Strong acid-nonionic surfactant lyotropic liquid-crystalline mesophases as media for the synthesis of carbon quantum dots and highly proton conducting mesostructured silica thin films and monoliths
Author
Olutaş, E. B.
Balcı, F. M.
Dag, Ö.
Date
2015Source Title
Langmuir
Print ISSN
0743-7463
Electronic ISSN
1520-5827
Publisher
American Chemical Society
Volume
31
Issue
37
Pages
10265 - 10271
Language
English
Type
ArticleItem Usage Stats
107
views
views
112
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Abstract
Lyotropic liquid-crystalline (LLC) materials are important
in designing porous materials, and acids are as important in chemical
synthesis. Combining these two important concepts will be highly
beneficial to chemistry and material science. In this work, we show that
a strong acid can be used as a solvent for the assembly of nonionic
surfactants into various mesophases. Sulfuric acid (SA), 10-lauryl ether
(C12E10), and a small amount of water form bicontinuous cubic (V1), 2Dhexagonal (H1), and micelle cubic (I1) mesophases with increasing SA/
C12E10 mole ratio. A mixture of SA and C12E10 is fluidic but transforms to a
highly ordered LLC mesophase by absorbing ambient water. The LLC
mesophase displays high proton conductivity (1.5 to 19.0 mS/cm at room
temperature) that increases with an increasing SA content up to 11 SA/
C12E10 mole ratio, where the absorbed water is constant with respect to the
SA amount but gradually increases from a 2.3 to 4.3 H2O/C12E10 mole
ratio with increasing SA/C12E10 from 2 to 11, respectively. The mixture of SA and C12E10 slowly undergoes carbonization to
produce carbon quantum dots (c-dots). The carbonization process can be controlled by simply controlling the water content of
the media, and it can be almost halted by leaving the samples under ambient conditions, where the mixture slowly absorbs water
to form photoluminescent c-dot-embedded mesophases. Over time the c-dots grow in size and increase in number, and the
photoluminescence frequency gradually shifts to a lower frequency. The SA/C12E10 mesophase can also be used as a template to
produce highly proton conducting mesostructured silica films and monoliths, as high as 19.3 mS/cm under ambient conditions.
Aging the silica samples enhances the conductivity that can be even larger than for the LLC mesophase with the same amount of
SA. The presence of silica has a positive effect on the proton conductivity of SA/C12E10 systems.
Keywords
Carbon filmsCarbonization
Conductive films
Crystalline materials
Mixtures
Nanocrystals
Porous materials
Proton conductivity
Semiconductor quantum dots
Silica
Surface active agents
Ambient conditions
Carbon quantum dots
Carbonization process
Lower frequencies
Lyotropic liquid crystalline
Mesostructured silica
Mesostructured silica films
Proton conducting
Nonionic surfactants
Permalink
http://hdl.handle.net/11693/20959Published Version (Please cite this version)
http://dx.doi.org/10.1021/acs.langmuir.5b02225Collections
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