Laser-induced breakdown spectroscopy (LIBS) is a rapid chemical analysis technology that is well developed for the analysis of trace elements in gases, liquids, and solids. It uses a high power laser pulse to induce a short duration high temperature plasma in the sample. As the plasma cools, it emits spectral peaks corresponding to the elements in the periodic table. Recent research has extended LIBS via filament-induced breakdown spectroscopy (FIBS), which has better sensitivity and greater stability. However, FIBS is intrinsically limited by the intensity of the guided laser in the filamentation itself.
Plasma grating-induced breakthrough spectroscopy (GIBS) could overcome the limitations of FIBS. However, efficient laser ablation in liquid remains a major challenge because plasma excitations are hampered by the inevitable formation of shock waves and microbubbles, as well as dramatic changes in liquid pressure surrounding the ablation region.
As published in Advanced Photonics Nexus, researchers have recently combined FIBS and GIBS as an effective technique for the sensitive detection of trace metals in liquid. They demonstrated the combination of strong non-linear interactions of filaments (coplanar and non-collinear) with different plasma lattices, to achieve a technical innovation called “F-GIBS” (Filament and Plasma Lattice Induced Breakdown Spectroscopy). F-GIBS was implemented using liquid jets for the analysis of aqueous solutions.
This plasma excitation technique properly avoids the harmful effects of fluid surface fluctuations and bubbles created by powerful plasma explosions. Two femtosecond laser beams are coupled non-collinearly to establish plasma gratings that cover almost the entire jet and excite the liquid sample. The third filament was aligned to nonlinearly connect to the plasma grids in the same plane (perpendicular to the liquid jet). Nonlinearly coupled filaments entered the liquid jet across the air-water interface without random filament breakage.
According to senior author Heping Zeng, a professor at the State Key Laboratory of Precision Spectroscopy of East China Normal University, “F-GIBS provides a promising technique for detecting trace elements in aqueous solutions with improved sensitivity. Regenerative excitations of plasma gratings presented in this work can serve to improve some other already well-developed two-pulse LIBS techniques, such as plasma reheating and laser-induced fluorescence, with plasma re-excitation in much shorter time delays, facilitating the convenient use of lasers from the same sources. “
Reference: Hu M, Li F, Shi S, et al. Detection of trace metals in water by filament-induced breakthrough spectroscopy and plasma gratings. APN. 2023;2(1):016008. doi: 10.1117/1.APN.2.1.016008
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