Summary

Development and Functionalization of Electrolyte-Gated Graphene Field-Effect Transistor for Biomarker Detection

Published: February 01, 2022
doi:

Summary

The present protocol demonstrates the development of electrolyte-gated graphene field-effect transistor (EGGFET) biosensor and its application in biomarker immunoglobulin G (IgG) detection.

Abstract

In the current study, graphene and its derivatives have been investigated and used for many applications, including electronics, sensing, energy storage, and photocatalysis. Synthesis and fabrication of high quality, good uniformity, and low defects graphene are critical for high-performance and highly sensitive devices. Among many synthesis methods, chemical vapor deposition (CVD), considered a leading approach to manufacture graphene, can control the number of graphene layers and yield high-quality graphene. CVD graphene needs to be transferred from the metal substrates on which it is grown onto insulating substrates for practical applications. However, separation and transferring of graphene onto new substrates are challenging for a uniform layer without damaging or affecting graphene's structures and properties. Additionally, electrolyte-gated graphene field-effect transistor (EGGFET) has been demonstrated for its wide applications in various biomolecular detections because of its high sensitivity and standard device configuration. In this article, poly (methyl methacrylate) (PMMA)-assisted graphene transferring approach, fabrication of graphene field-effect transistor (GFET), and biomarker immunoglobulin G (IgG) detection are demonstrated. Raman spectroscopy and atomic force microscopy were applied to characterize the transferred graphene. The method is shown to be a practical approach for transferring clean and residue-free graphene while preserving the underlying graphene lattice onto an insulating substrate for electronics or biosensing applications.

Introduction

Graphene and its derivatives have been investigated and used for many applications, including electronics1,2, sensing3,4,5, energy storage6,7, and photocatalysis1,6,8. Synthesis and fabrication of high quality, good uniformity, and low defects graphene are critical for high-performance and highly sensitive devices. Since the development of Chemical vapor deposition (CVD) in 2009, it has shown colossal promise and set its place as an essential member of the graphene family9,10,11,12,13. It is grown on a metal substrate and, later for practical uses, is transferred onto insulating substrates14. Several transferring methods have been used to transfer CVD graphene recently. The poly (methyl methacrylate) (PMMA) assisted method is the most used among the different techniques. This method is particularly well-suited for industrial usage because of its large-scale capability, lower cost, and high quality of the transferred graphene14,15. The critical aspect of this method is getting rid of the PMMA residue for CVD graphene's applications because the residues can cause declination of the electronic properties of graphene14,15,16, cause an effect on biosensors' sensitivity and performance17,18, and create significant device-to-device variations19.

Nanomaterials-based biosensors have been significantly investigated over the past decades, including silicon nanowire (SiNW), carbon nanotube (CNT), and graphene20. Because of its single-atom-layer structure and distinctive properties, graphene demonstrates superior electronic characteristics, good biocompatibility, and facile functionalization, making it an attractive material for developing biosensors14,21,22,23. Due to field-effect transistors (FET) characteristics such as high sensitivity, standard configuration, and cost-effective mass producibility21,24, FET is more preferred in portable and point-of-care implementations than other electronics-based biosensing devices. The electrolyte-gated graphene field-effect transistor (EGGFET) biosensors are examples of the stated FETs21,24. EGGFET can detect various targeting analytes such as nucleic acids25, proteins24,26, metabolites27, and other biologically relevant analytes28. The technique mentioned here ensures the implementation of CVD graphene in a label-free biosensing nanoelectronics device which offers higher sensitivity and accurate time detection over other biosensing devices29.

In this work, an overall process for developing an EGGFET biosensor and functionalizing it for biomarker detection, including transferring CVD graphene onto an insulating substrate, Raman, and AFM characterizations of the transferred graphene, are demonstrated. Furthermore, fabrication of EGGFET and integration with a polydimethylsiloxane (PDMS) sample delivery well, bioreceptor functionalization, and successful detection of human immunoglobulin G (IgG) from serum by spike-and-recovery experiments are also discussed here.

Protocol

1. Transferring chemical vapor deposition of graphene Cut the graphene sheet on a copper substrate in half (2.5 cm x 5 cm) using scissors. Apply heat resistive tape to fix the four corners of the graphene square on a spinner gasket (see Table of Materials). NOTE: The purchased graphene has a dimension of 5 cm x 5 cm (see Table of Materials). Spin-coat the sheet of the graphene with a thin layer (100-200 nm) of PMMA 495K A4 spinning at 500 rpm…

Representative Results

The representative results show the transferred CVD graphene characterized by Raman and AFM, respectively. The G peak and the 2D peaks of the Raman image give comprehensive information regarding the existence and the quality of the transferred monolayer graphene32 (Figure 1). Standard lithography processes30,31 were applied for fabricating the GFET device, as shown in Figure 2. <s…

Discussion

The purchased CVD graphene on copper film needs to be trimmed to the right size for the following fabrication steps. Cutting of the films can cause wrinkling, which needs to be prevented. The parameters provided in the fabrication step can be referred to for plasma etching of graphene, and these numbers could be varied when using different instruments. The etched sample must be closely monitored and inspected to ensure complete graphene etching. Multiple pre-cleaning methods can be applied to clean the substrates, such a…

Disclosures

The authors have nothing to disclose.

Acknowledgements

The experiments were conducted at West Virginia University. We acknowledge the Shared Research Facilities at West Virginia University for device fabrication and material characterization. This work was supported by the US National Science Foundation under Grant No. NSF1916894.

Materials

1-pyreneutyric acid N- hydroxysuccinimide ester Sigma Aldrich 457078-1G functionalization
Asylum MFP-3D Atomic Force Microscope Oxford Instruments graphene characterization
AZ 300 MIF MicroChemicals AZ 300 MIF photoresist developer
AZ 300 MIF MicroChemicals AZ 300 MIF photoresist
Bovine Serum Albumin Sigma Aldrich 810014 blocking
Branson 1210 Sonicator SONITEK sample cleaning
Copper Etchant Sigma Aldrich 667528-500ML removing copper film to release graphene
Dimethyl Sulfoxide (DMSO) VWR 97063-136 functionalization
Disposable Biopsy Punches, Integra Miltex VWR 21909-144 create well in PDMS
Gold etchant Gold Etch, TFA, Transene 658148 enchant
Graphene Graphene supermarket 2" x 2" sheet biosensing element of the device
IgG aptamer Base Pair Biotechnologies customized bioreceptor
Keithley 4200A-SCS Parameter Analyzer Tektronix measurement and detection
KMG CR-6 KMG chemicals 64216 Chromium etchant
Kurt J. Lesker E-beam Evaporator Kurt J. Lesker metal deposition
Laurell Technologies 400 Spinners Laurell Technologies WS-400BZ-6NPP/LITE thin film coating
March PX-250 Plasma Asher March Instruments sample cleaning
Nickel etchant Nickel Etchant, TFB, Transene 600016000 etchant
OAI Flood Exposure OAI photolithography
Phosphate Buffered Saline (PBS) Sigma Aldrich 806552-500ML buffer
PMMA 495K A4 MicroChemicals PMMA 495K A4 Photoresist for assisting graphene transferring
Polydimethylsiloxane (PDMS) Sigma Aldrich Sylgard 184 sample delivery well
Renishaw InVia Raman Microscope Renishaw graphene characterization
Sodium Hydroxide (NaOH) Sigma Aldrich 221465-25G functionalization
Suss Microtech MA6 Mask Aligner Suss MicroTec photolithography
Thermo Scientific Cimarec Hotplate Thermo Scientific SP131635 sample and device Baking

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Cite This Article
Ishraq, S., Sun, J., Liu, Y. Development and Functionalization of Electrolyte-Gated Graphene Field-Effect Transistor for Biomarker Detection. J. Vis. Exp. (180), e63393, doi:10.3791/63393 (2022).

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