A differentially selective chemosensor for a ratiometric response to Zn2+ and Al3+ in aqueous media with applications for molecular switches

A multifunctional fluorescent chemosensor (PMN) for Al3+ and Zn2+ has been developed, which displays a dual-mode and "off–on" fluorescence response upon addition of Al3+ or Zn2+ at two different wavelengths. This was possibly due to the inhibition of PET and CN isomerism, and the activation of chelation-enhanced fluorescence (CHEF). Moreover, PMN exhibited a preferential second mode of selectivity for Al3+ as it ratiometrically displaces Zn2+ from the [PMN + Zn2+] complex. Such fluorescence modulation behavior mimics the performance of an "OR" logic gate. It also shows an excellent performance in the "dipstick" method.