Inhibiting proton interference in PET chemosensors by tuning the HOMO energy of fluorophores

Fluorescent chemosensors are widely used in chemical engineering, bio-engineering, medical engineering, and environmental engineering. A lot of the chemosensors are based on photo-induced electron transfer (PET) process. In complicated practical systems, the proton is always the most serious interference factor. Herein a new method is proposed for PET chemosensor design to overcome the proton interference: to tune the ΔG of the electron transfer process by introducing different substituents of the sensor molecules. Chemosensors for Zn2+ detection are demonstrated. When the highest occupied molecular orbital (HOMO) energy levels of the fluorophores (4-substituted 1, 8-naphthalimide) are lower than the HOMO energy level of protonated receptor (dipicolylamine-H+), the fluorescence responding to Zn2+ ions is not influenced by pH, meanwhile, the chemosensors can work in acidic media with pH below the pKa values. This should reveal a new criterion for designing of PET based chemosensors for selectivity improvement.