Question

Find the force between a charged circular loop of radius b

Answer 1

science.sciencemag.org

Single-crystal nanorings formed by epitaxial self-coiling of polar nanobelts

Xiang Yang Kong, Yong Ding, Rusen Yang, Zhong Lin Wang

Science 303 (5662), 1348-1351, 2004

Freestanding single-crystal complete nanorings of zinc oxide were formed via a spontaneous self-coiling process during the growth of polar nanobelts. The nanoring appeared to be initiated by circular folding of a nanobelt, caused by long-range electrostatic interaction. Coaxial and uniradial loop-by-loop winding of the nanobelt formed a complete ring. Short-range chemical bonding among the loops resulted in a single-crystal structure. The self-coiling is likely to be driven by minimizing the energy contributed by polar charges, surface area, and elastic deformation. Zinc oxide nanorings formed by self-coiling of nanobelts may be useful for investigating polar surface–induced growth processes, fundamental physics phenomena, and nanoscale devices.