Simultaneous ratiometric fluorescence determination and removal of copper ions by a magnetic nanocomposite

The exploitation of a bifunctional material for both identifying and extracting heavy metal ions (HMIs) is essential but still poses a major hurdle. In this work, a novel magnetic fluorescent nanocomposite (Fe₃O₄/CD@SiO₂-QD) was successfully prepared for the specific detection and removal of Cu²⁺. Magnetic fluorescent nanoparticles (Fe₃O₄/CDs) exhibiting blue fluorescence were synthesized via a one-step hydrothermal approach, and a magnetic ratiometric fluorescence sensor was prepared after SiO₂ and red fluorescent CdTe quantum dots were coated on the surface. When Cu²⁺ is present in the solution, the red fluorescence of the magnetic ratiometric fluorescence sensor is quenched, and the blue fluorescence remains essentially unchanged, resulting in a ratiometric fluorescence effect, which can be used for the sensitive determination of Cu²⁺; the magnetism can be used concurrently for the removal of Cu²⁺ to achieve detection and removal, and the detection results exhibit good linearity within the 2.5-100 μM range, with a limit of detection of 0.23 μM. This method was used for the spiked determination of copper ions in actual samples, with recoveries ranging from 93.02 to 107.31%. In addition, the sensor effectively removes Cu²⁺, and each gram of magnetic ratiometric fluorescence sensor can remove up to 72 mg of copper ions. Therefore, our prepared magnetic fluorescence sensor can introduce an innovative strategy for the determination and removal of copper ions in environmental or biological samples.