Gas-phase nucleation of nanoparticles

Vapor-phase precursors can be non-thermally dissociated in a plasma to generate reactive ions and radicals.

At high pressures (~atmospheric), the molecular fragments collide and homogeneously nucleate small clusters. The short residence time (τ<1 millisecond) afforded by the microplasma geometry allows the production of narrow dispersions of ultrasmall nanoparticle (<1 nm to 5 nm).

Microplasma mediated catalyst-free hydrocarbon conversion

Recently, atmospheric pressure microplasmas have received attention as an effective mode for synthesizing carbon nanoparticles, particularly nanodiamonds, from hydrocarbon precursors. As yet, the reaction chemistry and efficiency of these processes are not well understood. In this ongoing research, mass spectrometry and gas chromatography is utilized as the primary tool for analyzing how these hydrocarbon precursors react and dissociate within an atmospheric pressure microplasma environment.

Non-lithographic surface modification

Plasmas are essential to integrated circuit (IC) manufacturing for etching and deposition of thin films.

Microplasmas are an atmospheric-pressure, localized source of electrons, ions, and radicals that can be used to selectively modify thin films in space and time.

We have developed a rastered microplasma tool that can be scanned across a substrate to “write” arbitrary patterns. Currently, we are interested in the reduction of supported metal ions to form catalytic and conductive metal patterns.

Plasma-liquid electrochemistry

Plasmas are normally formed in the gas phase between two solid electrodes. Atmospheric-pressure stability combined with relatively low gas temperatures allow microplasmas to be operated with liquid electrodes including aqueous electrolytes.

When microplasmas are coupled with liquids, the gas-phase species interact with the solution and initiate electrochemical reactions. We are interested in a fundamental understanding of these plasma-liquid electrochemical processes and novel material applications.

Contact-charging of materials

Electrostatic charging of flowing particle (granular) systems has been observed in a wide range of contexts from industrial applications such as fluidized beds and aerosol inhalers to natural phenomena such as sand storms and volcanic plumes. We have developed a methodology to investigate the contact charging of granular materials due solely to particle-particle interactions in a controlled environment.

Although all particles in our system are chemically identical and there should be no apparent driving force for charge transfer, charging occurs nonetheless, such that smaller particles tend to charge negatively while larger particles tend to charge positively.

These tendencies have been surmised to be universal and independent of granular material type.