The ability of graphene to transduce an adsorption event of ions into a detectable electrical signal has sparked a lot of interest for its use in sensors. However, a low concentration of the chemically active sites for binding analytes on the graphene surface has significantly prevented its applications so far. Here, we report on implementation of the van der Waals heterostructure based on a monolayer graphene and an ∼1-nm-thick molecular carbon nanomembrane (CNM) in a solution-gated field-effect transistor (FET) for pH sensing. The nondestructive functionalization of a graphene FET with the amino-terminated CNM (NH2-CNM) enables the induction of chemically active groups in the vicinity of the graphene sheet, maintaining its charge carrier transport properties. We applied complementary characterization techniques, including Raman spectroscopy, x-ray photoelectron spectroscopy, and optical and atomic force microscopy as well as field-effect and electrical impedance measurements to characterize the engineered NH2-CNM/graphene devices. We demonstrate their high pH resolution with a minimum detectable pH change of ∼0.01 at pH 2 and ∼0.04 at pH 12, with a response time in the range of seconds, and we apply an electrical double-layer model to rationalize the experimentally observed performance theoretically. The developed device concept enables the engineering of microscale pH sensors for applications in biological and environmental sciences.

1.
E. W.
Hill
,
A.
Vijayaragahvan
, and
K.
Novoselov
, “
Graphene sensors
,”
IEEE Sens. J.
11
,
3161
3170
(
2011
).
2.
S.
Mao
,
J.
Chang
,
H.
Pu
,
G.
Lu
,
Q.
He
,
H.
Zhang
, and
J.
Chen
, “
Two-dimensional nanomaterial-based field-effect transistors for chemical and biological sensing
,”
Chem. Soc. Rev.
46
,
6872
6904
(
2017
).
3.
Z.
Meng
,
R. M.
Stolz
,
L.
Mendecki
, and
K. A.
Mirica
, “
Electrically-transduced chemical sensors based on two-dimensional nanomaterials
,”
Chem. Rev.
119
,
478
598
(
2019
).
4.
J.
Ping
,
J. E.
Blum
,
R.
Vishnubhotla
,
A.
Vrudhula
,
C. H.
Naylor
,
Z.
Gao
,
J. G.
Saven
, and
A. T. C.
Johnson
, “
pH sensing properties of flexible, bias-free graphene microelectrodes in complex fluids: From phosphate buffer solution to human serum
,”
Small
13
,
1700564
(
2017
).
5.
Z.
Tehrani
,
S. P.
Whelan
,
A. B.
Mostert
,
J. V.
Paulin
,
M. M.
Ali
,
E. D.
Ahmadi
,
C. F. O.
Graeff
,
O. J.
Guy
, and
D. T.
Gethin
, “
Printable and flexible graphene pH sensors utilising thin film melanin for physiological applications
,”
2D Mater.
7
,
024008
(
2020
).
6.
H.
Shi
,
N.
Poudel
,
B.
Hou
,
L.
Shen
,
J.
Chen
,
A. V.
Benderskii
, and
S. B.
Cronin
, “
Sensing local pH and ion concentration at graphene electrode surfaces using in situ Raman spectroscopy
,”
Nanoscale
10
,
2398
2403
(
2018
).
7.
M.
Yuqing
,
C.
Jianrong
, and
F.
Keming
, “
New technology for the detection of pH
,”
J. Biochem. Biophys. Methods
63
,
1
9
(
2005
).
8.
Y. H.
Qin
,
H. J.
Kwon
,
M. M. R.
Howlader
, and
M. J.
Deen
, “
Microfabricated electrochemical pH and free chlorine sensors for water quality monitoring: Recent advances and research challenges
,”
RSC Adv.
5
,
69086
69109
(
2015
).
9.
B.
Zhan
,
C.
Li
,
J.
Yang
,
G.
Jenkins
,
W.
Huang
, and
X.
Dong
, “
Graphene field-effect transistor and its application for electronic sensing
,”
Small
10
,
4042
4065
(
2014
).
10.
P. K.
Ang
,
W.
Chen
,
A. T.
Wee
, and
K. P.
Loh
, “
Solution-gated epitaxial graphene as pH sensor
,”
J. Am. Chem. Soc.
130
,
14392
14393
(
2008
).
11.
D.
Akinwande
,
C.
Huyghebaert
,
C. H.
Wang
,
M. I.
Serna
,
S.
Goossens
,
L. J.
Li
,
H. P.
Wong
, and
F. H. L.
Koppens
, “
Graphene and two-dimensional materials for silicon technology
,”
Nature
573
,
507
518
(
2019
).
12.
I.
Fakih
,
F.
Mahvash
,
M.
Siaj
, and
T.
Szkopek
, “
Sensitive precise pH measurement with large-area graphene field-effect transistors at the quantum-capacitance limit
,”
Phys. Rev. Appl.
8
,
044022
(
2017
).
13.
W.
Fu
,
M. E.
Abbassi
,
T.
Hasler
,
M.
Jung
,
M.
Steinacher
,
M.
Calame
,
C.
Schönenberger
,
G.
Puebla-Hellmann
,
S.
Hellmüller
,
T.
Ihn
, and
A.
Wallraff
, “
Electrolyte gate dependent high-frequency measurement of graphene field-effect transistor for sensing applications
,”
Appl. Phys. Lett.
104
,
013102
(
2014
).
14.
A. K.
Geim
and
K. S.
Novoselov
, “
The rise of graphene
,”
Nat. Mater.
6
,
183
191
(
2007
).
15.
F.
Schedin
,
A. K.
Geim
,
S. V.
Morozov
,
E. W.
Hill
,
P.
Blake
,
M. I.
Katsnelson
, and
K. S.
Novoselov
, “
Detection of individual gas molecules adsorbed on graphene
,”
Nat. Mater.
6
,
652
655
(
2007
).
16.
I.
Heller
,
S.
Chatoor
,
J.
Männik
,
M. A.
Zevenbergen
,
J. B.
Oostinga
,
A. F.
Morpurgo
,
C.
Dekker
, and
S. G.
Lemay
, “
Charge noise in graphene transistors
,”
Nano Lett.
10
,
1563
1567
(
2010
).
17.
A.
Castro Neto
,
F.
Guinea
,
N. M.
Peres
,
K. S.
Novoselov
, and
A. K.
Geim
, “
The electronic properties of graphene
,”
Rev. Mod. Phys.
81
,
109
162
(
2009
).
18.
Y.
Ohno
,
K.
Maehashi
,
Y.
Yamashiro
, and
K.
Matsumoto
, “
Electrolyte-gated graphene field-effect transistors for detecting pH and protein adsorption
,”
Nano Lett.
9
,
3318
3322
(
2009
).
19.
Z.
Cheng
,
Q.
Li
,
Z.
Li
,
Q.
Zhou
, and
Y.
Fang
, “
Suspended graphene sensors with improved signal and reduced noise
,”
Nano Lett.
10
,
1864
1868
(
2010
).
20.
J.
Ristein
,
W. Y.
Zhang
,
F.
Speck
,
M.
Ostler
,
L.
Ley
, and
T.
Seyller
, “
Characteristics of solution gated field effect transistors on the basis of epitaxial graphene on silicon carbide
,”
J. Phys. D
43
,
345303
(
2010
).
21.
W.
Fu
,
C.
Nef
,
O.
Knopfmacher
,
A.
Tarasov
,
M.
Weiss
,
M.
Calame
, and
C.
Schönenberger
, “
Graphene transistors are insensitive to pH changes in solution
,”
Nano Lett.
11
,
3597
3600
(
2011
).
22.
B.
Mailly-Giacchetti
,
A.
Hsu
,
H.
Wang
,
V.
Vinciguerra
,
F.
Pappalardo
,
L.
Occhipinti
,
E.
Guidetti
,
S.
Coffa
,
J.
Kong
, and
T.
Palacios
, “
pH sensing properties of graphene solution-gated field-effect transistors
,”
J. Appl. Phys.
114
,
084505
(
2013
).
23.
X. B.
Tan
,
H. J.
Chuang
,
M. W.
Lin
,
Z. X.
Zhou
, and
M. M. C.
Cheng
, “
Edge effects on the pH response of graphene nanoribbon field effect transistors
,”
J. Phys. Chem. C
117
,
27155
27160
(
2013
).
24.
L.
Zuccaro
,
J.
Krieg
,
A.
Desideri
,
K.
Kern
, and
K.
Balasubramanian
, “
Tuning the isoelectric point of graphene by electrochemical functionalization
,”
Sci. Rep.
5
,
11794
(
2015
).
25.
K. S.
Novoselov
,
V. I.
Fal'ko
,
L.
Colombo
,
P. R.
Gellert
,
M. G.
Schwab
, and
K.
Kim
, “
A roadmap for graphene
,”
Nature
490
,
192
200
(
2012
).
26.
V.
Georgakilas
,
M.
Otyepka
,
A. B.
Bourlinos
,
V.
Chandra
,
N.
Kim
,
K. C.
Kemp
,
P.
Hobza
,
R.
Zboril
, and
K. S.
Kim
, “
Functionalization of graphene: Covalent and non-covalent approaches, derivatives and applications
,”
Chem. Rev.
112
,
6156
6214
(
2012
).
27.
M.
Gobbi
,
E.
Orgiu
, and
P.
Samorì
, “
When 2D materials meet molecules: Opportunities and challenges of hybrid organic/inorganic van der Waals heterostructures
,”
Adv. Mater.
30
,
1706103
(
2018
).
28.
R.
Phillipson
,
C. J.
Lockhart de la Rosa
,
J.
Teyssandier
,
P.
Walke
,
D.
Waghray
,
Y.
Fujita
,
J.
Adisoejoso
,
K. S.
Mali
,
I.
Asselberghs
,
C.
Huyghebaert
,
H.
Uji-i
,
S.
De Gendt
, and
S.
De Feyter
, “
Tunable doping of graphene by using physisorbed self-assembled networks
,”
Nanoscale
8
,
20017
20026
(
2016
).
29.
G.
Rajesh
,
Z.
Gao
,
A. T. C.
Johnson
,
N.
Puri
,
A.
Mulchandani
, and
D. K.
Aswal
, “
Scalable chemical vapor deposited graphene field-effect transistors for bio/chemical assay
,”
Appl. Phys. Rev.
8
,
011311
(
2021
).
30.
S.
Adam
,
E. H.
Hwang
,
V. M.
Galitski
, and
S. D.
Sarma
, “
A self-consistent theory for Graphene Transport
,”
PNAS
104
,
18392
18397
(
2007
).
31.
P.
Salvo
,
B.
Melai
,
N.
Calisi
,
C.
Paoletti
,
F.
Bellagambi
,
A.
Kirchhain
,
M. G.
Trivella
,
R.
Fuoco
, and
F. D.
Francesco
, “
Graphene-based devices for measuring pH
,”
Sensor Actuat. B Chem.
256
,
976
991
(
2018
).
32.
A.
Turchanin
and
A.
Gölzhäuser
, “
Carbon nanomembranes
,”
Adv. Mater.
28
,
6075
6103
(
2016
).
33.
M.
Woszczyna
,
A.
Winter
,
M.
Grothe
,
A.
Willunat
,
S.
Wundrack
,
R.
Stosch
,
T.
Weimann
,
F.
Ahlers
, and
A.
Turchanin
, “
All-carbon vertical van der Waals heterostructures: Non-destructive functionalization of graphene for electronic applications
,”
Adv. Mater.
26
,
4831
4837
(
2014
).
34.
C.
Neumann
,
R. A.
Wilhelm
,
M.
Küllmer
, and
A.
Turchanin
, “
Low-energy electron irradiation induced synthesis of molecular nanosheets: Influence of the electron beam energy
,”
Faraday Discuss.
227
,
61
79
(
2021
).
35.
Z.
Tang
,
A.
George
,
A.
Winter
,
D.
Kaiser
,
C.
Neumann
,
T.
Weimann
, and
A.
Turchanin
, “
Optically triggered control of the charge carrier density in chemically functionalized graphene field effect transistors
,”
Chem. Eur. J.
26
,
6473
6478
(
2020
).
36.
E.
Rossi
,
S.
Adam
, and
S. D.
Sarma
, “
Effective medium theory for disordered two-dimensional graphene
,”
Phys. Rev. B
79
,
245423
(
2009
).
37.
X.
Li
,
W.
Cai
,
J.
An
,
S.
Kim
,
J.
Nah
,
D.
Yang
,
R.
Piner
,
A.
Velamakanni
,
I.
Jung
,
E.
Tutuc
,
S. K.
Banerjee
,
L.
Colombo
, and
R. S.
Ruoff
, “
Large-area synthesis of high-quality and uniform graphene films on copper foils
,”
Science
324
,
1312
1314
(
2009
).
38.
X.
Zhang
,
E.
Marschewski
,
P.
Penner
,
T.
Weimann
,
P.
Hinze
,
A.
Beyer
, and
A.
Gölzhäuser
, “
Large-area all-carbon nanocapacitors from graphene and carbon nanomembranes
,”
ACS Nano
12
,
10301
10309
(
2018
).
39.
C.
Jang
,
S.
Adam
,
J. H.
Chen
,
E. D.
Williams
,
S.
Das Sarma
, and
M. S.
Fuhrer
, “
Tuning the effective fine structure constant in graphene: Opposing effects of dielectric screening on short- and long-range potential scattering
,”
Phys. Rev. Lett.
101
,
146805
(
2008
).
40.
S.
Adam
, in
Graphene Nanoelectronics
, edited by
H.
Raza
(
Springer
Berlin Heidelberg
,
2011
), pp.
357
394
.
41.
J.
Xia
,
F.
Chen
,
J.
Li
, and
N.
Tao
, “
Measurement of the quantum capacitance of graphene
,”
Nat. Nanotechnol.
4
,
505
509
(
2009
).
42.
I.
Meric
,
M. Y.
Han
,
A. F.
Young
,
B.
Ozyilmaz
,
P.
Kim
, and
K. L.
Shepard
, “
Current saturation in zero-bandgap, top-gated graphene field-effect transistors
,”
Nat. Nanotechnol.
3
,
654
659
(
2008
).
43.
A.
Turchanin
,
D.
Käfer
,
M.
El-Desawy
,
C.
Wöll
,
G.
Witte
, and
A.
Gölzhäuser
, “
Molecular mechanisms of electron-induced cross-linking in aromatic SAMs
,”
Langmuir
25
,
7342
7352
(
2009
).
44.
J.
Park
,
W. H.
Lee
,
S.
Huh
,
S. H.
Sim
,
S. B.
Kim
,
K.
Cho
,
B. H.
Hong
, and
K. S.
Kim
, “
Work-function engineering of graphene electrodes by self-assembled monolayers for high-performance organic field-effect transistors
,”
J. Phys. Chem. Lett.
2
,
841
845
(
2011
).
45.
H.-J.
Butt
,
K.
Graf
, and
M.
Kappl
,
Physics and Chemistry of Interfaces
(
John Wiley & Sons
,
2013
).
46.
I.
Heller
,
S.
Chatoor
,
J.
Männik
,
M. A.
Zevenbergen
,
C.
Dekker
, and
S. G.
Lemay
, “
Influence of electrolyte composition on liquid-gated carbon nanotube and graphene transistors
,”
J. Am. Chem. Soc.
132
,
17149
17156
(
2010
).
47.
M.
Batzill
, “
The surface science of graphene: Metal interfaces, CVD synthesis, nanoribbons, chemical modifications, and defects
,”
Surf. Sci. Rep.
67
,
83
115
(
2012
).
48.
M.
Gutman
and
E.
Nachliel
, “
The dynamics of proton exchange between bulk and surface groups
,”
Biochim. Biophys. Acta Bioenerg.
1231
,
123
138
(
1995
).
49.
H.
Wang
,
Y.
Wu
,
C.
Cong
,
J.
Shang
, and
T.
Yu
, “
Hysteresis of electronic transport in graphene transistors
,”
ACS Nano
4
,
7221
7228
(
2010
).
50.
C.
Backes
,
A. M.
Abdelkader
,
C.
Alonso
,
A.
Andrieux-Ledier
,
R.
Arenal
,
J.
Azpeitia
,
N.
Balakrishnan
,
L.
Banszerus
,
J.
Barjon
,
R.
Bartali
, et al., “
Production and processing of graphene and related materials
,”
2D Mater.
7
,
022001
(
2020
).
51.
A.
Veligura
,
P. J.
Zomer
,
I. J.
Vera-Marun
,
C.
Józsa
,
P. I.
Gordiichuk
, and
B. J. v.
Wees
, “
Relating hysteresis and electrochemistry in graphene field effect transistors
,”
J. Appl. Phys.
110
,
113708
(
2011
).
52.
A.
Turchanin
,
A.
Beyer
,
C. T.
Nottbohm
,
X. H.
Zhang
,
R.
Stosch
,
A.
Sologubenko
,
J.
Mayer
,
P.
Hinze
,
T.
Weimann
, and
A.
Gölzhäuser
, “
One nanometer thin carbon nanosheets with tunable conductivity and stiffness
,”
Adv. Mater
21
,
1233
1237
(
2009
).

Supplementary Material

You do not currently have access to this content.