Forster resonance energy transfer (FRET) has found extensive applications in the fields of medical diagnostics, biosensors, solar cells and light emitting diodes (LEDs). Research efforts have been made to improve the FRET interaction and make it more efficient over a longer separation. During the past decades, a number of reports have shown that the FRET efficiency can be improved and the Forster radius can be increased by localized surface plasmons (LSPs) supported by single or randomly distributed metal nanoparticles. Surface lattice plasmons (SLRs) supported by periodic arrays of metal nanoparticles form a special class of plasmonic resonances with unique properties. This thesis addresses the question of whether the FRET process can be modified by the presence of SLRs.To this aim, the optical properties of the pure donors and acceptors (organic emitters) as well as mixtures between donors and acceptors on glass (without SLRs) are first experimentally characterized by both steady-state PL and time-resolved measurements. According to these measurements, the concentration dependence of the lifetime and the decay rates for the pure donors and pure acceptors are analyzed. Then, the dependence of FRET rate and FRET efficiency on concentration is obtained. Due to the little knowledge on the interaction between SLRs and the FRET process, it is still not clear if SLRs can enhance or inhibit the FRET process. In order to clearly investigate how the FRET process is influenced by the SLRs, a mixture with intermediate FRET interaction (the FRET efficiency of around 60%) deposited on top of a metal nanoparticle array exhibiting SLRs is applied. This mixture as well as the pure donors and acceptors on the SLRs are also experimentally analyzed by steady-state and lifetime measurements as compared to those on glass. From these results the strong emission enhancement for the pure emitters can be clearly verified. Moreover, the time-resolved measurements indicate that the FRET process is much faster than the plasmonic interaction. Due to this weak plasmonic interaction, the FRET rate and FRET efficiency is not influenced by this plasmonic nanostructure in these particular conditions.
|Date of Award||31 Aug 2014|
|Supervisor||Andrea Fiore (Coach)|