Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
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Article Citation - WoS: 16Citation - Scopus: 15Understanding Plasmon Coupling in Nanoparticle Dimers Using Molecular Orbitals and Configuration Interaction(Royal Soc Chemistry, 2019) Alkan, Fahri; Aikens, Christine M.We perform a theoretical investigation of the electronic structure and optical properties of atomic nanowire and nanorod dimers using DFT and TDDFT. In both systems at separation distances larger than 0.75 nm, optical spectra show a single feature that resembles the bonding dipole plasmon (BDP) mode. A configuration interaction (CI) analysis shows that the BDP mode arises from constructive coupling of transitions, whereas the destructive coupling does not produce significant oscillator strength for such separation distances. At shorter separation distances, both constructive and destructive coupling produce oscillator strength due to wave-function overlap, which results in multiple features in the calculated spectra. Our analysis shows that a charge-transfer plasmon (CTP) mode arises from destructive coupling of transitions, whereas the BDP results from constructive coupling of the same transitions at shorter separation distances. Furthermore, the coupling elements between these transitions are shown to depend heavily on the amount of exact Hartree-Fock exchange (HFX) in the functional, which affects the splitting of CTP and BDP modes. With 50% HFX or more, the CTP and BDP modes mainly merge into a single feature in the spectra. These findings suggest that the effects of exact exchange must be assessed during the prediction of CTP modes in plasmonic systems.Article Citation - WoS: 12Citation - Scopus: 12External Complexation of Bodipys by Cb[7] Improves In-Cell Fluorescence Imaging(Royal Soc Chemistry, 2022) Ayhan, Mehmet Menaf; Ozcan, Emrah; Alkan, Fahri; Cetin, Metin; Un, Ilker; Bardelang, David; Cosut, BonyeminOrganic luminescent compounds with high emission properties play a crucial role in fluorescence labelling and optoelectronic devices. In this work, we prepared three water soluble BODIPY derivatives (B-4, B-5, and B-6) which are weakly fluorescent due to non-radiative relaxation pathways (charge transfer: CT or heavy atom effect). However, CB[7] significantly improves BODIPY fluorescence by similar to 10 fold for B-4, and by similar to 3 fold for B-5. The (TD)DFT analyses suggest that for B-4 and B-5, the CT state is blue-shifted as a result of the external binding of CB[7] near the pyridinium groups. This effect favoured a radiative decay through a locally-excited (LE) pi ->pi* transition state of BODIPYs resulting in a CB[7]-induced emission increase in solution (and in the solid state), without compromising singlet-to-triplet intersystem crossing (ISC). The improved emission of the BODIPY center dot CB[7] complexes was used for the fluorescence imaging of U87 cells illustrating the relevance of this approach. These results suggest that BODIPY center dot CB[7] complexes could be used as theragnostic agents by combining fluorescence imaging and treatment by photodynamic therapy.Article Citation - WoS: 34Citation - Scopus: 35A Hybridized Local and Charge Transfer Excited State for Solution-Processed Non-Doped Green Electroluminescence Based on Oligo(p-Phenyleneethynylene)(Royal Soc Chemistry, 2020) Usta, Hakan; Alimli, Dilek; Ozdemir, Resul; Tekin, Emine; Alkan, Fahri; Kacar, Rifat; Can, AyseWe herein report a new highly efficient green emissive hot-exciton molecule, 1,4-bis((4'-diphenylamino3-cyano-[1,1'-biphenyl]-4-yl)ethynyl)-2,5-bis(2-ethylhexyloxy)benzene (2EHO-TPA-CNPE) that consists of an extended D'-pi'-A-pi-D-pi-A-pi'-D' molecular p-system with diphenylamino end units (D') and ethynylene/phenylene spacers (pi/pi'). The new molecule exhibits high photoluminescence (PL) quantum efficiencies (Phi(PL) = 0.95 (solution) and 0.45 (spin-coated neat thin-film)), and a strong PL solvatochromic behavior revealing significant changes in excited state energies/characteristics (locally excited (LE) -> hybridized local and charge transfer (HLCT) - charge-transfer (CT)) depending on solvent polarity. Highly efficient (radiative exciton yield (eta(r)) = 50-59% >> 25%) green-emitting OLEDs were fabricated in a conventional device architecture by employing (non-)doped thin-films reaching a maximum current efficiency (CEmax) of 12.0 cd A(-1) and a maximum external quantum efficiency (EQE(max)) of 5.5%. The emission profile of the non-doped OLED has CIE 1976 (u', v') chromaticity coordinates of (0.10, 0.55) corresponding to a night vision imaging system (NVIS) compatible Green A region. 2EHO-TPA-CNPE-based OLED devices of industrial relevance were also fabricated by ink-jet printing the emissive layer and by fabricating an inverted architecture, which possessed respectable device performances of 2.4-6.1 cd A(-1). The solid-state solvation effect in OLED devices yields HLCT electronic behavior resulting in high Zr's, which is confirmed by TDDFT to originate from energetically/spatially favorable reverse intersystem crossings (RISCs) (T-2/3 -> S-1). As a unique observation, delayed fluorescence due to this RISC was evident in the PL decay lifetime measurement with a ns-scale lifetime of similar to 10 ns. These results clearly allow a better understanding of the structure-photophysical property-electroluminescence relationships in this new class of oligo(p-phenyleneethynylene)-based hot-exciton molecules, and it could open up new opportunities for high-performance solution-processed optoelectronic/sensing applications.