A paper-based fluorescent and colorimetric portable device with smartphone application for Fe3+ sensing

Technological advances provide the possibility to develop a quantitative detection platform based on the smartphone as a detector. In this work, we reported a portable, simplified and on-site colorimetric method for Fe3+ sensing owing to the rhodamine-grafted paper and smartphone mini application. According to a rhodamine-based probe RhBUEA, the rhodamine-grafted cellulose filter paper (Paper-g-RhBUEA) was prepared via ARGET ATRP as a fluorescent and colorimetric sensor for Fe3+, and their physicochemical properties were characterized by XPS, ATR-FTIR, SEM, EDS and spectrophotometer. Simultaneously, the influence of the RhBUEA concentration on the grafting rate and fluorescence intensity was studied. Based on the recipe of 0.056 mol/L RhBUEA, Paper-g-RhBUEA showed excellent selectivity and sensitivity for Fe3+ monitoring in the study of fluorescent and colorimetric properties. The detection limit of the fluorescent and colorimetric recognition is 0.19 μM and 1.4 μM, respectively. To increase the portability of Fe3+ sensing, a smartphone WeChat mini application named “Colorimetric detector” was developed. The colorimetric detection platform integrating the Paper-g-RhBUEA as a probe, and the smartphone app as a processor permitted convenient and on-site colorimetric quantitative detection of Fe3+ in environmental water.