New pyrazoline-basedpHfluorescentprobeshavebeensynthesizedandcharacterized.Theseprobes
respond toacidicpHwithshortresponsetime(lessthan1min),highselectivityandsensitivity.They
have goodreversibilityandnearlynointerferencefromcommonmetalions.Theseprobesaresuitablefor
strong acidconditionsandcanquantitativelydetectpHvaluebasedonequilibriumequation,pH = pKa −
log(Ia − Ix)/(Ix − Ib)
, withverygoodlinearrelationship.Moreover,using 1H NMRanalysis,weverified
that theprotonationofthenitrogeninthiazoleweakenedthethiazolering’sabilitytodonateelectrons
to pyrazolinemoietyandchangedtheintramolecularchargetransferthatwasactuallythemechanism
of thefluorescencequenchingphenomenonunderstronglyacidicconditions.Moreimportantly,these
probes canimagestrongacidityin Saccharomyces cerevisiae.