The Journal of Physical Chemistry C, 2020, vol 124, 5, pp. 3364-3372
DOI:10.1021/acs.jpcc.9b10220
Abstract
Using a combination of several experiments, we identify the landscapes of the widely reported superstability of suspensions formed by codispersion of nanosheets of clay and carbon. Primarily, two distinct, abrupt transitions within this superstability are observed. This observation made on a series of model laponitegraphene oxide superstable two-dimensional sheet suspensions further identifies that the mutual approach barrier (cumulative of van der Waals and electrostatic interactions) between carbon sheets progressively increases across the three distinct regimes of superstability generated by these transitions. However, the claycarbon intersheet barrier is negligible in all regimes. By structure elucidation, we furthermore show the presence of structures formed by dispersed nanosheets in each regime. Across the three regimes, the noninteger fractal dimensions of structures undergo a transition from near-planar (fractal dimensions ∼2) to mass fractals (fractal dimensions ∼3) and again to near-planar sheets (fractal dimensions ∼2). During the second transition, along with redispersion, syneresis initiates. The variations observed in the suspension bulk elastic modulus across these landscapes corroborate a structural transition from dispersed nanosheets to interconnected networks, followed by redispersion of nanosheets. Our congruent identifications, besides revealing the landscape of superstability of these suspensions, open up frontiers for further explorations and aid in the optimal exploitation of these suspensions for numerous currently identified and potentially futuristic applications.
