Newspaper is known to turn yellow over time. We show here that this yellowing process is sensitive to oxygen when exposed to UV light, leading to oxygen sensing. Oxygen sensing is critical to many applications, including industrial process control and breath analysis, but the existing oxygen sensors have limitations, especially for breath analysis that operates at 100% humidity. The UV irradiation also triggers fluorescence emission from newspaper, and the fluorescence intensity depends on oxygen concentration, providing an additional oxygen sensing method. Newspaper is stable in ambient air, and reactive to oxygen only with UV activation, which overcomes the instability issue of a typical colorimetric sensor in ambient air. The newspaper oxygen sensor works in 100% relative humidity air, containing various interferents. These unique properties of newspaper promise low cost and reliable oxygen sensing applications.
Keywords: breath analysis; optical sensing; oxygen sensing; paper-based sensor; yellowing of newspaper.