Moisture-Sensitive Ratiometric Color-Changing Response: a Useful Tool for Precision Farming

Anthra[1,2-d]imidazole-6,11-dione-based charge transfer probes have been developed for the detection of water impurities in a wide range of laboratory-used organic solvents. The deprotonated (anionic) forms of the probe molecules, obtained upon addition of basic anions such as fluoride, demonstrate a ratiometric color-changing response (blue to yellow in presence of F- and red to yellow with CN- ion) even in the presence of a trace amount of moisture (detection limit: 0.008 wt %). Considering their high sensitivity and "naked-eye" response, the anionic receptors are utilized for the quantification of moisture level or water impurity in a wide range of real-life samples, such as building raw materials, packaged food items, soil, plant leaves, and so on. Determination of the moisture level of plant leaves or soil samples is particularly important for precision farming as it helps the farmers to schedule the irrigation events. Finally, low-cost, reusable, and optical kit-based dye-coated paper strips were developed for rapid, on-location detection as well as quantification purposes. Since such a sustainable approach does not involve any sophisticated instruments or complex sample preparation steps, the general public with little knowledge of science or technology will be able to use it without much difficulty.