Heterogeneous Photochemistry: A Story of Trial and Error

In my last update, I had just started to test our catalyst in photochemistry conditions. Some control experiments had to be repeated and this is what I have been focused on for late June and early July. I have gotten behind with blog posts as I got busy with work so this post will cover late June and early July and my next post will cover the last week or so. These controls are crucial because they verify that the catalyst is the active part of our system, rather than other components. This stage is very important because no one has done this before and we need to know why our system is working. This stage of testing must be completed before this project will be able to move forward.

The first experiment executed was trying to reproduce the results from our first exploratory study. This experiment was inconsistent and the results were poor. Instead of rerunning this experiment, the other controls that were positive from before were rerun to see if they were only a minor contributor to the overall results from the experiment. The first controls only contributed insignificantly overall so that experiment was not rerun. The second control was rerun but the results were inconsistent and had enough activity that the experiment needed to be repeated. This was then repeated two more times. Each time the procedure was changed to be different in only one way to try to isolate the problem. This system of trial and error did not solve the problem so for now we have moved on to a different control, with only our chromophore and semiconductor.

This new control with just the chromophore had similar challenges. After being run four times with a slightly varying procedure each time, the results were also inconsistent and too active to not be considered part of the activity of the system.  Our next step is going to be trying to get good activity with the catalyst in conditions we know work. After that, the controls will be revisited.

The system of trial and error with these controls has been a good test of my knowledge of why our procedure for photochemistry has been designed this way. The results have made me analyze what each step of the procedure does and if there are more effective ways to have the intended result. These challenging results have helped make me a better chemist and further understand the mechanics of my project. My future work includes running the catalyst in known optimal conditions and rerunning the positive controls.



  1. rjdirisio says:

    What are some steps that you can take to improve consistency? It seems like a pretty great idea to have a semiconductor, but the formation of these large (or small) nanoparticles seems to be giving you your inconsistent issue. Are there ways to measure growth?