Nanocomposites enable us to tune parameters that are crucial for use of such materials for neutron-optics applications. By careful choice of properties such as species (isotope) and concentration of contained nanoparticles, diffractive optical elements for long-wavelength neutrons are feasible. Nanocomposites for neutron optics have so far been tested successfully in protonated form, containing high amounts of 1 H atoms, which exhibit rather strong neutron absorption and incoherent scattering. At a future stage of development, chemicals containing 1 H could be replaced by components containing more favourable isotopes, such as 2 H or 19 F. In this note, we present results of Monte-Carlo simulations of the transmissivity of various nanocomposite materials for thermal and verycold neutron spectra. Our simulation results for deuterated and fluorinated nanocomposite materials predict the losses due to absorption and scattering to be as low as 2%, as well as the broadening of the beam cross section to be negligible.