Microfibrillated cellulose-based colorimetric sensor strips for detecting total iron in water

Microfibrillated cellulose (MFC), a sustainable material derived from biomass, stands out as an environmentally friendly alternative for developing chemical sensors owing to its advantageous properties, including high porosity, surface area, and available surface functional groups. Herein, we propose a simple and low-cost strategy for developing cellulose-based strips for the colorimetric detection of total iron in water. The strips were prepared by functionalizing MFC casting membranes with 1-(2-Thiazolylazo)-2-naphthol (TAN), which was then characterized by structural and morphological techniques. The sensing ability of the MFC@TAN strips towards total iron was evaluated under distinct reaction times by digital image colorimetry. Under optimal conditions, the strips yielded limits of detections of 0.08 and 0.09 mg L^-1 using the Blue (5 min) and Red (30 min) channels, respectively. Additionally, the sensor enabled total iron detection in tap water in the concentration range of 0.08-0.70 mg L^-1, showing no significant difference against the standard method. When compared to commercial papers, the MFC@TAN strips showed enhanced sensing performance due to their more porous and interpenetrating structure, which benefited the TAN immobilization and reaction with Fe²⁺. Our cellulose-based sensor strips offer a compelling combination of simplicity in manufacturing and cost-effectiveness, highlighting their potential for routine water analysis.