Enhanced Gas Sensitivity and Selectivity on Aperture-Controllable 3D Interconnected Macro–Mesoporous ZnO Nanostructures

Abstract

Three-dimensional (3D) macro-mesoporous structures demonstrate effective performance for gas sensing. In this work, we have designed and successfully prepared aperture-controllable three-dimensional interconnected macro-mesoporous ZnO (3D-IMM-ZnO) nanostructures by template-based layer-by-layer filtration deposition. XRD, SEM, and TEM have been used to characterize the obtained hexagonal wurzite 3D-IMM-ZnO nanostructures. Owing to its special 3D interconnected hierarchically porous structure, the 3D-IMM-ZnO nanostructures exhibit excellent gas sensing performances toward acetone and methanol. The 3D-IMM-ZnO nanostructure with the largest macropore demonstrates the best gas sensitivity owing to its largest cavity providing enough space for gas diffusion. On the basis of the results and analyses, we propose that the synergistic effect of electron liberation and electron density of acetone and the special structure make the 3D-IMM-ZnO nanostructures demonstrate better gas sensing properties than many other porous ZnO nanostructures and preferred selectivity to acetone.

Enhanced NOx Gas Sensing Properties of Ordered Mesoporous WO3/ZnO Prepared by Electroless Plating

“…At the higher magnification, homogeneous nanoparticles with size of about 100 nm were observed in Figure c,d. This kind of loosen structure could extremely facilitate the property of gas adsorption …”

“…The massive researches showed that ZnO had the faster response and recovery time, higher sensitivity toward NO x gas, and the study on ZnO‐based gas sensors attracted the researchers largely. Hitherto, the researchers have synthesized ZnO with different morphology, including nanorods, nanosheets, nanotubes, nanoparticles, nanoplates, nanofilms, and so forth . The different morphology has the considerable impact on the gas sensing performance of MOS gas sensors.…”

“…The ordered mesoporous MOS materials are a kind of attractive materials for gas sensing reactions . The mesoporous structures have been reported to show quite higher gas response, which are mainly attributed to their higher surface area and well‐defined porous structures . The gas response and response speed of mesoporous gas sensing materials can be improved by surface modification, the doping of catalytic or semiconductor materials to form a p–n junction, n–n or p–p heterojunction layer …”

Gas sensors using ordered macroporous oxide nanostructures

“…Ordered mesoporous metal oxides are regarded as a type of promising sensing materials for gas sensors because of their high specic surface areas and excellent gas accessibility. [130][131][132] The combination of macro-mesoporous (M/M) structures can not only provide highly connected diffusion channels but also engender surface accessibility, facilitating rapid sensing kinetics and high gas response. 133,134 For instance, Liu et al successfully prepared aperture-controllable 3D interconnected M/M ZnO (3D-IMM-ZnO) nanostructures by template-based Table 1 Gas-sensing properties of representative ordered macroporous metal oxide materials.…”

Crystallography at the nanoscale: planar defects in ZnO nanospikes

“…the absence of inversion symmetry, the piezoelectric effect is present in ZnO. With a direct bandgap of 3.37 eV and an exciton binding energy of 60 meV at room temperature, ZnO nanostructures are promoted for applications in the fields of electronic materials (Jebril et al, 2010;Gupta, 1990), opto-electronics (Keis et al, 2002;Kö nenkamp et al, 2000), sensor devices (Liu et al, 2016;Chai et al, 2012;Lupan et al, 2008) and field emitters (Wang et al, 2005;Li et al, 2004), among other sensor systems based on piezotronics (Wang, 2007). Many of these reports relied on anisotropic ZnO nanostructures, e.g.…”