| 1. |
- Gorman, Jeffrey, et al.
(författare)
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Deoxyribonucleic Acid Encoded and Size-Defined π-Stacking of Perylene Diimides
- 2022
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 144:1, s. 368-376
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Tidskriftsartikel (refereegranskat)abstract
- Natural photosystems use protein scaffolds to control intermolecular interactions that enable exciton flow, charge generation, and long-range charge separation. In contrast, there is limited structural control in current organic electronic devices such as OLEDs and solar cells. We report here the DNA-encoded assembly of pi-conjugated perylene diimides (PDIs) with deterministic control over the number of electronically coupled molecules. The PDIs are integrated within DNA chains using phosphoramidite coupling chemistry, allowing selection of the DNA sequence to either side, and specification of intermolecular DNA hybridization. In this way, we have developed a "toolbox" for construction of any stacking sequence of these semiconducting molecules. We have discovered that we need to use a full hierarchy of interactions: DNA guides the semiconductors into specified close proximity, hydrophobic-hydrophilic differentiation drives aggregation of the semiconductor moieties, and local geometry and electrostatic interactions define intermolecular positioning. As a result, the PDIs pack to give substantial intermolecular pi wave function overlap, leading to an evolution of singlet excited states from localized excitons in the PDI monomer to excimers with wave functions delocalized over all five PDIs in the pentamer. This is accompanied by a change in the dominant triplet forming mechanism from localized spin-orbit charge transfer mediated intersystem crossing for the monomer toward a delocalized excimer process for the pentamer. Our modular DNA-based assembly reveals real opportunities for the rapid development of bespoke semiconductor architectures with molecule-by-molecule precision.
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| 2. |
- Tyagi, Gunjan, et al.
(författare)
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Light Responsiveness and Assembly of Arylazopyrazole-Based Surfactants in Neat and Mixed CTAB Micelles
- 2022
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863. ; 2:12, s. 2670-2677
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Tidskriftsartikel (refereegranskat)abstract
- The self-assembly of an arylazopyrazole-based photosurfactant (PS), based on cetyltrimethylammonium bromide (CTAB), and its mixed micelle formation with CTAB in aqueous solution was investigated by small angle neutron and X-ray scattering (SANS/SAXS) and UV-vis absorption spectroscopy. Upon UV light exposure, PS photoisomerizes from E-PS (trans) to Z-PS (cis), which transforms oblate ellipsoidal micelles into smaller, spherical micelles with larger shell thickness. Doping PS with CTAB resulted in mixed micelle formation at all stoichiometries and conditions investigated; employing selectively deuterated PS, a monotonic variation in scattering length density and dimensions of the micellar core and shell is observed for all contrasts. The concentration- and irradiance-dependence of the E to Z configurational transition was established in both neat and mixed micelles. A liposome dye release assay establishes the enhanced efficacy of photosurfactants at membrane disruption, with E-PS exhibiting a 4-fold and Z-PS a 10-fold increase in fluorescence signal with respect to pure CTAB. Our findings pave the way for external triggering and modulation of the wide range of CTAB-based biomedical and material applications.
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