Fabrication of N-acetyl-l-cysteine-capped CdSe-polyelectrolytes @ Hydroxyapatite Composite Microspheres for Fluorescence Detection of Cu2+ Ions

N-Acetyl-l-cysteine-capped CdSe-polyelectrolytes @ hydroxyapatite (NAC-CdSe-PEs@HA) composite microspheres were fabricated through a stepwise layer-by-layer method and used for fluorescence detection of Cu2+ ions. The hollow HA microsphere was confirmed to be an ideal host to load CdSe quantum dots (QDs) due to their large surface area, well-defined porous structure, and large inner hollow size. Furthermore, the introduction of polyelectrolyte layers contributed to the increase of the loading amount and the electrostatic interaction between microsphere and QDs. Experiments results showed that among various metal ions investigated, Cu2+ exhibited the highest quenching effect on the fluorescence of CdSe QDs loaded in the composite microspheres. Additionally, the composite exhibited improved sensibility in detecting Cu2+ due to the presence of HA microspheres. Importantly, it is easy to separate and recycle the composite microspheres from the detection solution due to their relatively large size and high stability, thereby avoiding secondary contamination.