Yolk-shell structured Au@Ag@mSiO(2) as a probe for sensing cysteine enantiomers and Cu2+ based on circular dichroism

摘要

A yolk-shell structured Au@Ag@mSiO(2) probe was fabricated by coating a layer of mesoporous silica on the surface of a Au@Ag core-shell nanosphere, followed by partially removing the Ag shell. Mirror symmetrical chiral signals at similar to 258 nm in the UV region were observed for the probe upon coupling with cysteine enantiomers on the surface of Au@Ag. The intensity of the CD signal of the probe is enhanced by increasing l/d-Cys concentration, allowing the quantitative determination of the cysteine enantiomers. The developed method shows an excellent linear relationship between the CD signal and l-Cys concentration ranging from 10 mu M to 90 mu M with a limit of detection of 8.5 mu M. In the presence of Cu2+, the CD signal of the probe weakened due to the oxidation of l-cysteine to l-cystine catalyzed by Cu2+. Based on this phenomenon, a new strategy for the detection of Cu2+ can be developed. Under the optimized conditions, the CD signal decreases linearly with the log of the concentration of Cu2+ in the range from 1 to 250 nM with a detection limit of 0.1 nM.