We report a fast and highly reproducible chemical synthesis method for colloidal gold nanoparticles which are negatively charged in nonpolar solvents and coated with hydrophobic organic molecules. If a hexane droplet containing charged gold nanoparticles is mixed with a larger toluene droplet, nanoparticles immediately float to the air-toluene interface and form a close-packed monolayer film. After evaporation of the solvent molecules, the monolayer film of nanoparticles can be deposited to any substrate without any limit in size. The synthesis does not require a postsynthesis cleaning step, since the two immiscible liquid phases separate the reaction byproducts from gold nanoparticles and a minimal amount of coating molecules is used.

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It is shown that bi-layer (liquid/gas) flows through nanochannels (parallel carbon nanotube bundles) can result in a higher flow rate of liquid as compared to the case when the same liquid flows through the same channels subjected to the same pressure drop and occupies the whole bore. This enhancement of liquid flow happens because a much-less-viscous air layer moves so fast that it entrains the liquid layer occupying only a part of the nanochannel bore.

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