Publications (49) View all
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Article: Swelling the micelle core surrounding single-walled carbon nanotubes with water-immiscible organic solvents.
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ABSTRACT: Solvatochromic shifts in the absorbance and fluorescence spectra are observed when surfactant-stabilized aqueous single-walled carbon nanotube (SWNT) suspensions are mixed with immiscible organic solvents. When aqueous surfactant-suspended SWNTs are mixed with o-dichlorobenzene, the spectra closely match the peaks for SWNTs dispersed in only pure o-dichlorobenzene. These spectral changes suggest that the hydrophobic region of the micelle surrounding SWNTs swells with the organic solvent when mixed. The solvatochromic shifts of the aqueous SWNT suspensions are reversible once the solvent evaporates. However, some surfactant-solvent systems show permanent changes to the fluorescence emission intensity after exposure to the organic solvent. The intensity of some large diameter SWNT (n, m) types increase by more than 175%. These differences are attributed to surfactant reorganization, which can improve nanotube coverage, resulting in decreased exposure to quenching mechanisms from the aqueous phase.Journal of the American Chemical Society 12/2008; 130(48):16330-7. · 9.91 Impact Factor -
Article: Long-term improvements to photoluminescence and dispersion stability by flowing SDS-SWNT suspensions through microfluidic channels.
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ABSTRACT: Shearing single-walled carbon nanotubes (SWNTs) coated with sodium dodecyl sulfate in microfluidic channels significantly increases the photoluminescence (PL) intensity and dispersion stability of SWNTs. The PL quantum yield (QY) of SWNTs improves by a factor of 3 for initially bright suspensions; on the other hand, SWNT QYs in a "poor" suspension improve by 2 orders of magnitude. In both cases, the QYs of the sheared suspensions are approximately 1%. The increases in PL intensity persist for months and are most prominent in larger diameter SWNTs. These improvements are attributed to surfactant reorganization rather than disaggregation of SWNTs bundles or shear-induced alignment. The results also highlight potential opportunities to eliminate discrepancies in the PL intensity of different suspensions and further improve the PL of SWNTs by tailoring the surfactant structure around SWNTs.Journal of the American Chemical Society 09/2009; 131(35):12721-8. · 9.91 Impact Factor -
Article: Single step synthesis of Ge–SiOx core-shell heterostructured nanowires
Journal of Materials Chemistry 01/2009; 19:954. · 5.97 Impact Factor -
Article: Supercritical fluid preparation of copper nanotubes and nanowires using mesoporous templates
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ABSTRACT: Supercritical fluid decomposition of copper precursors in the presence of hexagonal mesoporous silica matrices are used to prepare ordered copper metal nanowire and nanotube arrays. Evidence is presented which shows that the pore-filling process is accompanied by large expansions of the pore-to-pore distance induced by the inclusion process. Preparation of these materials requires strict control as copper appears to catalyze the collapse of the mesoporous structure. The copper nanostructures exhibit the normal face-centred cubic crystal structure although there is a strong variation of the lattice parameter with size. UV–visible absorption spectra of copper nanowires within the mesoporous matrix as a function of copper loading exhibit effects related to the low dimensionality of the nanowires formed. Transmission electron microscopy images and changes in the surface area and pore size of the materials as a function of copper content suggest that the growth mode is radial rather than a random nucleation and growth mechanism.Journal of Physics Condensed Matter 11/2003; 15(49):8303. · 2.55 Impact Factor -
Article: Anomalous Properties of Poly (methyl methacrylate) Thin Films in Supercritical Carbon Dioxide
Macromolecules. 01/2002; 35:1928--1935.
