Week Eight: Sensing, Sensing, and More Sensing

Hi blog,

Wow, it’s the last April post and week eight already! This second month has truly flown by in a blink-of-an-eye.

In contrast to last week, this week I was able to get a lot done and completed three experiments. First, I repeated the same PFOS Water MIP experiment I did last week, with Fabrication on Monday and Sensing on Tuesday, but with an acid soak instead. Basically, instead of letting the electrode soak overnight in pure water, I added 200 uL of hydrochloric acid or HCl to the water vial (see image below).

Then, for the sensing, I characterized the electrode after taking it out of the overnight soak for the first time, and after that was done, I let the electrode sit in the same overnight water-acid solution for 40-minute intervals before characterizing. It spent a cumulative time of 160 minutes soaking. The scan after 80 minutes was sensing for 50 ppt PFOS, a very small amount as when I was micro-pipetting the PFOS into the vial, only a tiny drop was dispensed, and the scan after 120 and 160 minutes was sensing for 250 ppb PFOS. I micro-pipetted more PFOS into the vial after the 80-minute scan finished.

On Wednesday, I conducted another control sensing experiment with a bare electrode surface, but this time it was with an acid soak. For this experiment, I also prepared a vial of water with 200 uL HCl. Thus, during sensing, I repeatedly dipped the electrode back into the same vial for 40-minute intervals for a total of 120 minutes in the soak solution and four data points. This experiment only took one day because since this is the control, there was no overnight soak, so the first characterization (t0) was a “fake” post overnight soak scan.

Later that afternoon after I finished the control experiment, I fabricated a PFBS Water MIP. It was also a completely different procedure because I was doing it with a different ratio of o-PD:PFBS in solution and with an extraction solution of acetone and water. Before, all of the PFOS Water MIP extractions had been with methanol and water. PFBS is more soluble (dissolves to a greater degree) in acetone than methanol, so using more soluble solvent allows for more complete removal of template (PFBS).

I finished the sensing on Thursday; the electrode soaked in solution for a cumulative time of 160 minutes, and the t120 and t160 characterizations were sensing 500 ppb PFBS. I talked about my results for the PFBS Sensing with my coworker, and she and I have seen similar trends in our data. Lastly, I consolidated the data for all these experiments into a PowerPoint, which I am improving at organizing into slides every week.

I’m still having a little bit of trouble with the thin white wire connecting the reference electrode to the potentiostat in the fume hood (the other station’s harness is working fine for me). My coworker helped me troubleshoot and look for anything that could be disrupting the scan such as not having water at the top of the electrode (where it connects to the port on the lid connected to the potentiostat), so I think as long as I watch out for those details and apply the tips she gave me, I shouldn’t have any issues characterizing.

As for my research, I finally found a case study regarding the use of sensors to detect water contamination. Ten sensors were placed in multiple nodes of a contaminated water system in a town in Madrid, Spain to investigate how successful the detection ability of the sensors based on two factors: the volume of contaminated water and time detection. I’m also in the midst of writing my final paper.

To end this post, I just wanted to show a picture of the scrumptious, red-velvet waffle-on-a-stick that was being sold this week :).

Until next week,

Fiona

Citations

Shahra, E. Q., & Wu, W. (2020). Water contaminants detection using sensor placement approach in Smart Water Networks. Journal of Ambient Intelligence and Humanized Computing, 14(5), 4971–4986. https://doi.org/10.1007/s12652-020-02262-x

All images: Fiona Xu