Nano-structuring metal organic frameworks on semiconductor nanowire arrays for highly sensitive and selective chemical sensing

Chemiresistive sensing of gas molecules has been widely investigated for application in medical diagnostics and environmental monitoring, showing high sensitivity and low limits of detection toward various volatile organic compounds. While metal oxide semiconductors offer numerous advantages, such as ease of fabrication, high sensitivity, and fast response times, they often suffer of high insufficient selectivity. Here, we report the engineering of a low-temperature sensing platform consisting of nanostructured zeolitic imidazolate framework (ZIF-8) metal organic frameworks (MOFs) over InP semiconducting nanowire (NW) arrays. These devices were fabricated via top-down etching of InP NW arrays, aerosol deposition of flame-made ZnO nanoparticles, and their chemical vapor conversion to ZIF-8. The presence of ZIF-8 significantly enhances the device sensitivity over that of the pristine InP NW arrays by providing a high density of adsorption sites and faster reduction kinetics. Our optimal sensors can detect NO2 in a large concentration range from 0.1 to 8 ppm, in addition to showing relatively higher responses toward various gas molecules, including CO2, methanol, ethanol, acetone, and propane, in comparison with pristine InP NW sensors. Given the large family of MOFs with controllable pore size and chemical composition, our findings provide a flexible approach for engineering the selectivity of highly sensitive and miniaturized gas sensors for integration in miniaturized devices.