Silicon Nanocrystals in Liquid Media: Optical Properties and Surface Stabilization by Microplasma-Induced Non-Equilibrium Liquid Chemistry

Surface engineering of silicon nanocrystals directly in water or ethanol by atmospheric-pressure dc microplasma is reported. In both liquids, microplasma processing stabilizes the optoelectronic properties of silicon nanocrystals. The microplasma treatment induces non-equilibrium liquid chemistry that passivates the silicon nanocrystals surface with oxygen-/organic-based terminations. In particular, the microplasma treatment in ethanol drastically enhances the silicon nanocrystals photoluminescence intensity and causes a clear red-shift (�80 nm) of the photoluminescence maximum. The photoluminescence properties are stable after several days of storage in either ethanol or water. The surface chemistry induced by the microplasma treatment is analyzed and discussed.