The effect of the periodic boundary conditions of a ZnO-coated nanospring on its surface redox-induced electrical response.

A redox chemical sensor (chemiresistor) was constructed with a single ZnO coated silica nanospring. The chemiresistor response to toluene vapor as a function of the sensor temperature (T(NS)) and vapor temperature (T(V)) was measured and analyzed. The maximum sensitivity of the single ZnO coated nanospring device occurred at the sensor temperature (T(NS)) of 310 °C and at the vapor temperature (T(V)) of 250 °C. The characteristics of the electrical response of a single ZnO coated nanospring device were compared to those of a ZnO thin film. The single ZnO nanospring sensor was less responsive to small changes in toluene concentration relative to the ZnO thin film, but has a lower ultimate detection level. A computational model to simulate an electrical response of the single nanospring sensor and the thin film indicated that the differences between their response characteristics is due to the geometry of the nanospring and corresponding periodic boundary conditions imposed by the nanospring geometry, which is absent in a thin film.