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      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

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      Author
      Olutaş, E. B.
      Balcı, F. M.
      Dag, Ö.
      Date
      2015
      Source Title
      Langmuir
      Print ISSN
      0743-7463
      Electronic ISSN
      1520-5827
      Publisher
      American Chemical Society
      Volume
      31
      Issue
      37
      Pages
      10265 - 10271
      Language
      English
      Type
      Article
      Item Usage Stats
      107
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      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 films
      Carbonization
      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/11693/20959
      Published Version (Please cite this version)
      http://dx.doi.org/10.1021/acs.langmuir.5b02225
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      • Department of Chemistry 622
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