Iodide-assisted silver nanoplates for colorimetric determination of chromium(III) and copper(II) via an aggregation/fusion/oxidation etching strategy

The authors have studied the role of different ligands on the surfaces of silver nanoplates for regulating their analytical applications. Citrate-capped silver nanoplates are applied for the detection of chromium ions (Cr3+) based on aggregation of silver nanoplates. Cr3+ can cause aggregation through high affinity between Cr3+ and carboxylate groups of citrates, resulting in a color change from dark yellow to purple and at last colorless. The detection limit is 8.0 nM. This system shows excellent selectivity in the presence of a variety of other metal ions. Further, silver nanoplates coupled with iodide ions are employed for the colorimetric determination of copper ions (Cu2+) based on a new strategy of fusion/oxidation etching nanoplates. When Cu2+ is introduced into this silver nanoplate system, Cu2+ can oxidize I− to iodine (I2), which can further oxidize silver to form silver iodide (AgI). Simultaneously, the solution color changes from dark yellow to colorless. The lower limit detection is 0.27 μM. This assay exhibits excellent selectivity for Cu2+ over other environmental metal ions. It is perceived that this design concept will open up a fresh insight of simple, rapid and reliable detection of other heavy metal ions in drinking water and environmental samples.