Previous work has indicated that polycrystalline structural sensing materials have high response and poor stability; in contrast, single-crystalline materials exhibit low response and good stability. For developers, the difficulty is to maintain the balance of high response and good stability.

As reported recently in Nanotechnology, the Chinese group has synthesized single-crystalline ZnO nanosheets with a porous structure by annealing ZnS(en)0.5 (en=ethylenediamine) precursor. The substitution of S by O atoms rather than the decomposition of organic components in precursor was proposed as the formation mechanism. Formaldehyde and ammonia were employed as target gases for indoor air contaminant detection by the as-prepared ZnO nanosheets, which were configured as gas sensing devices.

In tests, the sensors showed high sensitivity, and short response and recovery times combined with long-term stability thanks to the special structure of ZnO nanosheets. The results confirm that it is feasible to fabricate highly sensitive and stable gas sensors based on porous single-crystalline nanomaterials and the team is now developing structures with improved multifunctional properties.