A colorimetric and fluorescent pH probe for imaging in E. coli cellsElectronic supplementary information (ESI) available. See DOI: 10.1039/c6ra24885c

A colorimetric and fluorescent pH probe 1-(4-methylphenyl)-3-(4-dimethylaminophenyl) acrylketone ( MDAK ) was facilely prepared. The probe exhibited strong pH-dependent behavior and responded linearly and rapidly to minor pH fluctuations within the range of 1.53-3.96. In addition, MDAK displayed a notably large Stokes shift of 121 nm. MDAK possessed a highly selective response to H + over other metal ions, amion acids and displayed good photostability and excellent reversibility. Furthermore, it can be applied to visualize extreme acidity in E. coli cells. MDAK exhibited turn-off fluorescence as the pH decreased. Simultaneously, the color of the solution changed from yellow to colorless.