Aggregation and self-assembly of single-walled carbon nanotubes through binding of novel earth abundant
metal COORDINATION complexes

Poler, J.C.1, Shcherbakov I.N.2 Banks D.J.1 McNeill C.X.1 
Mitchell J.B. 1

1 Chemistry, UNC Charlotte, Charlotte, NC, United States.
2 Chair of Physical and Colloid Chemistry, Southern Federal University, Rostov-on-Don, Russian Federation.
jcpoler@uncc.edu

SWNT’s have suitable mechanical and electrical properties which make them ideal for energy storage applications such as supercapacitors and battery electrodes.  To facilitate the design of these new materials we must fully understand dispersion stability, and supraparticle assemblage of SWNTs with various coagulants.  We have previously reported Ruthenium coordination complexes which have led to recent advances in our understanding of these interactions.  However the high cost and low natural abundance of ruthenium has led to similar pursuits, with earth abundant metal complexes specifically 4-(tert-butyl)-2,6-bis((2-(phthalazin-1-yl)hydrazono)-Dear methyl)phenol (μ2-methoxo) dizinc(II) (+2Zn2 hydrazone).  Binding studies yield a Langmuir isotherm with all possible binding sites being filled 1.36 μMol/mg SWNT. Dispersion stability and the onset of aggregation occur at 15 μM whereas similarly charged ruthenium complexes induce aggregates at 1.98 μM. Zeta potential measurements show expected changes in the SWNT’s zeta potential.  The repulsive barrier of the SWNTs collapses over time, initial zeta potentials of -38 mV switches to +28 mV, thus kinetic stability of the dispersion will be presented. Structural determination and morphology of these SWNT assemblies by SEM and light scattering will be presented.  Electrochemical and spectroscopic data will be presented.  Experimental data will be compared to computational analysis of SWNT assemblies.  These computational models can be used to understand morphology and method by which self-assemblage occurs.  Understanding dispersion interactions with the solvent and coagulants is the next step in the manipulation of SWNTs for their impressive properties.

Fig.1 DFT optimization of +2Zn2 hydrazone bound to a (7,7) SWCNT

Fig.2 Adsorption isotherm of +2Zn2 hydrazone bound to SWCNT dispersions.  Fit with BET model: qm = 1057 mg/g