Recent Advances on Metal Oxide Based Sensors for Environmental Gas Pollutants Detection

Abstract

Optimizing materials and associated structures for detecting various environmental gas pollutant concentrations has been a major challenge in environmental sensing technology. Semiconducting metal oxides (SMOs) fabricated at the nanoscale are a class of sensor technology in which metallic species are functionalized with various dopants to modify their chemiresistivity and crystalline scaffolding properties. Studies focused on recent advances of gas sensors utilizing metal oxide nanostructures with a special emphasis on the structure-surface property relationships of some typical n-type and p-type SMOs for efficient gas detection are presented. Strategies to enhance the gas sensor performances are also discussed. These oxide material sensors have several advantages such as ease of handling, portability, and doped-based SMO sensing detection ability of environmental gas pollutants at low temperatures. SMO sensors have displayed excellent sensitivity, selectivity, and robustness. In addition, the hybrid SMO sensors showed exceptional selectivity to some CWAs when irradiated with visible light while also displaying high reversibility and humidity independence. Results showed that TiO₂ surfaces can sense 50 ppm SO₂ in the presence of UV light and under operating temperatures of 298–473 K. Hybrid SMO displayed excellent gas sensing response. For example, a CuO–ZnO nanoparticle network of a 4:1 vol.% CuO/ZnO ratio exhibited responses three times greater than pure CuO sensors and six times greater than pure ZnO sensors toward H₂S. This review provides a critical discussion of modified gas pollutant sensing capabilities of metal oxide nanoparticles under ambient conditions, focusing on reported results during the past two decades on gas pollutants sensing.

Graphical Abstract

Keywords:

• Gas pollutants
• gas sensors
• low detection limit
• metal oxides
• mixed oxides
• nanomaterials
• selective detection
• Sol-Gel

Author contributions

All authors contributed to the study conception and design. Literature search, data collection, and analyses were performed by all authors. All authors contributed to the review in writing specific sections and commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

All data associated with this review can be found within the main manuscript.

Additional information

Funding

This work was funded by the Research Office at the American University of Sharjah [FRG22-C-S77]. The work is also partially supported by the Open Access Program from the American University of Sharjah.