Covalently Grafted Ionic Liquid−Graphene Based Electrochemical and
Photoelectrochemical Biosensors
Dr. Prasenjit Bhunia
Assistant Professor
Department of Chemistry
Silda Chandra Sekhar College
Jhargram, West Bengal
721515, India
1

Introduction
2 Graphene/RGO
 Two-dimensional π-conjugated structure
 Excellent electron acceptors and transporters
 Also, able to accelerate electron transfer and
effectively suppress charge recombination
Ionic Liquid
A metal- or metal oxide-free efficient photoelectrocatalyst and electrocatalyst with ionic liquid (1-(3-aminopropyl)-3-
methylimidazolium bromide (IL−NH2): Decom. Temp. >300 °C)
Why Ionic Liquid?
 Impart excellent conductivity to the RGO nanosheets
 Reduce the electronic band gap of RGO
 Act as a stabilizer for providing stable dispersion (essential for device fabrication)
 Act as a binder (for obtaining a stable film on the ITO substrate)
β-nicotinamide adenine dinucleotide (NADH)
 NADH and its oxidized form (NAD+) (i.e., NADH/NAD+ couple) comprise the cofactor system for
more than 300 dehydrogenase enzymes
 The NADH/NAD+ couple indeed plays a vital role in biological electron transport
 Selected as model biomolecule in this study to demonstrate the proof of concept
Electrochemical Sensors:
That measures the concentration of certain target molecule by
oxidizing or reducing the target molecule at an electrode through
measuring the resulting current.
Photoelectrochemical detection:
Coupling of photoirradiation with electrochemical detection and
then measuring the resulting current.

Imidazolium ionic liquid
grafted through
(a) amide linkage and
(b)epoxy ring opening
3
IL-RGO

(a)
(b) (c)
Characterization of IL-RGO
4
 X-ray photoelectron spectroscopy (XPS)
 Fourier transform infrared (FTIR) spectroscopy
 Raman spectra (excitation wavelength of 514 nm)
 Thermogravimetric analyzer
 X-ray diffraction (XRD) analysis
 Transmission electron microscopy (TEM)
 Atomic force microscopy (AFM)
 Electrochemical analyzer (CH Instruments, CHI842B)
Auxiliary electrode: Platinum wire
Reference electrode: Ag/AgCl
Working electrode: ITO (Modified)
Supporting electrolyte: 0.1 M phosphate buffer solution
(PBS) (pH 7.2)
 Light source: 300 W xenon lamp, equipped with a
monochromator (Newport, Oriel Instruments).

hν
Photoelectrochemical Sensing of NADH with IL-RGO
5
250 – 350 nm
including visible light
Applied potential 0.2 V
 Highest photocurrent
obtained in 300 nm
irradiation

Linear sweep voltammograms of IL-RGO-modified electrode
In 0.1M PBS (pH 7.2), Sweep rate: 10 mV s-1
6

hν
7
Proposed Mechanism

8
Electrochemical
Sensing of
NADH
IL-RGO
+
Redox
Mediator
(Azure A)
In presence of 0 &
200 μM NADH
In presence of 0 &
200 μM NADH
RGO
+0. 23 V
+0. 11 V
+0. 05 V
-0. 24 V
-0. 19 V

9
NADH detection
with
IL-RGO-AzA
IL-RGO-AzA
RGO-AzA
Amperometric Response
Applied potential: -0.05 V
Successive addition: 20 μM
NADH
(a) RGO
(b) RGO-AzA
(c) IL-RGO
(d) IL-RO-AzA
(a) RGO
(b) RGO-AzA
(c) IL-RGO
(d) IL-RO-AzA

Electrochemical
Sensing
of NADH with
N-doped IL-RGO
(N-IL-RGO)
10
N-IL-RGO
N-IL-RGO
IL-RGO
IL-RGO

N
Ribo
ADP
H H
NH2
O
N
Ribo
ADP
NH2
O
+ H+
+ 2e-
NADH NAD+
H
Electrochemical
Oxidation
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NADH detection
with
N-IL-RGO
Amperometric Response
Applied potential:
N-RGO-IL (-0.05 V), IL-RGO (0.0 V) & RGO-control (0.25 V)
Successive addition: 5 μM NADH
N-IL-RGO
IL-RGO
RGO-Control
R2 = 0.98
R2 = 0.99
R2 = 0.97

12
Summary
References
1. Bhunia and Dutta, ACS Appl. Electron. Mater. 3, 2021, 4009−4017.
2. Bhunia and Dutta, Ind. Eng. Chem. Res. 60, 2021, 8035–8042.
3. Bhunia and Dutta, Electrochem. Sci. Adv. 2021, e2100050. doi.org/10.1002/elsa.202100050.
 Ionic liquid has been covalently grafted with RGO nanosheets in a single step
 The hybrid material has been successfully applied as a photoelectrocatalyst towards NADH detection
 The hybrid material, after some modification has also been used as an efficient electrocatalysts towards
NADH sensing