Simple fluorescence "turn-off" assay for Congo red using commercial 2-aminophthalic acid

In this work, the fluorescence properties of 2-aminophthalic acid (NH₂-BDC) were studied. NH₂-BDC possessed excellent optical properties including bright blue emission with maximum emission at 425 nm, a high quantum yield of 38.49% and excellent photostability. And the fluorescence of NH₂-BDC could be selectively quenched by Congo red, which was ascribed to the inner filter effect. Accordingly, NH₂-BDC was further employed for fluorescence "turn-off" assay of Congo red with a linear range of 0.05-50 μM and a limit of detection of 1.72 μM. And the sensor was used for the detection of Congo red in real water samples with acceptable results.