Jenelle Booker

Self-Assembled Monolayers (SAM) as a Model for Photooxidation of Plastic Waste Using ATR-FTIR and Kinetic Modelling

April 10, 2021   /  

Name: Jenelle C. Booker
Major: Chemistry
Minor: Environmental Studies and German
Advisors: Karl J. Feierabend and Paul L. Edmiston

As of 2017, 8.3 billion metric tons of plastic exist world wide, and with their long lifetimes, will become chemically integrated into our environment. In order to understand the long-term impacts of plastic waste on human and wildlife health, this project sets the foundations for both a laboratory and kinetic model of plastic degradation, in particular plastic photo-oxidation. Assuming degradation occurs on the outermost surface of a plastic, photo-oxidation can be modelled using a singular layer of hydrocarbons—the chemical backbone of most plastics. This singular layer was created using a self-assembled monolayer (SAM) of chloro(dimethyl)octadecylsilane (CH3(CH2)17Si(CH3)2Cl) and was reacted with UV-C light and environmentally relevant concentrations of water vapor, oxygen, and ozone. To track photo-oxidation in realtime and to avoid disruption of the plastic monolayer, the SAM was formed on an attenuated total reflectance (ATR) germanium crystal, through which IR analysis could occur. In conjunction with ATR-IR analysis, a kinetic model was created to investigate the gas and photo-chemistry of the experimental set up, in particular the formation of hydroxyl free radicals–the key initiator in plastic photo-oxidation. By simulating plastic photo-oxidation in the lab, and therefore, determining the dominant products and mechanisms, the chemical impact of plastic waste can be explored quickly and at a lower cost than field sampling. This project is therefore instrumental in informing the environmental community the enduring effects of plastic waste on our natural environment.

Jenelle will be online to field comments on April 16:
10am-noon EDT (Asia: late evening, PST: 6-8am, Africa/Europe: early evening)

72 thoughts on “Self-Assembled Monolayers (SAM) as a Model for Photooxidation of Plastic Waste Using ATR-FTIR and Kinetic Modelling”

  1. Thanks for sharing your research! Could that be a nucleophilic substitution reaction that forms the SAM?

    1. Thank you for coming and thank you for your question. The SAM is terminated with chlorine and is reacting with the OH groups populating the surface. Initially, I thought of an acid-base reaction between OH and Cl. However, it’s possible that OH could be the nucleophile to bond to the electrophilic Si, pushing out Cl from chloro(dimethyl)octadecyl silane.

    1. Thanks Dr. Feierabend! Your guidance and support this semester is a big reason I made it through to the end.

  2. Thanks for sharing your work with us, Jenelle! You have so much to be proud of! Posselove.

    1. Thank you so much, Tete! The cross-over between environmental studies and chemistry is vast, and I’m happy to have contributed to the growing field. I can’t wait to see where future researchers take this project.

  3. Nice work Jenelle! I enjoyed your poster and talking with you about the results this week. I learned a lot.

    1. Thanks Dr. E! I enjoyed our conversation as well. Your insight into internal reflection spectroscopy was much appreciated!

  4. I enjoyed your narration, Jenelle! 🙂
    The nonlinear dependence of OH levels on water vapor was particularly interesting. What was the water concentration (or relative humidity) in the bottom-most Kinetiscope plot on your poster?

    1. Hi Dr. Faust! Thank you for watching. Water vapor and oxygen definitely presented an interesting relationship with OH production.. The bottom-most Kinetiscope plot is of ozone, where the relative humidity was set to that of Wooster, OH– 69%.

  5. Very important study. We’ve got to figure a way to get all this plastic to break down harmlessly

    1. Thank you for watching! I agree. There have been some studies about using microbes to degrade plastic into environmentally friendly compounds. Unfortunately, for most of the plastic at sea or on the coast, there’s no way around their photooxidation.

  6. Awesome project, Jenelle! It seems like your study created a strong foundation for future work on photooxidation of plastics – are there plans for next steps? Also, I feel you and your frustration with experimental techniques that don’t go to plan during the research process (ugh, lab instruments…) – but it looks like you had a lot of successes along the way – what aspect of the project are you most proud of? (I’m totally proud of you!)

    1. Thank you Dr. Pollock for coming and for your appreciation ! The project was stuck on validating the SAM on the crystal surface with ATR-IR, so that’s the first step. In the lab, more work will be done to actually perform the photo-oxidation on the SAM, so we can understand the mechanisms and products that result from plastic degradation. This requires developing an extraction method and GC-MS analysis of the products. In terms of the model, more work will be done to establish an equilibrium OH concentration, so the the concentration of OH in the flow cell can be properly estimated. There are so many turns this project could take!

  7. Fascinating!
    Hopefully your current research will led to reducing the negative effects of plastic on the environment, reducing the use of plastic products globally and processing remaining plastic waste into practical/usable equipment.
    Thank you for your work!

    1. Thank you so much for coming !! I appreciate your kind words. Later projects will identify the products produced as plastic degrades in the environment, so the chemical impact of plastic waste can be more clearly understood. I hoped my senior thesis would elaborate on the permanence of plastic in our environment, as even if we were to clean up all the plastic waste today, we would be left with tiny pieces smaller than a centimeter! I agree that there’s definitely something that needs to be done!

  8. Such a cool, interdisciplinary project, Jenelle! If you could go back and give yourself advice as you started this project, what would it be?

    1. Thank you for coming and for your question Dr. Morris! I think it’s difficult for researchers to stay inspired when experiencing road blocks or blind corners towards their research goals. Or at least it is for me! I would have advised myself to focus less on the goal and more on the process. I.S. is about demonstrating what you learned, and so, I would have put more time into learning the foundational information about my experimental equipment and techniques at the front end. I think it would have saved me a lot of time!

  9. Amazing work, Jenelle! This is a very practical project. I’ve learned a lot from your presentation. Super proud of you !!

  10. Jenelle, really enjoyed listening to how this model potentially shows the products of photo oxidation of plastics. Did you get consistent results (by-products) from the same plastics or did you test multiple types (i.e., plastic samples that included dyes)? Also, I know this wasn’t part of the study, but any idea on the magnitude of cost savings environmental scientists may see using your model vice using entire samples like state in your study? Thank You!

    1. Thank you so much for coming, Pops! As for your questions, I focused on synthesizing one plastic, composed of an 18 carbon chain. The name is chloro(dimethyl)octadecyl silane if you’d like to see its chemical structure. I started with a simple carbon chain, since they are the simplest form of plastics (see polyethylene). Plastic samples with dyes or non-carbon elements would be more specific, but the applications would not be as broad. In terms of the cost savings, if you don’t damage the ATR crystals like I did, I expect the costs to be pretty large. Using field samples is difficult, as more work has to be done to determine how long the plastic sample was exposed in the environment, which is essential in informing their results. Additionally, advanced weathering systems that could simulate a plastic’s extended time outside are expensive, but it’s an initial investment that pays over time. It’s hard to tell the cost savings, but synthesizing a plastic in lab seems a lot easier if not cheaper!

      1. Well thank you dear Daughter! So proud of you (as always) and thanks for answering the question. I think this model is a good launch pad for further research. Great job!

  11. Congratulations Jenelle! It is great to see some of the work you have accomplished and it looks there are a lot of promising next steps. What do you think was your greatest takeaway from this process?

    1. Hi Dr. Sobeck, thank you for coming! I’m excited to see the direction this project will take next. After integrating kinetic modeling into the project, I realized that great projects require the overlap between a variety of fields. Although I only intended to perform laboratory work, modeling the gas phase chemistry in the flow cell proved to be essential for analysis later on, as OH concentrations couldn’t be measured in lab. The biggest takeaway is that scientific research, and chemistry research in particular, requires the overlap of a variety of disciplines to produce a truly holistic study.

  12. Hi Jenelle! Great work on your IS–this topic is very interesting! Do you plan to utilize this project or environmental studies in your post-graduate studies?

    1. Hi Sydney! Thank you for coming, I’m glad you enjoyed it! I intend to come back in the fall to continue research on either SAMs or pesticides using the same ATR technique. Although less elaborated on in my poster, my project addresses micro plastics–irrevocable plastic debris about 5 mm small–which is a source of interest for many research groups looking at animal health. It would be an interesting pivot to work in understanding the environmental impact of microplastic’s from a more ecological standpoint.

  13. Congratulations Jenelle, I loved your poster presentation and the timeliness of your topic. I look forward to reading more of your IS to learn more!

  14. This is so amazing Jenelle! What sparked your interest in this IS topic? Congrats on an outstanding career at Woo!

  15. Really interesting work in a field I know so little about! Awesome job- I can’t wait to see what you do after Wooster!

  16. Congrats Jenelle! Unsurprisingly your research is awesome and it’s so cool to see everything you’ve worked on! I’m super excited to see all that you do in the future and hey, I miss seeing your face in Low!

  17. Great job on this project, it was very interesting! You mentioned that the monolayer is a small sample, less than 2% of the total penetration, but despite being small the signals are still expected to be large enough to validate the experimental procedures. Why is this and how did you prove that the signals are in fact large enough for the procedures to work?

    1. Hi Ciara, thanks for your question. I actually learned the answer to this question just yesterday! To begin, the reflectance inside the crystal means the IR beam is penetrating the SAM multiple times, so the detected signal is the sum of multiple penetrations (so 2% on 2% on 2% on… etc.). Additionally, the penetration of the beam follows the trend of exponential decay. This means that most of the IR beam penetration is focused right on the SAM and less on the open air above the SAM. I hope that answers your question! If not, I can answer some of your follow up questions. Thanks again for coming!

  18. Thank you all for coming! There’s about 15 minutes left for me to field comments, however, I will be returning throughout the day to respond to comments and hopefully discuss some of your questions. I appreciate your interest in my project, and I hope you have a great rest of your day!

  19. Jenelle! You never fail to amaze. I am so lucky to know such a smart & powerful woman! I absolutely cannot wait to see what is next for you. Ich liebe dich, Süße.

  20. You are brilliant! Love to see your work turn into reality. I am so proud of you Jenelle!

  21. Congratulations, Jenelle! I’m sure your research is going to be used for important environmental change.

  22. Yessssss: “the chemical impact of plastic waste can be explored quickly and at a lower cost than field sampling.” You have genuinely created something new and contributed to our natural environment. I truly love everything about this, a queen!

  23. Jenelle, this is such important work and you’ve done a great job explaining it. Congratulations and enjoy your success!

  24. Congratulations Jenelle! Yout presentation was awesome and I really enjoyed seeing your work

  25. Congratulations Jenelle! I learnt a lot from your poster presentation, and I’m so proud of all the work you’ve done! I can’t wait to see all you do in the future, you’re amazing!

  26. Wonderful work! This is a highly relevant topic and has so many future applications. Congrats on a project well done!

  27. Congratulations on finishing! Can’t wait to see what the world has in store for you! Images will miss you!

  28. Congratulations on an amazing I.S. and a great four years at Wooster. I’m so glad I was able to be apart of your journey and I have no doubts that you will do great things!!

  29. Hi Jenelle, Congrats on completing this important and relevant work! Your presentation was excellent and understandable, even by this *old* Wooster alum. 🙂 Best wishes for your future!

  30. Wow! I learned so much! What an impressive project with important environmental implications, Jenelle. Thank you for sharing your research.

  31. Look at Jenelle. Shining. Glowing. Radiant. Pure intelligence. You’ve done an amazing job here, and I am so proud of you!! Looking at your charts makes me miss organic chemistry, it’s so awesome to see similar ideas being put into action here.

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