CHEMISTRY: Droplets Hanging Around

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Science  22 Jun 2007:
Vol. 316, Issue 5832, pp. 1670b
DOI: 10.1126/science.316.5832.1670b

Microdroplets of common liquids deposited on surfaces typically evaporate in minutes if the surrounding ambient is not saturated in the corresponding vapor phase. Cheng et al. observed that microdroplets of 1-propanol and water in a 3-to-2 volume ratio showed remarkable stability when deposited on 1-decanethiolate monolayers self-assembled on gold surfaces. After initially undergoing evaporation to a volume of 0.2 μl, these microdroplets could persist for up to 5 hours. Variation of the volume ratio or deposition on substrates such as glass or polycarbonate led to rapid evaporation. The authors propose that the unusual stability results from the more volatile alcohol segregating to the bottom of the microdroplet near the hydrophobic alkyl chains, and the outer water-rich layer deriving stability from formation of a maximally hydrogen-bonded network. — PDS

J. Phys. Chem. B 111, 10.1021/jp069063f (2007).

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