The role of surface plasmons in metal-enhanced chemiluminescence

Mak, Jesse (2014) The role of surface plasmons in metal-enhanced chemiluminescence.

Abstract:Chemiluminescence is used in many analysis methods as a sensitive reporter of the presence of biological materials. In a chemiluminescent process, a chemical reaction involving the substance of interest leads to a reaction product in the excited state. This excited state can decay by the emission of photons. However, the quantum efficiency of this process is often low due to a multitude of non-radiative decay paths. Enhancing the radiative decay of the excited state is therefore of wide interest. Several studies have been performed to investigate the use of plasmons for this [1] however, none of these studies made use of plasmonic systems with well-characterized resonances. We study lucigenin chemiluminescence and methylene bluefluorescence near different-sized optical antennas. The plasmon resonances were characterized using 1) dark-field scattering spectroscopy and 2) spectroscopy of the intrinsic luminescence of the antenna material (gold).We observe an approximately linear relation between the resonance wavelength and antenna length, which is in good agreement with a Fabry-Perot resonator model for cylindrical antennas [2]. Lucigenin chemiluminescence has two major components that emit light: 1) N-methyl acridone, and 2) the lucigenin itself, excited by N-methyl acridone through Förster resonance energy transfer. We first study the emission of the second component, with excitation by light. Following this, we study the complete chemiluminescent system.We show that the antennas in fact darken the emission, and explore several explanations. The final part of the thesis presents a controlled study on the distance dependent enhancement of a fluorophore near an antenna. We observe fluorescence time traces with strong peaks whenever an emitter is in a favorable location with respect to the antenna, where enhancement occurs. Most intensity enhancement is observed for a 70x110 nm antenna, with an enhancement factor of ~4. We pioneer the use of photon count histograms as a tool to analyze the fluorescence peaks. We show that the histograms form a strong signature of enhanced emission near an optical antenna. We anticipate that this method could be generalized to provide subdiffractionlimited information on spatially-varying enhancement near a nanostructure.
Item Type:Essay (Master)
Faculty:TNW: Science and Technology
Subject:33 physics
Programme:Applied Physics MSc (60436)
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