Xiang Yang Kong

Polar-surface dominated ZnO nanobelts and the electrostatic energy induced nanohelixes, nanosprings, and nanospirals

We report the controlled synthesis of free-standing ZnO nanobelts whose surfaces are dominated by the large polar surfaces. The nanobelts grow along the a axis, their large top/bottom surfaces are the ±(0001) polar planes, and the side surfaces are (0110). Owing to the positive and negative ionic charges on the zinc- and oxygen-terminated ±(0001) surfaces, respectively, the nanobelts form multiloops of nanohelixes/nanosprings/nanospirals for the sake of reducing electrostatic energy introduced by the polar surfaces as well as balancing the difference in surface tension. The polar surface dominated ZnO nanobelts are likely to be an ideal system for understanding piezoelectricity and polarization induced phenomena at nanoscale.

Integration of metal oxide nanobelts with microsystems for nerve agent detection

We have assembled tin dioxide nanobelts with low-power microheaters for detecting dimethyl methylphosphonate (DMMP), a nerve agent simulant. The electrical conductance of a heated nanobelt increased for 5% upon exposure to 78 parts per billion DMMP in air. The nanobelt conductance recovered fully quickly after the DMMP was shut off, suggesting that the single-crystal nanobelt was not subject to poisoning often observed in polycrystalline metal oxide sensors. While the sensitivity can be improved via doping nanobelts with catalytic additives, directed assembly or growth of nanobelts on microsystems will potentially allow for the large-scale fabrication of nanosensor arrays.

Structures of indium oxide nanobelts

Indium oxide nanobelts of growth directions of [100] type (majority) and [120] type (minor) have been found. The two types of nanobelts have the top and bottom surfaces being (001), while the [100] type nanobelts have side surfaces of (010) and a rectangular cross-section, and the [120] type nanobelts have a parallelogram cross-section. The nanobelts have a perfect crystal structure without the presence of line or planar defects.