Electronic supplementary material
Titanium dioxide anchored graphene oxide nanosheets for highly selective voltammetric
sensing of dopamine
Durairaj S. Ruby Josephine1 .Kaliyamoorthy Justice Babu2 .George peter Gnana kumar2,*
.
Kunjithapatham Sethuraman1,*
1
School of Physics, Madurai Kamaraj University, Madurai-625021, Tamil Nadu, India
2
Department of Physical Chemistry, School of Chemistry, Madurai Kamaraj University,
Madurai-625021, Tamil Nadu, India
*Corresponding authors,
K. Sethuraman: e-mail: [email protected]; Tel. No: 91-9445252309
G. Gnanakumar: e-mail: [email protected]; Tel. No: 91-9585752997
Morphological and optical studies
The typical SEM images of graphene oxide (GO) and GO/TiO2 (graphene oxide/titanium
dioxide) nanocomposite (NC) are depicted in Fig. S1. All of the obtained SEM images confirmed
the sheet like features of GO (Fig. S1). The successful decoration of TiO2 nanoparticles (NPs) on
GO sheets has also been confirmed for the GO/TiO2 composite (Fig. S1(b)). The elemental
purity of GO/TiO2 NC was observed from the EDAX pattern of GO/TiO2 composite.
1
Fig. S1 (a, b) SEM images of GO and GO/ TiO2 nanostructures and (c) EDAX spectrum of
GO/TiO2 nanostructures.
PL spectroscopy
The PL spectra of GO and GO/TiO2 NC are depicted in Fig. S2. The PL spectrum of GO
showed a strong emission peak centered at 365 nm, corresponding to crystalline graphitic Sp2
network of GO. The PL spectrum of GO/TiO2 NC (Fig. S2 (b)) exhibited the similar emission
peak with the decreased intensity in comparison with GO (Fig. S2 (a)).
2
Fig. S2 PL spectra of (a) GO and (b) GO/ TiO2 nanocomposite.
DPV studies
The DPV technique was exploited for the selective detection of DA in the presence of
AA and UA and the DPV measurements were carried out at bare GCE and GO/TiO2/GCE in
0.1 M phosphate buffer containing 20 M DA, 2 mM AA and 0.2 mM UA (fig. S3). The bare
GCE exhibited poor selectivity in the ternary mixture as evidenced from the overlapped
voltammetric peaks for AA- DA (fig. S3 (a)). However, GO/TiO2/GCE exhibited three distinct
voltammetric peaks for AA, DA and UA with the peak potential at -0.04 (AA), 0.22 (DA) and
0.41 (UA) V vs. Ag/AgCl respectively (fig. S3 (b)). The separation of peak potentials of AA-DA
and DA-UA were found to be 0.26 and 0.19 V vs. Ag/AgCl, respectively, and are influential
enough to explore the DA selectivity. In addition, GO/TiO2/GCE exhibited high oxidation
current even under the lower concentration of DA (0.02 mM), which is 100 and 10 fold lower
than that of AA and UA. At pH=7.2, AA (pKa=4.10) and UA (pKa=5.27) exhibited the negative
charge, whereas DA (pKa=8.87) exhibited the positive charge [1]. Hence, it is clear that the
negatively charged GO/TiO2 exhibited the repelling effects against the negatively charged AA
and UA and electrostatically interacted with the positively charged DA, which facilitated the
selectivity of fabricated sensors toward DA.
3
Fig. S3 DPV curves of 20M DA, 2 mM AA and 0.2 mM UA in pH (7.2) phosphate buffer
on (a) bare GCE and (b) GO/TiO2/GCE (Amplitude: 0.05 V, Pulse width: 0.05 s, Sample
width: 0.02 s and Pulse period: 0.5 s).
Table S1 Figures of merit of recently reported nanomaterial based methods for
preconcentration of dopamine in presence of uric acid and ascorbate.
LODa
(μM)
Electrode materials
Linear
range (M)
GOb/GCEc
1.0–15
0.27
2
Graphene/GCEc
4.0–100
2.64
3
TiO2/Graphene/GCEc
5–200
2.0
4
Fe3O4/RGOd/GCEc
0.5–100
0.12
5
Au/RGOd/GCEc
6.8–4.1
1.4
6
GRe/SnO2/GCEc
0.5–500
0.13
7
Au/Graphene/GCEc
5–1000
1.86
8
Pt/RGOd/GCEc
10–170
0.25
9
Ag/RGOd/GCEc
10–800
5.4
10
4
Ref.
GNSf/GCEc
4–52
0.6
11
Tg- Graphene/GCEc
0.5–110
0.29
12
N-doped graphene/GCEc
100–450
0.93
13
Fe3O4/Gold electrode
0.15–400
0.03
14
TiO2/rGOd/GCEc
2–60
6.0
15
GNSf
2–1000
0.85
16
MWCNT-BPVCMh
5–300, 300–1000
2.28
17
Porous Cu2O
nanospheres-rGOd
Gold nanosheets
0.05–109.0
0.015
18
2–298
0.28
19
B-MWCNTsj
62–280
0.11
20
hnp-PtCuj
200–1000
25.1
21
Pdk-Np
0.1–151
0.030
22
Ni(Phen)l2]2+ - SWCNT
1–780
1
23
CNT-NiNCm
0.3–7, 7–240
0.1
24
MoS2n-RGO
5–545
0.05
25
f-RGOd nanosheet clusters
5–70, 100–600
3
26
P2W16V2o-AuPdp
103–1650
0.83
27
Pd Nps-GO
20–2280
–
28
GR-CSq
5–200
–
29
GOb/TiO2/GCEc
0.2–10
0.027
This
work
a
Limit of detection. bGraphene oxide. cGlassy carbon electrode. dReduced
f
graphene oxide. eGraphene.
Graphene nanosheet. gTryphtophan
h
functionalized. Multiwalled carbon nanotubes- electroactive polymer
composite. iMultiwalled carbon nanotubes. fhierrachial nanoporous
k
l
PlatiniumCopper
alloy.
palladium.
Nickel(II)-bis(1,10m
n
phenanthroline). Nickel (II) norcorrole. Molybdenum diSulphide
o
PolyPhosphorovanado tungstate. pGold-Palladium. qChitosan.
5
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