Large-scale synthesis of paratacamite nanoparticles with controlled size and morphology

A facile one-step procedure using epoxide as precipitation agent was applied to prepare paratacamite (γ-Cu₂(OH)₃Cl) nanoparticles with well-controlled size and morphology on a large scale at room temperature. The maximum production capacity in single reaction is as much as about 80 g, which is only limited by the volume of the facilities used in the laboratory. During the preparation, the hydrolysis of aquo complexes of metal ions was promoted by the ring opening reaction of epoxide through protonation of its oxygen. Owing to the low acidity of aquo Cu²⁺ complexes in solution, their partial hydrolysis occurred without further condensation of the generated hydroxide intermediate, resulting in the formation of precipitate instead of sol or gel. This induced the interposition of Cl^- ions into intermediate to form the structure of γ-Cu₂(OH)₃Cl. The chlorinated alcohol compound, resulting from the reaction, functionalised the surface of particles, leading to the high re-dispersibility of obtained powder in water and ethanol. As confirmed by the characterisation results, the particle size increased with the increasing of Cu²⁺ concentration and reaction time. On the other hand, by changing the precipitation agent, the morphology of the particle was transformed from cubic shape under using propylene oxide to the spherical shape that was composed of agglomerated small nanoparticles by using cyclohexene oxide.