ZnO@ZIF-8: Gas sensitive core-shell hetero-structures show reduced cross-sensitivity to humidity

• Published in: Sensors and actuators. B, Chemical Chemical, 2020-02, Vol.304, p.127184, Article 127184
• Main Authors: Nair, Sreeja Sreedharan, Illyaskutty, Navas, Tam, Benjamin, Yazaydin, A. Ozgur, Emmerich, Katja, Steudel, Annett, Hashem, Tawheed, Schöttner, Ludger, Wöll, Christof, Kohler, Heinz, Gliemann, Hartmut
• Format: Article
• Language: English
• Subjects: Composite materials; Cross-sensitivity; Detection; Ethene; Gas sensors; Gases; Heterostructures; Humidity; Metal oxide gas sensors; Metal oxides; Metal-organic frameworks; Nanorods; Organometallic compounds; Sensitivity; Thin films; Water vapor; Zeolites; ZIF-8; Zinc coatings; Zinc oxide; Zinc oxides; Zink oxide
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2019.127184

•After coating ZnO-based gas sensors with ZIF-8 the increase of relative humidity beyond 25% does not affect the sensor sensitivity.•The coating with ZIF-8 reduced the sensor’s cross-sensitivity to humidity.•A general increase of conductance after deposition of ZIF-8 on ZnO as sensor material has been detected for propene and ethene. A ‘lawn-like’ distribution of interconnected zinc oxide nanorods, coated with a metal-organic compound based on zeolitic imidazolate frameworks – ZIF-8 was prepared on microstructured thin-film interdigitated Pt-electrodes forming ZnO@ZIF-8 core-shell heterostructures and investigated as gas sensor material in relation to the identical, but uncovered pure ZnO-layer. This composite combines the gas sensing properties of the metal oxide ZnO with the specific properties of the metal-organic framework material which result in a distinct change of the conditions of gas sensing at the ZnO/ZIF-8-interface. Herein, for the first time it is reported that as prepared ZnO@ZIF-8 composite material is an attractive choice to reduce the cross-sensitivity to water vapour (humidity) in the gas sensing response towards propene and ethene. The observed change of sensitivity in relation to uncovered ZnO is discussed to be due to (i) the specific interaction of the ZIF-8 at the interface with the ZnO taking influence on the gas reaction processes, (ii) the diffusivity of ZIF-8 for the different gas components, and (iii) the sorption behaviour of the used gases at the ZnO interface and inside the ZIF-8 material.