Infrared fluorescence sensing of submicromolar calcium: pushing the limits of photoinduced electron transfer

A heptamethine cyanine–BAPTA conjugate was synthesized which signals calcium binding by an almost 4-fold increase in the emission intensity at the emission maximum of 782 nm. This significant enhancement factor opens new possibilities for the development of IR fluorescent chemosensors excitable with an inexpensive 780 nm laser diode and detectable with highly sensitive avalanche diodes.