Tag: Physical Chemistry

Optimization of Deposition Techniques for Thin Film Production and Analysis

Presenter(s): Madelyn Scott − Chemistry

Faculty Mentor(s): Cathy Wong, Kelly Wilson

Poster 15

Research Area: Physical Chemistry

Funding: Community for Minorities in STEM (CMiS) Travel Award Scholarship; Phil and Penny Knight Campus for Accelerating Scientific Impact

Organic semiconductors offer a green alternative to conventional conductive materials because they can be solution- processed on an industrial scale for use in solar cells and OLEDs. The electronic transitions in organic semiconducting materials determine their charge-carrying efficiency for use in such devices. Transient absorption spectroscopy can be used to track the population of mobile electron-hole pair combinations at controlled delay times after photogeneration by a laser pulse. This technique is typically used to study equilibrated systems, like static solutions or films, but not materials as they evolve. For in situ studies of non-equilibrated systems, the Wong Lab has developed a single-shot transient absorption (ssTA) spectrometer to measure the excited state dynamics of thin films during deposition by a capillary or slot die coater. The solution capillary is two microscope slides spaced by aluminum shims and housed in an aluminum frame. The slot die coater is an apparatus designed to mimic solution-processed films that are manufactured roll-to-roll on an industrial scale. In both deposition techniques, a mechanical slide pusher is attached to the deposition device and positioned over an aluminum
stage to produce films on microscope slides. Experimental parameters considered during optimization of each deposition method included the following: slide pusher velocity, cleaning methods of the deposition slides, temperature of the depositing solution, and materials constructing the slide pusher apparatus. It was determined that the slot die coater enables more control over film quality than the solution capillary, producing films with more homogenous solution coverage. As a result, the slot die coater will be incorporated into the spectroscopy apparatus for the first in situ ssTA measurements of non- equilibrated material systems.

Modeling the Behavior of Pyruvic Acid at the Air-Water Interface

Presenter(s): Benjamin Muller − Chemistry

Faculty Mentor(s): Brittany Gordon, Dr. Geraldine Richmond

Poster 16

Research Area: Physical Chemistry

Studying the air-water interface provides valuable knowledge on important environmental systems like atmospheric aqueous secondary organic aerosol (aqSOA). Many small, aqueous organics that are known to contribute to aqSOA formation can further react in the air-water phase to form hydrated molecules. Since the atmosphere is a complex and variable place with many phases and interfacial regions it is difficult isolating this hydration process within particular organic systems. Modeling this behavior of hydrated organics at this interface is largely unknown. Pyruvic acid (PA) is an abundant atmospheric ketone found in aqSOA. Our research objective is to examine PA at the planar air-water interface using vibrational sum- frequency spectroscopy (VSFS). Sum frequency is a technique that shines visible and infrared light where air and water meet to understand molecular populations and behaviors of ordered molecules. Surface tensiometry measurements from the Wilhelmy plate will reveal the time dependency between PA and this complex system. Both techniques will help characterize how depth, conformational populations and orientation changes between the bulk, surface, and subsurface. This research will act as a platform to easily branch out to other systems of organics for future air-water interfacial studies.