Highly selective nitric oxide sensor using terahertz metamaterials with a perovskite membrane

Abstract

Human breath contains hundreds of volatile organic compounds, which can be utilized to detect various physiological, cardiovascular, and endocrine disorders. For instance, the level of nitric oxide (NO) in exhaled breath can indicate chronic obstructive pulmonary disease. Analyzing exhaled gases offers a noninvasive way to diagnose diseases without posing any risk to humans. In the past twenty years, electronic sensors capable of detecting NO concentration at high temperatures have been developed. However, there has been limited research on optical detection within the ultraviolet to visible light spectrum, which can be harmful to the skin. In this study, we designed a split-ring resonator metamaterial that functions within the terahertz (THz) frequency range. We tuned the metamaterial's resonant frequency to align with the NO absorption frequency at 0.257 THz. To enhance the gas absorption capacity, we created a composite film layer of ZnTiO₃ and graphene, which was applied to the metamaterial. By sintering ZnTiO₃ powder at various temperatures, we increased the component sensitivity (ΔT/T) from 2% to 16.4%. This proposed metamaterial can be employed in both physical monitoring and the development of wearable electronic devices.