The mechanism by which small-molecule kinetic inhibitors bind and limit the growth of micron sized single-crystal tetrahydrofuran (THF) clathrate hydrates was explored using microfluidic devices coupled with cold stages and fluorescence microscopy. In pure THF/water solutions, cubic octahedral crystals were obtained at moderate supercooling degrees, while dendrite-like crystals were evident at high supercooling. Safranine O (SFO), a small dye molecule that inhibits ice growth, was tested as a potential kinetic inhibitor. THF hydrates grown in SFO solutions exhibited morphology changes, a hallmark of crystal growth inhibition, and were shaped as truncated octahedrons or hexagonal plates. Fluorescence microscopy demonstrated that SFO binds to the surface of THF hydrates on specific crystal planes. The inhibition activity of SFO was found to be lower than a known hydrate inhibitor, Polyvinylpyrrolidone (PVP), however, both completely halted crystal growth at a concentration-dependent manner. Cryo-TEM imaging revealed that bilayered lamellae with an average thickness of 4.2±0.2 nm covering several µm<sup>2 </sup>are formed in aqueous solutions containing millimolar concentrations of SFO. Altogether, these results indicate that SFO forms lamellar fibers in solution, which then bind to the surface of the hydrate and inhibit further growth. As an ice and hydrate inhibitor, SFO may bind to the surface of these crystals via ordered water molecules near its amine and methyl groups, reminiscent to how some antifreeze proteins bind ice.

Growth inhibition of clathrate hydrates by supramolecular inhibitors

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.