Cysteine-based silver nanoparticles as dual colorimetric sensors for cations and anions

Article abstract of DOI:10.1039/c6nj01486k

We report herein the synthesis of silver nanoparticles (Ag NPs), their characterization, and anion and cation sensing properties. Freshly prepared amide-triazole Ag NPs (3a-Ag NPs and 3b-Ag NPs) could detect fluoride and cations such as Hg²⁺ and Cd²⁺ in aqueous media with a color change from pink to brown. The cysteine-based Ag NPs 5b-Ag NPs showed a colorimetric response towards H₂PO₄^-, whereas 6-Ag NPs showed a colorimetric response towards H₂PO₄^- and HSO₄^- in aqueous media.

Full text of DOI:10.1039/c6nj01486k

View Article Online
View Journal
NJC
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: P. K. PPP, L.
Kathuria and H. V, New J. Chem., 2016, DOI: 10.1039/C6NJ01486K.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/njc

Please do not adjust margins
New Journal of Chemistry
Page 1 of 10
View Article Online
DOI: 10.1039/C6NJ01486K
Journal Name
ARTICLE
Cysteine-based silver nanoparticles as dual colorimetric sensors
for cations and anions
Received 00th January 20xx,
Accepted 00th January 20xx
P. P. Praveen Kumar, Lakshay Kathuria and V. Haridas *
We report herein the synthesis of silver nanoparticles (Ag NPs), their characterization, anion and cation sensing properties.
The freshly prepared amide-triazole Ag NPs (3a-Ag NPs and 3b-Ag NPs) could detect fluoride and cations such as Hg2+ and
Cd2+ in aqueous media with a color change from pink to brown. The cysteine-based Ag NPs 5b-Ag NPs showed colorimetric
DOI: 10.1039/x0xx00000x
www.rsc.org/
-
-
-
response towards H2PO4 , whereas 6-Ag NPs showed colorimetric response towards H2PO4 and HSO4 in aqueous media.
1. Introduction
strategy for making Ag NP-based sensors. 1,4 substituted 1,2,3-
amide-triazole unit is a well-studied recognition motif for the
Recently, a wide variety of nanomaterial’s are developed for anion.10
diverse applications in optoelectronics,1 catalysis,2 biomedical3
(A)
and for sensing.4 The strong localized surface plasmon
resonance (SPR) of these nanoparticles enabled sensing of
heavy metal ions and anions.5 Sensing of heavy metal ions and
anions in aqueous media is getting increasingly important in
recent years, because of the widespread environmental
pollution.6 The obvious and easily detectable color change
through the naked eye made nanoparticle-based detection
technique very simple and useful. Among the various NPs,
silver nanoparticles (Ag NPs) have the advantage of low cost
and a wide range of color tunability.7 The colorimetric response
of nanoparticle-based detection technique is because of two
reasons; color change due to direct interaction of Ag NPs with
analyte8 or interaction of the analyte with the surface capped
functionalities, resulting in the aggregation of Ag NPs.9
N
R
N
O
N
N
N
R
N
HN
NH
Introduction of ligands on to the surface of Ag NPs impart
stability and desired functionalities. If introduced ligand can
bind to the analyte molecule then color and aggregation
property of Ag NPs could change and these changes can be
monitored by spectroscopic techniques. Capping of Ag NPs
with ligand molecules containing recognition sites are useful
O
O
N
S
Ag
S
S
S
R
N
S
S
NH
HN
N
N
N
O
R
O
N
R
O
HN
HN
H
N
N
N
N
N
N
R
a.Department of Chemistry, Indian Institute of Technology Delhi, New Delhi -
110016, India
. Electronic Supplementary Information (ESI) available: [UV-visible data, 1H NMR,
13C NMR, ESI data of compounds are available. pH measurement and HR-TEM
studies are also available]. See DOI: 10.1039/x0xx00000x
Fig. 1 (A) an amide-triazole unit. (B) cysteine-based amide-
triazole containing Ag NPs.
A variety of triazole-functionalized metal nanoparticles has
been designed and utilized for various sensing applications.11-13
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
New Journal of Chemistry
Page 2 of 10
View Article Online
DOI: 10.1039/C6NJ01486K
ARTICLE
Journal Name
Recently, the design and synthesis of molecules that can sense experiments were performed by ZEISS EVO®18 instrument
both cations and anions have turned to be an emerging field in with an EHT of 20 kV. UV-visible spectra were recorded in
the supramolecular chemistry.14-15 The 1,4 substituted 1,2,3- Shimadzu double beam spectrophotometer, UV-2400 with 1 cm
triazole can interact with anion through –CH---X- and the quartz cell. Dynamic light scattering (DLS) experiment was
amide –NH---X- (X = anions) hydrogen bonding interactions, performed using Malvern Zetasizer ZS90 DLS spectrometer
while nitrogen of triazole unit can interact with metal ions. with 633 nm CW laser.
Hence, we envisioned that Ag NPs capped with amide-triazole
ligands can act as sensors for both anions and cations (Fig. 1).16
In order to fully utilize the amide-triazole moiety for sensing,
the ligands must bind the metal NPs through a different
functionality. We chose cysteine as a candidate, since it can be
functionalized by an amide-triazole unit, and the thiol can be
anchored to the metal part. Hence, the generated NPs will
display amide-triazole moiety, fully available for guest binding
(Fig. 1).
2. Experimental section
2.1 Chemicals
Silver nitrate (AgNO3, 99.9%), and sodium borohydride
(NaBH4, 99%), for the synthesis of Ag NPs, were purchased
from Sigma-Aldrich and used as received. Anion salts were
used in the form of sodium salts and purchased from Sigma-
Aldrich. The cation salts were used in the form of perchlorates
and were purchased from Sigma-Aldrich. Cystine was
purchased from SRL (India) and propargylamine from Alfa
Aesar.
Dicyclohexylcarbodiimide
(DCC)
and
N-
hydroxysuccinimide (NHS) were purchased from Sigma-
Aldrich.
Scheme 1. Synthesis of cystine-based molecules and Ag NPs
2.4. Sensing of cations and anions
2.2. Synthesis of cystine-based compounds and
Ag NPs
Cation and anion solutions were made in Millipore water (10
ꢀ
M) and were titrated against 2 mL aqueous solutions of Ag
N-Boc-cystine was coupled to propargylamine using DCC to
afford dialkyne core17, which was further reacted with p-
nitrophenyl azide18 to obtain amide-triazole derivative 3a
(Scheme 1). Ag NPs were prepared by the chemical reduction
method.19 To the well-stirred compound solution (1 mM) and
NaBH4 (2 mM) in ethanol was added a solution of AgNO3 in
ethanol (0.1 mM) and stirred for 4 h. It was then centrifuged
and the residue obtained was washed several times with ethanol
and was dispersed in water.
NPs and analyzed by UV-visible spectroscopy.
3. Results and discussion
3.1. Characterization of Ag NPs
The amide-based chelating ligands were synthesized by the
DCC coupling method, while amide-triazole ligands were
prepared by click reaction of the dialkyne and azide (Scheme
1). Ag NPs were prepared by chemical methods, utilizing the
2.3. Characterization
cystine-based (5b and 6) and amide-triazole compounds 3a and
3b as capping agents. The formation of Ag NPs was confirmed
by the immediate color change from colorless to pink, where an
ethanolic solution of compound and AgNO3 was treated with
NaBH4. The particles were centrifuged and dispersed in water
to obtain a light pink colored solution of Ag NPs. It is well-
known that Ag NPs exhibit different colors depending on the
size, morphology, pH, and capping agents.20 UV-visible spectra
showed the characteristic absorption between 430-450 nm
corresponding to the SPR band of Ag NPs (Fig. 2A).21-22 IR
Ag NPs were characterized by UV-visible spectroscopy, high-
resolution transmission electron microscopy (HR-TEM) and by
energy-dispersive X-ray spectroscopy (EDX). Samples for HR-
TEM were prepared by dissolving the compound in water. A 2
µl aliquot of the sample solution was placed on a 200 mesh
copper grid coated with carbon and excess fluid was removed
using a filter paper and samples were viewed using a
TECHNAI G2 (20STWIN) electron microscope. EDX-SEM
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
New Journal of Chemistry
Page 3 of 10
Journal Name
View Article Online
DOI: 10.1039/C6NJ01486K
ARTICLE
spectrum of 3a-Ag NPs showed two characteristic stretching
frequencies for –NO2– group at 1368 and 1531 cm-1 indicating
the capping on Ag NPs by 3a (Fig. 2B). Similarly, capping on
Ag NPs by 3b was evident from the IR stretching frequency
bands at 1387, 1525 cm-1 (for –NO2– group stretch) of 3b-Ag
NPs (Fig. 2B). IR spectra of the cysteine-based Ag NPs (5b-Ag
NPs and 6-Ag NPs) showed stretching frequency at 1720 and
1718 cm-1 respectively, characteristic of the ester carbonyl (Fig.
2B).
The shape and size of Ag NPs were obtained from HR-TEM
and DLS (Figs. 2C and S1, see ESI†) experiments. HR-TEM
images showed that these cysteine-based nanoparticles are
spherical and uniform in size. The designed nanoparticles have
an average size of 11-13 nm as evident from HR-TEM images
(Table S1, see ESI†). DLS data (Fig. S1, see ESI†) are in
agreement with HR-TEM data.
3.2. Stability of the Ag NPs
The aqueous Ag NPs solutions 3a-Ag NPs, 3b-Ag NPs, and 5-
Ag NPs showed a pH of 7.8. The effect of pH on the stability of
Ag NPs was investigated in the range of pH = 2.0-12.0 (Fig.
S3). The pH of the Ag NPs dispersion was adjusted using 0.01
M of HCl and NaOH solutions. The increase or decrease in pH
resulted in the decrease of absorption maxima followed by a
blueshift indicating that at higher and lower pH, the Ag NPs are
not stable (Fig. S3, see ESI†). The nanoparticles (3a-Ag NPs,
3b-Ag NPs, and 5-Ag NPs) are found to be stable in the pH =
7-7.8 as evident from the UV-visible spectral data. 6-Ag NPs
showed stability in the pH range of 6-8 (Fig. S3, see ESI†). In
all cases, individual samples were prepared at different pH
values and UV-Visible spectra were recorded at different pH
values.
The EDX data (Fig. S2, see ESI†) showed the presence of
elemental silver, carbon, oxygen, sulphur and nitrogen in all the
prepared Ag NPs. The presence of carbon, oxygen, sulphur and
nitrogen indicated the presence of amino acid on the surface of
these Ag NPs.
(A)
(B)
(C)
(B)
Fig. 2 (A) UV-visible spectra of Ag NPs in water (B) FT-IR spectra of Ag NPs capped with 3a, 3b, 5b and 6 (C) HR-TEM images of Ag
NPs (i) 3a-Ag NP (ii) 3b-Ag NPs (iii) 5b-Ag NPs (iv) 6-Ag NPs.
aqueous solution. Anions were used in the form of sodium
salts. Among the various anions tested, the 3a-Ag NPs
showed high selectivity for F- anion (Fig. S4, see ESI†).
When an aqueous solution of 3a-Ag NPs titrated with NaF
salt, the color of NPs changed from pink to brown color.
Addition of NaF resulted in the shift of absorption maxima
3.3. Anion Sensing
The changes in the position of SPR bands of Ag NPs
depends on the ligands or substances adsorbed on the
surface of nanoparticles. UV-visible spectra and naked eye
detection allowed the detection of anions by Ag NPs in
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
New Journal of Chemistry
Page 4 of 10
View Article Online
DOI: 10.1039/C6NJ01486K
ARTICLE
Journal Name
4E). The addition of H2PO4- to 3b-Ag NPs induced a color
change from pink to yellowish brown (Fig. 4E). UV-visible
absorption spectra for 3b-Ag NPs showed a drastic redshift
followed by a new absorption band in the UV-visible spectra
at 520 nm (Figs. 3A and 3D). Other anions did not exhibit
any colorimetric response with 3a-Ag NPs (Fig. 3D). The F-
binding to 3a-Ag NPs, was carried out in the presence other
anions (Fig. S4, see ESI†). The results showed no
interference from other anions (50 fold) on F- detection. A
linear equation exists between A430/A0 and [F-] with a
linearity coefficient of 0.993. The limit of colorimetric
detection (LOD) of 3a-Ag NPs was found to be 39 nM by
the three times standard deviation of blank signal (Fig. S5,
see ESI†).16
-
of 11 nm by the addition of H2PO4 (Fig. 4C). The
competitive binding experiments showed that 3b-Ag NPs
-
can sense both F- and H2PO4 without any interference from
the other anions (50 fold) tested (Fig. S4, see ESI†) with a
colorimetric detection limit of 44 nM for F- and 8 nM for
-
H2PO4 (Fig. S5, see ESI†) colorimetrically.16 The observed
color change for 3a-Ag NPs and 3b-Ag NPs with the anions
can be explained as follows. In the case of 3b-Ag NPs, the
free amino groups can act as a binding site for anions along
with the amide-triazole moiety, which in turn induces a high
degree of aggregation in these 3b-Ag NPs, resulting in an
intense reddish brown color after binding. This fact is
supported by the HR-TEM studies of these Ag NPs with
anion salts.
Compound 3b was prepared from 3a, by the deprotection of
Boc groups. The nanoparticles 3b-Ag NPs showed a pink
color and a SPR band at 435 nm (Fig. 2A). Among the
various anions tested, these nanoparticles were found to be
-
selective for F- and H2PO4 . The addition of F- ion induced a
redshift in the absorption spectra along with the formation of
a new band at 535 nm (Fig. 4B). Addition of F- into 3b-Ag
NPs, resulted in a color change from pink to red-brown (Fig.
(C)
(A)
(B)
(D)
(E)
Fig. 3 UV-visible titration data for (A) 3a-Ag NPs with and without NaF in water (B) 3b-Ag NPs with and without NaF in water. (C)
3b-Ag NPs with and without NaH2PO4 in water. D and E shows the colorimetric response of 3a-Ag NPs and 3b-Ag NPs towards
various anion salts.
The nanoparticles made from 5b and
Ag NPs) showed dark pink color due to the strong SPR
absorption band at 430 nm. Among the various anions
6
(
5b-Ag NPs and 6-
tested, the cysteine-based Ag NPs showed selectivity
towards H2PO4 and HSO4 as evident from the UV-visible
titration experiments (Figs. 4A-C) and by the colorimetric
-
-
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
New Journal of Chemistry
Page 5 of 10
View Article Online
DOI: 10.1039/C6NJ01486K
Journal Name
ARTICLE
response of these anions with 5b-Ag NPs and 6-Ag NPs
(Figs. 4D-E). The free amino group containing Ag NPs (5b-
The influence of pH in anion sensing has been studied by
measuring the pH of the Ag NPs solution before and after
the addition of various anion salts. It was observed that the
initial pH of Ag NPs (7.8) remains the same after the
addition of various anion salts except for acetate anion,
which caused a slight increase in pH from 7.8 to 8. But UV-
visible titration experiments and colorimetric assay
experiments showed that these Ag NPs cannot sense acetate
anion. These studies showed that the sensing ability of these
Ag NPs is due to the binding of analyte molecules with
amide-triazole, amide and free –NH2 protons.
-
Ag NPs) showed a high selectivity towards H2PO4 and
-
HSO4 (Figs. 4A-B and 4D). The addition of these anion
salts resulted in the decolorization of Ag NPs with a
blueshift in the absorption spectra with a decrease in the
absorption maxima. The competitive binding experiments
-
-
showed that these 5b-Ag NPs can sense H2PO4 and HSO4
strongly in the presence of other interfering anions (50 fold)
(Fig. S4, see ESI†) with a colorimetric LOD of 67 nM and
16 nM respectively (Fig. S5, see ESI†).16
Among the various anions tested, 6-Ag NPs showed a
-
discoloration after the addition of H2PO4 (Figs. 4C and 4E)
and UV-visible titration experiments showed a decrease in
-
absorbance as by the addition of H2PO4 to 6-Ag NPs (Fig.
4C). The altered selectivity of these Ag NPs towards various
anions can be attributed due to the lack of triazole –CH–
protons for binding anion. The involvement of triazole –
CH– protons for binding with F- anion in the case of 3b-Ag
NPs has been confirmed by 1H NMR studies (Fig. 5).
(A)
(B)
(C)
(D)
(E)
Fig. 4 UV-visible spectra of (A) 5b-Ag NPs with and without H2PO4- in water (B) 5b-Ag NPs with and without HSO4- salt in water (C)
6-Ag NPs with and without H2PO4- in water. D and E shows the colorimetric response of aqueous solutions of 5b-Ag NPs and 6-Ag
NPs alone and with added anion salts.
3.4. 1H NMR studies
spectrum of 3b-Ag NPs showed a downfield shift (ꢁδ = 0.14
ppm) and splitting for the –S–CH2– protons implying that
the ligand 3b is attached to the metal through sulphur (Figs.
5 and S6, see ESI†). The triazole proton in 3b-Ag NPs
showed no change in chemical shift compared to 3b
indicating, the absence of interaction of triazole moiety with
The capping of Ag NPs by ligand was confirmed with the
help of NMR studies in D2O (Fig. S6, see ESI†). The
compound 3b and 3b-Ag NPs are readily soluble in water
hence 1H NMR was recorded in D2O. The 1H NMR
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

Please do not adjust margins
New Journal of Chemistry
Page 6 of 10
View Article Online
DOI: 10.1039/C6NJ01486K
ARTICLE
Journal Name
H2PO4 ion. The other anion salts tested (Cl-, Br-, I- and
-
metal (Fig. S5, see ESI†). Interaction of anion salts with Ag
NPs was studied by 1H NMR titration experiments. The
-
HSO4 salts) induced no significant changes to the triazole
protons.
3.4. Cation sensing studies
The metal ion binding of amide-triazole bearing Ag NPs
(
3a-Ag NPs and 3b-Ag NPs) and cysteine Ag NPs (5b-Ag
NPs and 6-Ag NPs) were studied. Among the various metal
cations tested (Ag+, Mg2+, Pb2+, Cu2+, Co2+, Hg2+, Cd2+,
Fe2+, Ni2+, Zn2+, Fe3+), the triazole bearing Ag NPs showed a
selectivity towards Hg2+ and Cd2+ ions. The addition of Hg2+
and Cd2+ to a solution of 3a-Ag NPs and 3b-Ag NPs
resulted in a color change from pink to brown red with a
redshift of 8 nm in the UV-visible spectra (Figs. 6A-F).
Inorder to study the influence of other cations on Hg2+ and
Cd2+ binding to 3a-Ag NPs, and 3b-Ag NPs competitive
binding experiments were carried out in the presence of
other cations (50 fold) (Fig. S7, see ESI†). The results
indicate that the other cations did not interfere with the
sensing of Hg2+ and Cd2+. The colorimetric limit of
detection (LOD) for Hg2+ and Cd2+ was calculated by
plotting A430/A0 against the concentration [C] of M2+. The
LOD was found to be 18 nM for Hg2+, and 20 nM for Cd2+
(Fig. S5, see ESI†).16 Cysteine based Ag NPs (5b-Ag NPs
and 6-Ag NPs) did not show any color change or changes in
the UV-visible spectra by the addition of various cations,
ruling out their ability to bind cations.
Fig.5 1H NMR represents spectra of 3b-Ag NPs, after mixing
with various anion salts in D2O. (1 mM of Ag NPs: 10 mM of
anion salt) in D2O. Tetrabutylammonium anion salts were
used for the H NMR studies due to the poor solubility of
sodium salts in D2O.
1
addition of F- to a solution of 3b-Ag NPs in D2O, showed a
downfield shift of triazole –CH– protons ꢁδ = 0.34 ppm,
indicating the binding of F- ion with the acidic triazole –CH
(Fig. 6). The methylene (–CH2–) linked to triazole in 3b-Ag
NPs also showed a downfield shift of 0.07 ppm after the
-
interaction with F- ion. The addition of H2PO4 , induced a
downfield shift of the triazole –CH– protons (ꢁδ = 0.16
ppm), indicating the involvement of triazole –CH– in the
binding (Fig. 6). The methylene (–CH2–) linked to triazole
was deshielded by ꢁδ = 0.02 ppm, as a result of binding to
(C)
(B)
(A)
(D)
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
New Journal of Chemistry
Page 7 of 10
Journal Name
View Article Online
DOI: 10.1039/C6NJ01486K
ARTICLE
Fig. 6 UV-visible titration spectra for (A) 3a-Ag NPs with and without Hg2+ in water (B) 3a-Ag NPs with and without Cd2+ salt in
water (C) 3b-Ag NPs with and without Hg2+ in water (D) 3b-Ag NPs with and without Cd2+ salt in water. E and F show the
colorimetric response of 3a-Ag NPs and 3b-Ag NPs alone and with added metal salts.
interacts with the adjacent Ag NPs resulting in the formation
of aggregates (Fig. 7, panel B). The color change is
attributed to the interparticle coupled plasmon excitations in
the aggregated states.23 The designed Ag NPs with the
3.5. HR-TEM studies on the aggregation of Ag
NPs with anions and cations
HR-TEM studies were used to investigate the morphological
triazole –CH–, amide –NHs and free –NH2– on the surface
changes caused by anion and cations. The prepared Ag NPs
of the Ag NPs can interact with anions, leading to the
have uniform size and shape, as evident from HR-TEM
morphological changes.24 The cation induced aggregation of
studies (Fig. 2). Addition of NaF, NaH2PO4, and NaHSO4
amide-triazole-based Ag NPs (3a-Ag NPs and 3b-Ag NPs)
resulted in the aggregation of NPs (Fig.7, panel A) with an
were studied by HR-TEM (Fig. S8, see ESI†).
increase of particle size from 11 to 60 nm.
In the case of amide-triazole-based Ag NPs, the anion binds
to triazole –CH– proton and the bound Ag NPs further
Fig. 7 Panel A represents HR-TEM images for Ag NPs after mixing with anion salts. (i) 3a-Ag NPs with F- (ii) 3b-Ag NPs with F- (iii)
-
-
3b-Ag NPs with H2PO4 (iv) 5b-Ag NPs with H2PO4- (v) 5b-Ag NPs with HSO4- (vi)
6-Ag NPs with H2PO4 in water after the addition of
1 x 10-9 M sodium salts. Panel B shows cartoon diagram representing the aggregation of amide-triazole Ag NPs with anion/cation.
these Ag NPs can act as a dual colorimetric sensor for
various anions and cations. The present method has been
3.6. Advantages of present method
compared with the existing reports for the detection of
We have demonstrated an easy and simple method to
various anions and cations in water.25-26 But the dual
prepare Ag NPs and their sensing ability in water. The
colorimetric Ag NPs probes are not well explored and we
design strategy of amide-triazole based Ag NPs showed that
have achieved this by capping the Ag NPs with amide-
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
Please do not adjust margins

Please do not adjust margins
New Journal of Chemistry
Page 8 of 10
View Article Online
DOI: 10.1039/C6NJ01486K
ARTICLE
Journal Name
triazole based molecules. So in the present work, a novel,
simple, sensitive and fast colorimetric sensors were
developed.
6447-6450; (c) S. Szunerits and R. Boukherroub, Chem.
Commun., 2012, 48, 8999-9010; (d) Y. W. Lin, C. C. Huang
and H. T. Chang, Analyst, 2011, 136, 863-871.
(a) G. Aragay, J. Pons and A. Merkoci, Chem. Rev., 2011,
111, 3433-3458; (b) J. H. Duffus, Pure Appl. Chem., 2002,
74, 793-807.
(a) H. A. Kashmery, A. W. Clark, R. Dondi, A. J. Fallows, P.
M. Cullis and G. A. Burley, Eur. J. Inorg. Chem., 2014
4886–4895; (b) T. Shegai, S. Chen, V. D. Miljkovic, G.
Zengin, P. Johansson and M. Kall, Nat. Commun., 2011,
481, 2-6; (c) T. Huang and X. -H. X. Nancy, J. Mater.
Chem., 2010, 20, 9867-9876; (d) K. L. Kelly, E. Coronado,
6
7
4. Conclusion
In conclusion, we have designed and synthesized amide-
triazole and cysteine-based Ag NPs and demonstrated their
sensing ability towards various anions and cations. The
amide-triazole-based Ag NPs showed colorimetric response
-
towards F-, H2PO4 , Hg2+ and Cd2+ ions in water. Whereas
L. L. Zhao and G. C. Schatz, J. Phys. Chem., B 2003, 107
668–677.
(a) W. Ren, C. Zhu and E. Wang, Nanoscale, 2012, 4, 5902-
,
the cysteine-based Ag NPs showed selectivity towards
8
9
-
H2PO4- and HSO4 . These designed amide-triazole-based Ag
5909; (b) C. Sonnichsen, B. M. Reinhard, J. Liphardt and
A. P. A. Alivisatos, Nat. Biotechnol., 2005, 23, 741-745.
D. Vilela, M. C. Gonzalez and A. Escarpa, Analytica
Chimica Acta., 2012, 751, 24-43.
NPs can be used as a dual sensor probe for both cations and
anions at a pH of 7.8. The difference in the binding abilities
among the Ag NPs can be rationalized due to the different
functionalities on their surface. The easy synthesis, dual
sensing, colorimetric response along with their aqueous
solubility makes the work a considerable futuristic potential.
10 (a) B. Schuzle and U. S. Schubert, Chem. Soc. Rev., 2014,
43, 2522-2571; (b) V. Haridas, S. Sahu, P. P. Praveen
Kumar and A. R. Sapala, RSC Adv., 2012, 2, 12594-12605.
11 (a) W. J. Sommer and M. Weck, Langmuir, 2007, 23
,
11991-11995; (b) D. A. Fleming, C. J. Thode and M. E.
Williams, Chem. Mater., 2006, 18, 2327-2334.
12 (a) D. Huang, D. Yang, X. Feng, X. Lai and P. Zhao, New J.
Chem., 2015, 39, 4685-4694; (b) N. Li, P. Zhao, N. Liu, M.
Echeverria, S. Moya, L. Salmon, L.; Ruiz and D. Astruc,
Chem. Eur. J., 2014, 20, 8363-8369; (c) P. Zhao, N. Li, L.
Salmon, N. Liu, J. Ruiz and D. Astruc, Chem. Commun.,
2013, 49, 3218-3220.
Acknowledgements
We thank the Department of Science and Technology (DST
and DST-FIST) for funding and PPPK thanks the University
Grants Commission (UGC) New Delhi for the fellowship.
13 (a) I. -L. Lee, Y. -M. Sung and S. -P. Wu, RSC Adv., 2014,
25251-25256; (b) Y. -C. Chen, I.-L. Lee, Y. -M. Sung and S.-
4
P. Wu, Talanta, 2013, 117, 70-74; (c) J. Zhan, L. Wen, F.
Miao, D. Tian, X. Zhu and H. Li, New J. Chem., 2012, 36,
656-661; (d) H. Li, Y. Yao, C. Han and J. Zhan, Chem.
Commun., 2009, 4812-4814
References
14 (a) G. J. Park, Y. J. Na, H. Y. Jo, S. A. Lee, A. R. Kim, I. Noh
and C. Kim, New J. Chem., 2014, 38, 2587-2594; (b) Y. Li,
M. Ashizawa, S. Uchida and T. Michinobu, Polym. Chem.,
1
(a) T. Han, L. Liu, X. Wu, L. Chen. C. Wang, M. Hanif, L.
Lan, Z. Xie and Y. Ma, J. Phys. Chem. C 2016, 120
,
1847−1853; (b) S. –H. Jeong, H. Choi, J. Y. Kim and T. –W.
Lee, Part. Part. Syst. Charact., 2015, 32, 164-175; (c) M.-
G. Kang, T. Xu, H. J. Park, X. Luo and L. J. Guo, Adv. Mater.,
2010, 22, 4378–4383; (d) J. Zou, H. L. Yip, S. K. Hau and K.
Y. J. Alex, Appl. Phys. Lett., 2010, 96, 203301-203303.
(a) Y. Pan, J. Wang, Y. Wang and Z. Wang, Macromol.
Rapid Commun., 2014, 35, 635–641; (b) N. G. Bastus, F.
Merkoçi, J. Piella and V. Puntes, Chem. Mater., 2014, 26,
2836–2846; (c) J. A. Schuller, E. S. Barnard, W. Cai, Y. C.
Jun, J. S. White and M. L. Brongersma, Nat. Mater., 2010,
2011,
3, 1996-2005; (c) M. Alfonso, A. Espinosa, A.
Tarraga and P. Molina, Org. Lett., 2011, 13, 2078-2081.
15 Y. J. Na, Y. W. Choi, J. Y. Yun, K. -M. Park, P. -S. Chang and
C. Kim, Spectrochim. Acta A. Mol. Biomol. Spectrosc.,
2015, 136, 1649-1657.
16 (a) Y. Yao, D. Tian and H. Li, ACS Appl. Mater. Interfaces.,
2010, 2, 684-690; (b) B. Pergolese, M. Muniz-Miranda and
A. Bigottto, J. Phys. Chem., B. 2005, 109, 9665-9671.
17 V. Haridas, Y. K. Sharma, S. Sahu, R. P. Verma, S.
Sadanandan and B. G. Kacheshwar, Tetrahedron, 2011, 67
1873-1884.
18 (a) V. Haridas, S. Sahu and P. P. Praveen Kumar,
Tetrahedron Lett., 2011, 52, 6930-6935; (b) S. A.
2
3
9, 193-204.
(a) S. Mukherjee and C. R. Patra, Nanoscale, 2016,
8,
12444—2470; (b) E. C. Dreaden, A. M. Alkilany, X. Huang,
C. J. Murphy and M. A. EI-Sayed, Chem. Soc. Rev., 2012,
41, 2740-2779; (c) E. C. Dreaden, M. A. Mackey, X. H.
Huang, B. Kang and M. A. EI-Sayed, Chem. Soc. Rev., 2011,
40, 3391-3404; (d) X. Xiong, A. Busnaina, S. Selvarasah, S.
Somu, M. Wei, J. Mead, L. Chen, J. C. Aceros, P. Makaram
and M. R. Dokmeci, Appl. Phys. Lett., 2007, 91, 063101-
063103.
(a) B. Mu, J. Zhang, T. P. McNicholas, N. F. Reuel, S. Kruss,
and M. S. Strano, Acc. Chem. Res., 2014, 47, 979-988; (b)
S. Zheng, D. Baillargeat, H. –P. Ho and K. –T. Yong, Chem.
Soc. Rev., 2014, 43, 3426-3452; (c) K. Saha, S. S. Agasti, C.
Kim, X. Li and V. M. Rotello, Chem. Rev., 2012, 112, 2739-
2779.
Bakunov, S. M. Bakunova, T. Wenzler, M. Ghebru, K. A.
Werbovetz, R. Brun and R. R. Tidwell, J. Med. Chem.,
2010, 53, 254–272.
19 (a) X. Gao, Y. Lu, S. He, X. Li and W. chen, Anal. Chim.
Acta. 2015, 879, 118-125; (b) S. Hajizadeh, K. Farhadi, M.
Forough and R. E. Sabzi, Anal. Methods., 2011, 3, 2599-
2603; (c) H. Li, Z. Cui and C. Han, Sens. Actuators, B-Chem,
2009, 143, 87-92.
20 (a) P. J. Rivero, J. Goicoechea, A. Urrutia and F. J. Arregui,
4
5
Nanoscale Res. Lett., 2013,
21 (a) Y. Zhou, H. Zhao, C. Li, P. He, W. Peng, L. Yuan, L. Zeng
and Y. He, Talanta, 2012, 97 331-335; (b) K. G.
8, 101-110.
,
Stamplecoskie and J. C. Scaiano, J. Am. Chem. Soc., 2010,
132, 1825–1827.
(a) G. Wu, C. Dong, Y. Li, Z. Wang, Y. Gao, Z. Shen and A.
Wu, RSC Adv., 2015, 5, 20595-20602; (b) Y. Gao, X. Li, Y.
Li, T. Li, Y. Zhao and A. Wu, Chem. Commun., 2014, 50
,
8 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
New Journal of Chemistry
Page 9 of 10
Journal Name
View Article Online
DOI: 10.1039/C6NJ01486K
ARTICLE
22 M. Li, S. K. Cushing and N. Wu, Analyst, 2015, 140, 386-
406.
23 (a) R. Hu, G. Long, J. Chen, Y. Yin, Y. Liu, F. Zhu, J. Feng, Y.
Mei, R. Wang, H. Xue, D. Tian and H. Li, Sens. Actuator B-
Chem., 2015, 218, 191-195; (b) X. Jiang, D. Zhang, J.
Zhang, J. Zhao, B. Wang, M. Feng, Z. Dong and G. Gao,
Anal. Methods., 2013, 5, 3222–3227.
24 (a) Q. Lin, T. –T. Lu, X. Zhu, B. Sun, Q. –P. Yang, T. –B. Wei
and Y. –M. Zhang, Chem. Commun., 2015, 51, 1635-1638;
(b) Q. Lin, T. –T. Lu, J. –C. Lou, G. –Y. Wu, T. –B. Wei and Y.
–M. Zhang, Chem. Commun., 2015, 51, 12224-122227; (c)
Q. Lin, X. Liu, T. –B. Wei and Y. –M. Zhang, Sens. Actuator
B-Chem., 2014, 190, 459-463.
25 (a) W. Jin, P. Huang, F. Wu and L. H. Ma, Analyst, 2015,
140, 3507–3513; (b) W. Ren, C. Zhu and E. Wang,
Nanoscale, 2012, 4, 5902-5909.
26 (a) G. Tian, W. Wang, B. Mu, Y. Kang and A. Wang, J.
Colloid Interface Sci., 2016, 473, 84-92; (e) C. B. Rosen, D.
J. Hansen and K. V. Gothelf, Org. Biomol. Chem., 2013, 11
7916–7922.
,
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 9
Please do not adjust margins

Please do not adjust margins
New Journal of Chemistry
Page 10 of 10
View Article Online
DOI: 10.1039/C6NJ01486K
ARTICLE
Journal Name
Cysteine-based silver nanoparticles as
dual colorimetric sensors for cations and
anions
P. P. Praveen Kumar, Lakshay Kathuria and V.
Haridas *
Synthesis of amide-triazole-based Ag NPs and their sensing
ability towards anions and cations in aqueous solution was
investigated. The importance of amide-triazole as a binding
motif, in conjunction with Ag NPs, the mode of sensing
ability of these amide-triazole Ag NPs as dual colorimetric
sensor has been studied in detail.
10 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins