Enhanced sensitivity of fluorescence-based Fe( ii ) detection by freezing

The first example of combining the fluorescent probe-based freeze concentration effect with N-oxide chemistry is reported for the highly sensitive and selective detection of ferrous ion (Fe(ii)). Interestingly, our preliminary results demonstrated that the fluorescence intensity of Fe(ii) was markedly enhanced upon freezing, and the location of Fe(ii) in the freezing state was visualized by confocal microscopy using a cryostage.