Sonochemical shape control of copper hydroxysulfates

Shape control of inorganic nanoparticles generally requires the use of surfactants or ligands to passivate certain crystallographic planes. Additive free shape control methods utilize the differences in the growth rates of crystallographic planes. We combined this approach with the sonochemical method to synthesize copper hydroxysulfate (Brochantite) with morphologies ranging from flowers, to bricks, belts and needles. Sodium peroxydisulfate, which was used as the sulfate and hydroxide source, was decomposed thermally and/or sonically under various pH and temperature conditions. The relative release rates of the sulfate and hydroxide anions determined the final form of the crystals. This technique yielded products even at acidic pH, marking a distinction from the literature reactions, which start with stoichiometric amounts of sulfate and hydroxide anions and yield only a single crystal morphology.

► Brochantite was synthesized under sonochemical conditions without surfactants.
► Persulfate anion was the source of sulfate and hydroxide anions.
► Variation in pH and temperature leads to morphologies never observed before.
► Differences in morphology are related to the growth rate of the facets of the crystal.