Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7148

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Author: search.filters.author.Gülen, DemetSubject: search.filters.subject.Cyanines

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  • Article
    Citation - WoS: 2
    Citation - Scopus: 2
    Polarized Absorption Spectra of Highly Oriented Two-Dimensional Aggregates of Tetrachlorobenzimidazolocarbocyanine in Thin Films
    (Elsevier Ltd., 2008) Özçelik, Serdar; Gülen, Demet
    Reaching a control on the mesoscopic morphology and internal molecular arrangement of cyanine aggregates is an important step for realization of devices with tailor-made optical properties. Despite a wealth of research, understanding of the relationship between molecular organization, excitonic states and dynamics of aggregates is still preliminary. To this end, we have employed polarized absorption spectroscopy to investigate the relationship between internal molecular organization and excitonic states of J-aggregates in 1,1′,3,3′tetraethyl-5,5′,6,6′-tetrachlorobenzimidazolocarbocyanine (TTBC) thin films in poly-vinyl alcohol (PVA). Angular dependence of the UV-vis spectra has been measured at 11 different orientations between the electric field polarization and the macroscopic alignment axis. Aggregate spectral response consisted of an asymmetrically split Davydov pair of bands exhibiting opposite polarization: an H-band (505 nm, Lorentzian-like, polarized along the macroscopic film axis) and a J-band (594 nm, one-dimensional J-aggregate like band shape, polarized perpendicular to the macroscopic film axis). The polarized absorption observations were found to be consistent with a herringbone model for which the internal molecular arrangement, the excited state structure and dynamics have recently been detailed by us upon interpretation of isotropic absorption data in ionic aqueous solution.
  • Article
    Citation - WoS: 11
    Citation - Scopus: 11
    Investigation of Structure-Spectroscopy Relationship of Twodimensional J-Aggregates of Tetrachlorobenzimidazolorcarbocyanine Preferentially Oriented in Poly-Vinly Thin Films
    (Elsevier Ltd., 2009) Gülen, Demet; Atasoylu, Onur; Özçelik, Serdar
    The structure–spectroscopy–function relationship of 1,1 0 ,3,3 0 -tetraethyl-5,5 0 ,6,6 0 -tetrachlorobenzimidazolocarbocyanine (TTBC) aggregates is studied using a combination of experimental and theoretical techniques. The aggregates are macroscopically aligned in poly-vinyl-alcohol thin films by vertical spin coating. Angular dependence of the UV–Vis spectra is measured at eleven different orientations between the electric field polarization and the macroscopic alignment axis. The aggregates are characterized by a pair of Davydov split bands with opposite polarization behaviors: an H-band (505 nm) and a J-band (594 nm) polarized respectively, close to being parallel and perpendicular to the alignment axis. Spectral response is interpreted via simulations within the Frenkel exciton formalism. TTBC aggregates are shown to assume very similar internal molecular packing (herringbone) and dynamics of excited states (phononassisted intraband and interband relaxations) in ionic aqueous solution and in thin films. The general conclusions on the structure–spectroscopy–function relationship are expected to hold for other cyanine aggregates with the same generic spectral features.