Highly selective and sensitive determination of copper ion based on a visual fluorescence method

A novel ratiometric fluorescence sensor for rapid and on-site visual detection of Cu 2+ was designed and synthesized by integrating yellow-emission rhodamine fluorophore (RL) and red-emission CdTe@SiO 2 QDs. The as-prepared nanohybrid fluorescence sensor shows dual-emissions at 537   nm and 654   nm under a single excitation at 500   nm in the presence of Cu 2+ . Owing to the strong chelating ability of RL toward Cu 2+ , the yellow fluorescence of RL could be selectively enhanced while the red fluorescence of CdTe QDs is almost unchanged, leading to an obvious fluorescence color change from red to yellow, which could be used for visual and ratiometric detection of Cu 2+ . This nanohybrid sensor exhibits excellent selectivity, sensitivity and anti-interference to Cu 2+ detection and the detection limit is as low as 8.4   nM. Additionally, a simple device test strip for rapid and on-site detection of Cu 2+ has been designed by immobilizing the RL-CdTe@SiO 2 QDs on a common filter paper. This simple and effective paper-based sensor has a visual detection limit of 0.5   μM, showing its promising application for on-site and rapid sensing of Cu 2+ in pollution water.