Carbon dot@metal-organic frameworks with aggregation-induced emission for visual detection of ascorbic acid

With the increasing demand for in-situ detection, current fluorescence-based methods predominantly rely on "turn-on" or "turn-off" sensors, which are insufficient to meet the requirements for specific responses to ascorbic acid (AA). A sensitive multicolor-switching luminescent sensor based on fluorescence resonance energy transfer (FRET) was developed by encapsulating carbon dots (CDs) into aggregation-induced luminescence metal-organic framework (AIE-MOF) to prepare ratiometric luminescent probes (CDs@AIE-MOF) for the specific recognition and sensitive detection of AA. The fluorescent CDs acted as reference signals and a quencher to greatly quench the emission of AIE-MOF through the FRET mechanism. After the CDs@AIE-MOF probe binds AA, the absorption peak at 550 nm was significantly reduced, which could be attributed to the interaction between CDs and AA to form a binary complex. This altered the absorption properties of CDs at 550 nm, further inhibited the FRET behavior between CDs and AIE-MOF, and correspondingly restored the fluorescence of AIE-MOF. The obvious luminescence color change from orange-red to yellow to green during the sensing could be observed by the naked eye. The linear range was 0.02-255 μM, with a detection limit of 6.6 nM. Additionally, the interaction between the CDs and AIE-MOF was skillfully utilized to prepare fluorescent test paper for the highly sensitive and selective on-site visual detection of AA. This strategy provides more possibilities for dual-emission fluorescent probes for visual sensing.