A ratiometric hydrophilic fluorescent copolymer sensor based on benzimidazole chromophore for microbioreactors

The ratiometric approach is robust and insensitive to factors such as source intensity, photobleaching, or orientation of the patch. A novel ratiometric hydrophilic copolymer of N-(1-ethyl-2-(pyridin-4-yl)-1H-benzo[d]imidazol-5-yl)methacrylamide and 2-hydroxyethyl methacrylate (P(BIPy–HEMA)) containing pyridyl substituted benzimidazole moiety as pH sensor has been developed. Its fluorescence in aqueous system showed two obvious isosbestic points due to two-stepwise protonation. According to the linear curves of I462/I423 and I536/I462 to pH, such ratiometric pH values could be read directly without external calibration. Considering the hydrophilicity, stability and repeatability in aqueous environment, the fluorescent film with ratiometric characteristic over acidic pH range of 1.7–4.5 makes it high promising for online monitor in microbioreactors.