Al doped narcissus-like ZnO for enhanced NO2 sensing performance: An experimental and DFT investigation

A narcissus-like Al doped ZnO nanostructure was successfully synthesized via a facile, controllable and one-pot hydrothermal method. The materials as-prepared presented a hierarchical narcissus-like structure with self-assembled by nanosheets. Gas sesing test results revealed that the Al-doped narcissus-like ZnO nanostructure (2 at %, labeled as AZO-2) showed 3 folds gas sensing response (103.2 for NO₂ with 1 ppm) with shorter response-recovery time (53 s/21 s), lower detection concentration (0.1 ppm) compared with those of pure ZnO. Moreover, AZO-2 had lower operating temperature (240 °C) and and superior long-life stability (remained around 92.5 % after 35 days), which quite promising for practical applications. Density functional theory (DFT) calculation suggests that the adsorption energy of NO₂ on AZO-2 is 5.15 folds higher than that of pure ZnO, which is attributed to the change of electronic structure that enhances the interaction between NO₂ and the modified ZnO. The excellent sensing performance could be attributed to the increase of oxygen vacancy content due to the Al doping. Thus, the Al doped narcissus-like ZnO nanocrystals could provide an inspiration to regulate the electronic structure and design highly sensitive NO₂ gas sensor.