Ultrasensitive detection of lead (II) ion by dark-field spectroscopy and glutathione modified gold nanoparticles

Abstract Exposure to trace amounts of lead is known to harm human health, especially for children, which results in irreversible detriment to brain and nerve development. However, most of the sensor platforms using the colorimetric method to detect lead (II) ions (Pb2+) are difficult to reach a decent limit of detection (LOD) and a large detection range. This work presents a practical method to detect Pb2+ in aqueous-medium with the help of single-particle dark field spectroscopy, which allows us to obtain good LOD and wide detection range. Our results illustrate that the glutathione functionalized AuNPs are able to capture free AuNPs in the presence of Pb2+ to form multipliers. Such a process results in a significant spectral redshift of scattering spectra due to plasmonic coupling, which allows us to reach a good LOD of 3.5 pM, and a large linear quantifiable detection range from 10 pM to 10 µM. The performance of our sensor platform provides an alternative way to detect traces of Pb2+ in real-life water samples.