ZnO Nanowires/Self-Assembled Monolayer Mediated Selective Detection of Hydrogen.

We are proposing a novel self-assembled monolayer (SAM) functionalized ZnO nanowires (NWs)-based conductometric sensor for the selective detection of hydrogen (H₂). The modulation of the surface electron density of ZnO NWs due to the presence of negatively charged terminal amine groups (-NH₂) of monolayers leads to an enhanced electron donation from H₂ to ZnO NWs. This, in turn, increases the relative change in the conductance (response) of functionalized ZnO NWs as compared to bare ones. In contrast, the sensing mechanism of bare ZnO NWs is determined by the chemisorbed oxygen ions. The functionalized ZnO NWs exhibit an eight times higher response compared to bare ZnO NWs at an optimal working temperature of 200 °C. Finally, in comparison to studies in the literature involving strategies to enhance the sensing performance of metal oxides toward H₂, like decoration with metal nanoparticles, heterostructures, and functionalization with a metal-organic framework, etc., SAM functionalization showed superior sensing results.