A method for controlling starting of an internal combustion engine in a hybrid electric vehicle powertrain having multiple power flow paths to vehicle traction wheels from the engine and from an electric motor. The outer track conveyor member surrounds the inner track conveyor member. The core-shell structure, in which the inorganic materials are core and the organic materials are shell, is formed by first wrapping the inorganic materials with the organic materials in the same reactor. The first groove has a size greater than that of the second groove.