Graphene-on-gold surface plasmon resonance sensors resilient to high-temperature annealing

Abstract

Gold films coated with a graphene sheet are being widely used as sensors for the detection of label-free binding interactions using surface plasmon resonance (SPR). During the preparation of such sensors, it is often essential to subject the sensor chips to a high-temperature treatment in order to ensure a clean graphene surface. However, sensor chips used currently, which often use chromium as an adhesion promoter, cannot be subjected to temperatures above 250 °C, because under such conditions, chromium is found to reorganize and diffuse to the surface, where it is easily oxidized, impairing the quality of SPR spectra. Here we present an optimized preparation strategy involving a three-cycle tempering coupled with chromium (oxide) etching, which allows the graphene-coated SPR chips to be annealed up to 500 °C with little deterioration of the surface morphology. In addition, the treatment delivers a surface that shows a clear enhancement in spectral response together with a good refractive index sensitivity. We demonstrate the applicability of our sensors by studying the kinetics of avidin–biotin binding at different pH repeatedly on the same chip. The possibility to anneal can be exploited to recover the original surface after sensing trials, which allowed us to reuse the sensor for at least six cycles of biomolecule adsorption.

Real-time monitoring of cell adhesion on to a soft substrate by a graphene impedance biosensor

“…On rigid substrates such as silicon oxide, an annealing treatment at high temperatures ensures a persistently good adhesion, while at the same time ensuring a clean graphene surface. [36][37][38] On PDMS, however, we are limited by a temperature of 120°C, beyond which morphological changes occur, deforming the substrate irreversibly. 39 Secondly, PDMS is generally very sensitive to several organic solvents.…”