Highly sensitive and selective sensor based on silica-coated CdSe/ZnS nanoparticles for Cu2+ ion detection

A high performance fiber-optic sensor for Cu2+ ions is proposed based on monodispersed hydrophobic CdSe/ZnS nanoparticles encapsulated within a silica shell and immobilized on the tip of an optical fiber by a polyvinyl alcohol (PVA) polymer coating. The experimental results show that the core–shell CdSe/ZnS@SiO2 nanostructure exhibits a strong reduction in luminescence intensity following interaction with Cu2+ ions. The porous silica shell of the nanostructure also plays a key role in the fluorescence quenching process by preventing the aggregation of the CdSe/ZnS nanoparticles; thereby promoting the adsorption of the Cu2+ ions. There were linear relationships between the relative fluorescence intensity (I0/I) and the concentration for Cu2+ ions from 0 to 10 μM (R2 = 0.9858). The resolution of this sensor detected by a commercial hand-held spectrometer was about 0.9 μM and therefore it is an ideal solution for applications in chemical and medical detections. The use of a silica-coated CdSe/ZnS QD has a number of key advantages as compared to the organic ligand modified QDs, including better selectivity, higher sensitivity, better chemical stability, and more stable with wide pH value.