(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
(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.
(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.
(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.