Chemistry in Pictures: Emulsion in aquamarine

Each droplet in this glowing emulsion is held together by a special molecule: a fluorescent emulsifying agent. Rakesh Narani, a PhD student in the lab of Che-Jen Lin at National Dong Hwa University, made the droplets by combining the emulsifying agent with water, a fluorocarbon oil, and a hydrocarbon oil. The two oils normally don’t mix, so the emulsifier acts as an intermediate between them. Each emulsifier molecule has two different sidechains. One of the chains is only soluble in the fluorocarbon oil and stays anchored in that phase of the mixture. The other sidechain remains anchored in the hydrocarbon phase. If there’s enough of the emulsifier present, those two-sided molecules can completely encase droplets of the hydrocarbon oil and bring them into fluorocarbon/water phase.

In this case, the emulsifier is fluorescent and changes its color when it crowds together around the droplets versus when it floats off in the fluorocarbon phase. Narani and Lin want to use this color change—otherwise known as aggregation-induced emission—to sense biological and environmental pollutants.

Submitted by Rakesh Narani and Che-Jen Lin

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