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- 저자 : Elí (검색결과 2 건)
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Bidirectional Solvatofluorochromism of a Pyrrolo[3,2-<i>b</i>]pyrrole-Diketopyrrolopyrrole Hybrid
Ryu, Hye Gun,Mayther, Maximillian F.,Tamayo, Jesse,Azarias, Cloé,Espinoza, Eli M.,Banasiewicz, Marzena,Łukasiewicz, Łukasz G.,Poronik, Yevgen M.,Jeż,ewski, Artur,Clark, John,Derr, James B. American Chemical Society 2018 The Journal of Physical Chemistry Part C Vol.122 No.25
<P>Hybridization of electron donors and acceptors provides routes to long-wavelength absorbing and fluorescing dyes. Varying the coupling of low-lying charge-transfer (CT) states with the ground and different locally excited states profoundly affects the photophysics of such donor-acceptor conjugates. Herein, we hybridize an electron-deficient diketopyrrolopyrrole (DPP) moiety with an electron-rich pyrrolopyrrole (PP) that is symmetrically N-arylated with 4-nitrophenyl substituents. The lowest Franck-Condon state is located on the DPP ring structure and dominates the photophysics of the hybrid. Similar to the DPP moiety, the hybrid exhibits optical absorption that is invariant to the solvent media. The PP donor considerably modulates its fluorescence by undergoing electron transfer to the locally excited DPP to form a CT state. For nonpolar media, an increase in solvent polarity causes a bathochromic shift of the fluorescence reaching the longest wavelengths for chloroform and DCM. A further increase in the medium polarity moves the fluorescence maximum hypsochromically back to where it is for alkane solvents. This bidirectional solvatofluorochromism accompanies a polarity-induced increase in the nonradiative decay rates leading to a decrease in the emission quantum yield. The solvent dependence of the energy level of the CT state is responsible for the observed polarity-induced fluorescence behavior of the hybrid. This emission behavior, along with the solvent invariance of the absorption, results in multimodal sensitivity to the solvation environment.</P> [FIG OMISSION]</BR>
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Cruz-Silva, Rodolfo,Morelos-Gomez, Aaron,Kim, Hyung-ick,Jang, Hong-kyu,Tristan, Ferdinando,Vega-Diaz, Sofia,Rajukumar, Lakshmy P.,Elí,as, Ana Laura,Perea-Lopez, Nestor,Suhr, Jonghwan,Endo, Morin American Chemical Society 2014 ACS NANO Vol.8 No.6
<P>Graphene oxide (GO) has recently become an attractive building block for fabricating graphene-based functional materials. GO films and fibers have been prepared mainly by vacuum filtration and wet spinning. These materials exhibit relatively high Young’s moduli but low toughness and a high tendency to tear or break. Here, we report an alternative method, using bar coating and drying of water/GO dispersions, for preparing large-area GO thin films (<I>e.g.</I>, 800–1200 cm<SUP>2</SUP> or larger) with an outstanding mechanical behavior and excellent tear resistance. These dried films were subsequently scrolled to prepare GO fibers with extremely large elongation to fracture (up to 76%), high toughness (up to 17 J/m<SUP>3</SUP>), and attractive macroscopic properties, such as uniform circular cross section, smooth surface, and great knotability. This method is simple, and after thermal reduction of the GO material, it can render highly electrically conducting graphene-based fibers with values up to 416 S/cm at room temperature. In this context, GO fibers annealed at 2000 °C were also successfully used as electron field emitters operating at low turn on voltages of <I>ca.</I> 0.48 V/μm and high current densities (5.3 A/cm<SUP>2</SUP>). Robust GO fibers and large-area films with fascinating architectures and outstanding mechanical and electrical properties were prepared with bar coating followed by dry film scrolling.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2014/ancac3.2014.8.issue-6/nn501098d/production/images/medium/nn-2014-01098d_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn501098d'>ACS Electronic Supporting Info</A></P>
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