Revealing the correlation between gas selectivity and semiconductor energy band structure derived from off-stoichiometric spinel CdGa2O4.
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| Title: | Revealing the correlation between gas selectivity and semiconductor energy band structure derived from off-stoichiometric spinel CdGa2O4. |
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| Authors: | Wang, Tianshuang1 (AUTHOR), Sun, Peng1,2 (AUTHOR), Liu, Fangmeng2 (AUTHOR), Lu, Geyu1,2 (AUTHOR) |
| Source: | Sensors & Actuators B: Chemical. Feb2022:Part 2, Vol. 352, pN.PAG-N.PAG. 1p. |
| Subjects: | Energy bands, Spinel, Metal oxide semiconductors, Gas detectors, Narrow gap semiconductors, Band gaps |
| Abstract: | Herein, the spinel CdGa 2 O 4 and off-stoichiometric spinel CdGa 2 O 4 (CdO-CdGa 2 O 4) with 3D inverse opal spherical structure have been synthesized by the combination of ultrasonic spray pyrolysis technology and self-assembled hard-template method. The CdGa 2 O 4 , with band gap of 4.14 eV and baseline resistance of Mohm-level, exhibited excellent selectivity and high response to 1 ppm formaldehyde. On the other hand, the CdO-CdGa 2 O 4 composites (Cd:Ga atom ratio = 1.2:2), with band gap of 2.46 eV and baseline resistance of kohm-level, exhibited best sensing performance to 1 ppm NO 2 with negligibly low cross-responses (R air /R gas < 3.5) to any VOCs. Due to the semiconductor band gap is narrowed, and the conducting channel depending on the agglomeration of surface loaded CdO nanocrystals, the gas selectivity has been changed and the baseline resistance of off-stoichiometric spinel CdGa 2 O 4 was reduced by many orders of magnitude. Meanwhile, the improvement of gas response can be attributed to ordered bimodal-porous structure, and the n-n heterojunctions induced decrease in work function and enhancement in chemisorbed oxygen. Accordingly, the proposed correlation between gas selectivity change and band gap modulation can open new route for solving the shortcoming of poor selectivity of metal oxide semiconductor gas sensor. Benefiting from the gas selectivity change derived from the modulation of energy band structure, the CdGa 2 O 4 sensor exhibited excellent selectivity and high response to formaldehyde, but the off-stoichiometric spinel CdGa 2 O 4 sensor exhibited best sensing performance to NO 2 after band gap narrowing. [Display omitted] • The 3D inverse opal ideal and off-stoichiometric spinel CdGa 2 O 4 were prepared by USP method. • The CdGa 2 O 4 gas sensor exhibited excellent selectivity and high response to formaldehyde. • The n-n heterojunctions CdO-CdGa 2 O 4 composites was firstly used as sensitive materials for preparing NO 2 gas sensor. • Revealing the correlation between gas selectivity change and band gap modulation. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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