Hierarchical and hollow porous FeO nanoboxes (with an average edge length of ∼500 nm) were derived from metal-organic frameworks (MOFs) and the gas sensing characteristics were investigated. Sensors based on FeO nanoboxes exhibited a response (resistance ratio) of 1.23 to 0.25 ppm (ppm) hydrogen sulfide (HS) at 200 °C, the response/recovery speed is fast and the selectivity to HS is excellent. Remarkably, the sensor showed fully reversible response to 5 ppm of HS at 50 °C, demonstrating its promise for operating at near room temperature, which is favorable for medical diagnosis and indoor/outdoor environment monitoring. The excellent performance of the FeO nanoboxes can be ascribed to the unique morphology with high specific surface area (SSA) and porous nanostructure.

The dual function of a free-standing, flexible, and semi-transparent MoO3 nanopaper sensor to detect TMA and H2S in a highly selective manner.

Flexible and transparent sensors based on parallelly aligned In2O3 nanowires can detect ppb-level NO2 at room temperature under visible light (even under an iPhone screen). The sensing performances are maintained after bending and stability tests.

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