Gold nanoparticle-based probe for colorimetric detection of copper ions

Article abstract of DOI:10.1166/jnn.2017.12419

A new ligand 10-mercaptodecyl-1-iminodiacetic acid (MDIA) was synthesized and used to modify gold nanoparticles to provide a simple assay to repeatedly sense Cu²⁺ in the solution at room temperature. This functionalized gold nanosensor was applied for the detection of Cu²⁺ in water samples with sensitivity and simplicity. The chelation/aggregation process is reversible via addition of a strong metal ion chelator such as EDTA. This simple and fast colorimetric sensor is important in the application of copper ion detection in water quality during the emergency and early warning monitoring.

Full text of DOI:10.1166/jnn.2017.12419

Article
Journal of
Nanoscience and Nanotechnology
Vol. 17, 502–506, 2017
Copyright © 2017 American Scientific Publishers
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Gold Nanoparticle-Based Probe for Colorimetric
Detection of Copper Ions
Weiwei Chai, Qingyue Feng, Meijuan Nie, Chong Wang, Yangjing Jiang,
Huimin Zheng, and Mei-Jin Li∗
Key Laboratory of Analysis and Detection Technology for Food Safety (Ministry of Education and Fujian Province),
Department of Chemistry, College of Chemistry, Fuzhou University, Fuzhou 350108, P. R. China
A new ligand 10-mercaptodecyl-1-iminodiacetic acid (MDIA) was synthesized and used to modify
gold nanoparticles to provide a simple assay to repeatedly sense Cu2+ in the solution at room
temperature. This functionalized gold nanosensor was applied for the detection of Cu2+ in water
samples with sensitivity and simplicity. The chelation/aggregation process is reversible via addition
of a strong metal ion chelator such as EDTA. This simple and fast colorimetric sensor is important
in the application of copper ion detection in water quality during the emergency and early warning
monitoring.
Keywords: Gold Nanoparticles, Copper Ion, Colorimetric Sensor.
IP: 95.85.69.23 On: Mon, 08 Oct 2018 11:49:05
Copyright: American Scientific Publishers
1. INTRODUCTION
Delivered by InTgheentaapplications of Au nanoparticles (Au-NPs) in
analysis have drawn great interest due to their high
extinction and strong size- and distance-dependent optical
properties.9–13 The other feature that makes them partic-
ularly appealing is color changes induced by association
of Au-NPs which enables them as a good candidate for
the colorimetric assay to sensing of amino acids,14,15 pro-
teins,16–20 metal ions21–26 and so on. A kind of reusable
nanosensor based on functionalized Au-NPs with chelating
ligand for the simple and rapid detection copper ion in the
solution was developed in our work. The repeated sensing
procedure was shown in Scheme 1. The functionalized Au-
NPs showed red color in water, it would aggregate after
addition of copper ion with the color from red to purple
blue. The obtained Au-NPs-MDIA-Cu2+ composites were
redispersed in water, and the blue color would change to
red after addition of the chelator EDTA. Then the mix-
ture was centrifuged again to separate the copper complex
and functionalized Au-NPs which were reused in the next
sensing of copper ions.
In recent years, growing attention has been given to the
potential health hazards presented by copper, mercury,
lead, chromium, cadmium, and arsenic (As). Heavy metals
are among the most dangerous contaminants for the envi-
ronment and human beings. Rapid industrialization has led
to the deterioration in water quality due to various contam-
inants, many of which contain high levels of toxic pollu-
tants.1 Mostly heavy metals originate from anthropogenic
sources such as long-term discharge of untreated industrial
effluents.2 This is an alarm to safety of public health and
aquatic environment in earth.
Copper is a transition element essential to human health.
It produces numerous enzymes critical for life. Despite
the essential role of copper ion (Cu2+) for a number of
key metabolic enzymes,3 the toxicity of Cu2+ has aroused
extensive concern because of the increasing Cu2+ con-
centration in aquatic system from the increasing indus-
trial activities. Considerable work was carried out on the
Cu2+ sensor by the colorimetric assay recently.4–8 How-
ever, most of the methods were time-consuming, compli-
cated or costly. Therefore, it is still a great need for the
development of successful and reusable nanosensor for the
fast determination of copper ion in spent solution with high
sensitivity and simplicity in operation.
2. EXPERIMENTAL DETAILS
2.1. Materials
Compound methyl iminodiacetate and HO(CH2ꢀ10OH
were purchased from Aladdin Reagent Co. Br(CH2ꢀ10Br
and 10-bromodecyl-1-iminodiacetate were synthesized by
∗Author to whom correspondence should be addressed.
502
J. Nanosci. Nanotechnol. 2017, Vol. 17, No. 1
1533-4880/2017/17/502/005
doi:10.1166/jnn.2017.12419

Chai et al.
Gold Nanoparticle-Based Probe for Colorimetric Detection of Copper Ions
IP: 95.85.69.23 On: Mon, 08 Oct 2018 11:49:05
Scheme 1. The procedure for repeated sensing of copper ion in the solution.
Copyright: American Scientific Publishers
Delivered by Ingenta
modification of literature methods.27,28 Other chemicals
were analytical reagent graded and used as received. All
solutions were prepared with deionized water (Milli-Q,
Millipore).
shifts (ppm) were reported relative to tetramethylsilane
(Me4Si). Atomic Absorption Spectra (AAS) were carried
on a TAS-986 Flame Atomic Absorption Spectrophotome-
ter. UV-Vis absorption spectra were taken on a Lambda
750 spectrophotometer.
2.2. Instrumentations
2.3. Synthesis of 10-Mercaptodecyl-1-Iminodiacetic
Acid (MDIA)
10-Mercaptodecyl-1-iminodiacetic acid (MDIA) acid were
synthesized by a modification of a literature method for the
Electrospray mass spectra (ESI-MS) were recorded on a
Thermo Finnigan LCQ Deca XP max (Finnigan, USA)
spectrometer. 1H NMR spectra were measured on a
BRUKER AVANCE III 300 MHz spectrometer. Chemical
COOH
COOMe
COOMe
i
ii
HN
HN
N
Br(H2C)10
iii
COOMe
COOH
COOMe
COOH
HS(H2C)10
N
COOH
Scheme 2. The synthetic route of ligand. Reagent and conditions: (i) dry MeOH, H2SO4, reflux for 16 h; (ii) 1,10-dibromodecane (3 equiv.), dry
acetone, anhydrous K2CO3, reflux for 30 h; (iii) thiourea, reflux for 4 h.
J. Nanosci. Nanotechnol. 17, 502–506, 2017
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Gold Nanoparticle-Based Probe for Colorimetric Detection of Copper Ions
Chai et al.
1.0
2.4. Modification of Au-NPs
1
2
3
4
5
6
7
8
9
Citrate-stabilized gold colloids were prepared according
to literature method,27a the average diameter of the Au-
NPs was about 14 nm. MDIA (15 mg) was dissolved
in methanol, and it was added to 50.0 mL of citrate-
stabilized gold colloids, then the gold sols were stirred
overnight (12 h). The carboxylate-functionalized nanopar-
ticles were then centrifuged for 20 min (at 13000 g, 10 ꢀC,
TGL-16M, Xiangyi, China), followed by decantation of
supernatant, and subsequently dispersed in 50 ml deion-
ized water. MDIA-functionalized gold colloids (Au-NPs-
MDIA) generally appeared red after being centrifuged.
0.8
0.6
0.4
0.2
0.0
400
500
600
700
800
Wavelength/nm
3. RESULTS AND DISCUSSION
Figure 1. The absorption spectral and color changes of Au-NPs modi-
fied with MDIA after addition of the Cu2+. Inset shows the photograph
of the samples: 1, Au-MDIA; 2–9, the concentrations of the added Cu2+
to Au-NPs-MDIA were 0, 0.005, 0.05, 0.1, 0.2, 0.3, 0.5, 1 and 10 mM
respectively.
3.1. Response of Au-NPs-MDIA to Cu2+
Figure 1 shows the electronic absorption spectra of the
colloidal solutions of 14 nm gold nanoparticles after func-
tionalization with the ligand. The absorption bands of
Au-NPs-MDIA in water were at 520 nm with red color,
suggesting sufficient steric stabilization. TEM images
(Fig. 2) clearly show the mono-disperse of functionalized
gold nanoparticles. Upon the addition of Cu2+ to Au-
NPs-MDIA, the absorption intensity of Au-NPs-MDIA at
520 nm were found to decrease dramatically in intensity
while a new broad band appeared at about 560 nm with a
color change from red to purple, suggesting that Au-NPs-
synthesis of 11-bromoundecanethiol. The synthetic route
of ligand is shown in Scheme 2. The 10-bromodecyl-1-
iminodiacetate was treated with 1 equiv. of thiourea, and
it was heated to reflux for 3 h in 95% methanol. Then
the mixture treated with a slight excess of NaOH under
N2 for 40 min, and finally neutralized with dilute HCl.
The methanol was removed under reduced pressure, then
a large amount of water was added to the mixture to pro-
duce a white precipitate immediately. The white precip-
itate was obtained by filtration, then washed with water
and dried in vacuum to give the product as a white solid.
IP: 95.85.69.23 On: Mon, 08 Oct 2018 11:49:05
MDIA were ready to bind Cu2+ and aggregated subse-
Copyright: American Scientific Publishers
quently. TEM images (Fig. 2) clearly show the aggregate
Delivered by Ingenta
formation of Au-MDIA-Cu. The results showed that con-
jugation of the Cu2+ with functionalized Au-NPs-MDIA
facilitated aggregation of Au-NPs-MDIA due to the com-
plexation of the Cu2+ with carboxylate ligand on the sur-
face of the gold nanoparticles. A limit of detection (LOD)
of 1 × 10−4 mol/L for Cu2+ was obtained by the color
change. Figure 3 illustrates a typical calibration plot for
1
Yield: 50%. H NMR (MeOD, 400 MHz, Me4Si, ꢁ in
ppm) ꢁ: 3.94 (s, 2H, NCH2CO), 3.26 (m, 2H, SCH2), 2.50
(t, 2H, J = 7ꢂ2 Hz, NCH2), 1.73 (b, SH), 1.60 (m, 2H,
CH2), 1.38–1.34 (m, 14H, CH2). ESI-MS: m/z 306
{M+H}+.
Figure 2. TEM images of the MDIA-functionalized gold nanoparticles before (left) and after (right) addition of Cu(II).
J. Nanosci. Nanotechnol. 17, 502–506, 2017
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Chai et al.
Gold Nanoparticle-Based Probe for Colorimetric Detection of Copper Ions
0.84
0.81
0.78
0.75
0.72
0.69
0.66
while the color of Au-NPs-MDIA turned from purple to
red. The whole experiment process is rapid. It suggested
that EDTA would capture and bind to Cu2+ from Au-
NPs-MDIA surface due to the high affinity of EDTA
525 nm
Linear Fit of B
toward Cu2+
.
3.3. Reusing of the Functionalized Gold Nanoparticles
MDIA-functionalized gold nanoparticles had sufficient sta-
bility and generally appeared red after being centrifuged
twice. Figure 5 shows the spectra and the color of MDIA-
functionalized gold nanoparticles after addition of Cu2+
and EDTA. As shown in Figure 5, the modified gold
nanoparticles aggregated after addition of Cu2+, and its
color changed from red to purple. Upon addition of EDTA
to Au-NPs-MDIA-Cu2+, the color of Au-NPs-MDIA-Cu2+
was found to turn red. The mixture was centrifuged (at
13000 g, 10 degrees Centigrade) to separate the copper(II)
complex and the nanoparticles, then the residue Au-NPs-
MDIA was redispersed in distilled water which would
turn red again. Add equal quantity of Cu2+ to Au-NPs-
MDIA, the phenomena were similar as the above. So we
could reuse functionalized gold nanoparticles for the next
analysis.
0.0
0.1
0.2
0.3
0.4
0.5
C/mmol/L
Figure 3. The linearity of the absorption intensity at 520 nm versus the
added Cu2+ concentrations.
the sensing of Cu2+ based on the absorption changes at
ca. 520 nm. The absorption intensity is linearity with
the added concentration of Cu2+ from 5ꢂ0 × 10−6–5 ×
10−4 mol/L (R2 = 0ꢂ990) with a limit of detection 8ꢂ0 ×
10−7 mol/L (S/N = 3). The RSD of the signal (n = 5) was
3.9%, which showed that the reproducibility of the signal
based on a functionalized gold nanosensor for the detec-
tion of Cu2+ in water was good.
3.4. Adsorption of the Copper Ion in the
Acid Waste Solution
3.2. Response of Au-NPs-MDIA-Cu2+ Composites
to the Chelator EDTA
A series of standard copper(II) samples were prepared, the
IP: 95.85.69.23 On: Mon, 08 Oct 2018 11:49:05
concentration is 30, 40, 50, 60, 70 ꢃM, respectively. The
Copyright: American Scientific Publishers
standard working curve was obtained by Flame Atomic
Figure 4 shows the response of Au-NPs-MDIA solution
to the sequential addition of Cu2+ followed by EDTA
(0.25 M). Upon addition of EDTA to Au-NPs-MDIA-
Cu2+, the absorption spectra of Au-NPs-MDIA-Cu2+ was
found to increase dramatically in intensity with a blue shift
from 610 nm to 520 nm at room temperature (Fig. 4),
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Absorption Spectrometry (R = 0ꢂ998). The chemical bind-
ing affinity of a sorbent can be expressed in terms of
the distribution coefficient (Kd).30 Kd = ꢄCo −Cf ꢀV /CfM,
where Co and Cf are the initial and final concentrations in
the solution of the target species determined by ICP-MS,
V is the solution volume in milliliters, and M is the mass
1.0
1
1.5
2
3
4
0.8
0.6
0.4
0.2
0.0
5
1
2
3
4
5
6
7
8
9
1.2
6
7
8
9
10
11
12
0.9
0.6
0.3
0.0
400
500
600
700
800
400
500
600
700
800
Wavelength/nm
Wavelength/nm
Figure 4. The absorption spectral and color changes of Au-NPs mod-
ified with MDIA after addition of the Cu2+ and EDTA. Inset shows the
photograph of the samples: 1, Au-MDIA; 2, Au-MDIA-Cu2+; 3–12, the
concentrations of the added EDTA to Au-MDIA-Cu2+ were 1.25, 2.5,
3.75, 5, 6.25, 7.5, 8.75, 10, 11.25 and 12.5 mM respectively.
Figure 5. The absorption spectral and color changes of Au-NPs mod-
ified with MDIA after addition of the Cu2+ and EDTA. Inset shows
the photograph of the samples: 1, Au-MDIA; 2, Au-MDIA-Cu2+; 3,
Au-MDIA-Cu2+-EDTA; 4–6 and 7–9 repeat respectively.
J. Nanosci. Nanotechnol. 17, 502–506, 2017
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Gold Nanoparticle-Based Probe for Colorimetric Detection of Copper Ions
Chai et al.
in grams of the sorbent. 1 ml concentrated Au-NPs-MDIA
gold nanoparticles was added into 9 ml the acid etching
solution sample. The mixture was stirred for 30 min and
centrifuged. The upper clear solution was measured with
AAS. Then the absorption coefficient was calculated as
about 3051 ml/g, which was good in the high acid solution.
The functionalized gold nanoprticles would be reused in
the detection and separation of the copper(II) in solution.
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4. CONCLUSION
A simple colorimetric nanosensor for copper ion was
developed in this work. The main advantage of the
present method lies in the fact that the functionalized
gold nanoprticles would be reused in the detection of
the copper(II) in water. The method was simple and fast,
which was important in the application of copper ion
detection in water quality during the emergency and early
warning monitoring.
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Acknowledgments: This work was supported by
the National Natural Scientific Foundations of China
(Nos. 21171038 and J1103303) and the Program for
Changjiang Scholars and Innovative Research Team in
University (No. IRT1116).
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Received: 8 April 2015. Accepted: 10 September 2015.
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