The performance of catalysts composed of nanoparticles is affected by particle size, shape, and composition. As a result, advances in nanoparticle synthesis methods are expected to play an important role in the design and development of new catalysts. Here we present a novel approach to high-rate production of catalytic nanoparticles with controlled sizes and compositions.

In this method, nanoparticles are produced using a gas-liquid interface approach, i.e. a natural extension of the marine foam-aerosol (foamsol) cycle to manufacture POM nanoparticles. The foamsol cycle includes bubble formation, foam coalescence, and the non-equilibrium dynamics of foam bubble bursting, which leads to the formation of nanoparticles. Particles generated from this process are the greatest source of particulate matter in the atmosphere by both mass and number of particles. The sea aerosol in the atmosphere from bubbles is 3 times more than man-made particles (about 1000 million tons per year).

Catalytic nanoparticles composed of polyoxometalates (POMs) are synthesized using the foamsol method. POMs, polyoxoanions (i.e., PW₁₂O₄₀^3-) of the early transition elements, possess extraordinary molecular and electronic structure and are known to catalyze a diverse group of reaction types. Synthesis of POM nanoparticles would enhance the low surface areas associated with POM catalysts (1-5 m² g^-1), which limits the application of POMs in catalysis.

Particles were generated by bubbling through a solution containing self assembled clusters composed of a polyoxoanion (PW₁₂O₄₀^3-) core and hydrophobic cationic surfactant, dimethyl dioctadecylammonium (DODA), shell. The particles were dried and subsequently sampled using a TSI (St. Paul, MN) Model 3080 Scanning Mobility Particle Sizer in order to measure the size distribution. Dried particles were also collected on a diffusion plate and sized both before and after calcination at 100°C using Transmission Electron Microscopy (TEM). The effects of bubbling conditions and solution chemistry on particle size, agglomeration, and production rate are discussed.