Low temperature synthesis of ZnO particles using a CO2-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 CO2 (scCO(2)) at the low temperature of 60 degrees C. The synthesis was performed using CO2 and N-2 from 0.1 to 30.0 MPa for 18 h. As a result, ZnO yields increased with a rise in the CO2 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/CO2-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/CO2-organic complexes, which allows the low temperature synthesis of ZnO particles under dry conditions without using reactive materials, solvents and post-treatments.