Sonoluminescence spectroscopic analysis of samarium(II) in a colloidal suspension

Abstract

Colloidal suspensions of samarium(II)-containing nanoparticles with a size of up to 50 nm were prepared by multibubble ultrasonic dispersion of SmCl₂·0.5H₂O crystal powder with different contents in dodecane. During moving single-bubble sonolysis of these suspensions, a narrow band with a maximum at 704 nm, appeared in their luminescence spectra, against the broad structureless luminescence band (continuum), typical of most liquid–bubble systems. The recorded sonoluminescence band coincides in the position with the luminescence band of the Sm²⁺ ion in samarium chloride crystals, or in a suspension of samarium nanoparticles in dodecane. The appearance of the characteristic Sm²⁺ sonoluminescence band in the ultrasonic luminescence spectrum is caused by the entry of samarium salt nanoparticles into the moving (and thus deformed) bubble, which occurs by the known mechanism of injection of a liquid containing small nanoparticles through the deformed boundary of the gas cavity, and by the collisional electronic excitation of Sm²⁺ ions followed by emission of light in the bubble plasma, which periodically appears during the ultrasonic vibrations. The dependence of the maximum intensity of the Sm²⁺ band on the initial amount of dispersed samarium(II) salt was plotted, which can be used to determine Sm(II) on the basis of characteristic sonoluminescence intensity.