Tuning the Key Properties of Conjugated Materials in Single Crystals and in Singlet Oxygen Sensing Nanoparticles
Frausto, Fanny.
2018
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Abstract: Conjugated materials are used in various applications, such as in photovoltaics and sensors, in the solid state. While progress has been made in the understanding of these materials in the solid state, gaps in our knowledge remain. Conjugated materials' solid state packing influences their optoelectronic properties. However, there is limited understanding on how structure affects packing ... read moreand thus their optical and electronic properties. This thesis describes the structure-property relationships of conjugated materials in nanoparticles and single crystals. Chapter 2 describes diphenylacetylenes (tolan) derivatives along with other conjugated organic molecules with self-complementary aryl halides and halogen bond-accepting nitriles form 2D bricklayer packing motifs when halogen bonding occurs. When halogen bonding is absent, as occurred with fluorinated aryl bromides, the molecules adopt other packing motifs. These results suggest halogen bonding is potentially useful for producing rarely observed 2D bricklayer motifs in organic semiconductors. Chapter 3 describes that while fluorescent probes for the detection of singlet oxygen (1O2) have been an active area of research, most such probes rely upon change in intensity of a single band. Herein we report a FRET-based, 1O2-sensitive aqueous suspension of conjugated polymer nanoparticles (CPNs) comprising the energy donating host polymer poly[(9,9-dioctyl-2,7-divinylene-fluorenylene(-alt-co-(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene)] doped with an energy acceptor, the 1O2-sensitive thienoacene 5,12-bis(4-methoxyphenyl)-2-butyltetraceno[2,3-b]thiophene. Using a phthalocyanine-based sensitizer, our probe shows a rapid, ratiometric response to photosensitized 1O2 in water in both cuvettes and 96-well plates that compares favorably to the commercial 1O2-sensitive dye Singlet Oxygen Sensor Green. The response to irradiation of even nanomolar concentrations of photosensitizer demonstrates the sensitivity of our ratiometric probe. Chapter 4 describes effects of nanoparticle composition on energy transfer and ratiometric fluorescent response to 1O2 of a series of dye-doped CPNs. These CPNs are comprised of various conjugated polymer as polymer donor matrix and one of four different 1O2-sensitive acene acceptor dopants. In the dense chromophore matrix of the CPN, the quantum yield of fluorescence of each acene-doped CPN matches or exceeds that of the undoped CPN. Additionally, incorporation of a photoinert polymer poly(methyl methacrylate) provides an increase in the quantum yield of fluorescence in both doped and undoped CPNs. Reactivity with 1O2 of the acenes follows the same trend in the solid matrix of CPNs as previously found in dilute solution. The doping levels of acenes in the CP matrix have important implications for both the extent of energy transfer and the subsequent rates of ratiometric response. This study therefore lends important insight into the rational design of luminescent, stimuli-responsive CPNs.
Thesis (Ph.D.)--Tufts University, 2018.
Submitted to the Dept. of Chemistry.
Advisor: Samuel Thomas.
Committee: Clay Bennett, Elena Rybak-Akimova, Charlie Sykes, and Mindy Levine.
Keywords: Chemistry, Polymer chemistry, and Materials Science.read less - ID:
- v118rs13r
- Component ID:
- tufts:25021
- To Cite:
- TARC Citation Guide EndNote
