Tuning plasmon absorption of unmodified silver nanoplates for sensitive and selective detection of copper ions by introduction of ascorbate

Silver nanoplates as novel optical sensors for Cu2+ detection have been demonstrated. Silver nanoplates are synthesized via previous H2O2–NaBH4 cyclic oxidation–reduction reactions. With introduction of ascorbate as mild reductants, Cu2+ ions are reduced into Cu+ and the Cu+ is further reduced to Cu, which is deposited on the surface of the silver nanoplates. The deposition of the Cu on the surface of the silver nanoplates allows a significant red-shift of their plasmon absorption. Therefore, trace Cu2+ can be detected. The shift of the plasmon absorption wavelength of silver nanoplates is proportional to the Cu2+ concentration over a range of 40–340 μmol L−1 with a limit of detection of 9.0 μmol L−1. Moreover, such silver nanoplate-based optical sensors provide good selectivity for Cu2+ detection, and most other metal ions do not disturb its detection. Moreover, the practicality of the proposed sensor was tested. This Cu2+ assay is advantageous in its simplicity, selectivity, and cost-effectiveness.

Graphical abstractWith introduction of ascorbate as mild reductants, Cu2+ ions are reduced into Cu+, and the Cu+ is further reduced to Cu to deposit on the surface of the silver nanoplates, as confirmed by HR-TEM analyses. The deposition of the Cu on the surface of the silver nanoplates allows a significant red-shift of their plasmon absorption (44 nm shift), which provides an optical sensor for sensitive and selective detection of copper ions.Figure optionsDownload full-size imageDownload as PowerPoint slide