Langmuir isotherm is applied to analyze the laser-induced fluorescence from solutions containing silver nanoparticles and tris(2,2'-bipyridyl)ruthenium(II) chloride. Fluorescence enhancement factors based on the simple adsorption model are found to be 47-90, depending on the nanoparticle concentration. The enhancement is attributed to the laser-induced free-carrier absorption on the silver surfaces, which is a reverse saturable absorption process, at the excitation wavelength of 532 nm.