Photonics-Based Studies in Materials Science Using GUMBOS and NanoGUMBOS

Abstract

In this dissertation, development of new materials to the field of photonics, more specifically solar energy conversion and cancer therapy was studied. In particular, a series of group of uniform materials based on organic salts (GUMBOS) were developed for use as improved photosensitizers in dye-sensitized solar cells (DSSCs) and photodynamic therapy (PDT). GUMBOS are solid phase organic salts that are similar to ionic liquids, but with melting points ranging from 25 to 250 °C. Properties of GUMBOS can easily be tuned by changing the cation or anion used to form these materials. Thus, new materials can easily be produced with properties that are beneficial for applications in DSSCs or PDT. In this dissertation, porphyrin-based GUMBOS as well as nanomaterials derived from these GUMBOS (nanoGUMBOS) were synthesized and characterized as photosensitizers in DSSCs. These GUMBOS and nanoGUMBOS displayed interesting properties such as increased molar absorptivity and broadened absorption spectra, which are important characteristics for photosensitizers used in DSSCs. NanoGUMBOS-based photosensitizers were applied in DSSCs after precise optimization of the DSSCs structure with regard to the semiconductor (working electrode) and electrolyte. In another application, GUMBOS were developed as energy relay dyes (ERDs) in DSSCs due to the tunable properties of GUMBOS such as solubility, molar absorptivity, and fluorescence quantum yield. GUMBOS-based ERDs were applied in DSSCs, and increases in solar conversion efficiencies of up to 14.6% were observed. Interestingly, the magnitude of increase in solar conversion efficiency was found to depend on the counterion used in synthesis of GUMBOS-based ERDs. Finally, porphyrin- and phthalocyanine-based nanoGUMBOS were studied for application as photosensitizers in PDT. By using a facile, ion exchange reaction to form GUMBOS, a bulky cation was introduced to prevent aggregation of porphyrin and phthalocyanine dyes. Overall increases in singlet oxygen production were observed with GUMBOS in comparison to the parent compounds. Singlet oxygen quantum yields of porphyrin and phthalocyanine GUMBOS were 0.57 ± 0.05 and 0.55 ± 0.01 in comparison to yields from the parent dyes, which were 0.50 ± 0.02 and 0.46 ±0.04, respectively. As a whole, these studies demonstrate substantial advantages of GUMBOS-based materials in the field of photonics.