A new fluorescent boronic acid sensor based on carbazole for glucose sensing via aggregation-induced emission

A water-soluble fluorescent sensor based on carbazole pyridinium boronic acid (CPBA) was designed and synthesized. Its structure has been confirmed by CHN and ¹H and ¹³C NMR, FT-IR, and MS spectral data. Fluorescence studies of the synthesized chemosensor CPBA showed a selective ratiometric fluorescent response for glucose among different monosaccharides. The results specified that CPBA is a pH-sensitive sensor that behaves differently in the absence and presence of glucose in the pH range 4-10. The pH, DLS, Job's plot, UV-visible, and fluorescence titration studies showed that the selectivity of CPBA towards glucose is through the aggregation-induced emission (AIE) phenomenon. The fluorescence emission intensity of CPBA changes by more than 2100 fold by adding glucose, whereas it is 2 fold for fructose. The calculated binding constant value of CPBA for glucose (K = 2.3 × 10⁶ M^-1) is 85 times greater than for fructose, indicating the high affinity of the sensor for glucose.