Fluorescence of nanoparticles of organic matter dissolved in natural water

The fluorescence of nanoparticles of dissolved organic matter under 270-, 310-, and 355-nm excitation is studied for different molecular fractions. The fluorescence quantum yield of the colloidal (molecules of size 5–200 nm) and low-molecular-weight (molecules smaller than 5 nm) fractions are obtained. It is shown that the spectral position of the fluorescence peak depends on both the size of the molecules and the excitation wavelength.