Graphene Nanocomposite as Optical-Fiber Interface for the Spectroscopy of Aqueous Media: Study of the C-H Stretch

Abstract

Spectroscopic investigation of different modes of interatomic bonds has fascinated the research fraternity for a very long time. Study of the C-H stretch has been of particular importance. Here, we present a versatile spectroscopic technique using a graphene-based interface and utilize it to investigate the different Raman modes of the C-H stretch between water molecules and reduced graphene oxide (rGO). We infer such changes by studying the Raman fingerprint and the background of the spectrum using a highly multimode optical fiber evanescent wave setup. With this, we are able to interrogate the different C-H peaks using visible excitation with good resolution. The technique we demonstrate is noninvasive and can sustain very high power to probe dormant or weak Raman oscillators. We believe our system provides the complete information on the evolution of the interface as it changes with temperature, allowing for the study of thermodynamic changes at the molecular level. This unprecedented selective excitation of different Raman active oscillators paves the way to the further exploration of the molecular dynamics happening at such an interface.

Characterization of inhomogeneity at edges of graphene oxide films using tip‐enhanced Raman spectroscopy

“…[23] Based on these results, we believe that the graphite network structures are broken down at the edges of the GO plane, resulting in the high I D /I G ratio, and the dangling bonds are mainly terminated by C-H or C-O, O-H, and COOgroups dissociated from H 2 O molecules in an atmosphere. [5,30] We believe that inhomogeneous nanoscale structures or defects are formed at the edge or step-terrace of the GO plane owing to these chemical bonds. These inhomogeneous nanoscale structures or defects can reduce the electrical conductivity of flexible electronic devices, such as smartphones and tablets.…”

“…Furthermore, as can be seen in Figure 2a, a relatively sharp line superimposed on the background by a broad band at around 2900 cm −1 is observed at approximately 2920 cm −1 . [ 5 ] The broad band at around 2900 cm −1 is assigned to the (D + G) band, because the wavenumber added by 1350 cm −1 (D band) + 1580 cm −1 (G band) equals roughly 2900 cm −1 whereas the relatively sharp line might be ascribed to CH vibrational mode. [ 5 ] Figure 2b–d shows the far‐field Raman, TERS spectra of G band, and the intensity profile of D band along the arrow indicted in Figure 4b, respectively.…”

“…Raman spectroscopy is a powerful tool for characterizing carbon materials. Diamond [3][4][5] and graphite [5][6][7] exhibit single peaks at 1332 and 1581 cm À1 (G band), respectively. Graphene and GO exhibit broad bands at 1360 cm À1 assigned to the disorder mode (D band) and 1590 cm À1 ascribed to G band, respectively.…”

“…Graphene and GO exhibit broad bands at 1360 cm À1 assigned to the disorder mode (D band) and 1590 cm À1 ascribed to G band, respectively. [5][6][7][8][9][10][11][12] Tip-enhanced Raman scattering based on localized surface plasmon resonance and/or lightening rod effect and chemical enhancement [6][7][8][9][10][11][12][13][14] combines the chemical sensitivity of surface-enhanced Raman spectroscopy and the high spatial resolution of scanning probe microscopy (SPM), which consists of atomic force microscopy (AFM), or scanning tunneling microscopy (STM), and allows the chemical imaging of surfaces at the nanometer level. Tipenhanced Raman spectroscopy (TERS) has been rapidly used as a nondestructive SPM technique for surface chemical characterization [15] and has facilitated the investigation of single macromolecules at subnanometer spatial resolution.…”

“…Graphene and GO exhibit broad bands at 1360 cm −1 assigned to the disorder mode (D band) and 1590 cm −1 ascribed to G band, respectively. [ 5–12 ]…”