A bifunctional UIO-66-NH@ RhB-based fluorescence and colorimetric dual-mode ratiometric sensor and hydrogel-based smart phone-assisted naked eye detection of perfluorooctanesulfonate (PFOS).

A bifunctional fluorescent and colorimetric sensor based on UiO-66-NH₂@RhB was developed for the highly sensitive detection of perfluorooctanesulfonate (PFOS), a persistent environmental pollutant. The sensing mechanism relies on the inner filter effect (IFE), where Rhodamine B (RhB) modulates the fluorescence of UiO-66-NH₂, enabling effective PFOS recognition. In the presence of PFOS, UiO-66-NH@RhB exhibits dual emissions in blue fluorescence at 448 nm and red fluorescence at 565 nm at a single excitation wavelength. Upon the addition of increasing concentrations of PFOS, the blue fluorescence intensity increased and a small change was observed in the red fluorescence intensity. Besides, UiO-66-NH@RhB solutions display an excellent colorimetric response for PFOS and produce an obvious color change from red to colorless. The method demonstrated high sensitivity, achieving linear detection ranges of 1-10 nM with detection limits of 0.84 nM (fluorescence) and 0.91 nM (colorimetry). Furthermore, the dual-sensing platform successfully detected PFOS in real water samples with satisfactory outcomes. Its integration with a portable smartphone further enables intelligent, real-time, on-site monitoring and is successfully applied to monitoring PFOS in environmental samples. This study not only broadens the application of MOFs but also provides valuable insights for designing multifunctional sensors for diverse analytical applications.