Room-temperature H2 gasochromic behavior of Pd-modified MoO3 nanowire labels

Abstract

Abstract It is great significance to develop an effective eye-readable gas detection technology that would be safe, low-cost, and highly sensitive, serving as a vital complement to traditional H2 sensors. In this work, a class of flexible MoO3 nanowire labels (NWLs) modified with Pd nanoparticles have been successfully developed and studied as eye-readable hydrogen indicators at room-temperature. The nanowire labels turn from white to blue-gray even at a very low concentration (0.1%), where the eye-readable color change takes place in 65 s, and the color changes gradually from white to blue-gray. The reaction of MoO3 nanowire label with hydrogen is of high sensitivity, fast response and time-resolved. The process can be divided into two stages, i.e., fast and slow responses, which are dominated by H2 concentration and intrinsic properties of Pd MoO3, respectively. The color response is also reversible by annealing under air ambient at 200 °C for 2 h, and selective to hydrogen compared with other flammable gases (i.e., CO, CH3CH2OH, CH3OH). The gasochromic NWLs involve Pd-catalyzed reduction of MoO3 in the presence of hydrogen. They also exhibit the superior advantage of being flexible, which have promises applications in efficient eye-readable hydrogen detection.