The Z-scanning method is used to study nonlinear absorption in associates of colloidal zinc sulfide nanoparticles and organic dyes. The nonlinear absorption coefficients of associates of various dyes [thionine, erythrosine, and a pyridine salt of 3,3′-di-(γ-sulfopropyl)-4-4′,5-5′-dibenzo-9-ethylthiacarbocyanine betaine] and ZnS nanoparticles with a mean size of 2 nm are obtained at wavelengths of 1064 and 532 nm of 40-ps pulsed radiation of a YAG:Nd3+ laser. It is presumed that the nonlinear absorption of the ZnS nanoparticles at 1064 nm is caused by three-photon excitation of luminescence centers. The association of the dye molecules with the ZnS nanoparticles reduces the dip in the Z-scanning curves, and this is caused by the acceptor properties of the dyes and probably by the transfer of electron excitations from the luminescence centers of the ZnS nanoparticles to the dye molecules.
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