Theoretical insights into sensing performances of rhodamine-contained two-photon fluorescent probes for mercury ion

摘要

Acting as a caustic element with high cellular toxicity, mercury may cause serious damage to the neurological and endocrine systems of the living body. Hence, the rapid detection of mercury ions is of significant importance. In this work, photoabsorption and photoemission properties of a series of newly synthesized mercury ion chemosensors based on rhodamine is investigated using the time-dependent density functional theory. It shows that the fluorescent peaks of the probes are greatly redshifted from about 450 nm to about 530 nm with 5 to 12 times the fluorescence enhancement after reacting with mercury ions. Special attention has been paid to understanding the response mechanism of the probes, and the recognition of mercury ions controlled by the fluorescence resonance energy transfer process is verified theoretically. More importantly, the quadratic response theory has been used to calculate two-photon absorption properties of these novel chemosensors. With the presence of mercury ion, a two-photon absorption cross section for the studied probes increases from 35, 19, and 20 GM (1GM=10(-50)cm(4)s/photon) to 155, 147, and 63 GM, respectively, indicating the feasibility of the probes to be used in two-photon fluorescent microscopy imaging. The investigations demonstrate the donor effect on sensing performance of the sensors, which helps people to understand the structure-property relationships and further design more effective two-photon fluorescent probes for mercury ions.