Formation process of Cu2(OH)2CO3 and CuO hierarchical nanostructures by assembly of hydrated nanoparticles.

Cu2(OH)2CO3 and CuO hierarchical nanostructures with variable morphologies were synthesized by controlled heating hydrated nanoparticles. The growth of nanostructures started with nanoparticles which formed loose aggregates. The nanoparticles within aggregates reorganized to form urchin-like structures which consisted of dense nanorods. With the growth of nanorods, regular microspheres were formed. At the same time, the nanorods coalesced to form wedge-like structures. The various surface subunits were just the outer display of wedge-like structures under different conditions. CuO nanostructures were gained by pyrolysis of malachite precursors. The attractive electrostatic force was responsible for aggregation of nanoparticles. During growth of aggregates, nanorods acted as growing tips which adsorbed adjacent nanoparticles. The Brownian motion was responsible for reorientation of nanoparticles to achieve low-energy configuration. Adsorbed water played an important role during formation of malachite nanostructures. The effect of growing environments on nanostructures was investigated. XRD, SEM, TEM and BET and so on were used to characterize the products.