NOVEL OPTICAL PH-SENSOR BASED ON A BORADIAZA-INDACENE DERIVATIVE

A pH-optode is described based on thylamino)-4-difluorobora-3a,4a-diaz a-(s)-indacene (1) immobilized in a hydrogel matrix. Its uncharged for m is non-fluorescent, whereas the protonated form displays strong emis sion. The quenching of the emission can be mechanistically explained b y a PET (photoinduced electron transfer) from the dimethylamino group to the fluorophore. The perpendicular configuration at the C(8)-aryl b ond contributes to the efficiency of the on/off-switching behavior. In corporation of the dye into a hydrogel matrix results in a transparent sensor membrane which can be used to measure the pH in the range of 1 -3. The sensor shows high signal intensity, good reproducibility, and the response characteristic is stable over hours of operation even at low pH-values.