Sonotriboluminescence of aqueous suspensions of ZnS and Tb (acac)3•H2O crystals

Intense sonotriboluminescence was found under sonication on aqueous suspensions of ZnS and Tb(acac)3 center dot H2O crystals. These materials with intense triboluminescence are basic for many other luminescent applications, but their sonotriboluminescence in aqueous suspensions was still not studied. A broad band with a maximum at 470 nm and a side band at around 540 nm were observed in the sonotriboluminescence spectrum of zinc sulfide suspension. An intense emission of the Tb3+ ion was recorded with maxima at 488, 544, and 585 nm for a suspension of terbium acetylacetonate. These sonotriboluminescence spectra coincide with the photo-luminescence spectra of crystals. The sonication on aqueous suspensions leads to fragmentation and increases the active surface, the defects in the crystals involved into the luminescence excitation. It is shown that emission intensity during sonotriboluminescence of Tb(acac)3 center dot H2O suspensions is 400 times higher than that during sonoluminescence of terbium salts aqueous solutions. A possible mechanism for the excitation of sono-triboluminescence of zinc sulfide and terbium acetylacetonate aqueous suspensions is discussed. Obviously, the excitation of emitters under sonication of aqueous suspensions occurs during recombination of charges in crystals electrified upon their high-speed collisions. The sonotriboluminescence can be useful for developing a spectro-scopic method qualitatively monitor suspensions.