Combining localized surface plasmon resonance with anodic stripping voltammetry for heavy metal ion detection

In this proof-of-concept study, we proposed a dual detection method for heavy metal ions based on nanostructured sensor device. This sensor device, named nano Lycurgus cup array, was characterized with hybrid structure of nano-scaled cups and gold nanoparticles. The hybrid periodic nanostructure could trigger localized surface plasmon resonance (LSPR) phenomenon, which was highly sensitive to refractive index changes. Then electrochemical measurement of anodic stripping voltammetry (ASV) was combined with LSPR for synchronous heavy metal ions detection, i.e., galvanizing metal ions onto the surface of the nanodevice whilst quantitatively recording electrochemical signals. Combining the electrochemical method with LSPR measurement, the dual detection system demonstrated a detection limit of part-per-billion level for aqueous heavy metal ions, such as lead, copper, and zinc. The LSPR measurement demonstrated a higher signal to noise rate (SNR) than electrochemical measurement and promising accuracy even with the presence of mixed solution, and was proved immune to the mechanical fluidic disturbance during the stripping phase which would deteriorate electrochemical signal in traditional electrochemical voltammogram. By presenting electrochemical signals on the dimension of LSPR, our method could be applied in highly integrated detection systems for on-spot detection.