Marder, Seth R.

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Now showing 1 - 10 of 40
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    Applications of Molecular Dopants and Interface Modifiers for Electronic and Opto-Electronic Applications
    (Georgia Institute of Technology, 2019-10-08) Marder, Seth R.
    Organic, hybrid, and 2D materials have attracted interest for electronic applications due to their potential for use in low-cost, large-area, flexible electronic devices. Here we will report on recent developments pertaining to surface modifiers and dopants that could impact the charge injection/collection/transport processes in organic light emitting diodes, organic field effect transistors, and photovoltaic devices. In particular, we will examine how N-heterocylic carbenes assemble on gold substrates, the impact of the surface dipole on the work function of the gold. We will also discuss the development of metallocenes-based dimers as n-dopants and very briefly describe metal dithiolene complexes as p-dopants for organic semiconductors and their impact of device performance.
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    Engineered multifunctional nanophotonic materials for ultrafast optical switching
    (Georgia Institute of Technology, 2012-09-30) Marder, Seth R.
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    Photoelectron spectroscopy studies of plasma-fluorinated epitaxial graphene
    (Georgia Institute of Technology, 2012-05) Sherpa, Sonam D. ; Paniagua, Sergio A. ; Levitin, Galit ; Marder, Seth R. ; Williams, M. D. ; Hess, Dennis W.
    Fluorination of graphene has emerged as an attractive approach toward manipulating its physical, chemical, and electronic properties. To this end, we have demonstrated the viability of sulfur hexafluoride plasmas to fluorinate graphene as a safer alternat
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    Solution doping of organic semiconductors using air-stable n-dopants
    (Georgia Institute of Technology, 2012-02) Qi, Yabing ; Mohapatra, Swagat K. ; Kim, Sang Bok ; Barlow, Stephen ; Marder, Seth R. ; Kahn, Antoine
    Solution-based n-doping of the polymer poly{[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} [P(NDI₂OD-T₂)] and the small molecule 6,13-bis(tri(isopropyl)silylethynyl)pentacene (TIPS-pentacene) is realized with the air-stable dimers of rhodocene, [RhCp₂]₂, and ruthenium(pentamethylcyclopentdienyl)(1,3,5-triethylbenzene), [Cp*Ru(TEB)]₂. Fermi level shifts, measured by direct and inverse photoemission spectroscopy, and orders of magnitude increase in current density and film conductivity point to strong n-doping in both materials. The strong reducing power of these air-stable dopants is demonstrated through the n-doping of TIPS-pentacene, a material with low electron affinity (3.0 eV). Doping-induced reduction of the hopping transport activation energy indicates that the increase in film conductivity is due in part to the filling of deep gap states by carriers released by the dopants.
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    Deep in vivo two-photon imaging of blood vessels with a new dye encapsulated in pluronic nanomicelles
    (Georgia Institute of Technology, 2011-03) Maurin, Mathieu ; Stéphan, Olivier ; Vial, Jean-Claude ; Marder, Seth R. ; Van der Sanden, Boudewijn
    The purpose of this work was to validate the use of Pluronic fluorescent nanomicelles for in vivo two-photon imaging of both the normal and the tumor vasculature. The nanomicelles were obtained after encapsulating a hydrophobic two-photon dye: di-stryl benzene derivative, in Pluronic block copolymers. Their performance with respect to imaging depth, blood plasma staining, and diffusion across the tumor vascular endothelium was compared to a classic blood pool dye Rhodamin B dextran (70 kDa) using two-photon microscopy. Pluronic nanomicelles showed, like Rhodamin B dextran, a homogeneous blood plasma staining for at least 1 hour after intravenous injection. Their two-photon imaging depth was similar in normal mouse brain using 10 times less injected mass. In contrast with Rhodamin B dextran, no extravasation is observed in leaky tumor vessels due to their large size: 20-100 nm. In conclusion, Pluronic nanomicelles can be used as a blood pool dye, even in leaky tumor vessels. The use of Pluronic block co-polymers is a valuable approach for encapsulating twophoton fluorescent dyes that are hydrophobic and not suitable for intravenous injection.
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    Conference support for the 9th international symposium on functional π-electron systems
    (Georgia Institute of Technology, 2011-02-28) Marder, Seth R.
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    Remote doping of a pentacene transistor: Control of charge transfer by molecular-level engineering
    (Georgia Institute of Technology, 2010-09) Zhao, Wei ; Qi, Yabing ; Sajoto, Tissa ; Barlow, Stephen ; Marder, Seth R. ; Kahn, Antoine
    We demonstrate that holes from a p-doped N,N′-diphenyl-N,N′-bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (α-NPD) layer transfer to an adjacent pentacene film. The spatial separation of carriers from dopants, or remote doping, is demonstrated with a combination of photoemission spectroscopy and current-voltage measurements for a p-doped α-NPD/pentacene heterojunction. Increased conductivity of the pentacene film is observed in both nongated temperature-dependent conductivity and gated thin-film transistor measurements.
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    Optical and electronic processes in metal nanoparticle-conjugated organic materials
    (Georgia Institute of Technology, 2010-08) Perry, Joseph W. ; Marder, Seth R.
    Gold nanoparticles (ca. 3 nm in diameter) coated with bis(diarylamino)biphenyl-based thiols with two different alkyl spacers (propyl and dodecyl) between the chromophore and the surface-anchoring thiol group have been prepared and characterized with a variety of techniques. The excited-state dynamics of the dyes in close proximity to the nanoparticle surface were studied with the use of time-correlated single-photon counting technique and near-IR fs transient absorption spectroscopy. The excited states of the dyes in the hybrid metal / organic systems exhibit an ultrafast (<5 ps) deactivation as evidenced by the fs transient absorption measurements. The length of the alkyl spacer between the dye and the thiol group has a profound effect on the ultrafast dynamics of the photoexcited systems. An ultrafast formation (ca. 0.5 ps) of a cation-like species has been recorded for the system incorporating the propyl spacer but not for the dodecyl-linker system. The formation of the cation-like species has been shown to be less efficient in mixed-ligand system in which the bis(diarylamino)biphenyl-based thiol was diluted on the surface with dodecanethiol. Additionally, the ultrafast formation (ca. 1 ps) of a cation-like species with a similar spectroscopic signature has been observed in the solid state of the dye. A combination of the ultrafast dynamics and 1H NMR spectroscopic data has been used to discuss the observed behavior in terms of dye-dye interactions in the nanoparticle systems. Due to the surface curvature of the nanoparticle, the propyl spacer imposes a closer dye-dye distance than the dodecyl spacer, thus facilitating dye-dye interactions that lead to the formation of a charge transfer species involving two or more dye molecules.
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    Direct writing and characterization of poly(p-phenylene vinylene) nanostructures
    (Georgia Institute of Technology, 2009-12) Wang, Debin ; Kim, Suenne ; Underwood, William D. , II ; Giordano, Anthony J. ; Henderson, Clifford L. ; Dai, Zhenting ; King, William P. ; Marder, Seth R. ; Riedo, Elisa
    We report the use of thermochemical nanolithography to convert a precursor polymer film to poly(p-phenylene vinylene) with sub-100 nm spatial resolution, in ambient conditions. The local thermochemical conversion is verified by Raman spectroscopy, fluorescence imaging, and atomic force microscopy. This convenient direct writing of conjugated polymer nanostructures could be desirable for the design and fabrication of future nanoelectronic, nanophotonic, and biosensing devices.
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    Materials for eye and sensor protection
    (Georgia Institute of Technology, 2009-09-30) Perry, Joseph W. ; Marder, Seth R.