Sputtering onto Liquids: From Thin Films to Nanoparticles

Abstract

Herein, we describe the influence of discharge voltage on the formation of colloidal silver nanoparticles and/or thin films during sputtering onto castor and canola oil, two well-known vegetable oils, and also onto the synthetic medium chain caprylic/capric triglyceride oil. Stable spherical AgNPs of small sizes and size distributions were formed on castor oil in a large discharge voltage interval. The size of the formed NPs was shown to increase with discharge voltage increment. However, by performing sputtering under the same conditions (320 V, 150 s), metallic thin films were formed on canola and caprylic/capric triglyceride oils; and spherical nanoparticles on castor oil. The increase in the discharge voltage stopped film formation and started nanoparticle formation. Thin films were predominant for low coordinating oils and low discharge voltages. The mechanisms for the formation of nanoparticles or thin films by means of sputtering onto liquid substrates are discussed in details for the first time.