Fabrication of large-area Au nanoparticle decorated ZnO@ZIF-8 core-shell heterostructure nanorods for ppb-level NO2 gas sensing at room temperature

Metal-organic frameworks based heterostructures have gained wide attention recently for various applications. Specifically metal oxide and zeolitic imidazolate framework-8 (ZIF-8) nanocomposites have been synthesized for gas sensing with reasonable performance. In this work, large-area Au nanoparticle (NP) decorated ZnO@ZIF-8 core-shell heterostructure nanorods (NRs) are synthesized for ppb-level UV-activated NO2 sensing at room temperature. Large-area ZnO NRs are first grown and ZIF-8 shells are subsequently formed on ZnO with the result of various types of ZnO@ZIF-8 NRs. The ZnO@3ZIF-8 NRs have the highest response and Au NPs are finally decorated on the NR surfaces. The ZnO@3ZIF-8/Au sensor shows high responses of 260% and 34700% toward 0.05 and 3.75 ppm NO2 gas, respectively. An excellent linear sensitivity of 95.1 ppm–1 has been achieved and the estimated lowest detection limit is 0.3 ppb. It is noteworthy that the linear dynamic range is extended by at least 8 times after ZIF-8 addition and the sensitivity is enhanced by 12 times after Au NP decoration. The sensor is also highly NO2 selective against other gases including NO, NH3, SO2, CO, CH3OH, CH2O, C2H5OH, and C3H6O. The excellent performance of the ZnO@3ZIF-8/Au sensor shows good potential for environmental NO2 sensing.