Transformation of rusted iron into an IDE-based sensor for ethanol detection and self-powered humidity sensing

Abstract

Volatile organic compound (VOC) sensors and triboelectric nanogenerators (TENGs) are highly significant applications with broad potential across multiple fields, including non-invasive disease biomarker monitoring and sustainable energy harvesting for electronic devices. This study reports the synthesis of alpha-Fe2O3 nanoparticles derived from recycled iron screws using a closed-system nitric acid leaching process, followed by calcination, offering low-cost, eco-friendly, and added-value products that reduce the negative environmental impacts of waste materials. The synthesized material is thoroughly characterized to investigate its phase purity, surface morphology, and suitability for TENG and ethanolsensing applications. A spray coating technique was employed to deposit the alpha-Fe2O3 ink onto laserinduced graphene interdigitated electrodes (LIG-IDE) fabricated via CO2 laser engraving of a polyimide flexible substrate. The fabricated alpha-Fe2O3-based sensor exhibits multifunctional capabilities, owing to the material's biocompatibility. The alpha-Fe2O3-based sensor exhibits a high performance for ethanol detection at room temperature, with a sensor response of 47 and response/recovery times of 104/126 s, respectively, at 100 ppm. The TENG device exhibits stable output characteristics of 3 V and a maximum power of 9.5 nW. The electrical output from biomechanical motions confirms its potential for energy harvesting applications, and a further self-powered humidity sensor was demonstrated. These results highlight the excellent potential of alpha-Fe2O3 for both TENG applications and VOCs detection, recommending its use in environmental and industrial monitoring.