Plasma-assisted electrochemistry involves bringing a microplasma into contact with an electrolyte containing metal salts (in this case, silver nitrate – see figure). The plasma is a source of electrons that reduce the silver ions in solution, and then collect into silver nanoparticles. This technique is a safer alternative to synthesis methods that involve toxic chemical-reducing agents such as sodium borohydride. It does not produce undesired by-products, and the shape and size of the nanoparticles can be better controlled. Researchers need to be able to strictly control the size of the nanoparticles as well as the interparticle spacing, since these parameters influence the particles' resonance frequency and hence the way they behave in a device.

In particular, our work has shown that microplasma-assisted electrochemistry parameters could be used to control the growth of silver nanoparticles in the absence of a chemical reducing agent, both with and without a stabilizer (such as fructose) and with and without stirring. This result is important on two fronts. First, and as mentioned, the absence of a toxic reducing agent leads to a much more environmentally- and human-health friendly synthesis method while providing a good degree of control over nanoparticle size, spacing and surface chemistry. Second, since stabilizers can obscure the signal from molecules of interest in a sensing device, a stabilizer-free nanoparticle synthesis technique overcomes this problem nicely.

Full details of the research can be found in the journal Nanotechnology.