KIT-5-Assisted Synthesis of Mesoporous SnO2 for High-Performance Humidity Sensors with a Swift Response/Recovery Speed

• Published in: Molecules (Basel, Switzerland) Switzerland), 2023-02, Vol.28 (4), p.1754
• Main Authors: Vojisavljević, Katarina, Savić, Slavica M., Počuča-Nešić, Milica, Hodžić, Aden, Kriechbaum, Manfred, Ribić, Vesna, Rečnik, Aleksander, Vukašinović, Jelena, Branković, Goran, Djokić, Veljko
• Format: Article
• Language: English
• Subjects: Climate change; Crystal defects; Crystal growth; Crystals; Humidity; mesoporous silica template; Metal oxides; Molecular dynamics; Morphology; Nanomaterials; Pore size; Powder; Recovery time; Relative humidity; response–recovery behavior; Room temperature; Sensitivity; Sensors; small- and wide-angle X-ray scattering; Sol-gel processes; Tin dioxide; tin-dioxide thick-film humidity sensor; transmission electron microscopy; Water vapor; X ray photoelectron spectroscopy
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules28041754

Developing highly efficient semiconductor metal oxide (SMOX) sensors capable of accurate and fast responses to environmental humidity is still a challenging task. In addition to a not so pronounced sensitivity to relative humidity change, most of the SMOXs cannot meet the criteria of real-time humidity sensing due to their long response/recovery time. The way to tackle this problem is to control adsorption/desorption processes, i.e., water-vapor molecular dynamics, over the sensor’s active layer through the powder and pore morphology design. With this in mind, a KIT-5-mediated synthesis was used to achieve mesoporous tin (IV) oxide replica (SnO2-R) with controlled pore size and ordering through template inversion and compared with a sol-gel synthesized powder (SnO2-SG). Unlike SnO2-SG, SnO2-R possessed a high specific surface area and quite an open pore structure, similar to the KIT-5, as observed by TEM, BET and SWAXS analyses. According to TEM, SnO2-R consisted of fine-grained globular particles and some percent of exaggerated, grown twinned crystals. The distinctive morphology of the SnO2-R-based sensor, with its specific pore structure and an increased number of oxygen-related defects associated with the powder preparation process and detected at the sensor surface by XPS analysis, contributed to excellent humidity sensing performances at room temperature, comprised of a low hysteresis error (3.7%), sensitivity of 406.8 kΩ/RH% and swift response/recovery speed (4 s/6 s).