Bare Nanoparticle Quenching and Future Work

Towards the end of this summer I was able to reproduce fluorescence quenching on bare nanoparticles. Upon photoexcitation by the laser (or sunlight), there is a locally enhanced electromagnetic field produced around the nanoparticle. As mentioned in previous posts, a fluorophore oriented closer to the surface of a plasmonic particle will experience a greater EM field. However, fluorophores located too close or touching the surface of a particle will undergo quenching of fluorescence because of the significantly stronger EM field. To save some time, I will not go into a lengthy discussion on the exact science behind quenching, mainly because I don’t understand most of it. In this context all we are concerned with is the fact that fluorophores located on the surface of bare nanoparticles are showing a decreased fluorescence enhancement. As opposed to positive ratios, the quenched particles show up as dark spots on a bright background, meaning these particles are emitting less photons than the background dye. A typical correlated fluorescence scan and LSPR image of bare NPs can be seen below. After analyzing 25 particles, the average enhancement was 0.84 ± 0.07. 25 particles isn’t necessarily a substantial amount, but the quenching measurements thus far prove the background theory.

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Analyzing Fluorescence Enhancement for Medium-Thick SCNPs

Sorry for the long hiatus, the last few weeks of research were quite hectic. Simultaneously trying to wrap-up experimentation for the summer, compiling tons of data, and preparing for the coming semester is a daunting task.

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Correlating Single Dye Molecule Fluorescence with Nanoparticle LSPR

It’s always tough when research doesn’t go the way you initially planned. Spending weeks on a certain project only to discover that the data doesn’t fully prove the hypothesis is beyond frustrating. Alas, that’s science.

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Data, Thou Art A Fickle Mistress

Since my last blog, I have run A LOT of fluorescence scans on silica coated silver nanoparticles. It’s safe to say that my daily emotions are directly linked to the outcomes and efficiency of these scans. One day I could successfully analyze fluorescence enhancement ratios for up to 20 nanoparticles and another day I could get as little as 2. For instance, I severely misaligned the laser on accident one day and it took us over an hour to fix the problem! Sometimes I feel like even the laser hates Mondays…But, alas, I am making progress on compiling data.

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Reading and Glass Slide Preparation Control Experiment

When I first found out that I would be doing physical chemistry research over the summer, I had no idea how much actual reading was involved. Out of the three weeks that I’ve been here, I would say that about 75% of the time I was scanning through stacks on stacks of articles and googling words that stumped me. This is not necessarily a negative thing because I have learned so much background information on my project that has given me a better appreciation of the nuances involved in photovoltaic research. However, if I have to read the words localized surface plasmon resonance (LSPR), quantum yield, radiative decay rate, or extinction spectra again anytime soon I might go crazy. The fact that we digest so much literature in the Wustholz lab is not because we have nothing important to do but because we currently only have 1 laser and confocal microscope to split between five students. Unlike regular organic and synthesis labs where multiple people can be doing separate tasks beneath their individual hoods, our lab’s main work involves using the laser for extended periods of time. Thus, if we aren’t on the “scope” then we are either working up data from scans or wading through the vast sea of research papers.

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