A graphene field-effect capacitor sensor in electrolyte

Chen, Si; Zhang, Zhibin; Ma, Lixia; Ahlberg, Patrik; Gao, Xindong; Qiu, Zhijun; Wu, Di; Ren, Wencai; Cheng, Hui‐Ming; Zhang, Shi-Li

doi:10.1063/1.4759147

Cited by 29 publications

(16 citation statements)

References 32 publications

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“…In aqueous media, molecular binding on a graphene surface creates a self-assembled monolayer (SAM) and forms an electrical double layer (EDL), which is a thin layer at the interface of an electrolyte solution and a charge surface in which counter ions dominate co-ions in concentration(Fujimoto and Awaga 2013). In our device, the EDL can be represented as a parallel-plate capacitor on the graphene surface(Chen et al 2012), across which a top-gate voltage V gs is applied and controls the carrier density and the electrical conductivity of graphene.…”

Section: Resultsmentioning

confidence: 99%

An aptameric graphene nanosensor for label-free detection of small-molecule biomarkers

Wang

Kim

Zhu

et al. 2015

Biosensors and Bioelectronics

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This paper presents an aptameric graphene nanosensor for detection of small-molecule biomarkers. To address difficulties in direct detection of small molecules associated with their low molecular weight and electrical charge, we incorporate an aptamer-based competitive affinity assay in a graphene field effect transistor (FET), and demonstrate the utility of the nanosensor with dehydroepiandrosterone sulfate (DHEA-S), a small-molecule steroid hormone, as the target analyte. In the competitive affinity assay, DHEA-S specifically binds to aptamer molecules pre-hybridized to their complementary DNA anchor molecules immobilized on the graphene surface. This results in the competitive release of the strongly charged aptamer from the DNA anchor and hence a change in the conductance of the graphene, which can be measured to achieve the detection of DHEA-S. We present experimental data on the label-free, specific and quantitative detection of DHEA-S at clinically appropriate concentrations with an estimated detection limit of 44.7 nM, and analyze the trend observed in the experiments using molecular binding kinetics theory. These results demonstrate the potential of our nanosensor in the detection of DHEA-S and other small molecules in biomedical applications.

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Section: Resultsmentioning

confidence: 99%

An aptameric graphene nanosensor for label-free detection of small-molecule biomarkers

Wang

Kim

Zhu

et al. 2015

Biosensors and Bioelectronics

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“…However, high gating potentials will inevitably cause specific adsorption of ions at the graphenesolution interface, which can be efficiently used for ion and pH sensing applications of graphene, in both the transistor and capacitor modes [13]. Our future effort will be devoted to amending the present model of graphene capacitance in the presence of specific adsorption in an electrolyte.…”

Section: Discussionmentioning

confidence: 98%

“…However, it is possible to invert the function p 3 in Eq. (13) to express the potential as φ h = p −1 3 (E h ), which may be then substituted on the right-hand side of Eq. (15) to give the DL capacitance as a function of the electric field at the Stern plane, C d = C d (E h ).…”

Section: B Capacitance Of Diffuse Layermentioning

confidence: 99%

“…On the other hand, it was recently demonstrated that operating a graphene field effect device in the capacitor mode exhibits more sensitivity to variations in both the ion concentration and the pH of an aqueous solution of salt than operating such a device in the transistor mode [13]. This is related to the well-known fact that, when a semimetal such as graphite [14] or the conductive single crystalline diamond [15,16] are used as electrodes in an aqueous electrolyte, the overall capacitance of the EDL is dominated by the so-called quantum capacitance (QC) of such electrodes, which is in contrast to the case of an ideal metallic electrode [10].…”

Section: Introductionmentioning

confidence: 98%

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Capacitance of graphene in aqueous electrolytes: The effects of dielectric saturation of water and finite size of ions

Sharma

Mišković

2014

Phys. Rev. B

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We present a theoretical model for electrolytically top-gated graphene, in which we analyze the effects of dielectric saturation of water due to possibly strong electric fields near the surface of a highly charged graphene, as well as the steric effects due to the finite size of salt ions in an aqueous electrolyte. By combining two well-established analytical models for those two effects, we show that the total capacitance of the solution-gated graphene is dominated by its quantum capacitance for gating potentials 1 V, which is the range of primary interest for most sensor applications of graphene. On the other hand, at the potentials 1 V the total capacitance is dominated by a universal capacitance of the electric double layer in the electrolyte, which exhibits a dramatic decrease of capacitance with increasing gating potential due to the interplay of a fully saturated dielectric constant of water and ion crowding near graphene.

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“…For more accurate and consistent results, each of these physical and chemical parameters must be considered and optimized accordingly [34]. ISFETs can be based on many materials as their detectors such as membranes and graphene [35]. Because of the physical and electrical properties of graphene, it can be applied as a sensing material in the structure of FETs [35].…”

Section: Introductionmentioning

confidence: 99%

Analytical modelling of monolayer graphene-based ion-sensitive FET to pH changes

et al. 2013

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Graphene has attracted great interest because of unique properties such as high sensitivity, high mobility, and biocompatibility. It is also known as a superior candidate for pH sensing. Graphene-based ion-sensitive field-effect transistor (ISFET) is currently getting much attention as a novel material with organic nature and ionic liquid gate that is intrinsically sensitive to pH changes. pH is an important factor in enzyme stabilities which can affect the enzymatic reaction and broaden the number of enzyme applications. More accurate and consistent results of enzymes must be optimized to realize their full potential as catalysts accordingly. In this paper, a monolayer graphene-based ISFET pH sensor is studied by simulating its electrical measurement of buffer solutions for different pH values. Electrical detection model of each pH value is suggested by conductance modelling of monolayer graphene. Hydrogen ion (H+) concentration as a function of carrier concentration is proposed, and the control parameter (Ƥ) is defined based on the electro-active ions absorbed by the surface of the graphene with different pH values. Finally, the proposed new analytical model is compared with experimental data and shows good overall agreement.

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A graphene field-effect capacitor sensor in electrolyte

Cited by 29 publications

References 32 publications

An aptameric graphene nanosensor for label-free detection of small-molecule biomarkers

An aptameric graphene nanosensor for label-free detection of small-molecule biomarkers

Capacitance of graphene in aqueous electrolytes: The effects of dielectric saturation of water and finite size of ions

Analytical modelling of monolayer graphene-based ion-sensitive FET to pH changes

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