Reduced Graphene Oxide Field Effect Research Articles

Amine and Thiol Cofunctionalized Reduced Graphene Oxide Field-Effect Transistor for the Selective Detection of Formaldehyde

Amine and Thiol Cofunctionalized Reduced Graphene Oxide Field-Effect Transistor for the Selective Detection of Formaldehyde

Hybrid Modeling and Sensitivity Analysis on Reduced Graphene Oxide Field-Effect Transistor

The reduced graphene oxide (RGO) field-effect transistor (FET) has been developed and applied in various areas. However, the effective modeling and sensitivity analysis on RGO FET is still a very challenging problem due to the randomness of bandgap and density of states (DOS) in RGO. In this paper, we propose to solve the RGO FET modeling problem by integrating the data-driven thinking and the graphene FET model to develop a hybrid model. The proposed model takes advantages of the similarities between graphene and RGO to generalize the existing graphene FET model, and employs RGO FET drain-current data to characterize the specificity of the model. The basic idea in the proposed model is to modify the graphene DOS to approximate the RGO DOS so that the charge density, mobility and other parameters can be achieved through the approximated RGO DOS. We validate the model accuracy with the RGO FET based sensors that detect chemical concentrations in the aqueous environment. The RGO FET sensitivity analysis is also demonstrated to provide guidance for RGO FET application and manufacturing.

Graphene Field Effect Transistor Biosensors Based on Aptamer for Amyloid-β Detection

The development of cost-efficient, sensitive and specific methods to detect amyloid-beta 42 ( $\text{A}\beta 42$ ) biomarkers in cerebrospinal fluid and serum-samples is of considerable interest to enable early and reliable diagnosis of Alzheimer’s disease as a precondition for future disease-modifying therapies. This paper presents a reduced graphene oxide field effect transistor (r-GO FET) for label free ultrasensitive detection of an $\text{A}\beta 42$ -biomarker with RNA aptamer. The channel in the device was formed by reduction of graphene oxide nanosheets by self-assembly process. As a result, the interaction between $\text{A}\beta 42$ and RNA aptamer on the surface of r-GO channel caused a linear response in the shift of the gate voltage ( $\text{V}_{\mathbf {TG}}$ ) where the minimum conductivity occurs. The r-GO FET can detect the biomarker in range of 1ng/ml to 1pg/ml at pH 7.4 with high specificity. The developed r-GO FET is a low-cost, highly sensitive and selective method for detecting tiny concentrations of $\text{A}\beta 42$ , which would also enable measurements in serum-samples.

Reduced graphene oxide-based field effect transistors for the detection of E7 protein of human papillomavirus in saliva.

Several challenging biological sensing concepts have been realized using electrolyte-gated reduced graphene oxide field effect transistors (rGO-FETs). In this work, we demonstrate the interest of rGO-FET for the sensing of human papillomavirus (HPV), one of the most common sexually transmitted viruses and a necessary factor for cervical carcinogenesis. The highly sensitive and selective detection of the HPV-16 E7 protein relies on the attractive semiconducting characteristics of pyrene-modified rGO functionalized with RNA aptamer Sc5-c3. The aptamer-functionalized rGO-FET allows for monitoring the aptamer-HPV-16 E7 protein binding in real time with a detection limit of about 100 pg mL−1 (1.75 nM) for HPV-16 E7 from five blank noise signals (95% confidence level). The feasibility of this method for clinical application in point-of-care technology is evaluated using HPV-16 E7 protein suspended in saliva and demonstrates the successful fabrication of a promising field effect transistor biosensor for HPV diagnosis.Graphical abstract

Electrical and Label-Free Quantification of Exosomes with a Reduced Graphene Oxide Field Effect Transistor Biosensor.

Exosomes are small membrane-bound nanovesicles with a size of 50-150 nm which contain many functional biomolecules, such as nucleic acids and proteins. Due to their high homology with parental generation, they are of great significance in clinical diagnosis. At present, the quantitative detection of low concentrations of cancer-derived exosomes present in biofluids is still a great challenge. In this study, we develop an electrical and label-free method to directly detect exosomes with high sensitivity based on a reduced graphene oxide (RGO) field effect transistor (FET) biosensor. An RGO FET biosensor modified with specific antibody CD63 in the sensing area was fabricated and was used for electrical and label-free quantification of exosomes. The method achieved a low limit of detection down to 33 particles/μL, which is lower than that of many other available methods. In addition, the FET biosensor was employed to detect exosomes in clinical serum samples, showing significant differences in detecting healthy people and prostate cancer (PCa) patients. Different from other technologies, this study provides a unique technology capable of directly quantifying exosomes without labeling, indicating its potential as a tool for early diagnosis of cancer.

Clinical available circulating tumor cell assay based on tetra(4-aminophenyl) porphyrin mediated reduced graphene oxide field effect transistor

Circulating tumor cell (CTC) assay is one of the emerging “liquid biopsy” for cancer's diagnostic, an easy-to-operate and state-of-the-art CTC sensor is the imperative need of clinical medical laboratory. A label-free and solid-state sensor for clinical sample's CTC detection based on an aptamer (AS1411) functionalized graphene field effect transistor (GFET) by using tetra(4-aminophenyl) porphyrin mediated reduced graphene oxide as the channel material. Objects are CTCs of A549, MDA-MB-231, HeLa and HUVEC (as a control) in buffer solutions and EDTA anti-coagulant whole blood samples, as well as the anti-coagulant clinical blood samples from 49 breast cancer patients and 5 healthy persons. The sensitivities for CTCs in the range of 10 - 106 cells/ml are 3.14, 3.32, 2.60%/log10(cells/ml) for A549 (R2 = 0.97), MDA-MB-231 (R2 = 0.96) and HeLa (R2 = 0.98), respectively. Meanwhile, the selectivity for CTCs is also confirmed by the low sensitivity and R2 for HUVEC which are −0.13%/log10(cells/ml) and 0.50. Furthermore, whole blood interference is found to make the sensing range narrow. At last, their applications in grading clinical blood samples are found to be in agreements with the parallel diagnostic conclusions of these patients, samples of adenofibroma and effect of chemotherapy can also be identified. The aptamer specific, directly electronic CTC detection is accomplished by the proposed GFET based CTC sensor, it can provide a novel analytical technique for cancers' clinical assay.

Cascading reaction of arginase and urease on a graphene-based FET for ultrasensitive, real-time detection of arginine

Herein, a biosensor based on a reduced graphene oxide field effect transistor (rGO-FET) functionalized with the cascading enzymes arginase and urease was developed for the detection of L-arginine. Arginase and urease were immobilized on the rGO-FET sensing surface via electrostatic layer-by-layer assembly using polyethylenimine (PEI) as cationic building block. The signal transduction mechanism is based on the ability of the cascading enzymes to selectively perform chemical transformations and prompt local pH changes, that are sensitively detected by the rGO-FET. In the presence of L-arginine, the transistors modified with (PEI/urease(arginase)) multilayers showed a shift in the Dirac point due to the change in the local pH close to the graphene surface, produced by the catalyzed urea hydrolysis. The transistors were able to monitor L-arginine in the 10–1000 μM linear range with a LOD of 10 μM, displaying a fast response and a good long-term stability. The sensor showed stereospecificity and high selectivity in the presence of non-target amino acids. Taking into account the label-free, real-time measurement capabilities and the easily quantifiable, electronic output signal, this biosensor offers advantages over state-of-the-art L-arginine detection methods.

Pulse-Driven Capacitive Lead Ion Detection with Reduced Graphene Oxide Field-Effect Transistor Integrated with an Analyzing Device for Rapid Water Quality Monitoring.

Rapid and real-time detection of heavy metals in water with a portable microsystem is a growing demand in the field of environmental monitoring, food safety, and future cyber-physical infrastructure. Here, we report a novel ultrasensitive pulse-driven capacitance-based lead ion sensor using self-assembled graphene oxide (GO) monolayer deposition strategy to recognize the heavy metal ions in water. The overall field-effect transistor (FET) structure consists of a thermally reduced graphene oxide (rGO) channel with a thin layer of Al2O3 passivation as a top gate combined with sputtered gold nanoparticles that link with the glutathione (GSH) probe to attract Pb2+ ions in water. Using a preprogrammed microcontroller, chemo-capacitance based detection of lead ions has been demonstrated with this FET sensor. With a rapid response (∼1-2 s) and negligible signal drift, a limit of detection (LOD) < 1 ppb and excellent selectivity (with a sensitivity to lead ions 1 order of magnitude higher than that of interfering ions) can be achieved for Pb2+ measurements. The overall assay time (∼10 s) for background water stabilization followed by lead ion testing and calculation is much shorter than common FET resistance/current measurements (∼minutes) and other conventional methods, such as optical and inductively coupled plasma methods (∼hours). An approximate linear operational range (5-20 ppb) around 15 ppb (the maximum contaminant limit by US Environmental Protection Agency (EPA) for lead in drinking water) makes it especially suitable for drinking water quality monitoring. The validity of the pulse method is confirmed by quantifying Pb2+ in various real water samples such as tap, lake, and river water with an accuracy ∼75%. This capacitance measurement strategy is promising and can be readily extended to various FET-based sensor devices for other targets.

Scanning Electrochemical Microscopy as a Characterization Tool for Reduced Graphene Oxide Field Effect Transistors

Scanning Electrochemical Microscopy as a Characterization Tool for Reduced Graphene Oxide Field Effect Transistors

Ultrasensitive Label-Free Detection of PNA–DNA Hybridization by Reduced Graphene Oxide Field-Effect Transistor Biosensor

A reduced graphene oxide (R-GO)-based field-effect transistor (FET) biosensor used for ultrasensitive label-free detection of DNA via peptide nucleic acid (PNA)-DNA hybridization is reported. In this work, R-GO was prepared by reduction of GO with hydrazine, and the FET biosensor was fabricated by drop-casting the R-GO suspension onto the sensor surface. PNA instead of DNA as the capture probe was employed, and DNA detection was performed through PNA-DNA hybridization by the R-GO FET biosensor. The detection limit as low as 100 fM was achieved, which is 1 order of magnitude lower than that of the previously reported graphene FET DNA biosensor based on DNA-DNA hybridization. Moreover, the R-GO FET biosensor was able to distinguish the complementary DNA from one-base mismatched DNA and noncomplementary DNA. Interestingly, the fabricated DNA biosensor was found to have a regeneration capability. The developed R-GO FET DNA biosensor shows ultrasensitivity and high specificity, indicating its potential applications in disease diagnostics as a point-of-care tool.

Facile preparation of an n-type reduced graphene oxide field effect transistor at room temperature

We introduce a facile method to prepare an n-type reduced graphene oxide field effect transistor at room temperature via a typical Benkeser reduction using lithium and ethylenediamine.

Detection of Protein by Reduced Graphene Oxide Field-Effect Transistor

ABSTRACTWe confirmed a specific detection of immunoglobulin E(IgE) by using an aptamer immobilized reduced graphene oxide(rGo) field effect transistor(FET). A detection limit and dynamic range were estimated 8.1 ng/ml and 10000 respectively. These characteristics are comparable with current fluorescent markers. Although a mobility of rGo FET was around 5 cm2/V.sec, and this is two to three orders lower than mechanically exfoliated pristine graphene FET, a sensitivity of it was only one order lower than using pristine graphene.

Reduced graphene oxide field-effect transistor for label-free femtomolar protein detection

We report reduced graphene oxide field effect transistor (R-GO FET) biosensor for label-free ultrasensitive detection of a prostate cancer biomarker, prostate specific antigen/α1-antichymotrypsin (PSA-ACT) complex. The R-GO channel in the device was formed by reduction of graphene oxide nanosheets networked by a self-assembly process. Immunoreaction of PSA-ACT complexes with PSA monoclonal antibodies on the R-GO channel surface caused a linear response in the shift of the gate voltage, Vg,min, where the minimum conductivity occurs. The R-GO FET can detect protein-protein interactions down to femtomolar level with a dynamic range over 6-orders of magnitude in the Vg,min shift as a sensitivity parameter. High association constants of 3.2nM−1 and 4.2nM−1 were obtained for the pH 6.2 and pH 7.4 analyte solutions, respectively. The R-GO FET biosensor showed a high specificity to other cancer biomarker in the phosphate buffered saline solutions as well as in the human serum.

PH Sensing Characteristics and Biosensing Application of Solution-Gated Reduced Graphene Oxide Field-Effect Transistors

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Reduced Graphene Oxide Field Effect Transistor for Multi-Stimuli Responsiveness

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Dual n-type doped reduced graphene oxide field effect transistors controlled by semiconductor nanocrystals

Here, we demonstrate a rapid and simple method for doping a reduced graphene oxide (rGO) field effect transistor (FET) with nanocrystals to produce dual n-type behavior with light and bias voltage. This convenient method promises industrial level doping of graphene transistors.

Real‐Time DNA Detection Using Reduced Graphene Oxide Field Effect Transistors

DNA sensing: Single strands of DNA are covalently attached to nanometer-thick layers of reduced graphene oxide, forming an FET device capable of sensitive, label-free detection of complementary DNA hybridization.

High yield fabrication of chemically reduced graphene oxide field effect transistors bydielectrophoresis

We demonstrate high yield fabrication of field effect transistors (FET) using chemicallyreduced graphene oxide (RGO) sheets. The RGO sheets suspended in water were assembledbetween prefabricated gold source and drain electrodes using ac dielectrophoresis. With theapplication of a backgate voltage, 60% of the devices showed p-type FET behavior, whilethe remaining 40% showed ambipolar behavior. After mild thermal annealing at200 °C, all ambipolar RGO FET remained ambipolar with increased hole andelectron mobility, while 60% of the p-type RGO devices were transformed toambipolar. The maximum hole and electron mobilities of the devices were 4.0 and1.5 cm2 V − 1 s − 1 respectively. High yield assembly of chemically derived RGO FET will have significantimpact in scaled up fabrication of graphene based nanoelectronic devices.