γ-Al2O3 nanoparticle production by arc-discharge in water: in situ discharge characterization and nanoparticle investigation

gamma-Al2O3 crystalline nanoparticles (NPs) are for the first time produced by the arc-discharge in water method. The discharge is studied in situ during the NP formation by simultaneously recording the voltage and current waveforms, emitted light intensity and time-resolved optical emission spectra and snapshots of the discharge. The microstructure of the NPs is investigated by high-resolution transmission electron microscopy, the chemical purity is confirmed by x-ray photoelectron spectroscopy and the crystalline structure by x-ray diffraction. The results experimentally demonstrate the successive phases that lead to the supersaturation condition governing this gas-phase bottom-up process for dielectric NP production.