Charged ultrafine nanoparticle synthesis by spark-discharge

This study presents an optimized spark-discharge generator circuit that enhances unipolar ion production (up to 10⁹ ions/cm³) without any ionizers, enabling efficient generation of charged ultrafine nanoparticles (<5 nm). By sustaining high voltage on both electrodes during discharge, the system achieves stable and controllable unipolar ionization. Systematic evaluation of key parameters (interelectrode gap, electrode material, discharge frequency, capacitance, gas flow/type, and voltage polarity) reveals optimal conditions for ion generation. Deposition experiments on silicon substrates and TEM grids confirm a 4-fold increase in sub-5 nm charged nanoparticle production compared to conventional designs, as validated by TEM, SEM and optical profilometry.