The aggregation of conjugated polymers in common organic solvents is investigated using fluorescence correlation spectroscopy (FCS), burst analysis, and microscopy. Poly(3-hexylthiophene) and poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] are both shown to form weakly bonded non-emissive aggregates in toluene that persist even at picomolar concentrations. These aggregates decrease the bulk emission intensity in solution but do not affect the fluorescence spectra or lifetimes, consistent with a static quenching mechanism. Passing the solutions through a syringe filter causes an increase in the number of emitters as measured by FCS, indicating that this process dissociates the aggregates. Films cast from solutions that have been filtered are more uniform and significantly more emissive than those made from unfiltered solutions. These results show that FCS is a highly sensitive probe of non-emissive aggregates in solution that have a deleterious effect on the emission properties and overall quality of spin-cast thin films, even at sub-nanomolar concentrations.

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The American Chemical Society (ACS) Project SEED (Summer Experiences for the Economically Disadvantaged) program has been exposing students to chemistry-related research for over half a century. The program was created and designed to recruit and prepare high school students from economically challenged households to explore and build their confidence in chemistry and STEM, enter college, and hopefully pursue a STEM career. Historically, the students engaged in a summer research experience on college campuses, industrial laboratories, or government facilities, working alongside a scientist mentor. However, the 2020 summer on-campus experiences were not possible due to COVID-19 mitigation efforts. Thus, even after the program planning and recruitment for the experience was well underway, the program pivoted to a virtual camp. The camp's format was substantially different from the on-campus experiences, with 291 students nationwide participating in webinars, small group discussions, and completing assignments based on a schedule with due-dates. Gathering a combination of quantitative and qualitative data before and after the camp revealed increases in the students' professional skills, STEM identity, and college preparation. We failed to find a change in their professional identity. We determined that students participating in future Project SEED programming could benefit from engaging in a combination of oncampus and online events to experience authentic laboratory research and gain a more global perspective of chemistry careers and the potential for extended networking with other Project SEED participants and alumni.