Raman imaging and stress quantification in self-assembled graphene oxide fiber 'Latin Letters'.

To probe the intrinsic stress distribution in terms of spatial Raman shift ( ω) and change in the phonon linewidth ( Γ), here we analyze self-assembled graphene oxide fibers (GOF) 'Latin letters' by confocal Raman spectroscopy. The self-assembly of GOF 'Latin letters' has been explained through surface tension, π-π stacking, van der Waals interaction at the air-water interface and by systematic time-dependent investigation using field emission scanning electron microscopy analysis. Intrinsic residual stress due to structural joints and bending is playing a distinct role affecting the E2g mode (G band) at and away from the physical interface of GOF segments with broadening of phonon linewidth, indicating prominent phonon softening. Linescan across an interface of the GOF 'letters' reveals Raman shift to lower wavenumber in all cases but more so in 'Z' fiber exhibiting a broader region. Furthermore, intrinsic stress homogeneity is observed for 'G' fiber distributed throughout its curvature with negligible shift corresponding to E2g mode vibration. This article demonstrates the significance of morphology in stress distribution across the self-assembled and 'smart-integrable' GOF 'Latin letters'. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]