Browsing by Subject "Chromophores"
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Item Open Access Design strategies for ratiometric chemosensors: modulation of excitation energy transfer at the energy donor site(2009) Guliyev, R.; Coskun, A.; Akkaya, E. U.Excitation energy transfer, when coupled to an ion-modulated ICT chromophore, creates novel opportunities in sensing. The direction of energy transfer and the point of ICT modulation can be varied as desired. In our previous work, we have shown that energy transfer efficiency between two energetically coupled fluorophores will be altered by the metal ion binding to the ICT chromophore carrying a ligand. There are two beneficial results: increased pseudo-Stokes shift and expanded dynamic range. Here, we explored the consequences of the modulation of energy transfer efficiency at the energy donor site, in a molecular design which has an ICT type metal ion-sensitive chromophore placed as the energy donor in the dyad. Clear advantages emerge compared to the acceptor site modulation: unaltered emission wavelength in the red end of the visible spectrum, while keeping a large Stokes shift and the ratiometric character. © 2009 American Chemical Society.Item Open Access Fabrication of supramolecular n/p-nanowires via coassembly of oppositely charged peptide-chromophore systems in aqueous media(American Chemical Society, 2017-07) Khalily, M. A.; Bakan, G.; Kucukoz, B.; Topal, A. E.; Karatay, A.; Yaglioglu, H. G.; Dana, A.; Güler, Mustafa O.Fabrication of supramolecular electroactive materials at the nanoscale with well-defined size, shape, composition, and organization in aqueous medium is a current challenge. Herein we report construction of supramolecular charge-transfer complex one-dimensional (1D) nanowires consisting of highly ordered mixed-stack π-electron donor-acceptor (D-A) domains. We synthesized n-type and p-type β-sheet forming short peptide-chromophore conjugates, which assemble separately into well-ordered nanofibers in aqueous media. These complementary p-type and n-type nanofibers coassemble via hydrogen bonding, charge-transfer complex, and electrostatic interactions to generate highly uniform supramolecular n/p-coassembled 1D nanowires. This molecular design ensures highly ordered arrangement of D-A stacks within n/p-coassembled supramolecular nanowires. The supramolecular n/p-coassembled nanowires were found to be formed by A-D-A unit cells having an association constant (KA) of 5.18 × 105 M-1. In addition, electrical measurements revealed that supramolecular n/p-coassembled nanowires are approximately 2400 and 10 times more conductive than individual n-type and p-type nanofibers, respectively. This facile strategy allows fabrication of well-defined supramolecular electroactive nanomaterials in aqueous media, which can find a variety of applications in optoelectronics, photovoltaics, organic chromophore arrays, and bioelectronics.Item Open Access Novel molecular building blocks based on the boradiazaindacene chromophore: applications in fluorescent metallosupramolecular coordination polymers(2009) Bozdemir, Ö. A.; Büyükcakir, O.; Akkaya, E. U.We designed and synthesized novel boradiazaindacene (Bodipy) derivatives that are appropriately functionalized for metal-ion-mediated supramolecular polymerization. Thus, ligands for 2-terpyridyl-, 2,6-terpyridyl-, and bipyridyl-functionalized Bodipy dyes were synthesized through Sonogashira couplings. These fluorescent building blocks are responsive to metal ions in a stoichiometry-dependent manner. Octahedral coordinating metal ions such as Zn II result in polymerization at a stoichiometry corresponding to two terpyridyl ligands to one Zn II ion. However, at increased metal ion concentrations, the dynamic equilibria are re-established in such a way that the monomeric metal complex dominates. The position of equilibria can easily be monitored by 1H NMR and fluorescence spectroscopies. As expected, although open-shell Fe II ions form similar complex structures, these cations quench the fluorescence emission of all four functionalized Bodipy ligands. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA.Item Open Access Optimization of distyryl-Bodipy chromophores for efficient panchromatic sensitization in dye sensitized solar cells(2011) Kolemen, S.; Cakmak, Y.; Ertem, E.; Bozdemir, O. A.; Erten-Ela, S.; Marszalek, M.; Yum, Jun-Ho; Zakeeruddin, S.; Nazeeruddin, M.; Gratzel, M.; Akkaya, E. U.Versatility of Bodipy (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) dyes was further expanded in recent dye-sensitized solar cell applications. Here we report a series of derivatives designed to address earlier problems in Bodipy sensitized solar cells. In the best case example, an overall efficiency of a modest 2.46% was achieved, but panchromatic nature of the dyes is quite impressive. This is the best reported efficiency in liquid electrolyte solar cells with Bodipy dyes as photosensitizers.Item Open Access Synthesis of symmetrical multichromophoric bodipy dyes and their facile transformation into energy transfer cassettes(2010) Bozdemir, O. A.; Cakmak, Y.; Sozmen F.; Ozdemir, T.; Siemiarczuk, A.; Akkaya, E. U.Multichromophoric boron-dipyrromethene (Bodipy) dyes synthesized on phenylene-ethynylene platforms have been be converted to energy transfer cassettes in a one-step chemical transformation. Excitation energy transfer processes in these highly symmetrical derivatives were studied in detail, including time-re-solved fluorescence spectroscopy techniques. Excitation spectra and the emission lifetimes suggest efficient energy transfer between the donor and acceptor chromophore. These novel energy transfer cassettes, while highlighting a short-cut approach to similar energy transfer systems, could be useful as large pseudo-Stokes shift multichromophoric dyes with potential applications in diverse applications.Item Open Access Towards unimolecular luminescent solar concentrators: bodipy-based dendritic energy-transfer cascade with panchromatic absorption and monochromatized emission(2011) Bozdemir, O. A.; Erbas-Cakmak, S.; Ekiz, O. O.; Dana, A.; Akkaya, E. U.A polymer-embedded dendritic, bodipy-based panchromatic absorber with a built-in energy gradient concentrates incident solar radiation at a terminal chromophore, resulting in a monochromatized emission directed to the sides of the polymer waveguide (see picture). This particular design minimizes self-absorption losses from the peripheral antenna units with an impressive S factor of 10 000.