An extremely sensitive fluorescent sensor based on a phenylboronic acid monolayer was developed for detecting
saccharide molecules. The fluorescent sensor was prepared by assembling a monolayer of 4-mercaptophenylboronic
acid (4-MPBA) onto a gold-coated compact disk. The change in the fluorescence of the 4-MPBA monolayer was
extremely obvious in basic methanolic buffer containing monosaccharides down to the picomolar level. The
fluorescence spectra demonstrated that the 4-MPBA monolayer was sensitive to monosaccharides and disaccharides, and
the affinity of the monolayer toward saccharides was in the order of glucose < fructose < mannose < galactose < maltose > lactose > sucrose. Additionally, the fluorescence intensity of 4-MPBA monolayer was restorable after cleaning with weak acid, indicating that the reported fluorescent sensor with the detection limit of glucose down to the picomolar level is reusable for sensing saccharides.