Abstract: Analyzing Dye-Sensitized and Plasmon Enhanced Photocatalysis Using Single Molecule Spectroscopy

For my upcoming research project in the summer, I plan on investigating dye-sensitized and plasmon-enhanced photocatalysis using single molecule spectroscopy techniques. The global energy demand is predicted to increase over 25% by year 2040. Solar energy is a clean alternative to harmful fossil fuels, and one method of harnessing this energy is via dye sensitized photocatalysis (DSP) systems. Although currently inefficient, we plan on studying underlying kinetics to further improve the practicality of these systems. This is done via single molecule spectroscopy (SMS) techniques that allow for us to truly understand the photophysics behind DSP systems. In our DSP system, we will be studying Eosin-Y chromophore on a TiO2 substrate under both air and N2 conditions. By studying the interactions of this dye with a substrate, we can begin to have a understanding of the efficiency and kinetics of the electron transfer that is associated with solar energy harvesting. Additionally, I hope to incorporate plasmonic systems with our DSP system to possibly reveal alternative methods to further improve efficiency of solar conversion.


My time was well spent this summer in lab. I gained greater confidence and knowledge of procedures and protocol in lab, but I also learned a great deal about the underlying chemistry behind my project and topic in general. The main objective of my project was to learn more about the underlying kinetics of Rhodamine 560 (R560) compared to Rhodamine B (RB), which was previously studied on the 532nm laser. R560 studies were done by a previous student, but on a 470nm laser, so my job was to obtain data for R560 back on the 532nm laser to compare the Rhodamine derivative to RB, and see whether differences between R560 and RB were due to laser wavelength or because of difference in structure and underlying kinetic behaviors. Data for R560 specifically entails blinking traces of single molecule scans, which graph intensity vs. time, in order to track fluorescence and electron transfer kinetics.

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August Update

As my summer research is beginning to approach its end, I have been furthering the studies I discussed in my last blog post. I completed my parsed time data set for R560 and RB dyes using the 532nm laser. Examining these data sets using Clauset analysis, I found out how well the early/late times for the dyes fit to power law, log normal, and weibull fits. The fits gave a trend contradictory to the original hypothesis that RB should show differences between early and late, while R560 should not show any difference.

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July Update

For these past two weeks, I have been working to parse times of blinking traces in dyes R560 and RB. Blinking traces show intensity vs. time, following fluctuations in emissive intensities, and gives information regarding electron transfer kinetics. The purpose of parsing these traces is to separate early and late sections of the trace, and analyzing the statistical difference between the two. For R560, the dye’s structure does not change with excitation from the laser, so the blinking traces which show no difference when looking at the early versus the late components of the whole blinking trace. However, for RB, the dye undergoes dealkylation with excitation into R560, so the early and late components should demonstrate statistical difference.

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June Update

From late May to now, I have been working on getting in the groove of things, becoming more accustomed to lab procedure. The goal of my project is to confirm the underlying kinetic behavior of Rhodamine 560 (R560), in comparison to previously studied Rhodamine B (RB), which was previously done on a 532nm laser. I started by working towards obtaining consistent single molecule scans of RB using this laser, different to the 470 I was using during the school year. Starting at higher concentrations before working towards single molecule concentrations, I had to find optimal power settings for corresponding concentrations. To find optimal power settings, I ran multiple scans at various power settings on the laser to obtain a high amount of photon counts while simultaneously preventing photobleaching of the RB dye. After this, it was a matter of refining my preparation of the dye solution for scans and ensuring I was collecting data in the correct manner.

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