Nanoporous anodic alumina-based gas sensors: insights into advances and perspectives.

Achieving high-performance gas sensing requires materials and transduction mechanisms that enhance sensitivity, selectivity, and stability, while addressing challenges such as cross-sensitivity and real-time operation. Conventional sensor platforms often involve trade-offs between response time, detection limits, and environmental robustness. Nanoporous anodic alumina (NAA) fabricated by electrochemical oxidation-anodization-of aluminum provides a tunable platform for engineering gas sensors with tailored structural and physicochemical properties, enabling diverse transduction mechanisms and sensor configurations. This review categorizes NAA-based gas sensors into two major groups: electrochemical and optical sensors. The distinct interplay between the nanoporous architecture of NAA and its dielectric properties enhances charge transport in electrochemical sensors while enabling precise optical confinement and modulation in optical sensing platforms. Ongoing efforts in structural modifications, surface functionalization, and hybrid material integration continue to refine the capabilities of NAA-based gas sensors. Tailored nanostructured coatings, such as functionalized metal oxides, polymer composites, and plasmonic nanostructures, present new pathways for improving sensitivity and selectivity. The integration of data-driven signal processing, including machine learning-assisted analysis, is transforming how sensor responses are interpreted, endowing gas sensors with enhanced discrimination and multiplex sensing capabilities. These advancements, combined with innovations in microfabrication and miniaturized sensor arrays, enable new forms of NAA-based gas sensors. This review provides an up-to-date overview of recent progress and emerging directions in the development of NAA-based gas sensing technologies.