Mechanisms of Colloidal Stabilization of Oxidized Nanocarbons in the Presence of Polymers: Obtaining Highly Stable Colloids in Physiological Media
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- 作者：Gislaine C. Padovani ; Romana Petry ; Camila A. Holanda ; Francisco A. Sousa ; Viviane M. Saboia ; Cristiane A. Silva ; Alexandre R. Paschoal ; Antonio G. Souza Filho ; Amauri J. Paula
- 刊名：Journal of Physical Chemistry C
- 出版年：2015
- 出版时间：August 13, 2015
- 年：2015
- 卷：119
- 期：32
- 页码：18741-18752
- 全文大小：726K
- ISSN：1932-7455
文摘
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 (鈮?.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., 味 potential), oxidation and 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.