Artist’s Dye Fading: Summary

This summer has seen a lot of frustration but also a lot of progress. The main focus of my work has been trying to figure out photo-physical behavior of purpurin, purpurin lake, and alizarin in different conditions in order to fill in the blanks from the previously accomplished single molecule studies. This new data allows us to more accurately interpret the single molecule data and gives us parameters for the Monte Carlo simulations. The single molecule data only tells us the relative behavior of the molecules by showing us a portion of the on and off lifetimes and the functions they are characterized by. In order for this data to have a physical interpretation we need to understand what sort of photo physical processes are happening which is where this summer’s research comes into play.

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Artist’s Dye Fading Part 4: July 26th – August 5th

The last part of my summer was mostly spent (summer)izing (lol) data from this summer. I will not be able to do research in the fall because I am studying abroad so I have to leave all of my summer findings in a state that allows my school year coworkers to pick up where I left off. Despite this, a few interesting findings were uncovered. Firstly I found that the fluorescence output of the dye purpurin noticeably degrades with consecutive scans in the fluorimeter. This could be useful in future work because it gives us an easy way to investigate the rate constant for the degradation of purpurin lake given that we know the power of the laser used in the fluorimeter. Knowing this rate constant will help us by filling in some of the blanks about the kinetics of this dye that cant be accurately extracted through our single molecule experiments. We also found that in terms of excitation wavelength dependent emission, Purpurin lake behaves more like alizarin than purpurin. This is significant because it not only supports the single molecule blinking data and excitation scan data (where purpurin behaves differently than purpurin lake and alizarin) but also because it support the hypothesis that alizarin and purpurin lake undergo excited state intramolecular proton transfer while purpurin does not.

Artist’s Dye Fading Part 3: July 1st – July 25th

Science can be a fickle mistress; sometimes I feel like i’m blasting through experiments and making good progress while at other times I feel as if I haven’t made much progress. For a while I thought that the dye Alizarin had contamination in it which was changing the fluorescence spectra. While I got past that debacle it did suck up alot of my time which could have otherwise been more gainfully employed.  With the summer more than halfway over I can start to feel the attrition set in. Up to this point the vast majority of my time has been spent on the fluorimeter trying to understand the photophysical behaviour of these molecules. However at this point there is not much more information that can be interpreted from any more spectrographic scans. This means that it is time for me to start transitioning from the experimental portion of this research to the theoretical part. The theoretical half of our research involves using matlab to simulate single molecule blinking data. Basically we have a set of rate constants that we put into the matlab program which then spits out data. Our goal is to set the parameters such that the simulated data matches up with the experimental data. These rate constants describe the photophysical behaviour of the dyes which can ultimately lead us to understand the physical mechanism by which the dyes fade. Besides this simulation, there are some other loose ends which need to be tied up such as confirming the chemical identity of Purpurin lake– the dye that we had to synthesize ourselves. Usually we would use techniques more familiar to us (fluorescence/absorbance) to determine the identity of the molecule– however purpurin lake has an annoying tendency to not dissolve in anything. This makes it hard to analyze chemically using solution state spectroscopy. Some techniques that we are considering using are x-ray crystallography, FT-IR spectroscopy, and NMR; all of which I have no idea how to do.

Artist’s Dye Fading Part 2: Jun 16th – Jun 30th

The new thing that I learned since the last post is that science is frustrating. As I continued with the solvatochromism studies it occured to me that I needed to carry out control experiments on the solvents that I was using. This led me to realize that some of the data that I was seeing was actually an artifact of the fluorimeter that I was using. Apparently there is a small amount of light that scatters off the solvent and gives rise to an emission peak which I had previously assumed was a result of Alizarin fluorescing. Fortunately by this point we had only made preliminary hypotheses based on the false data and any major disaster was avoided. This doesn’t change the fact that it is a pain in my butt. Although I think that the fluorimeter is stupid and that I shouldnt have to deal with this, I have learned a valuable lesson to always do control experiments.

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