Yesterday we finished our testing and Marvin has calculated that we now have over 80,000 points of data! Marvin is in the process of trying to figure out what all that data means and how to present it so it makes sense.
As we had experienced when we did the first round of testing last week, our second round of testing didn't go exactly as we had planned. After performing a few tests and not getting any readings from our measurements, everyone seemed to be stumped. We had one post doc and two grad students helping us try to figure out what was not working. After some mid-course adjustments, Marvin and I started to get SERS measurements that showed a "spike" in the correct area. This meant that our chips were detecting the DNT vapors. They were actually doing what we had designed them to do.
After getting a series of "good" measurements, we started to modify the samples to see if our chips could detect the presence of DNT at different temperatures and levels of concentrations. We also testing the effectiveness of our chip when the DNT was in an actual real-world setting in our lab.
Marvin got to be pretty good at working the SERS for this second round of testing. We found the amount of the NaOH solution sprayed onto the surface of the chip had a major impact on our measurements. If there was too much or too little solution, then we wouldn't get good results. The best results were when you took a measurement on an area that had just a little of the solution that had not yet evaporated. It was tricky at times finding these spots.
While Marvin has been crunching the data, I spent yesterday afternoon calculating the vapor pressures and associated concentrations of the DNT solutions we had tested. Because we were using solid DNT, it made the calculations tricky. I found a few articles that provided me with the information I needed to perform the calculations. I showed my calculations to one of the grad students and he provided me with comments. After revising my work, I calculated in one case we tested our chip's detection when the DNT vapors were at a concentration around 14 parts per billion!
Next Friday will be the last day of the RET and Marvin and I will be tied up most of the day. The Reinhard Lab Group typically has their project status meetings on Friday afternoons. Therefore, even though our formal final presentation and poster are not due until next week, Marvin and I have to get our presentation ready to present to the Reinhard Lab Group this Friday.