A soft templating method has been developed for the synthesis of hollow polydopamine nanocapsules with adjustable shell thickness. The method involves the use of an aqueous miniemulsion comprising submicron-size toluene droplets as templates. Dopamine polymerization is conducted at room temperature in the aqueous phase and/or at the droplet surfaces, thus forming hollow polydopamine nanocapsules. The core size is determined by the size of the initial toluene droplets, whereas the shell thickness can be readily tuned by adjusting the initial amount of dopamine. Nanocapsules of diameters as low as similar to 50 nm can be readily prepared using this novel approach. Dialysis was demonstrated to be an effective technique for removal of surfactant, hexadecane and unreacted monomer. This creative one-step method provides a new approach to the synthesis of hollow polydopamine nanocapsules, which has the potential to dramatically expand their commercial applications. (C) 2016 Elsevier Ltd. All rights reserved.