Influence of electrostatic interactions on spin-assembled single-walled carbon nanotube networks on amine-functionalized surfaces.
ABSTRACT Preferential interactions between self-assembled monolayers (SAMs) terminated with amine functional groups and single-walled carbon nanotubes (SWNTs) were exploited to produce nanotube networks (SWNTnts) via spin coating. We provide insight into the mechanisms of this system while simultaneously demonstrating a facile approach toward controllable arrays of SWNTnts. The chirality, density, and alignment of the SWNTnt was heavily influenced by adsorption onto amine-functionalized surfaces that were exposed to varying pH solutions, as evidenced by atomic force microscopy (AFM) and Raman spectroscopy. This pH treatment altered the charge density on the surface, allowing for the examination of the contribution from electrostatic interaction to SWNT adsorption and SWNTnt characteristics. Secondary and tertiary amines with methyl substitutions were utilized to confirm that adsorption and chirality specific adsorption is largely due to the nitrogen lone pair, not the neighboring hydrogen atoms. Thus, the nature of adsorption is predominantly electrostatic and not due to van der Waals forces or localized polarization on the SWNTs. Moreover, the overall density of SWNTnts is different for the various amines, indicating that the accessibility to the lone pair electrons on the nitrogen plays a crucial role in SWNT adsorption. With greater understanding of the amine-SWNT interaction, these findings can be utilized to control SWNTnt formation for the precise integration into electronic devices.
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ABSTRACT: In this paper, we report the formation of self-assembled monolayers (SAMs) of oleylamine (OA) on highly oriented pyrolytic graphite (HOPG) and graphene surfaces and demonstrate the potential of using such organic SAMs to tailor the electronic properties of graphene. Molecular resolution Atomic Force Microscopy (AFM) and Scanning Tunneling Microscopy (STM) images reveal the detailed molecular ordering. The electrical measurements show that OA strongly interacts with graphene leading to n-doping effects in graphene devices. The doping levels are tunable by varying the OA deposition conditions. Importantly, neither hole nor electron mobilities are decreased by the OA modification. As a benefit from this noncovalent modification strategy, the pristine characteristics of the device are recoverable upon OA removal. From this study, one can envision the possibility to correlate the graphene-based device performance with the molecular structure and supramolecular ordering of the organic dopant.Nanoscale 07/2013; · 6.23 Impact Factor
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ABSTRACT: Many electronic applications of single-walled carbon nanotubes (SWNTs) require electronic homogeneity in order to maximally exploit their outstanding properties. Non-covalent separation is attractive as it is scalable and results in minimal alteration of nanotube properties. However, fundamental understanding of the metallicity-dependence of functional group interactions with nanotubes is still lacking; this lack is compounded by the absence of methods to directly measure these interactions. Herein, a novel technology platform based on a recently developed atomic force microscopy (AFM) mode is reported which directly quantifies the adhesion forces between a chosen functional group and individual nanotubes of known metallicity, permitting comparisons between different metallicity. These results unambiguously show that this technology platform is able to discriminate the subtle adhesion force differences of a chosen functional group with pure metallic as opposed to pure semiconducting nanotubes. This new method provides a route towards rapid advances in understanding of non-covalent interactions of large libraries of compounds with nanotubes of varying metallicity and diameter; presenting a superior tool to assist the discovery of more effective metallicity-based SWNT separation agents.Small 09/2013; · 7.82 Impact Factor