Steady-state and fluorescence lifetime quenching of self-assembled diphenylalanine/coumarin nanostructures as a method to determine dissolved O2 in water

A fluorescent system formed by the combination of coumarin derivative and self-assembled peptide nanostructures was used as sensing system to determine dissolved oxygen (O2) in water samples. Detection was based on the sensing system fluorescence quenching by O2, measured by steady-state and time-resolved fluorescence spectroscopy and Stern-Volmer plot to correlate fluorescence intensity to O2 concentration in the samples. Also, fluorescence lifetime decays informed about the mechanisms in which the quenching is occurring, indicating that the sensing system is highly sensitive and selective to O2, since quenching occurs by a non-radiative energy transfer from electronic excited singlet states of the system to the O2 molecule. This process was evidenced by the system fluorescence lifetime decrease, yielding Singlet O2 as indicative that this system can also find other technological applications.