Fluorescence-based characterizations of the first two polycyclic aromatic hydrocarbons observed in interstellar space

The first two polycyclic aromatic hydrocarbons (PAHs) ever to be identified in interstellar space, 1- and 2-naphthonitrile, were spectroscopically analyzed in this project with an emphasis on their fluorescence properties. By providing spectroscopic quantities and spectral analyses, the further discovery of these two PAHs elsewhere in the universe can be facilitated. This is especially the case if either are present in the solar system, specifically in areas where future space missions plan to probe. This is because one experimental technique that was utilized in this research, synchronous fluorescence, is a useful, and established identification technique. However, it has recently been proposed to also be a potential complementary astrochemical identification technique that could be utilized in missions to planets or other satellites in the solar system. This is because spectra produced from this technique are identifiable, and significantly narrower than typical fluorescence emission spectra. Stemming from this logic, synchronous fluorescence spectra were measured for the two naphthonitrile isomers of interest, with the idea that the technique will be taken advantage of by the space industry in the future. To further investigate their spectroscopic properties, both molecules were thoroughly analyzed while dissolved in various solvents. Such analyses included absorption and fluorescence spectra, quantum yields, and fluorescence lifetimes. Each of these experiments were conducted in four solvents, namely water, acetonitrile, methanol, and cyclohexane. Fluorescence sensitivity to both polarity and oxygen were also explored via comparing emission intensities for solutions of ethanol and water, before and after being purged with Argon. These results highlight the dependence of a given fluorescence spectrum of 1- or 2-CN on its environment, in this case the solvent or its exposure to molecular oxygen. These results have implications on their emission properties in space. Additionally, the measured spectra have applicability for reference with optical telescope observations (direct collection of fluorescence emission), which are arguably even more significant than the collection of synchronous fluorescence spectra. Effects on the fluorescence of 1- and 2-CN were also explored by the use of host-guest chemistry. Host-guest experimentation was implemented in this research due to the convenient size and shape of 1- and 2-CN, as this indicated that they could possibly be incorporated within larger host molecules. Consequently, two host molecules were attempted for 1-CN, and one for 2-CN, where one displayed significant binding to 1-CN. These hosts were cucurbit(7)uril (CB[7]), and (2-hydroxypropyl)-β-cyclodextrin (β-CD), with CB[7] successfully suppressing the fluorescence of 1-CN. CB[7] inclusion was also attempted with 2-CN, however a negligible impact on its fluorescence was observed.