Graphene Synthesis and Functionalization with Collagen Into an Aqueous Dispersion Showing High Photo-Luminescence

Abstract

Near perfect graphene (G) was synthesized using Staudenmaier’s method followed by pyrolysis at 1050 � C as revealed by transmission electron microscopy (TEM), surface enhanced Raman spectroscopy (SERS) and scanning electron microscopy (SEM). The spots in the second Laue zone of the selected area electron diffraction (SAED) pattern of TEM were much brighter than the first, a clear indication of graphene formation. However, the main novelty of the work is in the functionalization of graphene to an aqueous dispersion using the protein collagen. The stability of graphene in collagen was better than in many of the dispersants commonly used. It seems from the confocal studies that collagen is able to attack the graphitic edges but not completely free the layers. Distinct changes have been observed in the X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) spectra post dispersion. The (002) XRD peak was shifted towards higher 2� position by 0.24 � in GC; the average crystallite size (∼ 26.68 nm) was also twice than that of synthesized graphene. The chemical environment around the carbon atom changed, as seen in the de-convoluted XPS spectra changes. The percentage concentration of sp 2 bonded carbon decreased sharply from 70.02 to 58.21 along with an increase of sp 3 character from 10.15 to 15.55. In addition, the GC dispersion showed excitation wavelength dependent