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Journal of Materials Chemistry A
Page 4 of 6
DOI: 10.1039/C7TA10103A
COMMUNICATION
Journal Name
other reported gelators, we carried out
spectroscopic and structural investigation into the xerogel. Kolkata for rheology measurements; Dr. T. K. Naiya, IIT(ISM)
Figure 3a presents the FTIR spectra of as-prepared , vis-a-vis Dhanbad and Dr. D. Mitra, University of Calcutta for heavy
a
detailed acknowledge Dr. Raju Mondal and Prof. P. Dastidar, IACS
1
that of the dried xerogel from MCH. The O-H stretching crude oil samples. SD acknowledges DST-Inspire and SS
frequency that appears at 3690 cm-1 in the as-prepared sample acknowledges UGC for scholarship.
shifts to 3420 cm-1 in the xerogel. This large hypsochromic shift
along with an overall broadening of the O-H stretching band is
Notes and references
indicative of the presence of intermolecular hydrogen bonding
in the xerogel. The role of H-bonding is however, best
demonstrated by the fact that addition of a few drops of a
competing H-bonding agent, such as methanol or acetic acid,
completely disrupts the diesel gel§§ (Figure 3b, Video V4).
Optical absorption spectroscopy offers a convenient way to
characterize the nature of NDI pi-stacking in the gel state (Fig
‡ We also synthesized
naphthalene dianhydride with n-dodecylamine and Phe,
followed by purification to separate from symmetrically
substituted NDI side-products (Supporting Information).
§ Toxicology experiment using live zebrafish were performed in
compliance with the CPCSEA rules and guidelines set by the
Institutional Animal Ethics Committee of IISER-Kolkata.
1 by a single-step condensation of
1
† While distillation of congealed crude oil can be carried out at
refineries, it is not possible to recover the gelator that remains in
the residue, subsequently used as bitumen. However, presence
of low molecular weight gelators in bitumen is known to
improve its mechanical properties, see Ref. 33.
3c). The absorption spectrum of molecularly dissolved
1 in
CHCl3 (10 µM) is characterized by well-defined vibronic
progressions at 380, 360 and 340 nm, typical of an isolated NDI
chromophore.34 In comparison, the solid-state absorption
spectrum of a thin dried film of the xerogel (from MCH) shows
§§ Methanol does not have a similar effect on crude-oil gel, in
which the gelator-oil interactions are presumably more robust.
a distinct reversal in the relative absorbance of the 0-0 (A0-0
)
and 0-1 (A0-1) vibronic features. The corresponding increase in
the A0-1/A0-0 ratio from 0.86 (in CHCl3) to 1.06 (in xerogel) is a
clear sign of exciton-coupled H-aggregation, through pi-
stacking.35 Powder X-ray diffraction (pXRD) pattern of MCH
xerogel (Figure 3c) is dominated by a sharp low-angle peak at
1
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2
θ
= 2.33°. In addition, several weaker reflections appear in
the wide-angle region, including a broad peak at 2θ = 25.3° (d
= 3.52 Å) that is consistent with the presence of pi-stacking in
the xerogel. The broad nature of XRD peaks indicates the
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Conclusions
To conclude, we report a small molecule based organogelator
that shows superior performance as a phase selective gelator
for a variety of crude and refined petroleum products from
water. Its unprecedented ability to congeal heavy crude oil in
tens of seconds, even when applied in the powder form, marks
a big improvement over the best reported organogelators till
date. Its ease of synthesis, low gelation concentration,
negligible aqueous solubility and bioavailability, ability to gel
oil at 0 °C, excellent mechanical, thermal and temporal
stability of the resultant gel, the ease of fuel recovery from gel,
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promising candidate for marine oil-spill remediation.
1 a very
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Conflicts of interest
There are no conflicts to declare.
Ying and H. Q. Zeng, Chem. Mater., 2016, 28, 4001-4008.
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Acknowledgements
The authors gratefully acknowledge IISER Kolkata and
Department of Science and Technology (DST), India (Project:
EMR/2014/000223) for financial support. We also
4 | J. Name., 2012, 00, 1-3
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