Enhancing the Dispersibility and Stability of Graphene in Water Using Porphyrin-Based Compounds

Although graphene's superior electrical, optoelectronic, thermal, and mechanical properties have been evident for 20 years now, its poor water dispersibility has hindered its incorporation in many types of applications and technologies. Strong examples of this are biomedical and environmental applications and devices that require non-toxic, biocompatible media and not toxic organic solvents like N-N'-Dimethylformamide, in which graphene is readily dispersible. In this work, we investigate a new way to prepare high-concentration and stable graphene dispersions in water by employing porphyrin-based compounds as stabilisers. To this end, electrochemically exfoliated graphene (EEG) and assess the potential of five porphyrins and metalloporphyrins are prepared to disperse EEG in water successfully. The dispersibility and stability of EEG in each porphyrin aqueous solution are evaluated by recording their UV-vis absorption spectra. Two of the synthesised compounds, namely sodium salt of 5,10,15,20-tetrakis(4-carboxyphenyl)-porphyrin or TCPP and sodium salt of [5,10,15,20-tetrakis(4-carboxyphenyl)-porphyrinato]tin(IV) or Sn-TCPP , are successful in stably dispersing EEG in water. The intermolecular interaction between the EEG flakes and [H₂TCPP]Na₄ and [Sn(OH)₂TCPP]Na₄ molecules are investigated via fluorescence emission spectroscopy. Finally, solid thin films of the EEG(TCPP) and EEG(Sn-TCPP) dispersions are prepared via spray-coating, and their optoelectronic properties and surface morphology are investigated.