Lead ion detection in turbid media by pulsed photoacoustic spectrometry based on dissolution of gold nanoparticles

In this paper, we present a pulsed photoacoustic configuration for the detection of lead ion in aqueous solution based on the dissolution of gold nanoparticle. The photoacoustic signal is generated by laser-induced nanobubble. This technique allows for a sensitive measurement of size changes of the gold nanoparticles in the presence of lead ions even in turbid samples. As a first step, the best gold nanoparticle size and concentration were determined. Using 1.25 nM of gold nanoparticle with a diameter of 11 nm containing 1 mM of 2-mercaptoethanol, a linear range from 1 nM to 2.5 μM and a limit of detection of 0.5 nM were obtained. Then, to study the response of our system to strong light scattering in the medium, the scattering coefficient of samples containing lead ions was incremented using spherical silica particles (diameter 500 nm). The results corroborate that the technique used in this work is almost insensitive to light scattering.