Drift Suppression of Solution-Gated Graphene Field-Effect Transistors by Cation Doping for Sensing Platforms

Abstract

Solution-gated graphene field-effect transistors (SG-GFETs) provide an ideal platform for sensing biomolecules owing to their high electron/hole mobilities and 2D nature. However, the transfer curve often drifts in an electrolyte solution during measurements, making it difficult to accurately estimate the analyte concentration. One possible reason for this drift is that p-doping of GFETs is gradually countered by cations in the solution, because the cations can permeate into the polymer residue and/or between graphene and SiO2 substrates. Therefore, we propose doping sufficient cations to counter p-doping of GFETs prior to the measurements. For the pre-treatment, GFETs were immersed in a 15 mM sodium chloride aqueous solution for 25 h. The pretreated GFETs showed that the charge neutrality point (CNP) drifted by less than 3 mV during 1 h of measurement in a phosphate buffer, while the non-treated GFETs showed that the CNP was severely drifted by approximately 50 mV, demonstrating a 96% reduction of the drift by the pre-treatment. X-ray photoelectron spectroscopy analysis revealed the accumulation of sodium ions in the GFETs through pre-treatment. Our method is useful for suppressing drift, thus allowing accurate estimation of the target analyte concentration.

Laser-induced tuning of graphene field-effect transistors for pH sensing

“…When looking at the location of the Dirac point for the pristine device, we can see that it was not around 0 V. This was most likely due to the final EBL step leaving residual PMMA onto the graphene and the SiO 2 substrate. It has been reported 28 that PMMA residues and SiO 2 substrate cause p-type doping and therefore shift the Dirac point. Others have observed this to sometimes be a continuous, approximately 1 nm thick layer that had significant effect on the sensory function of graphene.…”

“…2(c) and (d)). The sample was left to soak in a buffer solution for approximately 25 hours before starting the measurements, as it has been reported 28 to reduce the amount of drift when there are PMMA residues present on the graphene by countering the doping caused by the residues. The solution was changed by pumping the buffer from a separate container.…”

Ionic strength-sensitive and pH-insensitive interactions between C-reactive protein (CRP) and an anti-CRP antibody

“…Recently, label-free methods using field-effect transistors (FETs) [8], surface plasmon resonance [9], and quartz crystal microbalance [10] have been used to detect CRP. In particular, great progress has been made in designing and fabricating FETs using nanomaterials, including Si nanowires [8,11,12], carbon nanotubes [13], and graphene [14][15][16], leading to a sensitive and rapid analysis with miniaturized and integrated sensor platforms [17,18].…”

Graphene Solution‐Gated Field‐Effect Transistor for Ultrasound‐Based Wireless and Battery‐Free Biosensing

“…The stability of the CNP is a major issue for biosensors. [ 37–39 ] In PBS and in the chicken tissue, the position of the CNP point was found to be stable over the measurements of the Echo versus V gs transfer curve. Since this parameter is directly linked to the electric environment of the graphene channel, it is already possible to consider this type of device for applications, such as wireless pH sensing, ionic force sensing or any biosensing where the position of the CNP is modified.…”