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oil–water ratios, and different types of aqueous solution (saturated
NaCl, saturated CaCl2, KMnO4, CuSO4) but for all these cases the
selective gelation was unaltered. In addition, we also examined this
selective gelation at low temperatures (0–5 1C using an ice bath)
and importantly selective gelation time, efficiency and stability of
the solidified oils were found the same as the room temperature
method, increasing the robustness of our model system for
practical use (Fig. S8, ESI†).
Such effective phase-selective phenomenon was also observed
for others fuel oils including pump oil, silicon oil etc. and other
pure organic liquids. Considering the practical situation of oil
spill treatment, we also checked the selective gelation of a thin
layer of diesel (1 mm) floating on a large volume of water in a
petri dish, and within 20 s the resulting gel was sufficiently
strong enough that it could be scooped out by spatula (Fig. S9,
ESI†). Subsequently, oil and gelator both could be recovered via
distillation and the gelator could be reused for further batch of
experiments.
In conclusion, we have reported two new sugar-derived
Fig. 3 Selective gelation of the diesel layer in a biphasic mixture of diesel efficient organogelators for instant selective gelation of some
and water at room temperature: (1) mixture of 2 mL water and 0.8 mL
fuel oils from their oil–water mixtures at room temperature.
Selective gelation was very fast and to the best of our knowledge,
such a fast gelation time has not been reported to date. Our
diesel, (2) instantaneous selective gelation of the diesel layer after addition of
a solution of the gelator 2 (16 mg in 0.1 mL THF) and the diesel gel floating
on water, (3) within 45 s the gel holding up its own weight plus the weight of
gelators are very attractive as a model system for oil spill recovery
water in the inverted vial, (4) scooped organogel in spatula, (5) scooped
diesel gel (in several batches) taken in a round bottom flask, and (6) the because (1) they can be easily prepared in one step from easily
diesel collected in a round bottom flask after distillation.
accessible and cheap per-O-acetylated glucosamine, (2) being a
sugar derivative they are eco-friendly and biodegradable, (3) they
can offer very fast and efficient selective gelation of oils at room
of oil spill recovery from sea. Therefore, the PSG at room temperature, (4) both the oil and gelator can be recovered easily
temperature using the solution of gelator in a co-solvent was and the gelator can be reused, and (5) the selective gelation
studied. Although there are some reports of PSG at room efficiency and time were found to be unchanged at low tempera-
temperature using sonication,9b a change in the pH of the ture, allowing them a wide range of applications to clean up an
medium9c and shaking,9d using a solution of the gelator in a oil spill. Thus, all these advantages strongly point out their
co-solvent is quite practicable in real life applications to clean bright future in oil spill recovery.
up an oil spill. A concentrated solution of compound 2 (16 mg
We thank the Natural Science Foundation of China (21273141),
in 0.1 mL THF) was added by syringe at the interface of a 0.8 : 2 the Program for Changjiang Scholars and Innovative Research
mixture of diesel and water in a glass vial. It is worth noting that Team in University (IRT1070), and the 111 Project for financial
within 10 s, gelator 2 selectively gelled the diesel layer leaving the support. Mr Gang Wang is acknowledged for his help in the
water phase unaffected and within 45 s, the diesel gel was stiff fluorescence measurements.
enough to hold up its own weight plus the weight of the water
upon inversion of vial. Finally, the gel was scooped out using a
spatula and placed in a round bottom flask and vacuum distilled
to recover the diesel. The isolated diesel gel melted upon heating
Notes and references
Science, 2009, 323, 1558–1559; (c) A. M. Thayer, Chem. Eng. News, 2011,
to 91 1C (above the Tgel) and the diesel was subsequently distilled
off into a round bottom flask (Fig. 3). The residue in the round
bottom flask was characterized by mass spectrometry and thin
layer chromatography, and the gelator was found to be intact for
further use. The recovered gelator was used for selective gelation
studies three more times and after each cycle, its gelling ability
was retained. The PSG of 3 in petrol at room temperature was
also carried out using a similar process to that stated above, and
in this case the biphasic CGC (BCGC), gel melting temperature
and selective gelation time in the inverted vial condition were
1.5% w/v, 56 1C and 50 s respectively (Fig. S7, ESI†).
89, 12.
2 R. P. J. Swannell, K. Lee and M. Mcdonagh, Microbiol. Rev., 1996, 60,
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3 R. R. Lessard and G. Demarco, Spill Sci. Technol. Bull., 2000, 6,
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O. Carmody and S. Kokot, J. Porous Mater., 2003, 10, 159–170.
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6 (a) N. M. Sangeetha and U. Maitra, Chem. Soc. Rev., 2005, 34, 821–836;
(b) Low Molecular Mass Gelators Design, Self-assembly, Function, Top.
Curr. Chem., ed. F. Fages, 2005, vol. 256, p. 1; (c) in Molecular Gels
Materials with Self-Assembled Fibrillar Networks, ed. R. G. Weiss and
P. Terech, Springer, Dordrecht, 2006; (d) P. Terech and R. G. Weiss,
Chem. Rev., 1997, 97, 3133–3159; (e) O. Grownwald and S. Shinkai,
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Furthermore, to examine the robustness of the PSG phenom-
enon, we performed it under several conditions such as in different
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