Ratiometric sensor based on Ag⁺-mediated luminescence of Tb-DNA complexes for visual detection of 4-aminophenol

Development of accurate, convenient and portable methods for monitoring 4-aminophenol (4-AP) is extremely important because of its strong toxicity. Here, a ratiometric fluorescence sensor based on Ag⁺-enhanced luminescence of Tb-DNA complexes has been presented for the detection of 4-AP. The luminescence of Tb-DNA complexes is enhanced about 30 times by Ag⁺, which can trigger energy transfer from DNA to Tb³⁺ more efficiently. In the presence of 4-AP, Ag⁺ can be reduced into Ag⁰ owing to its strong reducibility, inducing the decrease of Tb-DNA complexes at 545 nm remarkably. Besides, 4-AP exhibits intrinsic fluorescence at 375 nm under the same conditions. Therefore, ratiometric detection of 4-AP can be achieved using F₃₇₅/F₅₄₅ as readout with a detection limit of 0.4 μM. Real water samples have been tsted to evaluate this method in practical application and satisfactory results have been obtained. Furthermore, the addition of 4-AP into Tb-DNA-Ag⁺ system induces a visible color variation from green to bluish violet, enabling visual detection of 4-AP under the assistance of a smartphone.