Sonication synthesis of micro-sized silver nanoparticle/oleic acid liquid marbles: A novel SERS sensing platform

Liquid marbles are entities made of a small amount of liquid encapsulated by micro/nano scale particles. The functionality of liquid marbles depends on both the core liquid and particle coating. In this work, functional silver nanoparticle (Ag NPs)/oleic acid liquid marbles are developed using Ag NPs to encapsulate micro-sized oleic acid liquid spheres, which is achieved via sonication. We demonstrate that both the size of the encapsulated spheres and the order of the Ag NPs coating are a function of the sonication time. These micro-sized liquid marbles are investigated for sensing an organic thiolate as a model material. Their capacity for increasing solar light absorption and energy conversion into heat is also studied. The liquid marbles generated after sonication for 60 min show the strongest Raman peak signals which originate from the thiolate. They also demonstrate the highest solar energy absorption. We ascribe these enhancements to the increased surface area of the Ag NPs/oleic acid spheres and the optimum order of Ag NPs to produce the strongest surface enhanced Raman scattering. The liquid marbles can be used for the development of future biosensors and solar-thermal absorbers.