A coumarin-functionalized gold nanosensor connected to polypeptide chains was developed for the sensitive detection of caspase-3 based on a FRET process.

A new ligand 10-mercaptodecyl-1-iminodiacetic acid (MDIA) was synthesized and used to modify gold nanoparticles to provide a simple assay to repeatedly sense Cu²⁺ in the solution at room temperature. This functionalized gold nanosensor was applied for the detection of Cu²⁺ in water samples with sensitivity and simplicity. The chelation/aggregation process is reversible via addition of a strong metal ion chelator such as EDTA. This simple and fast colorimetric sensor is important in the application of copper ion detection in water quality during the emergency and early warning monitoring.