A novel fluorescence enhanced route to detect copper(II) by click chemistry-catalyzed connection of Au@SiO2 and carbon dots

Pursuing for a simple, sensitive and inexpensive method of detecting copper ions is very essential for both environment and human health. Herein, a new strategy for fluorescence detection of Cu 2+ was designed which is based on the reduction of Cu 2+ to Cu + by sodium ascorbate to get cycloaddition reaction between 4-azidobenzoic acid-tagged Au@SiO 2 and propiolic acid-tagged carbon dots (CDs). The proposed approach not only possesses a good selectivity, but also has a linear relationship between the fluorescence intensity and the concentrations of Cu 2+ in the range of 0.1–100   nM with the detection limit of 0.08   nM (5.12   ×   10 −9   mg   mL −1 ), which is far below the limit value of 1.3   mg   mL −1 defined by U.S. Environmental Protection Agency in drinkable water. In the actual sample, the standard deviation ranges from 97.6% to 101.8%, indicating the high precision of present approach.