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Authors
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Dobschall, F.; Bittinger, S. C.; Tioka, C. T.; Struck, J.; Pariente, E.; Delville, M.-H.; Schlicke, H.; Vossmeyer, T.
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Title
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Photoactivated Detection of Volatile Organic Compounds Using Thin Films of Differently Shaped Titania Nanocrystals
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Date
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20.11.2025
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Number
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0
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Abstract
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Photoactivated chemiresistors based on metal oxides (MOXs) are promising alternatives to conventional thermally activated chemiresistors. They enable the highly sensitive detection of volatile organic compounds (VOCs) without requiring a high operating temperature. However, their sensing mechanism is not well understood. Here, we report the sensing characteristics of photoactivated chemiresistors based on thin films of titania nanocrystals. Their responses to VOCs are influenced by the shapes of the nanocrystals and the morphology of the films. Homogeneous thin films are fabricated by drop-casting suspensions of titania nanorods (TNRs) and titania nanoplates (TNPs). Further, drop-casting suspensions of titania nanobipyramids (TNBs) and commercial P25 nanocrystals result in inhomogeneous films with an island-like morphology. To remove the initial ligands and organic contaminants, the films are first cleaned via deep ultraviolet (DUV) treatment. Photoactivation of the cleaned films with UV light-emitting diodes (wavelength: 278 nm) results in photocurrents between ∼2 and ∼10 nA. Under continuous UV illumination, the films are exposed to various VOCs (ethanol, 1-propanol, 2-propanol, 1-butanol, toluene, 4-methylpentan-2-one, 1-butylamine, ethyl acetate) with concentrations from 25 to 200 ppm in purified dry air. All films respond highly sensitive and selectively to alcohol vapors. Of the four film materials, the P25-based sensor exhibits the highest photocurrent responses (up to ∼200 μA) along with short response (t<sub>80</sub>, 4 s) and recovery (t<sub>20</sub>, 8 s) times when dosed with 1-propanol vapor. In contrast, the TNP-based sensor exhibits the lowest response amplitudes (up to ∼2.5 μA) and significantly slower response and recovery dynamics. Dosing the sensors with humidified 1-propanol vapor revealed significantly attenuated or even inverted photocurrent responses. This humidity-induced impairment of performance complicates the technological application of such sensors. After several months, the sensitivity of the sensors decreases. However, additional DUV treatment largely restores the sensitivity, suggesting that the decrease in sensitivity is mainly caused by organic contaminants.
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Publisher
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American Chemical Society
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Wikidata
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Citation
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ACS Applied Nano Materials 8 (2025) 22955-22964
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DOI
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https://doi.org/10.1021/acsanm.5c03648
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