Quantitative water determination in THF/H2O mixtures using a sustainable holographic sensor with operational reusability

The development of efficient water sensors for organic media is critical for industrial solvent recycling and storage. In this work, reflection holograms recorded in a low-toxicity and water-based photopolymer are proposed as eco-friendly optical sensors for detecting water in tetrahydrofuran (THF). The proposed sensor shows a dynamic range from 0.03% (Limit of Detection) up to 7.00% v/v of water in THF. Furthermore, the device is reusable for concentrations 5.00% v/v, where the polymer matrix operates within an elastic regime that allows for consistent recovery. The optical response was monitored via Bragg wavelength shifts and diffraction efficiency variations, complemented by absorption and weight tracking analysis. Results reveal a dual sensing mechanism: swelling-induced redshifts in water-rich mixtures and shrinkage-induced blueshifts in nearly pure THF. Kogelnik’s Coupled Wave Analysis confirmed the reproducibility of the structural changes. This study demonstrates that biodegradable holographic sensors can provide a quantitative, sustainable, and reliable solution for monitoring solvent quality in industrial environments. • Sustainable photopolymer enables efficient holographic sensing in THF/H2O. • Reflection gratings detect 0.03–7.00% v/v water from clear wavelength shifts and color changes. • Swelling and shrinkage yield rapid, predictable, and quantifiable optical responses. • Sensors are reusable for water content ≤ 5.00% v/v after matrix stabi- lization.