Controlling the Energy Transfer in Dipole Chains

Soliton-like propagation of dipole reorientation in confined single-file water chains

Water molecules confined in a narrow nanotube channel orient themselves into a uniformly ordered single-file chain. Here, we report by means of comprehensive molecular dynamics simulations and soliton-model-based theoretical analysis that the reorientation (i.e., rotation) of a single water molecule in this dipole chain, triggered for example by an external charge, can induce successive reorientation of the rest of the water molecules, which propagates in a soliton-like manner. The resulting local potential energy peak separating the reoriented and the pending reorientation subsections moves with an unweakened peak intensity at a constant velocity in the ambient environment, and particularly, can penetrate or make a turn through a crossed nanotube junction. The propagation velocity depends on the strength of the external charge, in agreement with our sine-Gordon soliton-based theoretical analysis. We further show that this unidirectional propagation originates from the partially inhibited fluctuation in dipole orientation of reoriented water with respect to that of original ones. These findings may be helpful in the development of high-efficiency information transmitting, processing and storage devices and the understanding of functioning of biological water channels.

Signal transmission, conversion and multiplication by polar molecules confined in nanochannels

The mechanism of signal transmission, conversion and multiplication at molecular level has been of great interest lately, due to its wide applications in nanoscience and nanotechnology. The interferences between authentic signals and thermal noises at the nanoscale make it difficult for molecular signal transduction. Here we review some of our recent progress on the signal transduction mediated by water and other polar molecules confined in nanochannels, such as Y-shaped carbon nanotubes. We also explore possible future directions in this emerging field. These studies on molecular signal conduction might have significance in future designs and applications of nanoscale electronic devices, and might also provide useful insights for a better understanding of signal conduction in both physical and biological systems.

Molecular rotors and motors: recent advances and future challenges

At the "Molecular Rotors and Motors" symposium of the Spring 2009 ACS National Meeting in Salt Lake City (March 22-26), a diverse mix of talks addressed many current issues in the field. Speakers described topics that varied from single-molecule rotors and nanomachines to exquisite synthetic approaches toward building functional materials and mathematical and computational methods aimed at uncovering design opportunities and highlighting the fundamental limitations of molecular motors. While the realization of building useful nanomachines remains far off, a general consensus abounded that investigating biological systems and understanding the implications of the laws of thermodynamics and quantum mechanics for the behavior of nanostructures will help drive important advances in the quest for molecular machinery. Molecular rotors were demonstrated to have practical applications as probes for microviscosity, and many speakers presented experimental studies that indicated that highly directed translation and rotation of individual molecules, as well as interacting dipolar arrays, are just around the corner. While this Nano Focus is not intended to be a comprehensive review of the subject, it will focus on several key advances that were presented at the ACS meeting and highlight future challenges for the field of molecular rotors and motors.