Post-synthesis treatment of graphene oxide/silica particles nanocomposite with piranha acid for functionalization

Abstract

The discovery of 2D materials has led researchers to a broad material platform. Their excellent physical, chemical and electrical properties along with the layered structure have found applications in various fields. However, these materials also have limitations and functionalisation is one of the mechanisms that improves their properties. In our previous work, we observed surface-enhanced Raman spectroscopy (SERS) after covalent attachment of protein to the graphene nanocomposite where piranha acid was used to generate the functional groups. The current work describes the synthesis and characterisation of a graphene oxide-silica particle nanocomposite after piranha acid treatment at different time intervals. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy were performed to indicate structural changes which facilitated the protein attachment. The SEM and TEM results indicated that the sample which was piranha acid activated for 3 min displayed better arrangement of silica particles on the graphene sheets with exposition of the highest net surface area in the graphene sheet, compared to the other samples and determined to be the best functionalised nanocomposite for further applications. Morphological instability of the graphene sheets and clustering of silica particles were observed in the samples treated for more than 3 min. Interestingly, the same degree of graphitisation was observed in all the samples when I D /I G ratios {(≤0.99) ≠ 0} were determined by Raman spectroscopy.