Single ZnO nanocactus gas sensor formed by etching of ZnO nanorodElectronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02387d

Etching of materials on the nanoscale is a challenging but necessary process in nanomaterials science. Gas sensing using a single ZnO nanocactus (NC), which was prepared by facile isotropic nanoetching of zinc oxide nanorods (NR) grown by chemical vapor deposition (CVD) using an organic photoresist (PR) by a thermochemical reaction, is reported in this work. PR consists of carboxylic acid groups (COOH) and cyclopentanone (C 5 H 8 O), which can react with zinc and oxygen atoms, respectively, on the surface of a ZnO NR. The thermochemical reaction is controllable by varying the concentration of PR and reaction time. A gas sensor was fabricated using a single NC. Gas sensing was tested using different gases such as CH 4 , NH 3 and carbon monoxide (CO). It was estimated that the surface area of a ZnO NC in the case of 50% PR was found to increase four-fold. When compared with a single ZnO NR gas sensor, the sensitivity of a ZnO NC was found to increase four-fold. This increase in sensitivity is attributed to the increase in surface area of the ZnO NC. The formed single ZnO NC gas sensor has good stability, response and recovery time. A ZnO nanocactus with new morphology is prepared by a new etching process from a ZnO nanorod, which increases the surface area. A single nanocactus gas sensor shows 4 times higher response than a single bare ZnO nanorod.