A dual-emission Acf@bioMOF-1 platform as fluorescence sensor for highly efficient detection of inorganic ions

An anionic bio-MOF-1 with 1D square channels is applied as container for the adsorption of organic dyes owing to the porous structure and charge properties. Through ion exchange, cationic acriflavine (Acf) dye with the minimum size is selected as a fluorescent dye molecule to introduce into the pores of anionic bio-MOF-1 to obtain a self-calibrating dual-emitting fluorescent composite of Acf@bio-MOF-1, which exhibits two characteristic emission peaks at 385 and 582 nm. The composite acts as fluorescence sensing probe for the selective and sensitive detection of Fe3+, Al3+ and Cr2O72- among metal cations and anions and has a turn-off response to Fe3+ and Cr2O72- as well as a turn-on response to Al3+ at the same time. Particularly, Acf@bio-MOF-1 shows higher fluorescence quenching effects of 95% for Cr2O72- and 90% for Fe3+ and low detection limits of 0.25 mu M for Cr2O72- and 1.33 mu M for Fe3+, respectively. Such a special encapsulation strategy to form a dual-emission platform can be adopted to the detection of inorganic ions sensitively.