An effective turn-on/off rodamine-encapsulated UiO-67-NH2 fluorescent probe for simultaneous As5+/Fe3+ detection

Abstract

The development of metal ion detection probes with high sensitivity and selectivity is of utmost importance for the promotion of public health and environmental sustainability. In this work, a series of ratiometric fluorescent probes (RhB@UiO-67-NH₂) were successfully prepared using a one-pot method for the detection of metal ions, particularly As⁵⁺ and Fe³⁺. Notably, the ratiometric fluorescent probe RhB@UiO-67-NH₂ (1:4) demonstrates dual functionality as a Fe³⁺ turn-off probe and an As⁵⁺ turn-on probe. The limits of detection (LODs) for As⁵⁺ and Fe³⁺ using RhB@UiO-67-NH₂ (1:4) were determined to be 0.521 μM (39.03 ppb) and 0.107 μM (5.97 ppb), respectively, which were the lowest records of reported LMOFs so far. The fluorescence quenching of Fe³⁺ can be attributed to various mechanisms such as fluorescence resonance energy transfer (FRET), photoinduced electron transfer (PET), and competitive absorption (CA). Additionally, the fluorescence enhancement of As⁵⁺ is primarily due to absorbance-caused enhancement (ACE) and PET. Moreover, the composite material RhB@UiO-67-NH₂ (1:4) exhibited excellent anti-interference capability and reproducibility for detecting Fe³⁺ and As⁵⁺. The removal efficiency of As⁵⁺ by RhB@UiO-67-NH₂ (1:4) exceeded 50.9 % when the initial concentration of As⁵⁺ was below 20 mg/L. This work presents a valuable reference for future investigations and utilization of As⁵⁺ and Fe³⁺ sensing.