D E Milkie

Publications (6)47.64 Total impact

• Source

  Available from: upenn.edu

  Article: Carbon Nanotube Aerogels

  M. B. Bryning, D. E. Milkie, M. F. Islam, L. A. Hough, J. M. Kikkawa, A. G. Yodh
  Advanced Materials 01/2007; 19(5):661 - 664. · 13.88 Impact Factor
• Article: Photoluminescence from intertube carrier migration in single-walled carbon nanotube bundles.

  O N Torrens, D E Milkie, M Zheng, J M Kikkawa
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  ABSTRACT: Photoluminescence (PL) identifies spectroscopic signatures of intertube transfer of optically pumped carriers in single-walled carbon nanotube (SWNT) ensembles. Resonant photoexcitation of large band gap SWNTs produces strong PL from smaller band gap SWNTs. Magnetic alignment measurements associate the energy-transfer PL peaks with the formation of SWNT bundles, suggesting that efficient coupling results from physical contact.
  Nano Letters 01/2007; 6(12):2864-7. · 13.20 Impact Factor
• Source

  Available from: upenn.edu

  Article: Thermal conductivity and interfacial resistance in single-wall carbon nanotube epoxy composites

  M. B. Bryning, D E Milkie, M F Islam, J M Kikkawa, A G Yodh
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  ABSTRACT: We report thermal conductivity measurements of purified single-wall carbon nanotube (SWNT) epoxy composites prepared using suspensions of SWNTs in N-N-Dimethylformamide (DMF) and surfactant stabilized aqueous SWNT suspensions. Thermal conductivity enhancement is observed in both types of composites. DMF-processed composites show an advantage at SWNT volume fractions between [phi][approx]0.001 to 0.005. Surfactant processed samples, however, permit greater SWNT loading and exhibit larger overall enhancement (64[plus-or-minus]9)% at [phi][approx]0.1. The enhancement differences are attributed to a ten-fold larger SWNT/solid-composite interfacial thermal resistance in the surfactant-processed composites compared to DMF-processed composites. The interfacial resistance is extracted from the volume fraction dependence of the thermal conductivity data using effective medium theory. [C. W. Nan, G. Liu, Y. Lin, and M. Li, Appl. Phys. Lett. 85, 3549 (2004)].
  11/2005;
• Article: Controlled switching of optical emission energies in semiconducting single-walled carbon nanotubes.

  D E Milkie, C Staii, S Paulson, E Hindman, A T Johnson, J M Kikkawa
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  ABSTRACT: We present scanning photoluminescence (PL) microscopy of freely suspended single-walled carbon nanotubes grown by chemically assisted vapor deposition (CVD) across micron-sized open apertures. Scans of the PL emission versus excitation position show unusual "holes"having subwavelength spatial features associated with abrupt blue shifts of the emission energy. By varying the excitation polarization, energy, intensity, and position, we demonstrate that optical switching in some nanotubes is controllable in a highly nonlinear manner by adjusting the nonequilibrium carrier density in the nanotube. Technologically important attributes include large spectral contrast between on/off states at room temperature, a dramatic response to small changes in light intensity near threshold, and the possibility that electrical charge injection could also be used to control emission energies.
  Nano Letters 07/2005; 5(6):1135-8. · 13.20 Impact Factor
• Source

  Available from: upenn.edu

  Article: Direct measurement of the polarized optical absorption cross section of single-wall carbon nanotubes.

  M F Islam, D E Milkie, C L Kane, A G Yodh, J M Kikkawa
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  ABSTRACT: We determine optical absorption cross sections of single-wall carbon nanotubes for visible light copolarized and cross polarized with respect to the nanotube axis. The need for perfectly aligned ensembles in absorbance measurements is eliminated by using Raman scattering to measure the nematic order parameter in magnetically aligned nanotube suspensions. The absorbance data allow the first quantitative, spectral comparisons with theories of local field depolarization, and provide benchmark spectra for simple, rapid, and quantitative measurements of alignment within nanotube dispersions.
  Physical Review Letters 08/2004; 93(3):037404. · 7.37 Impact Factor
• Article: Magnetic heterogeneity and alignment of single wall carbon nanotubes

  M. F. Islam, D. E. Milkie, O. N. Torrens, A. G. Yodh, J. M. Kikkawa
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  ABSTRACT: Magnetic alignment studies demonstrate that a fraction of acid purified single wall carbon nanotubes (SWNTs) exhibit both linear-orbital (diamagnetic and/or paramagnetic) and ferromagnetic (FM) anisotropies. The latter are unexpected, as prior studies have assumed that remaining FM impurities are encapsulated and play no role in SWNT alignment. The data imply a FM easy axis aligned with the nanotube, permit direct estimates of the FM moment size, and provide a more accurate measure of the SWNT magnetic anisotropy. In light of recent observations of FM proximity effects in nanotubes, our observation of attached or intrinsic FM anisotropy in these systems is an important consideration for future studies of carbon nanotube magnetism.
  Phys. Rev. B. 71(20).