Synthesis of Graphene Oxide Nanosheets from Pencil Lead and In-situ Synthesis of Gold Nanoparticles on Graphene Oxide Nanosheets

In this paper we report the synthesis of graphene oxide (GO) from pencil lead using modified Hummer's method and in-situ synthesis of gold nanoparticles (AuNPs) by bioreduction of HAuCl₄ by polyphenolic biomolecules present in young leaves of tea(Camellia sinensis) extract in the presence of GO. The UV-Visible absorption spectrum of GO dispersion in water exhibits two bands at 228nm and a shoulder at ~300nm corresponding to π-π^* transitions of aromatic c-c bonds and n-π^* transitions of C=O bonds. In photoluminescence(PL) study. GO dispersion in water shows emission band at 555nm, when excited at 325nm. When AuNPs were embedded in GO nanosheets the bands at 228nm and ~300nm of GO disappears and two new UV-Visible bands at 272nm for phenol and 539 nm for transverse surface plasmon resonance (SPR) of AuNPs appears. When AuNPs were embedded on GO nanosheets the PL emission band at 555nm disappears, two new PL emission bands appears at 431 and 658nm. The physical and morphological characterizations were performed by FTIR, XRD and HRTEM. Morphological study revealed that the GO nanosheets were well dispersed in water and AuNPs were embeddedon the GO nanosheets.