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 (I-0/I) and the concentration for Cu2+ ions from 0 to 10 mu M (R-2 = 0.9858). The resolution of this sensor detected by a commercial hand-held spectrometer was about 0.9 mu M 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. (C) 2012 Elsevier B.V. All rights reserved.