Theoretical Insights on the Sensing Performance for Newly-synthesized Two-photon Fluorescent N₂H₄ Probes Based on...

The development of fluorescent probe for hydrazine (N₂H₄) detection has attracted much attention due to the important role of N₂H₄ plays in the fields of medicine, agriculture, biology and environments. In this paper, the optical properties and water solubility of two novel two-photon fluorescent molecular probes (Probe1 and Probe2) before and after the reaction with N₂H₄ are studied by using the density function theory. The results show that electronic distribution and transition dipole moment of the probes are obviously changed after the reaction with N₂H₄, thus the optical properties of the molecules are influenced and the detection of N₂H₄ are realized. In addition, photoinduced electron transfer processes for Probe1 and Probe2 in the presence of N₂H₄ are theoretically characterized, which explains the experimental observations from the microscopic mechanism. Special attention has been paid on the analysis of the two-photon absorption for the probes with the absence and presence of N₂H₄ by the response theory method. Both probes with good water solubility show large variation on the two-photon absorption cross section when reacts with N₂H₄. In particular, the two-photon absorption response of Probe2 is more obvious, so it possesses preferable two-photon fluorescence microscopic imaging ability. More importantly, the receptor effect on the sensing performances of the probes are demonstrated, providing a theoretical reference for the design and synthesis on more efficient two-photon fluorescence N₂H₄ probes. Our study provides necessary information on the response mechanism of the studied chemosensors and helps to establish the relationship between the structure and optical properties of two-photon fluorescence N₂H₄ probes.