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

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 electronics^1,2, sensing^3,4,5, energy storage^6,7, and photocatalysis^1,6,8. 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 (C....

Protocol

1. Transferring chemical vapor deposition of graphene

1. 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).
2. Spin-coat the sheet of the graphene with a thin layer (100-200 nm) of PMMA 495K A4 spinning at 500 rpm.......

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.......

Materials

Name	Company	Catalog Number	Comments
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