Laser-scribed graphene presents an opportunity to print a new generation of disposable electrochemical sensors.

Katie Griffiths,Matthew D Kowal,Richard B Kaner,John Hedley,Neil Keegan,Carl Dale

doi:10.1039/c4nr04221b

Abstract

Graphene application within electrochemical sensing has been widely reported, but mainly as a composite, which adds summative effects to an underlying electrode. In this work we report the use of laser-scribed graphene as a distinct electrode patterned on a non-conducting flexible substrate. The laser-scribed graphene electrode compared favourably to established carbon macroelectrodes when evaluating both inner sphere and outer sphere redox probes, providing promise of extensive utility as an electrochemical sensor. The laser-scribed graphene electrode demonstrated the fastest heterogeneous electron transfer rate of all the electrodes evaluated with a k(0) of 0.02373 cm s(-1) for potassium ferricyanide, which exceeds commercially available edge plane pyrolytic graphite at 0.00260 cm s(-1), basal plane pyrolytic graphite at 0.00033 cm s(-1) and the very slow and effectively irreversible electrochemistry observed using single layer graphene. Finally and most significantly, a proof of principle system was fabricated using the laser-scribed graphene as working electrode, counter electrode and underlying base for the Ag/AgCl reference electrode, all in situ on the same planar flexible substrate, removing the requirement of macroscale external electrodes. The planar three electrode format operated with the same optimal electrode characteristics. Furthermore, the fabrication is inexpensive, scalable and compatible with a disposable biosensor format, considerably widening the potential applications in electrochemical bio-sensing for laser-scribed graphene.

Highlights

A diverse range of chemical and biochemical analytes have been detected using carbon materials as electrodes, or components of electrodes, in electrochemical assays
Physicochemical characterisation of laser-scribed graphene electrodes The LSG electrodes were fabricated at wafer level using the LightScribe DVD label writing technology and a graphene oxide (GO) film to produce individual LSG electrode devices
Scanning electron microscopy images of the LSG surfaces were in line with previous literature that states the stacked graphite oxide sheets undergo rapid thermal shock on laser ablation causing reduction, exfoliation and expansion of the film indicative of graphene sheets, which do not restack.[27,28,29]

Summary

Introduction

A diverse range of chemical and biochemical analytes have been detected using carbon materials as electrodes, or components of electrodes, in electrochemical assays. Nanoscale edge plane/defect sites they possess.[4,5] It appears likely that EPPG has been sidelined to academic endeavours due to the manufacturing route and operation. It is cut from highly ordered pyrolytic graphite and housed in an external casing before operation using macroscale external reference and counter electrodes, making commercial exploitation problematic due to difficulties in mass production and miniaturisation. Screen printed carbon electrodes heralded a turning point in mass production of whole systems for numerous electrochemical sensing applications, utilising in-built reference and counter electrodes on a planar substrate, producing a notable commercial success, namely the multi-billion dollar glucose sensor.[3] Any material that can be very printed with properties akin to, or even better than EPPG should be very appealing

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