Single-Bubble Sonoluminescence of Suspensions of Nanoparticles of Al2O3, Cr2O3, and VK94-1 Ceramics in Water

As part of research on the development of sonoluminescence spectroscopy as a new analytical method, atomic and ionic lines and bands have been recorded in moving single-bubble sonoluminescence (M-SBSL) of a bubble in a standing ultrasonic wave in colloidal suspensions of Al2O3 and Cr2O3 nanoparticles (size < 50 nm) or VK94-1 corundum ceramics in water. In the spectra of this sonoluminescence with a resolution of ∆λ = 1.5 nm, atomic lines of Al and Cr were recorded, as well as molecular lines of SiO and ionic and atomic lines of Mn. The intensities of atomic lines can be used to determine the content of metal elements in the analyzed suspensions. The minimum detectable concentration, for example, of Cr was 2.5 × 10−4 mol/L. The electron temperature reached in the plasma core of the bubble at the end of the compression cycle (Te ≈ 7800 K) was determined from the distribution of relative intensities of atomic Cr lines. The obtained experimental data confirm the penetration of Al2O3 and Cr2O3 nanoparticles or VK94-1 ceramics into the cavitation bubble. This apparently predetermines the possibility of synthesizing ruby nanoparticles or nanoparticles similar to corundum ceramics in chemical composition from starting nanoparticles of a mixture of Al2O3 and Cr2O3 under high-temperature bubble plasma conditions. Thus, at a spectral resolution of ∆λ = 15 nm, the single-bubble sonoluminescence spectrum of a colloidal suspension of Al2O3 and Cr2O3 nanoparticles exhibits a band with a maximum at 695 nm characteristic of the photoluminescence of a suspension of ruby nanoparticles, as well as the photo- and sonoluminescence of a suspension of VK94-1 corundum ceramic nanoparticles.