Abstract: Organic semiconductor nanoparticles composed of fullerene C60 and/or metal-free phthalocyanine (denoted as Pc) were synthesized by a reprecipitation method, in which N-methyl-2-pyrrolidone (NMP) solutions dissolving C60 and/or Pc were injected into another solvent (e.g., water or ethanol, denoted as poor solvent). The - interaction between C60 and Pc molecules in the mixed NMP solution was confirmed as observing charge-transfer absorption band in the absorption spectrum. Therefore, it is presumed that the prepared composite nanoparticles consist of donor-acceptor (D-A) structure, which is in accordance with the X-ray diffraction result. The nanocomposites average size and morphology can be controlled by using different poor solvents or varying volume ratio of the NMP solutions to the poor solvent. Moreover, the obtained nanoparticles combined with Nafion were used as photocatalysts to remove trimethylamine (TMA). The sample containing the nanocomposites showed better activity to remove TMA than that containing only C60 or Pc nanoparticles under visible light, indicating that D-A structure is helpful to enhance the photocatalytic activity of the nanoparticles. The present research demonstrated a novel organic photocatalyst featuring D-A structure.