Gigahertz nanomechanical oscillators based on ions inside cyclic peptide nanotubes: a continuum study (Q520468)

In recent years, cyclic peptide nanotubes (CPN's) have attracted considerable attention in the field of nanoscience and nanotechnology owing to their remarkable properties such as a small size, ease of synthesis, diversity of physical and chemical properties and chemical and biological modifiability. Here, on the base of the continuum model the oscillatory behavior of Li\(^+\)Na\(^+\), Rb\(^+\), and Cl\(^+\) ions inside a D.-Ala cyclic peptide nanotube is investigated. Some new analytic expressions for evalution of the vdW potential energy and an interaction force between an ion and a CPN are first determined. Afterwards, the conservation of the mechanical law is utilized to propose a new expression for precise evaluation of the oscillation frequency into which effects of both geometrical parameters and initial conditions are incorporated. The validity and accuracy of the frequency formula are verified through comparing its results with the ones from solving the equation of motion in a numerical way employing the fourth-order Runge Kutta method. The effect of the number of peptide units on distributions of the vdW potential energy and interaction force is investigated and discussed in detail.