Molecules of zinc tetraphenylporphyrin were adsorbed on the surface of quantized MoS2 particles in water with a small amount of ethanol (95/5). Triplet decay kinetics of zinc tetraphenylporphyrin was studied by nanosecond laser flash photolysis and found to be strongly dependent on the ground state and triplet contents on the surface due to the triplet-ground state interaction and triplet-triplet annihilation. Monte Carlo calculations were performed to fit experimental triplet, decay kinetics.