Aluminum-doped ZnO nanopowders were synthesized via a sol-gel method at Al/Zn atomic ratios of 0, 0.02, and 0.04. The structural, morphological, and optical properties of the materials were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), UV–visible spectroscopy, and X-ray diffraction (XRD). Structural analysis confirmed that both pure and Al-doped ZnO samples crystallize in the hexagonal wurtzite structure, with no detectable secondary phases. Slight lattice distortions and variations in crystallite size were observed as the Al concentration increased. Thick-film chemoresistive sensors were fabricated by depositing the synthesized nanopowders onto alumina substrates with interdigitated platinum electrodes. The sensor based on ZnO:Al2% exhibited the best performance, with the highest response and faster response–recovery dynamics at an operating temperature of 250 °C. The improved sensing behavior is attributed to increased charge-carrier concentration and to oxygen vacancies formed by Al doping. These results demonstrate that moderate aluminum incorporation significantly improves the CO2 sensing performance of ZnO nanoparticles under controlled dry conditions, highlighting their potential as low-cost CO2-sensitive materials for preliminary environmental monitoring and smart agriculture applications. However, further selectivity and humidity-dependent tests are required to assess their performance under real operating conditions.
Effect of aluminum doping on the CO2 sensing performance of sol-gel synthesized ZnO nanoparticles
Alaya Y.;Bressi V.;Di Pietro R.;Donato N.;Neri G.;Espro C.
2026-01-01
Abstract
Aluminum-doped ZnO nanopowders were synthesized via a sol-gel method at Al/Zn atomic ratios of 0, 0.02, and 0.04. The structural, morphological, and optical properties of the materials were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), UV–visible spectroscopy, and X-ray diffraction (XRD). Structural analysis confirmed that both pure and Al-doped ZnO samples crystallize in the hexagonal wurtzite structure, with no detectable secondary phases. Slight lattice distortions and variations in crystallite size were observed as the Al concentration increased. Thick-film chemoresistive sensors were fabricated by depositing the synthesized nanopowders onto alumina substrates with interdigitated platinum electrodes. The sensor based on ZnO:Al2% exhibited the best performance, with the highest response and faster response–recovery dynamics at an operating temperature of 250 °C. The improved sensing behavior is attributed to increased charge-carrier concentration and to oxygen vacancies formed by Al doping. These results demonstrate that moderate aluminum incorporation significantly improves the CO2 sensing performance of ZnO nanoparticles under controlled dry conditions, highlighting their potential as low-cost CO2-sensitive materials for preliminary environmental monitoring and smart agriculture applications. However, further selectivity and humidity-dependent tests are required to assess their performance under real operating conditions.Pubblicazioni consigliate
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