The use of light to activate gas sensitivity in semiconductors (SCs) is an appealing alternative to thermal activation for the construction of low-power consumption gas sensors and for new applicative demands. For instance, the photosensitivity vs. NO2 of zinc oxide (ZnO) under UV radiation has been widely investigated so far. However, visible light would be preferable over UV because, first, UV can influence the analyte gas molecules, for example, reducing NO2 to NO, and second, LEDs employed as a source of UVB and UVC radiation have lower efficiency and quantum yield than LEDs that generate UVA or visible light [1]. Therefore, the aim of this preliminary work was to sensitize ZnO, i.e. a wide-gap SC oxide, to visible light by exploiting a cost-effective and economical strategy consisting in sodium (Na) doping. Pristine ZnO and Na:ZnO powders were obtained through a sol-gel process using zinc acetate and NaOH as Zn and Na precursors, respectively. The nanopowders were used as functional materials to produce thick films deposited by screen printing onto alumina substrates with gold interdigitated electrodes. The response vs. 2 ppm of NO2 of ZnO and Na:ZnO sensors activated through four LEDs with increasing wavelength (385, 468, 525 and 592 nm) is shown in Fig. 1a. The best response was obtained for Na:ZnO film illuminated with blue LED, which also demonstrated more performing kinetics than that of pure ZnO (Fig. 1b).
Preliminary study on visible light-activated chemoresistive gas sensor based on alkali-doped ZnO
Barbara Fabbri
;Elena Spagnoli;Emanuela Tavaglione;Arianna Rossi;Paolo Bernardoni;Vincenzo Guidi
2023
Abstract
The use of light to activate gas sensitivity in semiconductors (SCs) is an appealing alternative to thermal activation for the construction of low-power consumption gas sensors and for new applicative demands. For instance, the photosensitivity vs. NO2 of zinc oxide (ZnO) under UV radiation has been widely investigated so far. However, visible light would be preferable over UV because, first, UV can influence the analyte gas molecules, for example, reducing NO2 to NO, and second, LEDs employed as a source of UVB and UVC radiation have lower efficiency and quantum yield than LEDs that generate UVA or visible light [1]. Therefore, the aim of this preliminary work was to sensitize ZnO, i.e. a wide-gap SC oxide, to visible light by exploiting a cost-effective and economical strategy consisting in sodium (Na) doping. Pristine ZnO and Na:ZnO powders were obtained through a sol-gel process using zinc acetate and NaOH as Zn and Na precursors, respectively. The nanopowders were used as functional materials to produce thick films deposited by screen printing onto alumina substrates with gold interdigitated electrodes. The response vs. 2 ppm of NO2 of ZnO and Na:ZnO sensors activated through four LEDs with increasing wavelength (385, 468, 525 and 592 nm) is shown in Fig. 1a. The best response was obtained for Na:ZnO film illuminated with blue LED, which also demonstrated more performing kinetics than that of pure ZnO (Fig. 1b).I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
