the end, we demonstrate gold nanorods for enhancing fluorescence from single molecules and for fluorescence correlation spectroscopy at micromolar concentrations with single-molecule sensitivity. Show less
