Dyes-modified metal − organic frameworks composite as a sensitive, reversible and ratiometric fluorescent probe for the rapid detection of malachite green

• A novel ratiometric fluorescent probe 9-AA/RhoB@UiO-66-(COOH) 2 composite for malachite green was developed. • The probe exhibits excellent performances including good recyclability, rapid response, high sensitivity, good and stability. • The sensing mechanisms were explored systematiclly. • The probe was successfully exploited for sensing malachite green in real samples. In this work, a recyclable, sensitive, highly-stable and ratiometric fluorescent nanoprobe, 9-AA/RhoB@UiO-66-(COOH) 2 composite, has been designed and successfully developed by immobilizing acridin-9-amine (9-AA) and rhodamine B (RhoB) dyes on the surface of a carboxyl-functionalized metal–organic frameworks, UiO-66-(COOH) 2 , based on the strong electrostatic interaction. This probe exhibits characteristic emission bands at 432 and 460 nm originated from 9-AA and 603 nm originated from RhoB under the single excitation of 365 nm. After continuous addition of malachite green (MG), the blue emission was relatively unchangeable, whereas the red emission of 9-AA/RhoB@UiO-66-(COOH) 2 composite was significantly quenched, and the ratio of fluorescence intensity (F 460 /F 603 ) was linear with the concentration of MG in the range of 0–7.75 μM with a low limit of detection (LOD) of 0.079 μM. This probe can be facilely recycled by centrifugation and washing with ethanol. Furthermore, this proposed sensing system exhibits outstanding performances including rapid response, high sensitivity, good specificity and stability. This work will provide us a new research platform for MG sensing.