Controllable inkjet printing of graphene oxide and hydrophilic nanomaterials

Abstract

Graphene oxide(GO)ink has been widely researched but problems still exist with regards to its printability and conductivity. The following work aims to combat both these issues, leading to the formulation of a glycol-based GOinkwith optimised rheologyfor use witha Dimatix inkjet system. Results show superior print quality and resolution, with films characterised by robust AFM, Raman, XRD, FTIR and optical studies. Through the application of a two-step reduction process, incorporating both chemical and thermal treatments, the conductivity of films are able to exceed 50,000 S/m. This is the highest value reported to date for an inkjet-printed graphene film yet the corresponding sheet resistance (740 W/sq) and transmittance (29 %) remain poor compared to indium tin oxide films currentlyused in optoelectronic devices.This work also aimed to apply the techniques of printing GO to alternative hydrophilic nanomaterials. The synthesis of cadmium sulphide/DNA nanowires via a wet chemical method allows for the easy formulation of a novel semiconducting ink that is also compatible with an inkjet printing system. The printing of highlyresolved cadmium sulphide/DNA droplet arrays on glass is reported with characterisation by fluorescence microscopy, AFM and Raman. The fabrication of conductive nanowire devices is also accomplished by the printing of CdS/DNA features over interdigitated electrodes and sintering of material. Findings show that inkjet printing could be a successful method of processing these semiconducting nanowires towards labelling and gas sensing applications.