Simultaneous and instrument-free detection of quinine and crystal violet based on a dual-emissive Eu3+-functionalized metal-organic framework.

Simultaneous detection and quantification of multi-targets is a challenge using one single sensor in the complicated environment of real samples. Herein, we developed a dual-emissive sensor (EuUCHNA) that selectively and rapidly responds to crystal violet (CV) and quinine (QN), two commonly used anti-infective drugs for fungi, bacteria, and parasites, through distinct responsive modes. CV can effectively quench the blue and red fluorescent emission bands of EuUCHNA. By contrast, QN can remarkably enhance the blue emission band. The limit of detection (LOD) for CV and QN are 2.4 nM and 32.0 nM, respectively, which are superior to most of the reported sensors. EuUCHNA has been used to determine CV and QN in fish meat and fish pond water with good performance. Moreover, CV and QN can be simultaneously quantified by EuUCHNA in practical fish pond water. Furthermore, we constructed an instrument-free detection method via a smartphone with a color recognition app, which was successfully employed to detect CV and QN in fish pond water. This work provides a promising fluorescent sensor and a new analytical method for the simultaneous quantification of two targets in real samples using a single sensor.