Water dispersed fluorescent organic aggregates for the picomolar detection of ClO4- in water, soil and blood serum and the attogram detection of ClO4- in the solid state by a contact mode method

Article abstract of DOI:10.1039/c6tc01891b

Fluorescent organic aggregates (FOAs) of CS-1 have been used for the fluorescence based selective estimation of ClO₄^- ions. CS-1 undergoes self-aggregation to form FOAs (φ = 0.35) with a diameter of 140 ± 50 nm in aqueous medium. Dynamic light scattering and field emission scanning electron microscopy studies reveal that FOAs of CS-1 undergo further aggregation to form larger particles upon addition of ClO₄^- (10 pM-1 nM concentration) but at higher concentrations of ClO₄^- ions, these FOAs undergo dis-aggregation to give finally a molecularly dissolved complex of CS-1 and ClO₄^-. This ClO₄^- induced aggregation-dis-aggregation process of FOAs of CS-1 is associated with super-amplified fluorescence quenching following two domains of non-linear complexation with K_sv values of 2.42 × 10⁸ M^-1 and 3.59 × 10⁵ M^-1 and variation in the lifetime measurements of FOAs of CS-1 at different concentrations of ClO₄^-. The lowest limit of detection is 10 pM in solution and 6 × 10^-18 g cm^-2 in the solid state by a contact mode method with a selectivity of ～10 000 over other inorganic anions and allows the quantitative measurement of ClO₄^- ions using front surface steady state fluorescence of paper strips coated with CS-1. FOAs of CS-1 find applications in the determination of ClO₄^- in tap water, soil and also blood serum. Probe CS-2, which differs from CS-1 in lacking three methyl groups on the m-phenylene spacer, shows poor sensitivity (LOD 1.6 μM) towards ClO₄^-. DFT studies of CS-1 and CS-2 and their complexes with ClO₄^- reveal the effect of methyl substituents on their geometries.

Full text of DOI:10.1039/c6tc01891b

View Article Online
View Journal
Journal of
Materials Chemistry C
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: R. Kumar, S.
Sandhu, P. Singh and S. Kumar, J. Mater. Chem. C, 2016, DOI: 10.1039/C6TC01891B.
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/materialsC

Please do not adjust margins
Journal of Materials Chemistry C
Page 1 of 10
View Article Online
DOI: 10.1039/C6TC01891B
Journal Name
ARTICLE
Water dispersed fluorescent organic aggregates for detection of
-
picomolar ClO in water, soil and blood serum and atto g by
contact mode
4
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
Rahul Kumar, Sana Sandhu, Prabhpreet Singh* and Subodh Kumar*
-
www.rsc.org/
Fluorescent organic aggregates (FOAs) of CS-1 have been used for the fluorescence based selective estimation of ClO
4
ions. CS-1 undergoes self-aggregation to form FOAs (φ = 0.35) with diameter 140 ± 50 nm in aqueous medium. Dynamic
light scattering and field emission scanning electron microscopic studies reveal that FOAs of CS-1 undergo further
-
aggregation to form larger particles on addition of ClO
4
(10 pM – 1 nM concentration) but at higher concentrations of
-
4
-
-
4
ClO
ions, these FOAs undergo dis-aggregation to give finally molecularly dissolved complex of CS-1 and ClO
4
. This ClO
induced aggregation – dis-aggregation process of FOAs of CS-1 is associated with super-amplified fluorescence quenching
8
-1
5
-1
following two domains of non-linear complexation with Ksv values 2.42 x 10 M and 3.59 x 10 M and variation in Life
-
time measurements of FOAs of CS-1 at different concentrations of ClO
4
. The lowest limit of detection is 10 pM in solution
-18
2
and 6 x 10 g/cm by contact mode method with selectivity of ~10000 over other inorganic anions and allows quantitative
-
measurement of ClO
4
ions using front surface steady state fluorescence of paper strips coated with CS-1. FOAs of CS-1 find
-
applications in determination of ClO
4
from tap water, soil and also in the presence of blood serum. Probe CS-2, which
differs from CS-1 in lack of three methyl groups on the m-phenylene spacer, shows poor sensitivity (LOD 1.6 μM) towards
-
-
ClO
4 4
. DFT studies of CS-1 and CS-2 and their complexes with ClO reveal the effect of methyl substituents on their
geometries.
hydrophobic interactions, and covalent coupling etc. Even, the
mixing of a charged organic nano particles with oppositely
charged stimulant can induce aggregation – disaggregation
Introduction
The development of fluorescent probes based on single
molecular interaction with stimulant has attracted
considerable research interest over the past few decades
2
6,27
process
resulting in aggregation / disaggregation induced
a
1
-17
emission enhancement or quenching. Also, the interaction of a
FOA with single stimulant molecule can result in exciton
.
Due to strong interactions of anions with water molecules, the
design of anion recognition probes active in water with high
sensitivity and selectivity towards an anion is still a challenge.
Compared with these optical probes which remain dissolved at
molecular level, the fluorescent organic aggregates (FOAs)
which remain dispersed in water have received increasing
2
8-31
transfer
to large number of probe molecules in FOA
resulting in amplification of the signal.
-
Amongst anions, ClO4 disrupts thyroid iodine uptake in
human beings due to its ability to substitute iodide ion and has
2,33
3
increased concerns to its effects on human health
.
1
8-25
However, due to its weak coordination behavior, the efforts to
attention
owing to their higher selectivity and sensitivity
3
4-37
design molecules for its qualitative encapsulation
and
. In
through combination of stimulant induced changes in their
aggregate state and molecular interactions and thus result in
change in their optical properties at significantly lower
concentrations of the stimulant.
3
8-43
quantitative detection have met with a limited success
-
none of these cases ClO4 ions could be determined below
nano molar concentration and could be used for detection of
-
ClO ions in the presence of blood serum. Recently, our group
4
Fluorescent organic aggregates (FOAs) can be generated
through molecular self-assembly via a range of interactions,
such as electrostatic interactions, hydrogen bonding,
has shown that N-aryl benzimidazolium moieties linked
through an appropriate spacer can be used for fluorescence
-
based selective detection of ClO ions from tap water,
4
3
9,40
fireworks, live cell imaging etc.
Amongst other reports, Gao
et al have also reported an imidazolium based chemosensor
-
which undergoes ClO4 ions mediated aggregation induced
*
Department of Chemistry, UGC centre for advanced studies, Guru Nanak Dev
University, Amritsar 143005. Punjab, India
Fax:(+)91-183-228880
E-mail: subodh_gndu@yahoo.co.in.
4
fluorescence enhancement . However, in none of these cases
2
-
the detection limit for ClO4 ions could be attained in pico to
†
Footnotes relaꢀng to the ꢀtle and/or authors should appear here.
nano molar concentration range and also probably due to
strong interactions of the probe with blood serum, these could
Electronic Supplementary Information (ESI) available: [the spectra of CS-1, CS-2
and photophysical studies]. See DOI: 10.1039/x0xx00000x
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
Journal of Materials Chemistry C
Page 2 of 10
View Article Online
DOI: 10.1039/C6TC01891B
ARTICLE
Journal Name
-
not be used for detection of ClO
serum.
4
ions in the presence of blood
Herein, we report new chemosensors CS-1 and CS-2, which
differ only in substituents on the spacer between two
-
benzimidazolium moieties but CS-1 owing to its unique ClO
4
induced aggregation - disaggregation behaviour in water
HEPES buffer (2% DMSO)] exhibits highly selective and
sensitive fluorescence quenching. Conspicuously,
[
40
chemsosensor CS-2, like earlier reported chemosensors , does
not form aggregates and shows poor sensitivity (poorer by >
4
-
1
4
0 times) towards ClO ions and highlights the significance of
methyl groups present on the m-phenylene spacer in CS-1 in Scheme 2: Synthesis of chemosensors CS-1 and CS-2
achieving high sensitivity and selectivity.
†
CS-1 in water undergoes aggregation to form FOAs with a spectral data (Fig. S1-4, ESI ).
mixture of spherical and rod-like morphology (80-170 nm). DLS
and FE-SEM studies reveal that aggregation of these FOAs is
Before examining anion interaction studies of CS-1 and CS-
, the optical properties of CS-1 and CS-2 were recorded in
further enhanced in the presence of 10 pM to 1 nM DMSO and binary mixtures of DMSO : H O (v/v) to rationalize
2
2
perchlorate ions, as evident by increase in their size to 200 – the effect of aqueous medium. We have observed that with
ꢀ
5
00 ± 50 nm. Subsequently, at higher concentrations of ClO
4
the increase in volume fraction of water from 0% to 98% in
ions (5 µM), these FOAs undergo dis-aggregation to form DMSO, the absorption intensity of CS-1 continuously decreases
-
4
molecularly dissolved 1:1 complex of CS-1 and ClO . This and for the solutions containing > 60% water, the absorption
-
†
process of ClO
Scheme 1) is associated with continuous decrease in fluorescence spectra, we observed that as the volume fraction
fluorescence of the solution of CS-1 and allows determination of water increased from 0-40%, the emission intensity of CS-1
4
ions induced aggregation – disaggregation spectrum becomes broadened (Fig. S5A, ESI ). In case of
(
-
of 10 pM concentration of ClO
4
ions in solution phase and 6 x also increases with concomitant red-shift of the emission
g/cm by contact mode method using paper strips coated maxima by 10 nm from 430 nm to 440 nm. This could be
with CS-1 and quantitatively measuring front surface steady assigned to the change in environment around the molecularly
-18
2
10
-
-
-
-
state fluorescence. Significantly, other anions viz. F , Cl , Br , I , dissolved CS-1 molecules (Fig. 1).
-
-
CN , OH , H
-
-
-
-
2-
-
2 4 3 4 4
PO , NO , AcO , HSO , SO , SCN etc show
insignificant change in the fluorescence of CS-1 and do not
-
interfere in the estimation of ClO
4
.
CS-1 could be used for
in drinking water, soil samples and in the
presence of blood serum.
-
estimation of ClO
4
2
. Results and Discussion
CS-1 was synthesized in 94% yield by heating a 2:1 mixture
o
of compounds
subsequent anion exchange with PF
presence of NCH singlet at δ 5.84 and benzimidazolium C
1
and
2
in DMF at 90 C under N
2
with
-
6
(Scheme 2). The
-H
2
2
1
protons at δ 9.46 in its H NMR spectrum and appearance of
parent ion peak at 831.3148 in its HRMS spectrum confirm the
formation of CS-1. Similar reaction of
1 with dibromide 3 gave
chemosensor CS-2. The structures of chemosensors CS-1 and
1 13
CS-2 have been confirmed by H NMR, C NMR, and HRMS
Fig 1. Change in fluorescence intensity of CS-1 with increasing volume fractions of
water.
-
4
Scheme 1: Schematic presentation of mechanism of ClO
interaction with CS-1
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
Journal of Materials Chemistry C
Page 3 of 10
View Article Online
DOI: 10.1039/C6TC01891B
Journal Name
ARTICLE
Interestingly, further increase in water fraction from 40 to 98% of three methyl substituents on the m-phenylene spacer
in DMSO, the emission intensity decreases to a small extent directs its aggregation in water.
along with red-shift of the emission maxima to 460 nm (Fig. SI
The aggregation of CS-1 to form FOAs in water and their
-
5
B). These results indicate aggregation of CS-1 to form interaction with different concentrations of ClO
1
4
ions have
8-25
fluorescent organic aggregates (FOAs) in aqueous media
. In been confirmed by DLS experiments which have been truly
case of CS-2 on increasing volume fraction of water to 50%, supported by FE-SEM studies of the thin films prepared from
the emission maxima underwent gradual red-shift from 438 these solutions and fluorescence techniques (solution phase
nm to 450 nm due to change in the environment around and solid state). From DLS experiments we have observed that
molecules and further increase in volume fractions of water the solution of CS-1 in water (2% DMSO) shows the formation
did not affect the emission maxima or fluorescence intensity of FOAs with size 140 ± 50 nm (Fig. 2C). FE-SEM images of the
and points to non-aggregation of CS-2 in water. Therefore, in thin films of CS-1 also reveal the formation of FOAs (a mixture
case of CS-1, the increased hydrophobicity due to the presence of spherical and rod-like) with diameter 160 ± 50 nm (Fig. 2A-
B).
-
4
-11
Fig 2
.
(A-C) SEM image and DLS graph of CS-1 (5 µM); (D-F) SEM image and DLS graph of CS-1 in the presence of ClO
( 5 x 10 M); (G-I) SEM image and DLS graph of CS-1 in the
-
-6
-
-5
presence of ClO
4
4
(10 M); (J-L) SEM image and DLS graph CS-1 in the presence of ClO (1 x 10 M).
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
Journal of Materials Chemistry C
Page 4 of 10
View Article Online
DOI: 10.1039/C6TC01891B
Journal Name
ARTICLE
-11
-9
In FE-SEM the increasing concentration of CS-1 in the (5 x 10 M) undergo further aggregation and between 10 to
-
5
-
solution during drying of the films may be responsible for small 10 M ClO
increase in size of the FOAs as compared to those observed in state. Conspicuously, DLS results in HEPES buffer, reveal that
case of DLS experiments. the aggregates of only CS-1 has size 165+40 nm and on
Interestingly, FE-SEM of FOAs of thin film of the solution of addition of 5x10 M ClO
4
undergo disaggregation to molecularly dissolved
-11
-
4
the size of aggregates is increased
-
11
-
-6
-
CS-1 containing 5x10 M ClO
4 4
shows the aggregation of FOAs to 250-800 nm and in presence of 10 M ClO , the size of
-5
to larger size particles (280 - 500 nm) and these are in aggregates is reduced to 200 + 100 nm and finally at 10
-
consonance with DLS experiments pointing the formation of ClO
M
4
size of aggregates is further reduced to 60 + 30 nm. Also,
-5
2
00 – 500 ± 50 nm size aggregates (Fig. 2D-F). However, as we the average size of the aggregates of CS-1 and CS-1 + 10
-
M
-6
ions to 1 x 10 M ClO
-
further increased the concentration of ClO
4
4
ions remained stable even on recording DLS after 24h.
†
in the solution of CS-1 (5 µM), the size of the FOAs decreased (Fig. S6 ESI ).
to 150 ± 40 nm, in consonance with 120 ± 40 nm size of FOAs
The UV-Vis spectrum of FOAs of CS-1 (2 µM) in HEPES
as observed from DLS experiments (Fig. 2G-I). On further buffer (0.05 M pH 7.4, 2% DMSO) showed an absorption
-
-5
increasing the concentration of ClO
particles were well dispersed and their size was reduced to 30 of solution of CS-1 (2 µM) with NaClO
60 nm as observed under both FE-SEM images and DLS decrease in absorbance at 270 nm associated with increase in
experiments (Fig. 2J-L). Thus, CS-1 in 98% aqueous medium absorbance between 320-650 nm with an isosbestic point at
4
ions to 10 M, the maxima at 270 nm typical of aromatic moieties. The titration
4
showed gradual
–
-
-
290 nm (Fig. 3A). The plot of log[ClO ] concentration vs A /A
4
o
undergo self-assembly to form FOAs which on addition of ClO
4
-
4
-
4
Fig 3. (A) Effect of gradual addition of ClO
ions on the absorption spectrum of CS-1 (2 µM HEPES buffer – 2% DMSO, pH 7.4); (B) plot of A
o
/A vs log [ClO
]; (C) Effect of gradual
-
-
addition of ClO
4
ions on the emission spectrum (λex = 290 nm) of CS-1 (2 µM, HEPES buffer – 2% DMSO, pH 7.4); (D) plot of FI at 460 nm vs [ClO
4
] and inset shows decrease in FI of
CS-1 at 1, 10 and 100 nM concentration (error bars show ~ 2.6% error).
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 4
Please do not adjust margins

Please do not adjust margins
Page 5 of 10
Journal of Materials Chemistry C
View Article Online
DOI: 10.1039/C6TC01891B
Journal Name
ARTICLE
-
Table 1 Comparison of LOD of ClO
4
by CS-1 with literature reports
S.
No.
1
Journal Name
Phenomena
Solution
(Detection limit)
10 pM
Contact mode
(detection limit)
-2
6x10 g cm
-18
Present work
Aggregation-
disaggregation
aggregation
(0.01 nM)
NR
2
3
4
5
Chem. Commun., 2014, 50, 5623-5625
Chem.Commun., 2014, 50, 13994-13997
RSC Adv., 2013, 3, 14044-14047
Analyst, 2012, 137, 4913
No
10
-
-2
Dis-aggregation
Cavity based
Cavity based
60 nM
8x10 g cm
100 nM
No
No
100 nM
6
Chem. Commun., 2010, 46, 1070–1072
---
NR
Yes, (NR)
at 330 nm (the point of largest change in absorbance) shows follow linear equation I
-6
o
/I = 1 + Ksv[Q]. It gave non-linear
2
linear increase (R = 0.9886) in absorbance between 10-9 - 10
Stern-Volmer curve which was well fitted to the exponential
28,29
-
M ClO
4
(Fig. 3B). The appearance of absorption tail from 320 equation (I/I
-
o
= Aek[Q] + B)
, thereby confirming the super-
-
to 650 nm indicates that on gradual addition of ClO
relative amount of free molecules decreases and more values are found to be 2.42 x 10 M and 3.59 x 10 M ,
4
, the amplified quenching at low concentrations of ClO . The Ksv
8
4
-1
5
-1
-
-10
-7
-7
-5
-
aggregates are formed. The minimum detection limit for ClO
was 1 nM.
-
The addition of other anions (100 µM) viz F , Cl , Br , I , CN ,
4
respectively between 10 to 10 M and 10 to 10 M ClO
4
concentration.
-
-
-
-
ꢀ
The semi-log plot of log [ClO
etc. caused insignificant between 10 - 10 M (R = 0.9929) and 10 -10 M (R =
4
] vs I
o
/I shows linear increase
2
-
OH , H
-
- -
, AcO , HSO
-
2-
-10
-7
2
-7
-5
2
PO
4
, NO
3
4
, SO
4
†
ꢀ
change in the absorption spectrum of CS-1 (Fig. S6, ESI ). The 0.9944) ClO
solution of CS-1 (2 µM, HEPES buffer – 2% DMSO, pH 7.4) on ClO
excitation at λex 290 nm exhibited emission maxima at 460 nm ClO
4
concentration. The minimum detection limit for
ꢀ
4
4
was 10 pM (Fig. 4). The titration of solution of CS-1 with
ꢀ
in molecularly dissolved state i.e. in HEPES buffer –
ꢀ
4
4,45
(quantum Yield,
Φ
= 0.35)
. On addition of aliquots of DMSO (80: 20) shows poor sensitivity towards ClO
4
(LOD 2
4
NaClO , the fluorescence intensity at 460 nm was gradually µM) and highlights the role of aggregation of CS-1 in enhanced
-
quenched (Fig. 3C) and was associated with blue-shift of the sensitivity towards ClO
4
in 98% HEPES buffer (Fig. S9, ESI†).
ꢀ
emission maxima to 440 nm. The addition of all other anions The addition of 10 pM to 1000 nM ClO
4
ions to the solution of
CS-1 (2 µM, HEPES buffer – 2% DMSO, pH 7.4) in steps with ten
or the addition of aromatics viz. benzene, toluene, time increase in concentration shows change in fluorescence
-
-
-
-
-
-
-
-
-
-
(
2 4 3 4
100 µM) viz F , Cl , Br , I , CN , OH , H PO , NO , AcO , HSO ,
2
-
SO
4
phenol, benzoic acid, naphthalene and anthracene (50 µM color of the solution from bluish green to blue (Fig. 4, inset).
†
each) etc. (Fig. S8, ESI ) caused an insignificant change in the The analysis of Job’s plot obtained by both absorbance and
fluorescence of CS-1. The insignificant change in the fluorescence as output channels shows the inflexion point near
absorption intensity of CS-1 at 290 nm i.e. at excitation to 0.5 indicative of formation of 1:1 stoichiometric complex by
ꢀ
†
(Fig. S10, ESI ).
wavelength clearly points that quenching of fluorescence CS-1 with ClO
4
-
intensity on addition of ClO
4
ions to the solution of CS-1 is not
due to the decrease in the absorbance.
-
The plot of FI vs [ClO
quenched on addition of only 10 nM (0.005 equiv.) of ClO
ions, thereby indicating a super-amplified quenching effect
4
] revealed that ~ 56% of the FI was
-
4
-
(
Fig. 3D, inset). Therefore, when a ClO
4
anion interacts with
FOAs of CS-1, it may quench the emission of multiple
4
fluorophores in its vicinity. The lowest detection limit for the
6
-
4
analysis of ClO was 10 pM. This is significantly lower than the
-
4
permissible ClO concentration of 150 nM in drinking water.
The comparison of detection limits both in solution and
solid state of CS-1 with those of literature reports (Table 1)
-
4
-5
Fig 4. Plot of log [ClO
] vs I
o
/I showing change in I
o
/I with increase in concentration of
shows that CS-1 is > 6000 times more sensitive than earlier
-
-
-11
ClO
4
from 10 to 10 M; inset shows visual changes in the emission intensity and
reported probes for ClO
4
. The Stern–Volmer plot for the
-
color of the solution of CS-1 (under illumination of 365 nm) in blank solution and upon
-
4
quenching of fluorescence of FOAs of CS-1 by ClO did not
4
addition of increasing concentration of ClO ions.
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
Journal of Materials Chemistry C
Page 6 of 10
View Article Online
DOI: 10.1039/C6TC01891B
ARTICLE
The selectivity of FOAs of CS-1 towards ClO
Journal Name
-
4
f
was further The life time values were used to determine K (fluorescence
ascertained by the competition experiments where competing decay constant) and Knr (non-radiative decay constant) values
-
-
-
-
-
-
-
anions viz F , Cl , Br , I , CN , OH , H
-
-
-
ꢀ
2
PO
4 3 4 4
, NO , AcO , HSO , and at each concentration of ClO . The life time of CS-1 remained
2
-
ꢀ
-11
concentration 10 to 10
-9
SO
before addition of ClO
fluorescence quenching efficiency of ClO
large unaffected in the presence of several interfering anions in concentration of ClO
4
(100 µM each) were added to the solution of FOAs of CS- constant at ~ 8.9 ns between ClO
4
-
ꢀ
1
4
. As observed from the results, the M but at higher concentrations of ClO
4
, it gradually increased
ꢀ
4
f
remained by and to 13.6 ns. The K values decreased gradually with the increase
ꢀ
4
. The rate for non-radiative decay
†
(
Fig. S11, ESI ). This indicates that CS-1 is selective for (Knr) of the excited state of CS-1 increased when concentration
-
ꢀ
-11
-9
to 10 M but at higher
recognition of ClO
4
even in the presence of other anions. The of ClO
FI of aggregates of CS-1 remains constant between pH 4.7-8.7 concentrations, Knr also decreased gradually. In consonance
4
was raised from 10
ꢀ
and therefore permits the determination of ClO
broad pH range (Fig. S12, ESI ).
4
over this with DLS and FE-SEM results, the FOAs of CS-1 underwent
†
-11
further aggregation on addition of 10 to 10
-9
ꢀ
M
ClO
mediated further aggregation of free CS-1 aggregates is
4
. This
ꢀ
The solution of molecular probe CS-2 (2 μM, HEPES buffer ClO
.05 M – 2% DMSO, pH 7.4) did not undergo any change in its associated with fluorescence quenching – a process commonly
47
fluorescence intensity on addition of various anions viz F , Cl , observed in literature . But at higher concentrations of ClO ,
4
4
0
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
-
2-
Br , I , CN , OH , H
2
PO
4
ꢀ
, NO
3
, AcO , HSO
4
, SO
4
(100 µM) the aggregates of CS-1 underwent dissolution and the
ꢀ
but the addition of ClO
4
caused fluorescence quenching. On
ꢀ
interactions of CS-1 with ClO
ions to the solution of CS-2, the at molecular level (Fig. 6). At molecular level, the cavity of CS-1
fluorescence intensity of CS-2 remained unaltered even up to formed by two 1-(biphenyl)benzimidazolium moieties
4
were gradually shifted to that
gradual addition of ClO
4
ꢀ
-
addition of 500 nM ClO
fluorescence intensity only between 2-100 μM concentration of biphenyl rings and results in increased fluorescence life time
4 4
and showed gradual decrease in undergoes coordination with ClO ion. It restricts the rotation
ꢀ
4
of ClO ions. This is also associated with blue-shift of the from 8.9 to 13.6 ns. However, photo-induced electron
emission maxima by 20 nm. The lowest limit of detection for transfer
4
8,49
-
from biphenyl moiety to ClO
4
ion results in
ꢀ
ClO
Job’s plot of CS-2 and ClO
output channel shows the inflexion point close to 0.5
equivalent and points to the formation of 1:1 complex (Fig. mechanism in the presence of 10 to 10
4
by CS-2 is found to be 1.6 µM (Fig. 5). The analysis of formation of non-emissive excited state (Fig. S17) and results
ꢀ
4
obtained by fluorescence as in efficient fluorescence quenching.
Therefore, probe CS-1 follows static fluorescence quenching
-11
-9
ꢀ
M
ClO
concentration, the
4
, but at
†
-9
ꢀ
S13, ESI ). Therefore, probe CS-2 though selectively binds with higher concentrations i.e. at > 10 M ClO
but exhibits drastically decreased sensitivity in interaction of CS-1 with ClO
comparison to that observed for the probe CS-1
4
ꢀ
ꢀ
1
ClO
4
4
is shifted to dynamic process. H
-H O, 7:3) on
show < 0.05 ppm up-field
4
in comparison to probe CS-2 and shows that the shift of Bim C2-H and ArH doublet and point to the weak
.
NMR spectrum of CS-1 and CS-2 (DMSO-d
6
2
5
ꢀ
Therefore, probe CS-1 is nearly 10 times more sensitive addition of one equivalent of ClO
towards ClO
methyl substituents which though may not be directly interactions of CS-1 and CS-2 with ClO
interacting with ClO
of the CS-1
4
ꢀ
ꢀ
4
in molecularly
ꢀ
†
4
but drastically affect sensing properties dissolved state (Fig. S14-15, ESI ).
.
In order to evaluate the effect of methyl substituents on m-
phenylene spacer on the conformations of the probes CS-1
and CS-2, the U-conformational structures of the two
-
Mechanism of interaction of CS-1 with ClO
4
In order to provide an insight to the mechanism of molecules were optimized.
ꢀ
interaction of FOAs of CS-1 with ClO
4
anion, the effect of
ꢀ
concentration of ClO
determined.
4
on the life time of CS-1 was
Fig 6. The life time, rate constants for radiative (k
f
) and non-radiative (Knr) decay of
-
4
Fig 5. (A) Effect of gradual addition of ClO
ions on the emission spectrum (λex = 290
/I at 450 nm vs
-
excited state of CS-1 in the presence of different concentrations of ClO
4
.
nm) of CS-2 (2 µM, HEPES buffer – 2% DMSO, pH 7.4).); (B) Plot of I
o
-
[
4
ClO ] (Error bars show < 2.5% error).
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
Journal of Materials Chemistry C
Page 7 of 10
View Article Online
DOI: 10.1039/C6TC01891B
Journal Name
ARTICLE
The super-imposition of energy minimized structures of CS-1
Thus combination of factors viz the aggregation of CS-1 in
and CS-2 (Fig. 7A) shows that CS-1 is optimized as a more water due to enhanced hydrophobicity and the better pre-
compact structure with distance of 6.026 Å between C-2 organization of cavity in CS-1 due to hydrophobicity and steric
carbons of benzimidazolium moieties. In case of CS-2, the bulk of methyl substituents on linker between two
distance between C-2 of two benzimidazolium moieties is benzimidazolium moieties in comparison to that in probe CS-2
increased to 6.713 Å. This difference in conformations of CS-1 result in increased sensitivity and selectivity of CS-1 towards
-
and CS-2 could be assigned to the presence of three methyl ClO
4
.
substituents on m-phenylene ring which create enough steric
-
ClO
serum
In order to find the applications of CS-1 for the
4
ions determination in tap water, soil samples and blood
2
bulk on CH groups to decrease the cavity size of CS-1. Further,
the energy minimized structures of 1:1 complexes of CS-1 and
CS-2 reveal that CS-1 has to undergo minimal change in its
ꢀ
ꢀ
conformation during complex formation with ClO
undergoes significant conformational change during complex fixed amount of NaClO
4
anion. CS-2 determination of ClO
4
in tap water and in soil samples, a
4
was added to the tap water and soil
ꢀ
ꢀ
formation with ClO
4 4
. The ClO anion goes deep into the samples. The soil samples were suspended in water. The
ꢀ
cavity of CS-1 and three of its oxygen atoms form short water was filtered and was used for determination of ClO
4
ꢀ
contacts with BIM C2-H (2.13 – 2.38 Å) and ClO
4
oxygen using probe CS-1. Both categories of samples were analysed
ꢀ
atoms form anion-π interactions with π-cloud of the biphenyl for 0.1 nM – 1000 nM concentrations of ClO
4
ions. The
4
- ClO (1:1) complex, the π table 2 shows that in tap water samples maximum relative
ꢀ
and mesitylene rings. In CS-2
clouds of aryl rings do not participate in interaction with ClO
ꢀ
4
.
standard deviation was < 2.3% and pooled relative SD
(PRSD) = 1.8%; the maximum relative error was < 1.6% and
ꢀ
Therefore, CS-1 is better pre-organized to complex with ClO
than CS-2 (Fig. S16-17, ESI ). Also, in addition to electrostatic pooled relative error (PRE) was 1.3%. In case of soil
4
†
ꢀ
interactions between ClO
of the CS-1, the efficiency of electron transfer from HOMO of and pooled relative SD (PRSD) was 2.54%. The maximum
4
and the benzimidazolium moieties samples maximum relative standard deviation was < 3.54%
ꢀ
CS-1 to LUMO of ClO
selectivity of CS-1 towards ClO
LUMO of CS-1 and its complex with ClO
4
may at least partly contribute to the relative error was < 2.9% and pooled relative error (PRE)
ꢀ
4
. The analysis of HOMO and was 1.96%. The results clearly show that CS-1 can be used
ꢀ
ꢀ
4
4
shows that in case of for determination of ClO from both tap water and soil
free probe CS-1, the electron from biphenyl unit (HOMO) is samples, though the errors and deviations are higher in
excited to benzimidazolium ring (LUMO) but in its complex case of soil samples than determined for tap water.
ꢀ
with ClO
4
,
the electron from biphenyl (HOMO) is transferred Obviously, the soil contains more number of components
ꢀ
4
to ClO (LUMO). This results in non-radiative excited state and than tap water, which leads to higher deviations.
is so responsible for fluorescence quenching in CS-1
ꢀ
–
ClO
4
Further to investigate the biological application, the
fluorescence titration of CS-1 (2 µM) was carried out in the
presence of blood serum. It was found that in the presence of
blood serum the maxima of CS-1 was only marginally shifted
from 460 nm to 450 nm. The presence of a new band at 330
nm could be attributed to the aromatic amino acids in the
complex.
†
ꢀ
4
blood serum (Fig. S18, ESI ). On gradual addition of ClO to
the solution of CS-1 containing blood serum, the gradual
decrease in the fluorescence intensity was observed (Fig. 8).
-
Table 2 Application of CS-1 in determination of ClO
4
in tap
water and soil samples
ꢀ
Sr.
Conc. ClO
(nM)
4
Conc. determined ±
Relative
error (%)
a
No.
SD (ꢁM)
Tap water
1
2
3
4
5
0.1
1
10
100
1000
0.11 ± 0.002
1.28 ± 0.021
10.5 ± 0.15
102.3 ± 2.1
1001 ± 10.6
1.4
1.5
1.1
1.6
0.9
Soil samples
1
2
3
4
0.1
1
10
0.12 ± 0.002
1.14 ± 0.04
10.3 ± 0.3
1.4
2.9
2.0
100
105.6 ± 3.6
2.4
Fig 7. (A) The energy optimized structures of CS-1 (blue) and CS-2 (red) overlapped on
each other; (B) The energy minimized structures of 1:1 complexes of CS-1 and CS-2
5
Average ± standard deviation of three determinations
1000
1011.7 ± 13.2
1.01
-
a
with ClO
4
(The structure were optimized using B3LYP with basis set 6-311G*).
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
Journal of Materials Chemistry C
Page 8 of 10
View Article Online
DOI: 10.1039/C6TC01891B
ARTICLE
Journal Name
o
that ratio of I /I increases linearly with the increase in log
ꢀ
2
[
4
ClO ] between 10 pM - 10 μM with R = 0.9860. The lowest
ꢀ
4
detection limit for the analysis of ClO was determined as 10
pM.
-
Contact mode detection of traces of ClO
4
Finally we investigated the applicability of CS-1 in both
ꢀ
4
qualitative and quantitative detection of ClO using contact
mode method. For this we carried out experiments on paper
strips coated with CS-1. The paper strips were then visualized
under 365 nm UV light. We observed that the addition of 6 μl
-15
ꢀ
of 10
4
M ClO caused visible quenching of the fluorescence
intensity on the paper strip [Fig. 9A(ii)] and colour of the drop
casted area turned green, which is in consonance with solution
phase studies. Complete quenching of fluorescence intensity
-
4
Fig 8. Effect of gradual addition of ClO ions on the emission spectrum (λex = 290 nm) of
-
CS-1 (2 µM) in blood serum and plot of log [ClO
4
] vs I
o
/I shows linear change with
-
-11
-4
increase in concentration of ClO
4
from 10 to 10 M (Error bars show < 3% error).
-11
ꢀ
was observed with 10
M
ClO
4
[Fig. 9A(vi)] and addition of
results in dark colored area
ꢀ
higher concentrations of ClO
4
This decrease in intensity was also associated with blue-shift of
the emission maxima by 20 nm as observed in case of
titration of CS-1 in HEPES buffer. The titration results showed
developed on paper strip. Fig. 9A(i) shows no quenching of
fluorescence with water.
~
-
4
Fig 9. (A) Photographs of fluorescence quenching (under 365 nm UV light) of paper strips coated with CS-1 and different amounts of ClO
; (i) Paper strip with a drop of water; (ii)
-
15
-14
-13
-12
-11
-
-11
-
-
-
-
-
-
-
-
-
1
,
0
M; (iii) 10 M; (iv) 10 M; (v) 10 M; (vi) 10 M ClO solution (6 μL). (B) Paper strips with addition of 10 M solutions (6 μL) of ClO , F , Cl , Br , I , SCN , OH , NO , AcO
4 4 3
-
-
4
-
2-
4
2
-
CN , H
2
PO
, HSO
4
and SO
4
anions [The size of each paper strip is 1.0 cm ]. (C) Front surface steady-state fluorescence quenching of CS-1 with ClO . PS = fluorescence
−
14
−8
-
4
spectrum of CS-1 coated paper strip; PS + water = spectrum after addition of 200 μL of water to PS. 10 to10 corresponds to molar concentrations of ClO added to PS; (D) Plot
-
4
of fluorescence intensity of CS-1 vs log [ClO ] (M) (error < 2.8%).
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
Page 9 of 10
Journal of Materials Chemistry C
View Article Online
DOI: 10.1039/C6TC01891B
Journal Name
ARTICLE
ꢀ
-
detectable is 6 x 10 (153 mg, 0.5 mmol) was heated in DMF (3 ml) at 100 C under
o
Therefore, the minimum amount of ClO
4
1
9
2
-15
g/cm under 365 nm light illumination. For 6 μL of 10
M
N
2
atm for 24 h. After completion of the reaction, the solvent
. Further to was removed under vacuum. The crude residue was dissolved
in comparison to in methanol and was filtered to remove suspended impurities.
other anions, 10 M solution (6 μL) of each of the following To this filtrate, aqueous solution of NH PF (163 mg, 1 mmol)
was added drop wise with continuous stirring and stirring was
was added on the CS-1 coated paper strip and continued for 7-8 h. The white solid separated was filtered to
ꢀ
solution, amounts to
~3600 molecules of ClO
4
ꢀ
analyse the selectivity of CS-1 towards ClO
4
-
11
4
6
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
-
2 4 3 4
anions F , Cl , Br , I , CN , OH , H PO , NO , AcO , HSO ,
2
-
and SO
change in their fluorescence was observed. The results clealry get CS-1 as white solid (460 mg); yield 94 %; m.p. 247 C; H
reveal (Fig. 9B) that even on addition of 10000 times higher NMR (500MHz, DMSO-d ): δ 2.34 (s, 3H, CH ), 2.47 (s, 6H, 2 x
), 7.34 (s, 1H, ArH), 7.38 – 7.44 (m, 6H,
only a small change in fluorescence was observed only with ArH), 7.58 (d, 4H, J = 7.5 Hz), 7.79 – 7.90 (m, 14H, ArH), 8.38 (d,
4
o
1
6
3
ꢀ
-15
4 3 2
amounts of each of these anions than LOD of ClO (10 M), CH ), 5.84 (s, 4H, 2 x CH
1
3
iodide ions, which is well known to be the most interfering 2H, J = 8.5 Hz, ArH), 9.46 (s, 2H, BimC2H); C (125 MHz,
ꢀ
4 6
species with ClO due to similar size and basicity. The other DMSO-d ): δ 15.9, 20.1, 46.2, 127.0, 127.2, 127.3, 127.5,
anions did not cause any observable change in fluorescence of 128.3, 128.4, 128.8, 129.7, 132.0, 132.6, 132.7, 138.7, 140.6,
CS-1 coated paper strip. Therefore, CS-1 coated paper strips 141.3, 141.4, 142.5; HRMS m/z (TOF MS ES+) calculated for
ꢀ
are 10000 times or more selective towards ClO
4
over the
C
49
H
42
F
12
N
4
P
2
[
CS-1 – PF
6
] 831.3046, found 831.3148 [CS-1
2
–
+
other anions studied.
PF
6
using CS-1 coated paper 343.1758 [CS-1 – 2PF ] (100%).
6
] (40%), m/z calculated for [CS-1 – 2PF
2+
6
]
343.1699, found
ꢀ
In order for quantification of ClO
4
strips, the fluorescence spectra of the above paper strips
ꢀ
Synthesis of CS-2
The fluorescence spectrum of the paper strip coated with CS-1 The reaction of 1-(4-biphenyl)benzimidazole (
exhibits broad spectrum between 370 – 500 nm with two mmol) and 1,3-bis(bromomethyl)benzene ( ) (132 mg, 0.5
maxima at 430 and 470 nm which is in contrast to a sharp mmol) as described above gave chemosensor CS-2, white solid
4
treated with different concentrations of ClO were recorded.
1) (270 mg, 1
3
o
1
maxima at 460 nm in aggregate state of CS-1 in solution phase. (460 mg); yield 95.3 %; m.p. 232 C; H NMR (500 MHz, DMSO-
Therefore, in solid state, the aggregation behaviour of CS-1 is ): δ 5.89 (s, 4H, 2 x CH ), 7.48 (d, 2H, J = 7.0 Hz, ArH), 7.54 (t,
d
6
2
different from that in the solution phase. The intensity of the 5H, J = 7.5 Hz, ArH), 7.66 – 7.74 (m, 6H, ArH), 7.79 (d, 4H, J =
fluorescence spectrum gradually decreases with the gradual 7.5 Hz, ArH), 7.85 (s, 1H, ArH), 7.93 (t, 6H, J = 9.0 Hz, ArH), 7.98
ꢀ
increase in concentration of solution of ClO
plot of fluorescence intensity vs log [ClO
4
ꢀ
4
(Fig. 9C). The (d, 2H, J = 8.5 Hz, ArH), 8.05 (d, 4H, J = 8.5 Hz, ArH), 10.33 (s,
): δ 50.6, 114.3, 114.6,
] shows linear 2H, BimC2H); 13C (125 MHz, DMSO-d
6
change and is in agreement with exponential decrease in 126.2, 127.4, 127.6, 128.1, 128.9, 129.5, 129.7, 130.2, 131.3,
fluorescence intensity (Fig. 9D) with addition of ClO4ꢀ as 131.7, 132.7, 134.8, 138.9, 142.7, 143.3; HRMS m/z (TOF MS
-
+
] 789.2576, found
2+
observed in the solution phase. The Ksv value as determined ES+) calculated for C46
Ksv[Q]
H
36
+
F
12
N
P
4 2
[
CS-2 – PF
6
by exponential equation I/I
o
= Ae
6 6
+ B is found to be 1.49 × 789.2882 [CS-2 – PF ] (40%), m/z calculated for [2 – PF ]
2+
0 M and is in close agreement with Ksv (2.42 × 10 M ) that 322.1465, found 322.1618 [CS-2 – 2PF ] (100%).
8
8
-1
1
6
ꢀ
-9
4
observed in solution phase for the [ClO ] below 10 M. The
addition of water (200 μL) caused only a small quenching of
Conclusions
fluorescence intensity of the paper strip. Therefore, paper
-
strips coated with CS-1 were highly sensitive towards ClO
-8
4
and
ꢀ
Thus, probe CS-1 undergoes self-assembly to form
-14
could be used for quantification of 10 M - 10
solutions.
M ClO
4
fluorescent organic aggregates (FOAs) which further
-9
-
11
undergo aggregation in the presence of 10 - 10
ꢀ
M ClO
4
ꢀ
-9
4
and dis-aggregation with ClO at concentration > 10 M, as
revealed by both DLS and FE-SEM studies. This is associated
3
. Experimental Section
with super-amplified fluorescence quenching in the
ꢀ
General details of instruments, sample preparation are given presence of ClO
4
ions following two domains of non-linear
5
8
complexation with Ksv values 2.42 x 10 M and 3.59 x 10
-1
in supporting information.
-
1
ꢀ
M . The lowest limit of detection of ClO
solution phase and 6 x 10 g/cm by contact mode method
4
is 10 pM in
Synthesis of CS-1
-18
2
The solution of 1-(4-biphenyl)benzimidazole (
1) (270 mg, 1 and quantitatively measuring front surface steady state
mmol) and 2,4- bis(bromomethyl)-1,3,5-trimethylbenzene (
2)
fluorescence using paper strips coated with CS-1. FOAs of
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
Journal of Materials Chemistry C
Page 10 of 10
View Article Online
DOI: 10.1039/C6TC01891B
ARTICLE
CS-1 find applications in determination of ClO
Journal Name
ꢀ
from tap 25 A. Singh, T. Raj, T. Aree and N. Singh, Inorg. Chem., 2013, 52
3830−13832.
6 S. Sandhu, R. Kumar, P. Singh, A. Mahajan, M. Kaur and S.
Kumar, ACS Appl. Mater. Interfaces., 2015,
, 10491−10500.
,
4
1
water, soil and also in the presence of blood serum. The
life-time measurement studies, K and Knr results highlight
the participation of both dynamic and static mechanisms
2
2
f
7
7 S. Kumar, P. Singh, A. Mahajan and S. Kumar, Org. Lett.,
2013, 15, 3400-3403.
ꢀ
4
depending on the concentration of ClO . Therefore, the
present study provides a new insight into the design of self- 28 H. Feng, Y. Zheng, Chem. Eur. J., 2014, 20, 195-201.
ꢀ
29 L. Zhang, C. Zhao, J. Zhou and T. Kondo, J. Mater. Chem. C.,
2
4
assembled molecular probes for the detection of ClO ions.
013, 1, 5756-5764.
3
3
0 V. Balzani, P. Ceroni, S. Gestermann, C. Kauffmann, M. Gorka
and F. Vogtle, Chem. Commun., 2000, 853–854.
1 Y. Sun, Z. Chen, E. Puodziukynaite, D. M. Jenkins, J. R.
Acknowledgements
Reynolds and K. S. Schanze, Macromolecules, 2012, 45
632−2642.
2 B. C. Blount, D. Q. Rich, L. Valentin-Blasini, S. Lashley, C. V.
Ananth, E. Murphy, J. C. Smulian, B. J. Spain, D. B. Barr, T.
Ledoux, P. Hore and M. Robson, Environ. Sci. Technol., 2009,
43, 7543–7549.
3 T. Zhang, Q. Wu, H. W. Sun, J. Rao, K. Kannan, Environ. Sci.
Technol., 2010, 44, 6947–6953.
4 M. A. Saeed, J. J. Thompson, F. R. Fronczek and Md. A.
Hossain, Cryst. Eng. Commun., 2010, 12, 674–676.
,
This work was supported by Department of Science and
Technology, New Delhi (SR/S1/OC-75/2012). We thank UGC
for UPE programme to the university and CAS status to the
department and DST for FIST programme. RK and SS
acknowledge UGC and DST for fellowships.
2
3
3
3
Notes and references
1
P. A. Gale, N. Busschaert, C. J. E. Haynes, L. E. Karagiannidis, 35 L. Yang, Y. Li, L. Jiang, X. Feng and T. B. Lu, Cryst. Eng.
I. L. Kirby, Chem. Soc. Rev., 2014, 43, 205 – 241.
Commun., 2009, 11, 2375–2380.
L. E. S. Figueroa, M. E. Moragues, E. Climent, A. Agostini, R. 36 M. J. Hynes, B. Maubert, V. McKee, R. M. Town and J.
2
Martınez-Manez, F. Sancenon, Chem. Soc. Rev., 2013, 42
489 – 3613.
X. Li, X. Gao, W. Shi, H. Ma, Chem. Rev. 2013, 114, 590 – 659.
,
Nelson, J. Chem. Soc. Dalton Trans., 2000, 2853–2859.
37 G. Morgan, V. McKee and J. Nelson, Chem. Commun., 1995,
1649-1652.
3
3
4
H. J. Kim, M. H. Lee, L. Mutihac, J. Vicens, J. S. Kim, Chem. 38 S. D. Taylor, W. Howard, N. Kaval, R. Hart, J. A. Krause and W.
Soc. Rev., 2012, 41, 1173 – 1190.
Y. Zhou, J. Yoon. Chem Soc. Rev. 2012, 41, 52 - 67.
M. Wenzel, J. R. Hiscock, P. A. Gale, Chem. Soc. Rev., 2012,
B. Connick, Chem. Commun., 2010, 46, 1070–1072.
39 R. Kumar, S. Kumar, P. Singh, G. Hundal, M. S. Hundal and S.
Kumar, Analyst., 2012, 137, 4913 – 4916.
5
6
4
1
, 480 – 520.
40 P. Singh, L. S. Mittal, V. Vanita, R. Kumar, G. Bhargava, A.
Walia and S. Kumar, Chem.Commun., 2014, 50, 13994-
13997.
7
8
N. Kaur, S. Kumar, Tetrahedron, 2011, 67, 9233 – 9264.
Y. Zhou, Z. Xu, J. Yoon, Chem. Soc. Rev., 2011, 40, 2222 –
2
P. A. Gale, Chem. Soc. Rev., 2010, 39, 3746 – 3771.
0 C. Caltagirone, P. A. Gale, Chem. Soc. Rev., 2009, 38, 520 –
235.
41 A. Sahana, A. Banerjee, S. Lohar, A. Chottapadhyay, S. K.
Mukhopadhyay and D. Das, RSC Adv., 2013, 3, 14044 –
14047.
42 C. Gao, G. Gao, J. Lan and J. You, Chem. Commun., 2014, 50,
5623-5625.
43 K. Kaur, V.K. Bhardwaj, N. Kaur and N. Singh, Inorg. Chem.
Commun., 2012, 26, 31-36.
44 W. H. Melhuish, J. Phys. Chem., 1961, 65, 229-235.
45 J. N. Demas, G. A. Crosby, J. Phys. Chem., 1971, 75, 991-
1024.
46 J. Mokac, A. M. Bond, S. Mitchell, G. Scollary, Pure Appl.
Chem., 1997, 69, 297-328.
47 Z. Zhelev, H. Ohba, R. Bakalova, J. Am. Chem. Soc., 2006,
128, 6324−6325.
48 A. Li, J. Wang, F. Wang, Y. Jiang, Chem. Soc. Rev., 2010, 39,
9
1
5
63.
1 X. Chen, X. Tian, I. Shin, J. Yoon, Chem. Soc. Rev., 2011, 40
783 – 4804.
2 J. Ma, P. K. Dasgupta, Anal. Chim. Acta., 2010, 673, 117–
25.
1
1
,
4
1
1
1
3 D. T. Quang, J. S. Kim, Chem. Rev., 2010, 110, 6280–6301.
4 K. Kaur, R. Saini, A. Kumar, V. Luxami, N. Kaur, P. Singh, S.
Kumar, Coord. Chem. Rev., 2012, 256, 1992–2028.
1
1
1
1
1
5 H. S. Jung, X. Chen, J. S. Kim, J. Yoon, Chem. Soc. Rev., 2013,
42
, 6019 - 6031.
6 Y. Yang, Q. Zhao, W. Feng, F. Li, Chem. Rev., 2013, 113
92−270.
7 F. Wang, L. Wang, X. Chen, J. Yoon, Chem. Soc. Rev., 2014,
, 4312 – 4324.
8 J. Suk, Z. Wu, L. Wang and A. J. Bard, J. Am. Chem. Soc., 2011,
33, 14675–14685.
,
1
3729–3745
43
49 T. Gunnlaugsson, H. D. P. Ali, M. Glynn, P. E. Kruger,G. M.
Hussey, F. M. Pfeffer, C. M. G. Santos, J. Tierney, Journal of
Fluorescence, 2005, 15, 287-299.
1
9 Q. Zhao, K. Li, S. Chen, A. Qin, D. Ding, S. Zhang, Y. Liu, B. Liu,
J. Z. Sun and B. Z. Tang, J. Mater. Chem., 2012, 22, 15128–
1
5135.
0 J. Wang, X. Xu, L. Shi, and L. Li, ACS Appl. Mater. Interfaces.,
013, , 3392−3400.
1 H. Sharma, A. Singh, N. Kaur, and N. Singh, ACS Sustainable
Chem. Eng., 2013,
, 1600−1608.
2 X. Zhang, X. Zhang, B. Yang, Y. Zhang, and Y. Wei, ACS Appl.
Mater. Interfaces., 2014,
, 3600−3606.
3 A. Singh, S. Kaur, A. Kaur, T. Aree, N. Kaur, N. Singh and M. S.
Bakshi, ACS Sustainable Chem. Eng., 2014, , 982−990.
4 H. Sharma, V. K. Bhardwaj, and N. Singh, Eur. J. Inorg. Chem.,
014, 5424–5431.
2
2
2
2
2
2
5
1
6
2
2
1
0 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins