Pressure effect on ZnO nanoparticles prepared via laser ablation in water

ZnO nanoparticles were prepared via laser ablation of metallic Zn in neat deionized water at pressures up to ∼31 MPa and at constant ablation time, fluence, and wavelength. The high-pressure products were compared with those prepared at 1 atm, and the effect of water pressure on the product size and photoluminescent properties was studied. The results indicate that the use of pressure permits to control the particle size, the position of their exciton emission peak, and the intensity of their visible emission. While smaller and more homogeneous in size ZnO particles were produced at elevated pressures, their UV emission peak blue-shifted and green emission was enhanced. At pressures ∼22 MPa, a discontinuity in the improvement of the product green emission was observed, which should be related to the appearance of supercritical water in the ablated zone.