Critical coagulation concentrations for several inorganic and metallodendrimer coagulants have been determined for dispersion of single-walled carbon nanotubes in nonaqueous solvent. The behavior of the nanotubes is not consistent with previously reported coagulations from aqueous electrolytes and is not described using classical Derjaguin, Landau, Verwey, and Overbeek theory of lyophobic colloids. Nanoscale rigid dendrimers are studied as they interact and bind to the carbon nanotubes. With a diameter of 5.8 nm and a charge of +20, these metallodendrimers bind strongly and specifically to the nanotubes. Systematic studies of aggregating nanotubes and nanoparticles are required to more completely understand the complex interactions between the nanotubes and the matrix in which they are dispersed. Strategies for directed self-assembly of the nanotubes have implications for the potential three-dimensional nanomanufacturing of nanoscale sensors and actuators.

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The rational design of supraparticle assemblies requires a detailed understanding of directed assembly processes. The stability of dispersions of nanoscale materials, like single-walled carbon nanotubes (SWCNTs), is still not fully understood, nor are the mechanisms of aggregation and assembly. A detailed balance of attractive van der Waals type interactions with various repulsive barrier mechanisms is needed to control the assembly of industrially viable and functional hybrid-nanoscale supraparticles. We report a detailed study of SWCNT dispersion stability and aggregation kinetics as a function of the nature of the coagulant used in various solvent systems. We explore three classes of coagulants that vary in charge, size, shape, solvation energy, and the ability to bind to the SWCNTs. We use these kinetic data to assess the tube-solvent-coagulant-tube interactions. We compare the relative contributions from two types of repulsive barriers. We find that tube-mediated structured solvent around the SWCNTs does not sufficiently describe our measured kinetic data. A DLVO type, electrical double layer repulsion is used to rationalize our observations. The data presented in this paper require a more detailed theoretical understanding of the physico-chemical environment near nanoparticle surfaces such as aggregating SWCNTs.

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Most chemists draw the direction of an electric dipole backwards. This inconsistency in sign convention is more than a trivial oversight or matter of convenience. We are introducing an incorrect convention that is central to our student’s understanding of fundamental thermodynamics; which way is up? As a student matures from general chemistry to organic through analytical, physical, inorganic, and biochemistry they are reintroduced to similar, powerful concepts that hold our discipline together. However, this reconnection of chemical principles comes with each subdiscipline’s own idiosyncrasies and a highly contextual framework. Reexamination of a central concept from the perspective of a new subdiscipline should not introduce misconceptions about that concept. When misconceptions introduced through chemical language can be avoided, we should change the way we speak.