Multimodel characterization of fluorescence enhancement in silver nanoparticle aggregates


Metal nanoparticles that support localized plasmon resonances, like those made of silver or gold are known to enhance the spectroscopic signals of dye molecules in their vicinity. In small nanoparticles aggregates, such a dimers and trimers, there is a focusing of the electromagnetic field at the hot-spot in between the particle, which gives rise to much larger enhancements than single particles.

Up to now, there were extensive studies on the enhancement of Raman scattering from the hot-spot in nanoparticle aggregates, but very little research was done on Fluorescence enhancement in hot-spots. We have recently developed a simple system in which aggregation of silver nanoparticles with dye-labeled DNA produce very high enhancement of the fluorescence. We have already done some macroscopic studies on the system, and wish to continue with microscopic studies on these nanoscale aggregates.

Enhancement of fluorescence from dye-labeled DNA co-aggregated with silver particles when measured in a cuvette


The proposed MSc. Project includes multimodal characterization of the Nanoparticle aggregates and their fluorescence properties. This will include SEM microscopy to find the aggregate structures, Dark field microscopy and spectroscopy to measure the Plasmon resonance absorption of the aggregates, and fluorescence lifetime microscopy and spectroscopy to study the fluorescence intensity, lifetime and bleaching properties of the aggregates.

The main questions we ask are:


What is the distribution of the fluorescence enhancement when measuring it on different aggregates? We expect that if the dye-labeled DNA is randomly distributed, then few aggregates will be highly enhancing, and all the others will be much less bright.


Is there a change in the lifetime of the fluorescence compared to the dye-labeled DNA alone? Is the change in lifetime correlates with enhancement level? From theoretical considerations we predict that the brightest clusters will also have the shortest lifetimes.


Do we see a correlation between the fluorescence spectrum from the dye, and the Plasmon absorption spectrum of the aggregate, as we expect from theory?


If you are interested in this Master assigment, you can contact:

Dr. Ron Gill

Phone: 053 – 489 3161