A General Solution to Mitigate Water Poisoning of Oxide Chemiresistors: Bilayer Sensors with Tb₄O₇ Overlayer

Abstract

Water poisoning, the dependence of gas‐sensing characteristics on moisture, in oxide chemiresistors remains a long‐standing challenge. Various approaches are explored to mitigate water poisoning but they are often accompanied by significant deterioration of sensing capabilities such as gas response deterioration, gas selectivity alteration, and sensor resistance increase up to unmeasurable levels. Herein, a novel sensor design with a moisture‐blocking Tb4O7 overlayer is suggested as a facile and universal strategy to remove moisture poisoning without sacrificing intrinsic sensing properties. A submicrometer‐thick coating of Tb4O7 overlayer on In2O3 sensors effectively eliminates the humidity dependence of the gas‐sensing characteristics without significantly altering the gas response, selectivity, and sensor resistance. Furthermore, the general validity of the water‐blocking effect using the Tb4O7 overlayer is confirmed in diverse gas sensors using SnO2, ZnO, and Pd/SnO2. The negligible moisture interference of the bilayer sensor is explained in terms of the hydrophobic nature of the Tb4O7 overlayer and the prevention of formation of the OH radical by the interaction between Tb4O7 and In2O3. A universal solution to design diverse humidity‐independent gas sensors with different gas selectivities can open up new pathways toward building accurate and robust gas sensors with new functionalities and high‐performance artificial olfaction.

Solution-processed metal doping of sub-3 nm SnO2 quantum wires for enhanced H2S sensing at low temperature

“…It is believed that water vapor consumes the active sites for sensing and forms less reactive hydroxyl groups (OH), causing changes in the sensor resistance and deteriorating the sensing response. 48,49 Our sensors also show excellent selectivity toward H 2 S from the tests with the interfering gases of CH 4 , CO, H 2 , toluene, and formaldehyde (Fig. 3e).…”

Designing oxide chemiresistors for detecting volatile aromatic compounds: recent progresses and future perspectives

“…In their pristine form, the sensors using WO 3 , TiO 2 , ZnO, SnO 2 and In 2 O 3 generally show neither high response nor high selectivity to BTX gases. 60–64 However, the loading of noble metal catalyst is known to be effective to enhance BTX sensing characteristics. The representative BTX sensing materials are Pd–SnO 2 nanowires (B), 32 Pd–Bi 2 O 3 (core)/ZnO(shell) nanorods (B), 33 Pt(core)/ZnO(shell) nanoparticle (T, B), 34 Pd–SnO 2 yolk–shell spheres (X, T), 35 PdO–ZnO flowers (T), 36 Pd–WO 3 ·H 2 O nanocubes (X), 37 Pt–SnO 2 nanowires (T), 32 Au–ZnO nanoparticles (T), 38 Au–TiO 2 nanostructures (T), 39 Au–WO 3 ·H 2 O nanocubes (X, T), 40,41 and Ru–In 2 O 3 nanosheets (X).…”

“…In contrast, the sensor resistance remains similar regardless of catalyst coating since the conduction along the lower sensing region in the bilayer design is barely affected by outlying catalytic overlayer. 64,119,123 Lastly, nanoscale or relatively thin overlayer can reform or oxidize analyte gases without the sacrifice of gas transport. In the initial stage of bilayer sensor design, thick porous support layer (thickness: ∼100 μm) loaded with noble metal catalysts has been generally coated on sensing film to achieve high selectivity to gases with low reactivity mainly by suppressing the cross responses to other reactive interference gases via oxidative filtering.…”

Highly Selective and Sensitive Detection of Breath Isoprene by Tailored Gas Reforming: A Synergistic Combination of Macroporous WO3 Spheres and Au Catalysts

“…In contrast, oxide semiconductor chemiresistors with higher operation temperatures are advantageous for isoprene detection. Furthermore, oxide semiconductors exhibit high sensitivity and rapid responding speed, − which can be a viable alternative to achieve real-time analysis of exhaled isoprene in a cost-effective manner. However, several problems remain to be solved.…”