Journal
JOURNAL OF PHYSICAL CHEMISTRY C
Volume 119, Issue 32, Pages 18741-18752Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpcc.5b04274
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Funding
- CNPq/FUNCAP through DCR [0024.00898.01.00/13]
- CNPq [307317/2010-2, 446800/2014-7]
- FUNCAP through PRONEX [PR2-0054-00022.01.00/11]
- UFC
- FUNCAP
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There are successful protocols for dispersing carbon nanotubes and graphene oxide in physiological media by using biocompatible polymers, which enable their use in nanomedicine. However, there is not a clear understanding regarding the mechanisms of the colloidal stabilization manifested (i.e., electric, steric, electrosteric, or through depletion forces). Here we show that the manifestation of a particular mechanism of stabilization for oxidized carbon nanotubes (CNTs) and graphene oxide (GO) in the presence of Pluronic F-127 (PF127) and short- and long-chain polyethylene glycol (PEG 1500 or 35000, respectively) depends on a proper matching between the nanocarbon morphology and the polymer chain length, chemical structure, and concentration. The high aspect ratio one-dimensional morphology of CNTs enables an initial steric and electrosteric stabilization through the nanotube wrapping (i.e., adsorption) by PF127 present in low concentrations (<0.1%). Depletion stabilization for CNTs manifests when PF127 is present in high concentrations (>= 1.0%), thus enabling the formation of highly stable CNT colloids even in a 0.9% NaCl saline solution. This depletion stabilization depends little on the CNT structure (i.e., single-walled or multiwalled), surface charge (i.e., xi potential), oxidation carboxylation degrees, or nanotube length. On the other hand, large-sized sheets of GO could be colloidally stabilized in 0.9% NaCl only in the presence of PEG 35000 through repulsive depletion forces, whose manifestation occurs with a polymer concentration threshold of 5.0 wt %. Comparatively, in a physiological saline solution, PF127 is able to colloidally stabilize CNTs to a much larger extent than PEG 35000 stabilizes the large GO sheets.
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