A quantum dot, which is an ultrafine grain, has a core-shell structure having a core portion and a shell portion protecting the core portion. The surface of the shell portion is covered with two kinds of surfactants, a hole-transporting surfactant and an electron-transporting surfactant, which are concurrently present. Moreover, the hole-transporting surfactant has a HOMO level which tunneling-resonates with the valence band of the quantum dot and the electron-transporting surfactant has a LUMO level which tunneling-resonates with the transfer band of the quantum dot. Thus, a nanograin material which has good carrier transport efficiency and is suitable for use in a photoelectric conversion device is achieved.