A controllable water signal transistor

We performed molecular dynamics simulations to study the regulating ability of water chains confined in a Y-shaped nanochannel. It was shown that a signal at the molecular level could be controlled by two other charge-induced signals when the water chains were confined in a Y-shaped nanochannel, demonstrating promising applications as water signal transistors in nanosignal systems. The mechanism of a water signal transistor is similar to a signal logic device. This remarkable ability to control the water signal is attributed to the strong dipole-ordering of the water chains in the nanochannel. The controllable water signal process of the Y-shaped nanochannel provides opportunities for future application in the design of molecular-scale signal devices.

Electrostatic Stabilization of Graphene in Organic Dispersions

The exfoliation of graphite to give graphene dispersions in nonaqueous solvents is an important area with regards to scalable production of graphene in bulk quantities and its ultimate application in devices. Understanding the mechanisms governing the stability of these dispersions is therefore of both scientific interest and technological importance. Herein, we have used addition of an indifferent electrolyte to perturb few-layer graphene dispersions in a nonaqueous solvent (1,2-dichloroethane) as a way to probe the importance of interparticle electrostatic repulsions toward the overall dispersion stability. At a sufficient electrolyte concentration, complete sedimentation of the dispersions occurred over 24 h, and the relationship between dispersed graphene concentration and electrolyte concentration was consistent with a dispersion stabilized by electrostatic repulsions. We also found that an increased oxygen content in the graphite starting material produced dispersions of greater stability, indicating that the extent of oxidation is an important parameter in determining the extent of electrostatic stabilization in nonaqueous graphene dispersions.

Long-term colloidal stability of 10 carbon nanotube types in the absence/presence of humic acid and calcium

The colloidal stabilities of ten carbon nanotubes (CNTs) having varying physico-chemical properties were compared in long-term experiments. The presence of Suwannee River Humic Acid (SRHA) increased the fraction of CNTs in the supernatants (4-88% for the various CNT types) after addition in pre-dispersed form and 20 days of shaking and 5 days of settling. These suspensions were monomodal, containing individually suspended CNTs with highly negative surface charges. Calcium (2 mM) removed most of the CNT types from the supernatant, due to CNT-agglomerate formation initiated by reduction in surface charge. The amount of SRHA adsorbed to the different CNT types did not correlate (r(2) < 0.1) with the percentage of CNTs remaining in suspension. Multiple linear regression analysis revealed that the oxygen content and the diameter of the CNTs significantly influenced the percentage of stabilized CNTs, resulting in an increased fraction of functionalized and large-diameter CNTs that remained in suspension.