Research ArticleMATERIALS SCIENCE

Dynamic assembly of liquid crystalline graphene oxide gel fibers for ion transport

See allHide authors and affiliations

Science Advances  02 Nov 2018:
Vol. 4, no. 11, eaau2104
DOI: 10.1126/sciadv.aau2104
  • Fig. 1 In situ observation of dynamic self-assembly of GO gel fibers.

    (A) Schematic of the experimental set-up: The assembly apparatus was installed on the stage of a POM, and the assembly process was recorded with a high-speed camera focused on the glass nozzle tip. The final GO hydrogel fibers can be reeled on a bobbin as shown in the photo. (B) Schematic illustration showing flow-driven alignment of GO sheets and formation of hydrogel fiber. (C and D) POM snapshots capturing different assembly behaviors of GO gel fibers (C) without and (D) with the addition of NH4OH in the CaCl2 coagulation solution. Snapshots were taken at various rates of the take-up roller (v2). Note that the crossed polarizers were rotated 45° from the fiber axis. (E and F) POM images showing degree of alignment in GO gel fibers obtained at (E) 3v1 in the CaCl2-only coagulation solution and (F) 4v1 in the NH4OH and CaCl2 coagulation solution.

  • Fig. 2 Enhanced molecular interactions of GO.

    Photo (A) and schematic illustrations (B) showing experimental setup to observe the formation of GO hydrogel by diffusion of coagulants. The coagulant (Ca2+) diffuses into GOLC dispersion through the pores in membrane and induces gelation. GO sheets also undergo partial deoxygenation after the addition of NH4OH, which increases their π-π interaction. (C) Stress-strain curves of both the original and modified GO gels under uniaxial compression. (D and E) Frequency dependence of (D) viscosity and (E) storage modulus (G′) of both types of GO gels. (F and G) XPS spectra of the samples showing (F) Ca 2p and (G) C 1s bands. a.u., arbitrary units. (H) XRD patterns of GO powder and freeze-dried GO gels.

  • Fig. 3 Tailoring the microstructure of GO gel fibers.

    (A to D) POM images of (A and C) 4v1-GO gel fibers and (B and D) v1-GO gel fibers taken between (top) 45°-rotated and (bottom) parallel crossed polarizers with respect to the gel fiber axis. (E and F) SEM images of (E) 4v1-GO gel fibers and (F) v1-GO gel fibers show different sheet alignment. (G and H) SAXS patterns of (G) 4v1-GO gel fibers and (H) v1-GO gel fibers. f denotes Herman’s orientation function.

  • Fig. 4 Effect of ordered NIC structures on ionic conductivity.

    (A) Schematic illustration showing the experimental setup for measuring the ionic conductivity of NICs. (B) Schematic illustrating the different ion transport pathways in 4v1- and v1-GO gel fibers. (C) Ionic conductivity of the NICs at various salt (KCl) concentrations from 1 μM to 1 M. (D) Typical I-V curves and (E) Nyquist plots measured in 0.1 mM KCl solution. (F) Digital photograph of an arched GO gel fiber bridging the two reservoirs. The bending ratio is represented as arch height (t) divided by length (l). (G) I-V curves of NIC at bent and straight states and after 100 cycles of bending. (H) Ionic resistance depending on the length of NICs derived from fig. S13.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/11/eaau2104/DC1

    Fig. S1. Characterization of GOLC dispersion.

    Fig. S2. Analysis of velocity profile.

    Fig. S3. Estimation of time scale for Ca2+ diffusion.

    Fig. S4. Diameter and extension rate of ejected fluid at v2 = 5.5v1 as a function of distance.

    Fig. S5. POM images and birefringence intensity profiles of gel fibers.

    Fig. S6. Sol-gel transition and gel behavior of GO solution.

    Fig. S7. Zeta potential of GO as a function of pH in aqueous dispersion at a concentration of 0.05 mg ml−1.

    Fig. S8. XPS spectra of GO gels.

    Fig. S9. Raman spectra of GO gels.

    Fig. S10. Determination of the degree of orientation in gel fibers.

    Fig. S11. Stress-strain curves of dried GO fibers under 10% min−1 of tensile strain.

    Fig. S12. Determination of the degree of orientation in dried fibers.

    Fig. S13. I-V curves of NICs of different lengths.

    Fig. S14. Experimental setup for measuring the ionic conductivity of NICs.

    Fig. S15. Removal of Ca2+ by ion exchange in GO gel fibers.

    Fig. S16. Modeling of GO gel fiber nanochannels using the configuration of GO films.

    Table S1. Yield stress values of GO gels prepared with different amounts of NH4OH.

    Table S2. Quantitative XPS analyses of cylindrical gels and gel fibers.

    Table S3. Comparison of mechanical properties of our GO fibers with previously reported GO fibers and other nanocarbon-based fibers.

    Table S4. Structural parameters of dried GO fibers.

    Table S5. Comparison of ionic conductivity of GO gel fibers with various nanosheet films.

    Movie S1. In situ observation of dynamic assembly of GO gel fiber at v2 = v1.

    Movie S2. In situ observation of dynamic assembly of GO gel fiber at v2 = 3v1.

    References (3950)

  • Supplementary Materials

    The PDF file includes:

    • Fig. S1. Characterization of GOLC dispersion.
    • Fig. S2. Analysis of velocity profile.
    • Fig. S3. Estimation of time scale for Ca2+ diffusion.
    • Fig. S4. Diameter and extension rate of ejected fluid at v2 = 5.5v1 as a function of distance.
    • Fig. S5. POM images and birefringence intensity profiles of gel fibers.
    • Fig. S6. Sol-gel transition and gel behavior of GO solution.
    • Fig. S7. Zeta potential of GO as a function of pH in aqueous dispersion at a concentration of 0.05 mg ml−1.
    • Fig. S8. XPS spectra of GO gels.
    • Fig. S9. Raman spectra of GO gels.
    • Fig. S10. Determination of the degree of orientation in gel fibers.
    • Fig. S11. Stress-strain curves of dried GO fibers under 10% min−1 of tensile strain.
    • Fig. S12. Determination of the degree of orientation in dried fibers.
    • Fig. S13. I-V curves of NICs of different lengths.
    • Fig. S14. Experimental setup for measuring the ionic conductivity of NICs.
    • Fig. S15. Removal of Ca2+ by ion exchange in GO gel fibers.
    • Fig. S16. Modeling of GO gel fiber nanochannels using the configuration of GO films.
    • Table S1. Yield stress values of GO gels prepared with different amounts of NH4OH.
    • Table S2. Quantitative XPS analyses of cylindrical gels and gel fibers.
    • Table S3. Comparison of mechanical properties of our GO fibers with previously reported GO fibers and other nanocarbon-based fibers.
    • Table S4. Structural parameters of dried GO fibers.
    • Table S5. Comparison of ionic conductivity of GO gel fibers with various nanosheet films.
    • References (3950)

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). In situ observation of dynamic assembly of GO gel fiber at v2 = v1.
    • Movie S2 (.mp4 format). In situ observation of dynamic assembly of GO gel fiber at v2 = 3v1.

    Files in this Data Supplement:

Stay Connected to Science Advances

Navigate This Article