Spark ablation metal nanoparticles and coating on TiO₂ in the aerosol phase

Abstract. Generation and characterisation of metal nanoparticles (NPs) gained attention in recent years due to their significant potential in applications as diverse as catalysis, electronics or energy storage. Despite the high interest in NPs, their characterisation remains challenging and detailed quantitative information on size, number concentration and morphologies are key to understand their properties. In this study we generated NPs from four metals, Au, Pt, Cu and Ni, via spark ablation in the aerosol phase, which allows to produce NPs as small as 1 nm in high quantities and purity. Particles were characterised with transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDX) as well as online aerosol particle size distribution measurement techniques. Particle size modes for the four metals ranged between 3 nm and 5 nm right after generation. Differences in number and size of particles generated can be rationalised with thermodynamic properties of the metals such as melting point or surface free energy. The four metal NPs were also coagulated with larger TiO₂ NPs of about 120 nm size and the metal surface coverage of the TiO₂ particles was characterised with electron microscopy and EDX spectroscopy. This detailed characterisation of NPs mixtures will be essential for a fundamental understanding of spark ablation generated particles and their applications for material sciences.