Low temperature synthesis of ZnO particles using a CO 2 -driven mechanism under high pressure.

Low temperature synthesis of ZnO particles without using reactive materials, solvents and post-treatments is still a serious challenge for both fundamental research and industrial applications. In this research, we report the dry synthesis of ZnO particles only by using Zn(acac) 2 and supercritical CO 2 (scCO 2 ) at the low temperature of 60 °C. The synthesis was performed using CO 2 and N 2 from 0.1 to 30.0 MPa for 18 h. As a result, ZnO yields increased with a rise in the CO 2 pressure and reached 67% at 30.0 MPa while N 2 medium gave low yields below 4.9% regardless of the pressure. Additionally, the detailed characterization results and the phase behavior observations evidentially showed the formation of zinc-CO/CO 2 -organic complexes in the solid phase of Zn(acac) 2 powder under scCO 2 , resulting in the accelerated formation of ZnO particles. These findings suggest that scCO 2 has potential value to drive the formation reaction of zinc-CO/CO 2 -organic complexes, which allows the low temperature synthesis of ZnO particles under dry conditions without using reactive materials, solvents and post-treatments.