Fluorescent porous organic cage with good water solubility for ratiometric sensing of gold(III) ion in aqueous solution

Fluorescent porous organic cage with good water solubility is of great interest but still challenging for its fluorescent sensing application. Poor water solubility and single signal of most previous probes are unfavorable for the monitoring of Au3+ generated from the potential dissociation of gold nanoparticles in environmental and biological samples. Here we report a water-soluble porous organic cage as a ratiometric fluorescent probe for Au3+ in aqueous solution. The prepared porous organic cage with good water solubility showed specific redox interaction with Au3+ in pH 5, leading to the change of dual emission at 420 and 484 nm. Based on the change of fluorescence ratio, a simple ratiometric sensing method for Au3+ from the dissociation of gold nanoparticles in aqueous solution was developed. The proposed method gave a calibration function of F484/F420 = 0.0370[Au3+] + 0.5689 (where F484/F420 is the intensity ratio of fluorescence at 484 nm to that at 420 nm; [Au3+] in μM) (R2 = 0.9975) in the concentration range of 1–60 μM, the limit of detection (3s) of 8 nM, and the relative standard deviation of 0.26% for 10 replicate detections of 50 μM Au3+. The recoveries of spiked Au3+ in domestic wastewater and human serum samples ranged from 94.66% to 105.61%.