Gas Adsorption at Metal Sites for Enhancing Gas Sensing Performance of ZnO@ZIF-71 Nanorod Arrays

Abstract

The detection of trace amount of volatile organic compounds (VOCs) has been covered by tons of researches, which are dedicated to improve the detection limit and insensitivity to humidity. In this work, we have synthesized ZnO@ZIF-71 nanorod arrays (NRAs) equipped with the adsorption effect at metal site that promoted the detection limit of ethanol and acetone, to which also have great selectivity. The gas sensor not only exhibits shorter response/recovery time (53/55% for ethanol, 48/31% for acetone), but also excellent insensitivity to humidity and improved detection limit (10× improved at 21 ppb for ethanol, 4× at 3 ppb for acetone) at low working temperature (150 °C). By the analysis of in situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and calculation of density functional theory (DFT), the mechanism of enhanced gas sensing performance from ZnO@ZIF-71 NRAs is proved. It shows ethanol and acetone gas molecules can be adsorbed at the metal sites of ZIF-71. This work provides a new idea to improve the detection limit and humidity-insensitivity of gas sensor toward specific gas molecules.

Application of Metal-Organic Framework-Based Composites for Gas Sensing and Effects of Synthesis Strategies on Gas-Sensitive Performance

“…[80,91], while ZIF-71 is used to detect larger gas molecules (e.g., ethanol, acetone, etc.) [95]. In addition, although ZIF-71 is slightly less insensitive to humidity than ZIF-8, it can still be used to reduce the cross-sensitivity of water vapor [80].…”

“…Gas permeation through the MOF consists of three steps: (1) adsorption of the gas in the MOF, (2) diffusion of the gas within the MOF, and (3) desorption [108]. The enhancement of gas adsorption may also contribute to the gassensitive performance, as evidenced by the study of Zhou et al [95]. They synthesized ZnO@ZIF-71 nanorod arrays, and found that compared with pure ZnO, it has better selectivity for ethanol and acetone, and its response is also improved.…”

Advances in Doped ZnO Nanostructures for Gas Sensor

“…Reliable methods to facilitate real‐time monitoring of toxic gases are urgently needed. Recently, gas sensors have attracted extensive attention for their role in monitoring the atmospheric environment, medical diagnosis, volatile organic compounds (VOCs) and toxic gases [2a,b,c,d,e] . For example, in terms of environmental monitoring, ZnO sensors can be used to detect industrial exhaust emissions and automobile exhaust (eg: NOx, SOx, COx) [1a,3] .…”

“…In non‐invasive medical diagnosis, the ZnO sensor can detect the concentration of H 2 S and acetone in human breath to determine the disease, such as halitosis and diabetes [2b,4] . The metal oxides semiconductor (MOS) gas sensor was widely investigated owing to its high response, low production cost and long‐term stability [2d,5] …”

Enhanced Sensitivity of Hydrogenated Cu0.27Co2.73O4 Nanooctahedrons Having {111} Facets and the Sensing Mechanism of 3-Coordinated Co/Cu Atoms as Active Centers

“…Generally, the physical and chemical performances of semiconductor nanocrystals can be minutely adjusted by their shape and exposed crystal faces, which determine the arrangement and coordination of the surface atoms. − Thus, the shape and crystal facet-controlled synthesis of semiconductor nanocrystals draw considerable research interest. − As an essential p-type semiconductor, the CuCo 2 O 4 nanocrystal has extensively been investigated due to its high conductivity, nontoxicity, corrosion resistance, low cost, and potential applications in Li-ion batteries, supercapacitors, electrocatalysis, − photocatalysis, fuel cells, magnetism, and gas sensors. However, little research has been conducted on the influence of exposed crystal planes on performance.…”