Chemiresistive sensors based on core-shell ZnO@TiO2 nanorods designed by atomic layer deposition for n-butanol detection

Constructing heterostructures with efficient modulation of electron transfer at the heterointerface affords great opportunity for electronic devices. Herein, a high performance nanosensor based on core-shell ZnO@TiO2 nanorods is successfully realized for n-butanol detection. The n-n heterointerface formed between TiO2 and ZnO allows for vast variation of conductivity due to electron confinement induced by their different works functions and enhances the response on exposure to gaseous molecules. Studies reveals that the shell thickness of TiO2 has a great impact on the sensor performances, and the sensor based on ZnO@TiO2 nanorods with 6.4 nm-thick TiO2 shell delivers outstanding gas sensing properties in terms of high sensitivity, low detection limit (133 ppb), fast response-recovery, and excellent selectivity towards n-butanol detection. The mechanism for the improved gas sensing function is ascribed to the heterojunctions of core-shell nanostructure, the enhanced oxygen adsorption due to the TiO2 shell and the fully electron-depleted TiO2 shell layer with a thickness comparable to the Debye length. The strategy presented here is generally applicable and can provide some hints to design efficient electronic sensors with optimized performances.