Directional Freezing of a Nanoparticle Suspension to Increase the Sensitivity of Laser-Induced Breakdown Spectroscopy

The paper proposes and investigates a method for increasing the sensitivity of laser-induced breakdown spectroscopy by directed freezing of particle suspensions. When certain freezing conditions are met, particles are displaced by the phase-interface front and are concentrated on the surface, thus increasing the intensity of emission lines. This method implemented two freezing configurations wherein one results in the formation of a densely packed flat layer of particles and the other concentrates particles in a small volume on the sample surface. In the first case, with unidirectional front movement, the signal is amplified to a maximum of 15 to 20 times compared to a liquid sample. The concentration in a small volume made it possible to increase the intensity by almost an order of magnitude compared to unidirectional freezing with low particle concentrations. This method can be used both for studying the elemental analysis of the particles themselves and the substances adsorbed on their surface.