Week 3 -- First trial, optimization

Although this week was mostly at Disneyland, I did manage to get some work done. To recap, on Monday last week (which is when I wrote the blog) I obtained a flaky and dark teal result, which was the catalyst. I decided to crush it instead of break it into chunks for two main reasons: one was for easy measurement: literature mentioned masses of around 0.2 to 0.4 grams, and it would be easier to measure out small flakes than large chunks. Second, smaller flakes would allow for a greater surface area of the catalyst to be exposed to the solution, allowing for more interaction with the dye and the catalyst, potentially allowing more degradation.

The methylene blue solution in stock was liquid, while the literature used a solid that was dissolved. I found that a vast majority of the solution’s constituents wouldn’t inhibit reaction rate, though the existence of some alcohols in the solution would compete for the OH radical groups. However, the concentration of the alcohol I deemed to be sufficiently low enough for there to be little effect on the rate. As for H2O2 concentration, the paper didn’t say the exact concentration, probably since they referenced another paper (locked behind an expensive paywall) but it would present its own issue. Normally, H2O2 is good for the system: it generates ROS allowing for the removal of dye. However, it forms an “inverse parabola” relationship with quantity: too little, and not enough ROS are generated and therefore not much degradation happens, while too many leads to competition in the active sites. Therefore, I chose three values, all from other literature that don’t necessarily deal with Cu-CS but with similar photocatalysts: 5mM, 10mM and 20mM, to see which one works the best. Next week, I hope to finalize my procedure and within a week or two, meet with Mr. Wang.