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Conductive organic polymers can be formulated with polymers that incorporate fine dispersed metallic particles. In this work, we present a general model for ferrogels which are chemically cross-linked polymer networks swollen with a ferrofluid. Our aim is to study the effect of the shape and/or material (conductivity) anisotropy on the effective electrical conductivity of the ferrogel in the presence of an external magnetic field. Our theory can reproduce the known results and provides a link between the particle properties and orientation distribution and the effective electrical conductivity. To this end, we find that material (conductivity) anisotropies are more important for yielding a high effective electrical conductivity than shape anisotropies, while magnetic fields can offer a correction. [ABSTRACT FROM AUTHOR]

The two-dimensional material phosphorene has become a focus of the scientific community recently. On the basis of molecular dynamics simulations, we utilize phosphorene as a model material to study the behavior of water molecules confined by two phosphorene plates with nonflat surfaces. As the relative position of the two plates changes, the water molecules first stay in a melting process at 230 K and then exhibit a freezing process. The disparate variations of local confinements induced by the mismatch of the two plates are the key for understanding this extraordinary behavior of water. Our results imply that such nonflat surfaces could be an important factor for understanding or controlling the dynamics of water. The phenomena reported here may enrich the knowledge of water and inspire more applications of similar materials. [ABSTRACT FROM AUTHOR]

Understanding the flow of liquidsand particularly water in nanochannelsis important for scientific and technological applications, such asfor filtration and drug delivery. Here we perform molecular dynamicssimulations to investigate the transfer of single-file water moleculesacross straight or nonstraight single-walled carbon nanotubes (SWCNTs).In contrast with the macroscopic scenario, the nonstraight nanostructurecan increase the water permeation. Remarkably, compared with the straightSWCNT, the nonstraight SWCNT with the minimal bending angle of 35°in the simulations can enhance the water transport up to 3.5 times.This enhancement mainly originates from the Lennard-Jones interactionbetween water molecules and nonstraight nanostructures. Our work offersan additional freedom to design high-flux nanochannels by choosingnonstraight nanostructures and provides an insight into water flowacross biological water nanochannels, which are often nonstraightsince they are composed of integral membrane proteins. [ABSTRACT FROM AUTHOR]

Achieving a fast, unidirectional flow of single-file water molecules (UFSWM) across nanochannels is important for membrane-based water purification or seawater desalination. For this purpose, electro-osmosis methods are recognized as a very promising approach and have been extensively discussed in the literature. Utilizing molecular dynamics simulations, here we propose a design for pumping water molecules in a single-walled carbon nanotube in the presence of a linearly gradient electric (GE) field. Such a GE field is inspired by GE fields generated from charged ions located adjacent to biological membrane water nanochannels that can conduct water in and out of cells and can be experimentally achieved by using the charged tip of an atomic force microscope. As a result, the maximum speed of the UFSWM can be 1 or 2 orders of magnitude larger than that in a uniform electric (UE) field. Also, inverse transportation of water molecules does not exist in case of the GE field but can appear for the UE field. Thus, the GE field yields a much more efficient UFSWM than the UE field. The giant pumping ability as revealed is attributed to the nonzero net electrostatic force acting on each water molecule confined in the nanotube. These observations have significance for the design of nanoscale devices for readily achieving controllable UFSWM at high speed. [ABSTRACT FROM AUTHOR]

On the basis of molecular dynamics simulations, we investigate water permeation across a single-walled carbon nanotube (SWCNT) under the influence of four symmetrical half-rings, each having six LiF dipolar molecules. The flux remains almost fixed as the separation, R, between the rings and SWCNT is larger than 1.562 nm, but decreases significantly as 0.944 nm < R< 1.562 nm, and reaches zero as R< 0.944 nm. This nanochannel shows an excellent on−off gate that is both effectively resistant to dipole noises and sensitive to available signals. The finite element method reveals that the electrostatic field generated by LiF molecules plays a unique role in achieving the gating of the water SWCNT. Each water molecule tends to stay at the most stable state by moving to the location with the highest field strength in order to maintain its lowest electric energy. These findings may have biological implications because membrane water nanochannels made up of proteins accompanied with co-ions and counterions (due to ionization) share a similar single-file water chain inside the SWCNT with dipoles. The Appendix shows a possible link between the model system and a membrane water nanochannel with co-ions and counterions. Furthermore, our observations may have significance for the design of SWCNT-based nanoscale devices with dipolar molecules. [ABSTRACT FROM AUTHOR]