CuO/ZnO Bi-layered nanoarchitecture for room temperature CO2 sensing at low concentration
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Date
2025
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Abstract
Bi-layered ZnO/CuO nanostructured films have been examined for CO2 gas sensing applications. X-ray diffrac
tion, Fourier transform infrared, and Raman spectroscopy confirm the formation of a hexagonal wurtzite ZnO
and a monoclinic CuO. Scanning electron and atomic force microscopies' observations reveal homogeneous,
dense, and quasi-porous surfaces with smooth spherical sponge-like (ZnO), rough spherical-like (CuO and ZnO/
CuO), and rough flat plate-like (for CuO/ZnO) grains morphologies with a few cracks. UV–visible spectroscopy
shows greater transmittance (45–90 %) in the infrared and visible domains, while the energy bandgap decreases
significantly from 3.3 eV for ZnO to 1.5 eV for the remaining films. The measurements of the sensor's electrical
characteristics at room temperature, including current-voltage (I–V), sensitivity-concentration (S–C), and
current-time (I-t), indicate a sensitivity to the presence of CO2 gas and that the fabricated sensor exhibits
excellent sensitivity and faster response/recovery times. Indeed, the ZnO thin-film sensor recorded the highest
sensitivity of 44.77 % at 31 ppm carbon dioxide concentration at room temperature. Based on the results ob
tained, a sensing mechanism is proposed. The findings demonstrate that metal oxide multilayered nanostructures
are promising candidates for applications such as gas sensing, photocatalysis, and UV photodetection