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

•The gas sensing performance of the composite was effectively tuned by controlling the amount Al species.•The composite exhibits excellent gas sensing property and long-life stability.•The DFT calculation reveals that the adsorption energy of NO2 on AZO-2 was enhanced obviously compared to pure ZnO. 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.