Senior Design Expo 2023

Applied Physics & Applied Mathematics
Degradation Mechanisms of Polyethylene Terephthalate (PET)
Fatima Begum, Department of Applied Physics and Applied Math
Advisor: Professor Sanat Kumar and Nico Mendez, Department of Chemical Engineering
Plastic pollution in the Earth’s oceans is undoubtedly an important topic of research. More
specifically, its subsequent degradation into microplastics and nanoplastics is of large interest
because sampling it from the ocean has proven to be difficult. As a result, research efforts are
focused on simulating this degradation with polyethylene terephthalate (PET) to analyze its
properties and degradation mechanisms (chemical, thermal, and oxidative). In this study, 50 µm
PET film was placed into water and heated for times ranging from one to ten days. The water,
hypothesized to contain degraded PET particles, was analyzed through dynamic light scattering
(DLS) to determine the number of degraded particles in the solution. These degraded films were
then photographed using scanning electron microscopy (SEM) and atomic force microscopy
(AFM) to analyze the properties of the surface. Differential scanning calorimetry (DSC) was
used to measure and calculate the degree of melting. Lastly, a polarized light microscope was
used to take images of the solutions.
In general, the DLS demonstrated that PET films that were degraded for longer tended to have
higher count rates (~400 kcps) than those that were degraded for shorter periods of time (~100
kcps). As a result of more degradation, the sample degraded for 8 days had a rougher surface
(.28) than the control sample (.19), according to the AFM images. The degree of melting was
about .4 according to the DSC measurements. The SEM images show variations in the sizes and
shapes of the degraded microplastics. Finally, the polarized light microscope images illustrate
that the degraded microplastic is in fact semicrystalline as opposed to solely amorphous.
Keywords: PET, film, hydrolysis, chemicrystallization, microplastics, degradation, crystallinity,
thermal degradation, oxidative degradation, Dynamic Light Scattering (DLS), Scanning Electron
Microscopy (SEM), Atomic Force Microscopy (AFM), Differential Scanning Calorimetry
(DSC), polarized light microscopy
Optimizing growth of AuNPs in DNA origami cages to tune optical properties
Margot Szamosszegi, Huajian Ji, Eric Shen, Oleg Gang
The goal of this project is to optimize the growth of functionalized gold nanoparticles (AuNPs)
inside DNA origami frames and assembled lattices to create prescribed nanostructures with
stronger tunable optical responses. By investigating the growth parameters of these systems, this
work aims to develop a better understanding of their behavior and pave the way for further
exploration into the design and application of DNA-based optical devices. Results show that the
growth of free AuNPs can be effectively controlled and maintained a spherical morphology
beyond 30 nm, while the growth of AuNPs in DNA origami cages proved more challenging due
to possible AuNP aggregation and confinement effects from the DNA framework. The growth of
AuNPs in DNA origami lattices yielded irregular AuNP geometries and unreliable results due to
AuNP encapsulation within several layers of DNA origami frames. These results serve as a
useful starting point for researchers in the field and have opened up exciting avenues for further
work to optimize AuNP growth parameters and fully unlock the potential of DNA-based optical
materials.
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