Plasmas formed at sub-millimeter spatial scales operate stably and close to non-thermally at atmospheric pressure and are a source of ions, electrons, and other electronically excited states at ambient conditions. Overall, these features make microplasmas suitable for novel electrochemical applications where gas-phase species (e.g electrons) in the plasma can directly interact with ionic aqueous electrolytes to initiate redox reactions.

 

In this talk, we will present two approaches to microplasma-based electrochemistry that we have developed for nanoparticle synthesis. In one approach, microplasmas are formed at the surface of a liquid electrolyte and operated similar to an electrochemical cell with the plasma as the cathode and a solid metal immersed in the electrolyte as the anode [1]. Metal cations in solution such as Ag+ are electrochemically reduced by the plasma to solid metal, resulting in the formation of metal nanoparticles without any chemical reducing agent. Alternatively, thin films of metal cations dispersed on a polymer are electrochemically reduced by a rastered microplasma [2]. This configuration allows microscale patterns of metal nanoparticles to be produced without the need for lithography. Recently, we have extended our patterning method to the reduction of metallopolymers which are novel molecular structures that can be used as a template for metal ion and metal particle formation [3]. This strategy has enabled patterns of metal nanoparticles to be prepared which are beyond lithographic limits. We will discuss our experimental techniques in detail, as well as the properties of the nanoparticles as assessed by UV-Visible absorbance spectroscopy, X-ray diffraction, and transmission electron microscopy.

 

1. C. Richmonds et al., Appl. Phys. Lett. 93, 131501 (2008).

2. S. W. Lee et al., Adv. Func. Mater., doi:10.1002/adfm.201100093

3. S. W. Lee et al., in preparation.