Effect of liquid chemistry and discharge parameters on the size distribution of Ag nanoparticles produced by sputtering onto castor oil and polyethylene glycol

The influence of sputtering parameters on the size distribution of silver (Ag) nanoparticles (NP) synthesized by sputtering onto castor oil and polyethylene glycol (PEG600) was investigated. The sputtered species arriving at the substrate were described in terms of flux and kinetic energy. In both liquids, about 99% of the NPs measured were ⩽5 nm in diameter, with most NPs in the range 1–2 nm and 1–2.5 nm in PEG600 and castor oil, respectively. Overall, larger NPs were obtained in castor oil than in PEG600 (40%–55% and 8%–35% of NPs >2 nm in castor oil and PEG600, respectively). In PEG600, the grey color of the solutions indicated aggregation, already after deposition. The flux variation, ranging from ∼120 to 300 µ g·cm −2 ·min −1 , did not appear to strongly influence the NP size. Larger proportions of NPs >2 nm seemed primarily triggered by higher kinetic energies, as almost 30% more NPs >2 nm were counted for kinetic energies of 12–18 eV compared to 3–6 eV. The castor oil solutions exhibited an orange color, suggesting no notable aggregation of the NPs. The size distributions were not significantly dependent on flux and kinetic energy, as the proportion of NPs <2 nm varied from 45%–59% for all conditions studied here. This difference in behavior between liquids was attributed to their chemical structures, governing the NP coordination. Hence, limiting the species mobility, the higher coordinating castor oil restricted NP aggregation. While the sputtering parameters influenced the NP size differently depending on the liquid chemistry, their impact on the NP size was overall limited in the deposition parameter range investigated herein.