Time-resolved in-situ nanoparticle size evolution during magnetron sputtering onto liquids

Aggregation and growth of silver nanoparticles (Ag NPs) occur both at the plasma-liquid interface and inside the silicone oil during and after the magnetron sputtering. Despite the same amount of deposited silver, the growth kinetics of Ag NPs in silicone oil vary at different deposition rates. Stirring helps to disaggregate the particle lumps. The Light Extinction Spectroscopy (LES) technique is employed for the first time to in-situ and real-time characterize the particle size distribution (PSD) during and after the sputtering of the silver atoms onto silicone oil, i.e., Sputtering onto Liquids (SoL) process. The effects of the deposition rate and the stirring speed on the PSDs are analyzed. Based on De Brouckere mean diameters, the size evolution of Ag NPs over time is monitored. Via the LES technique, Ag NPs bigger than 20 nm are detected, and the PSDs are shown to be poly-disperse, which is also supported by the ex-situ TEM measurements and in-situ time-resolved absorption spectra. At higher deposition rates, larger NPs are formed. Faster stirring does not substantially influence the final size but promotes the formation of smaller NPs (<20 nm). Low colloidal stability of Ag NPs in silicone oil is also observed.