PubMed İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/397
Browse
6 results
Search Results
Article Citation - WoS: 22Citation - Scopus: 24The Design and Fabrication of Supramolecular Semiconductor Nanowires Formed by Benzothienobenzothiophene (BTBT)-Conjugated Peptides(Royal Soc Chemistry, 2018) Khalily, Mohammad Aref; Usta, Hakan; Ozdemir, Mehmet; Bakan, Gokhan; Dikecoglu, F. Begum; Edwards-Gayle, Charlotte; Guler, Mustafa O.pi-Conjugated small molecules based on a [1]benzothieno[3,2-b]benzothiophene (BTBT) unit are of great research interest in the development of solution-processable semiconducting materials owing to their excellent charge-transport characteristics. However, the BTBT -core has yet to be demonstrated in the form of electro-active one-dimensional (1D) nanowires that are self-assembled in aqueous media for potential use in bioelectronics and tissue engineering. Here we report the design, synthesis, and self-assembly of benzothienobenzothiophene (BTBT)-peptide conjugates, the BTBT-peptide (BTBT-C-3-COHN-Ahx-VVAGKK-Am) and the C-8-BTBT-peptide (C-8-BTBT-C-3-COHN-Ahx-VVAGKK-Am), as -sheet forming amphiphilic molecules, which self-assemble into highly uniform nanofibers in water with diameters of 11-13(+/- 1) nm and micron-size lengths. Spectroscopic characterization studies demonstrate the J-type - interactions among the BTBT molecules within the hydrophobic core of the self-assembled nanofibers yielding an electrical conductivity as high as 6.0 x 10(-6) S cm(-1). The BTBT -core is demonstrated, for the first time, in the formation of self-assembled peptide 1D nanostructures in aqueous media for potential use in tissue engineering, bioelectronics and (opto)electronics. The conductivity achieved here is one of the highest reported to date in a non-doped state.Article Citation - WoS: 11Citation - Scopus: 13Solution-Processable Indenofluorenes on Polymer Brush Interlayer: Remarkable N-Channel Field-Effect Transistor Characteristics Under Ambient Conditions(Amer Chemical Soc, 2023-08-15) Can, Ayse; Deneme, Ibrahim; Demirel, Gokhan; Usta, HakanThe development of solution-processable n-type molecularsemiconductorsthat exhibit high electron mobility (& mu;(e) & GE;0.5 cm(2)/(V & BULL;s)) under ambient conditions, along withhigh current modulation (I (on)/I (off) & GE; 10(6)-10(7)) andnear-zero turn on voltage (V (on)) characteristics,has lagged behind that of other semiconductors in organic field-effecttransistors (OFETs). Here, we report the design, synthesis, physicochemicaland optoelectronic characterizations, and OFET performances of a libraryof solution-processable, low-LUMO (-4.20 eV) 2,2 & PRIME;-(2,8-bis(3-alkylthiophen-2-yl)indeno[1,2-b]fluorene-6,12-diylidene)dimalononitrile small molecules, & beta;,& beta;& PRIME;-C (n) -TIFDMTs, having varied alkyl chain lengths (n = 8, 12, 16). An intriguing correlation is identifiedbetween the solid-isotropic liquid transition enthalpies andthe solubilities, indicating that cohesive energetics, which are tunedby alkyl chains, play a pivotal role in determining solubility. Thesemiconductors were spin-coated under ambient conditions on denselypacked (grafting densities of 0.19-0.45 chains/nm(2)) ultrathin (& SIM;3.6-6.6 nm) polystyrene-brush surfaces.It is demonstrated that, on this polymer interlayer, thermally induceddispersive interactions occurring over a large number of methyleneunits between flexible alkyl chains (i.e., zipper effect) are criticalto achieve a favorable thin-film crystallization with a proper microstructureand morphology for efficient charge transport. While C-8 and C-16 chains show a minimal zipper effect upon thermalannealing, C-12 chains undergo an extended interdigitationinvolving & SIM;6 methylene units. This results in the formationof large crystallites having lamellar stacking ((100) coherence length & SIM;30 nm) in the out-of-plane direction and highly favorablein-plane & pi;-interactions in a slipped-stacked arrangement. Uninterruptedmicrostructural integrity (i.e., no face-on (010)-oriented crystallites)was found to be critical to achieving high mobilities. The excellentcrystallinity of the C-12-substituted semiconductor thinfilm was also evident in the observed crystal lattice vibrations (phonons)at 58 cm(-1) in low-frequency Raman scattering. Two-dimensionalmicrometer-sized (& SIM;1-3 & mu;m), sharp-edged plate-likegrains lying parallel with the substrate plane were observed. OFETsfabricated by the current small molecules showed excellent n-channelbehavior in ambient with & mu;(e) values reaching & SIM;0.9cm(2)/(V & BULL;s), I (on)/I (off) & SIM; 10(7)-10(8), and V (on) & AP; 0 V. Our study notonly demonstrates one of the highest performing n-channel OFET devicesreported under ambient conditions via solution processing but alsoelucidates significant relationships among chemical structures, molecularproperties, self-assembly from solution into a thin film, and semiconductingthin-film properties. The design rationales presented herein may openup new avenues for the development of high-electron-mobility novelelectron-deficient indenofluorene and short-axis substituted donor-acceptor & pi;-architectures via alkyl chain engineering and interface engineering.Article Citation - WoS: 36Citation - Scopus: 36Selective Remanent Ambipolar Charge Transport in Polymeric Field-Effect Transistors for High-Performance Logic Circuits Fabricated in Ambient(Wiley-VCH Verlag GmbH, 2014-10-06) Fabiano, Simone; Usta, Hakan; Forchheimer, Robert; Crispin, Xavier; Facchetti, Antonio; Berggren, MagnusArticle Citation - WoS: 27Citation - Scopus: 29Revisiting the Role of Charge Transfer in the Emission Properties of Carborane-Fluorophore Systems: A TDDFT Investigation(Amer Chemical Soc, 2022-06-05) Tahaoglu, Duygu; Usta, Hakan; Alkan, FahriIn this study, we performed a detailed investigation of the S-1 potential energy surface (PES) of o-carborane-anthracene (o-CB-Ant) with respect to the C-C bond length on o-CB and the dihedral angle between o-CB and Ant moieties. The effects of different substituents (F, Cl, CN, and OH) on carbon- or boron-substituted o-CB, along with a pi-extended acene-based fluorophore, pentacene, on the nature and energetics of S-1 -> S-0 transitions are evaluated. Our results show the presence of a non-emissive S-1 state with an almost pure charge transfer (CT) character for all systems as a result of significant C-C bond elongation (C-C = 2.50-2.56 angstrom) on o-CB. In the case of unsubstituted o-CB-Ant, the adiabatic energy of this CT state corresponds to the global minimum on the S-1 PES, which suggests that the CT state could be involved in emission quenching. Despite large deformations on the o-CB geometry, predicted energy barriers are quite reasonable (0.3-0.4 eV), and the C-C bond elongation can even occur without a noticeable energy penalty for certain conformations. With substitution, it is shown that the dark CT state becomes even more energetically favorable when the substituent shows -M effects (e.g., -CN), whereas substituents showing +M effects (e.g., -OH) can result in an energy increase for the CT state, especially for partially stretched C-C bond lengths. It is also shown that the relative energy of the CT state on the PES depends strongly on the LUMO level of the fluorophore as this state is found to be energetically less favorable compared to other conformations when anthracene is replaced with pi-extended pentacene. To our knowledge, this study shows a unique example of a detailed theoretical analysis on the PES of the S-1 state in o-CB-fluorophore systems with respect to substituents or fluorophore energy levels. Our findings could guide future experimental work in emissive o-CB-fluorophore systems and their sensing/optoelectronic applications.Article Citation - WoS: 124Citation - Scopus: 127Molecular Engineering of Organic Semiconductors Enables Noble Metal-Comparable SERS Enhancement and Sensitivity(Nature Publishing Group, 2019-12-03) Demirel, Gokhan; Gieseking, Rebecca L. M.; Ozdemir, Resul; Kahmann, Simon; Loi, Maria A.; Schatz, George C.; Usta, HakanNanostructured molecular semiconductor films are promising Surface-Enhanced Raman Spectroscopy (SERS) platforms for both fundamental and technological research. Here, we report that a nanostructured film of the small molecule DFP-4T, consisting of a fully pi-conjugated diperfluorophenyl-substituted quaterthiophene structure, demonstrates a very large Raman enhancement factor (>10(5)) and a low limit of detection (10(-9) M) for the methylene blue probe molecule. This data is comparable to those reported for the best inorganic semiconductor- and even intrinsic plasmonic metal-based SERS platforms. Photoluminescence spectroscopy and computational analysis suggest that both charge-transfer energy and effective molecular interactions, leading to a small but non-zero oscillator strength in the charge-transfer state between the organic semiconductor film and the analyte molecule, are required to achieve large SERS enhancement factors and high molecular sensitivities in these systems. Our results provide not only a considerable experimental advancement in organic SERS figure-of-merits but also a guidance for the molecular design of more sensitive SERS systems.Article Citation - WoS: 47Citation - Scopus: 45Enabling Three-Dimensional Porous Architectures via Carbonyl Functionalization and Molecular-Specific Organic-SERS Platforms(Nature Portfolio, 2021-10-21) Deneme, Ibrahim; Liman, Gorkem; Can, Ayse; Demirel, Gokhan; Usta, HakanNanostructured films of organic semiconductors with low lying LUMO orbitals can enhance Raman signals via a chemical enhancement mechanism but currently the material choice is limited to fluorinated oligothiophenes. Here, the authors investigate the growth of a porous thienoacene film enabled by carbonyls and demonstrate molecular specific organic-SERS platforms. Molecular engineering via functionalization has been a great tool to tune noncovalent intermolecular interactions. Herein, we demonstrate three-dimensional highly crystalline nanostructured D(C7CO)-BTBT films via carbonyl-functionalization of a fused thienoacene pi-system, and strong Raman signal enhancements in Surface-Enhanced Raman Spectroscopy (SERS) are realized. The small molecule could be prepared on the gram scale with a facile synthesis-purification. In the engineered films, polar functionalization induces favorable out-of-plane crystal growth via zigzag motif of dipolar C = O center dot center dot center dot C = O interactions and hydrogen bonds, and strengthens pi-interactions. A unique two-stage film growth behavior is identified with an edge-on-to-face-on molecular orientation transition driven by hydrophobicity. The analysis of the electronic structures and the ratio of the anti-Stokes/Stokes SERS signals suggests that the pi-extended/stabilized LUMOs with varied crystalline face-on orientations provide the key properties in the chemical enhancement mechanism. A molecule-specific Raman signal enhancement is also demonstrated on a high-LUMO organic platform. Our results demonstrate a promising guidance towards realizing low-cost SERS-active semiconducting materials, increasing structural versatility of organic-SERS platforms, and advancing molecule-specific sensing via molecular engineering.