Tb-Metal Organic Frameworks-Referenced Bathocuproine Disulfonate Enable Fluorescence Distinguishing Cu+ from Cu2+

As the main existing form of copper, Cu+ plays vital roles in human health. It is highly significant to detect Cu+ selectively in biological matrixes especially in the coexistence of Cu2+. Herein, a ratiometric fluorescence sensor has been fabricated to discriminate Cu+ from Cu2+ and realize ratiometric detection of Cu+ by using Tb-MOFs and bathocuproine disulfonate (BCS). The sensor exhibits two fluorescence emissions at 400 nm from BCS as the response signal and 548 nm from Tb-MOFs as the reference signal. BCS can chelate with Cu+ selectively to form a stable adduct, inducing the fluorescence quenching of BCS through static quenching. When Cu+ is added, the intensity at 400 nm decreases significantly while that at 548 nm changes negligibly. Notably, the presence of Cu2+ exhibits no effect on the emissions both at 400 nm and 548 nm. Thus, Tb-MOFs-BCS system enable discrimination of Cu+ from Cu2+ and fast ratiometric detection of Cu+ within 1 min. The fluorescence ratio (F548/F440) shows a good linear relationship in Cu+ concentrations ranging from 1-200 nM with a low limit of detection of 0.3 nM, which is 1-3 orders magnitude lower than those of other methods. The high selectivity and sensitivity of this method enables the detection of Cu+ in human serum successfully.