ZnO nanoparticles formation by reactions of bulk Zn with H2O and CO2 at sub- and supercritical conditions: II. Morphology and properties of nanoparticles

Oxidation of solid and liquid zinc by water (temperature 335–648 °C, pressure 13.7–31.2 MPa, water density 0.045–0.420 g/cm3), supercritical CO2 (514–600 °C, 7.1–24.4 MPa, 0.041–0.158 g/cm3), mixture of H2O/CO2 (140–600 °C, 30 MPa, water density 0.026–0.569 g/cm3, initial ratio of [H2O]0/[CO2]0 = 0.46–2.75 mol/mol) has been studied. On the basis of scanning and transmission of electron microscopy data, we have demonstrated that depending on the process conditions nanoparticles with the size of 2–100 nm, nanorods and nanowhiskers with the diameter of 10–100 nm and length of up to 50 μm, mechanically solid nanostructured ceramics are synthesized. The presence of (Zn)n clusters with the size below 5 nm has been found in ZnO nanoparticles synthesized in supercritical water and H2O/CO2 mixture. Higher level perfection of nanocrystals formed at zinc oxidation by subcritical water has been revealed by means of room temperature photoluminescence study.

Graphical abstractTEM and SEM analyses show synthesis of ZnO nanoparticles, nanorods and nanowhiskers, mechanically solid nanostructured ceramics and (Zn)n clusters in ZnO nanoparticles. Room temperature photoluminescence study reveals greater structural perfection of ZnO nanoparticles, formed at Zn oxidation by subcritical water.Figure optionsDownload full-size imageDownload as PowerPoint slide