Carbon Dioxide Detectors based on Al‐ and Ni‐Doped ZnO

• Published in: Physica status solidi. A, Applications and materials science Vol. 219; no. 21
• Main Authors: Lozano-Rosas, Ricardo, Hernandez, Angelica Guadalupe, Elizalde-González, María P., Robles-Águila, Maria Josefina, Tangirala, Venkata Krishna Karthik
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01-11-2022
• Subjects: Al-doped ZnO; Aluminum; Carbon dioxide; CO2 detectors; Crystal dislocations; Crystallites; Dislocation density; Gas sensors; Lattice parameters; Morphology; Nanoparticles; Ni-doped ZnO; Nickel; Selectivity; Sol-gel processes; Ultrasonic testing; ultrasonic-assisted sol–gel; Zinc oxide; Zinc oxides
• ISSN: 1862-6300; 1862-6319
• DOI: 10.1002/pssa.202200247

In this work, zinc oxide (ZnO), nickel (Ni) and aluminum (Al)‐doped ZnO nanoparticles are synthesized via an ultrasound‐assisted sol–gel technique. X‐ray diffraction analysis reveals a correlation between structural parameters (lattice parameters, crystallite size, dislocation density and micro‐strain) and the dopant ions incorporation. Scanning electron microscopy studies show changes in morphology in doped samples derived from the effect of restriction on the growth dynamics. A growth mechanism is proposed in order to explain the properties of ZnO‐based sensors. Gas sensing tests are carried out, delivering the best results as follows: an 89% sensing response at 500 ppm of carbon dioxide (CO2), 0.54 MΩ s−1 of sensitivity, and 52/48 s for average response and recovery times respectively, in the Ni‐doped ZnO sample. Additionally, selectivity evaluations for all samples are also performed. By comparing the obtained structural and morphological characteristics with the gas sensing properties of the samples, Ni‐doped ZnO samples have optimal characteristics for CO2 detection due to the high surface area and abundant oxygen vacancies resulting from the Ni incorporation. The gas sensing mechanism of each sample is also reported and discussed in detail.
Herein, undoped, Ni, and Al‐doped ZnO gas sensors are fabricated using chemical deposition techniques. Due to small crystallite size, distorted microstructure, higher ion incorporation, spherical‐like morphology, and a large depletion layer, the Ni‐doped ZnO sensor exhibits an enhanced sensing response (≈89%) toward CO2 gas in comparison with undoped and Al‐doped ZnO sensors.