Naked-eye colorimetric and switch-on fluorescence chemosensor based on a rhodamine derivative for Hg2+: Smartphone device, test-kit and food sample applications

A new rhodamine-based switch-on fluorescent and colorimetric chemosensor (RHEN) was fabricated for the determination of Hg2+. The RHEN showed a noticeable colorimetric response for Hg2+ from "colorless" to "pink" under daylight. When exposed to Hg2+, the fluorescence at 582 nm from the probe RHEN was remarkably enhanced, attend by a color change from "colorless" to "dusty rose color" under 365 nm UV lamp. The RHEN had a notable specificity and selectivity for Hg2+ and depicted an excellent sensing performance for detecting lowly concentrated Hg2+ (LOD; 0.11 mu M). The binding phenomenon between RHEN and Hg2+ was identified by Job's method, MALDI TOF-MS and FT-IR spectroscopy. Moreover, the fabricated chemoprobe RHEN was not only utilized to identify Hg2+ in fish samples with satisfactory results (95.28-111.66 %) but also was successfully used for test-paper and cotton swab applications. Smartphone application also showed that RHEN could be used as a potent tool for on-site sensing of Hg2+ without the need for complicated device.