Covalently functionalized reduced graphene oxide by organically modified silica: a facile synthesis of electrically conducting black coatings on glass

Abstract

The fabrication of black and electrically conducting films on glass substrate derived from covalently functionalized reduced graphene oxide (FRGO) has been reported in this work. Graphene oxide (GO) was first prepared following the Hummers method and then functionalized using an organically modified silicon alkoxide, 3-glycidoxypropyltrimethoxysilane (GLYMO) in an ordered fashion. Catalyst (aluminium acetylacetonate) induced selective polymerization of the epoxy groups of GO and GLYMO was found to occur via the formation of ethereal (–C–O–C–) linkages. The formation of such linkages was confirmed by IR, Raman, TGA, X-Ray diffraction and TEM studies. Finally the functionalized graphene oxide (FGO) films were subjected to thermal reduction in an inert (N₂) atmosphere to obtain FRGO films. These hard FRGO films are electrically conducting and appeared as black coatings on glass. By varying the loading (20–30 wt%) of GO with the covalently bonded organically modified silica, the sheet resistance values can be tuned in a linear way from 0.8 × 10⁶ to 1.4 × 10³ Ω □⁻¹. The uniform current–voltage (I–V) characteristics of the films can be nicely correlated with the sheet resistance values.