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Spectrophotometric determination of mercury(II) ions based on their stimulation effect on the peroxidase-like activity of molybdenum disulfide nanosheets

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Yuan Lu at Lanzhou University
Yuan Lu
Jing Yu at The University of Hong Kong
Jing Yu
Weichun Ye at Lanzhou University
Weichun Ye
Xin Yao
Xin Yao
Xin Yao
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Abstract and Figures

The authors describe a colorimetric method for the determination of Hg(II) ions by exploiting the peroxidase-lile activity of few-layered MoS2 nanosheets (MoS2-NSs). These were prepared by sonication-induced exfoliation of bulk MoS2 crystals in aqueous surfactant solution. The MoS2-NSs were found to acts as a peroxidase mimic that is capable of oxidizing the substrate 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2) to give a blue product with an absorption maximum at 652 nm. The addition of Hg(II) strongly accelerates the kinetics of this reaction. It is shown that the enzyme mimic possesses a high affinity for TMB and a lower pseudo-Michaelis-Menten constant. The stimulating effect of Hg(II) is seriously influenced by the change of surface charge. The use of nanosheets covered with (negatively charged) polystyrene sulfonate results in a decrease in the formation of blue dye, while those covered with (cationic) poly(diallyldimethyl ammonium) ions cause a small increase. Under optimal conditions, the peroxidase-like activity of MoS2-NSs is affected by Hg(II) in the 2.0 to 200 μM concentration range. The method has a detection limit (LOD) of 0.5 μM which is much below the allowed level in cosmetics (1 ppm; ca. 5 μM). The method display excellent sensitivity, selectivity and stability. It was applied to the determination of total mercury in cosmetic samples, and results compared well with results obtained by ICP-AES. Graphical abstract A spectrophotometric assay for mercury - (II) determination is reported that is based on Hg2+-stimulation effect on the 3,3′,5,5′-tetramethylbenzidine (TMB)-H2O2 reaction system catalyzed by MoS2 nanosheets.
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ORIGINAL PAPER
Spectrophotometric determination of mercury(II) ions based
on their stimulation effect on the peroxidase-like activity
of molybdenum disulfide nanosheets
Yuan L u
1
&Jing Yu
1
&Weichun Ye
1
&Xin Yao
1
&Panpan Zhou
1
&Haixia Zhang
1
&
Suqin Zhao
2
&Lipei Jia
1
Received: 29 February 2016 /Accepted: 25 May 2016 / Published online: 17 June 2016
#Springer-Verlag Wien 2016
Abstract The authors describe a colorimetric method for the
determination of Hg(II) ions by exploiting the peroxidase-lile
activity of few-layered MoS
2
nanosheets (MoS2-NSs). These
were prepared by sonication-induced exfoliation of bulk MoS
2
crystals in aqueous surfactant solution. The MoS2-NSs were
found to acts as a peroxidase mimic that is capable of oxidizing
the substrate 3,3′,5,5′-tetramethylbenzidine (TMB) in the pres-
ence of hydrogen peroxide (H2O2) to give a blue product with
an absorption maximum at 652 nm. The addition of Hg(II)
strongly accelerates the kinetics of this reaction. It is shown
that the enzyme mimic possesses a high affinity for TMB and a
lower pseudo-Michaelis-Menten constant. The stimulating ef-
fect of Hg(II) is seriously influenced by the change of surface
charge. The use of nanosheets covered with (negatively
charged) polystyrene sulfonate results in a decrease in the for-
mation of blue dye, while those covered with (cationic)
poly(diallyldimethyl ammonium) ions cause a small increase.
Under optimal conditions, the peroxidase-like activity of
MoS2-NSs is affected by Hg(II) in the 2.0 to 200 μMconcen-
tration range. The method has a detection limit (LOD) of
0.5 μM which is much below the allowed level in cosmetics
(1 ppm; ca. 5 μM). The method display excellent sensitivity,
selectivity and stability. It was applied to the determination of
total mercury in cosmetic samples, and results compared well
with results obtained by ICP-AES.
Keywords Peroxidase mimic .Spectrophotometric assay .
Molybdenum disulfide nanosheets .Surface charge effect .
Mercury(II) detection
Introduction
Natural enzymes can specifically and efficiently catalyze the
chemical reactions under mild conditions and accordingly
have been applied extensively in various fields. However,
their large scale applications are restricted due to some intrin-
sic drawbacks such as low stability (easy denaturation and
digestion), high cost, and rigorous stage requirements [1,2].
Therefore, development of artificial enzyme mimics as highly
stable and low-cost alternatives to natural enzymes [3–5]isof
significant interest.
In 2007, Gao et al. reported that Fe
3
O
4
nanoparticles (NPs)
possess intrinsic peroxidase-like activity similar to horserad-
ish peroxidase (HRP) [6]. Inspired by this, more and more
nanomaterials have also been proven to possess unexpected
peroxidase-like activities for potential applications in biomed-
ical and environmental detection. These nanomaterials in-
clude magnetic NPs [7,8], noble metal NPs [9–11], and car-
bon nanomaterials [12]. Similarly, molybdenum disulfide
nanosheets (MoS
2
-NSs) as a two-dimensional layered-struc-
ture have also been found to exhibit excellent peroxidase-like
activity and further used to construct an optical hydrogen per-
oxide (H
2
O
2
) assay [13,14]. Furthermore, a sensitive and
selective colorimetric assay was fabricated for visual detection
of glucose in diabetic serum samples, which was based on the
Electronic supplementary material The online version of this article
(doi:10.1007/s00604-016-1886-4) contains supplementary material,
which is available to authorized users.
*Weichun Ye
yewch@lzu.edu.cn
*Haixia Zhang
zhanghx@lzu.edu.cn
1
Department of Chemistry and State Key Laboratory of Applied
organic Chemistry, Lanzhou University, Lanzhou 730000, China
2
College of Physics and Electronic Information Engineering, Qinhai
University for Nationalities, Xining 810007, China
Microchim Acta (2016) 183:2481–2489
DOI 10.1007/s00604-016-1886-4
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... Based on the mentioned reasons, monitoring Hg 2+ becomes an increasing demand. As a consequence, several methods have been developed to determine Hg 2+ ions, including atomic absorption spectroscopy, electrochemical methods, chromatographic and optical methods [93]. However, the nanomaterial-based colorimetric strategies are prominent among them, due to their simple, cost-effective, and rapid mechanism of analysis. ...
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