A Glimpse Into The Nature Of Particles Created During Pulsed Laser Ablation Of Arsenic Compounds In Ambient Gases

Abstract

: The composition of particles resulting from pulsed laser ablation is not well understood, although it is anticipated that molecules from the ablated material undergo varying degrees of breakdown, depending on factors such as laser wavelength, energy, pulse width, matrix properties, and gas atmosphere. As reliable arsenic characterization and speciation techniques are available, a fundamental study was undertaken to shed light on the behavior of arsenic compounds (arsenic pentoxide, dimethylarsenic acid, and arsenobetaine within a cellulose matrix, along with pure elemental arsenic), using a pulsed 213 nm Nd:YAG laser and ablation in different gas atmospheres (He, Ar/CO 2 [99/1 %], Ar/O 2 [80/20 %], and O 2 ) at atmospheric pressure. The generated arsenic, collected in aerosol form on inline syringe filters (0.2 μm), was subjected to sequential dissolution, yielding water-soluble, HCl-soluble, and insoluble fractions. The water-soluble fraction was analyzed for arsenic species using chromatographic techniques in combination with element-specific detection. The analysis revealed that extremely complex processes take place during laser ablation, not only (partially) stripping organoarsenic species from their methyl groups and lowering the valence state, but also creating conditions for the synthesis of methylated arsenic species from arsenic pentoxide and generating more or less soluble nano/micro/macro particles for all arsenic compounds. These findings contribute to a more nuanced understanding of the multifaceted photochemical transformations that may occur during laser ablation of molecules.