Mechanistic and thermodynamic aspects of a pyrene-based fluorescent probe to detect picric acid

Article abstract of DOI:10.1039/c9nj02342a

A remarkable flourescent (FL)-based Schiff base probe [(2E/Z)-2-(9-pyrenylmethylene)yrenylmethyle-thiophene-carboxylic acid or PTC] was employed for the rapid analytical detection of Cu²⁺ and picric acid (PA) up to the nM level. Although, there have been several literature reports on the utilization of fluorescent probes for the efficient sensing of explosives in the last few years, there has been no such report on the reaction spontaneity between a 'probe-explosive' ensemble in equilibrium. Herewith, in the present study, for the first time, a detailed thermodynamic investigation was performed and reported. Temperature-dependent thermodynamic studies revealed a high negative Gibbs free energy, with ΔG values of -120.3 kJ mol^-1 to -123.0 kJ mol^-1 obtained for the PTC-PA adduct. Interestingly, there was a steady decrease in the ΔG values with the increase in temperature along with a consecutive increment in the Stern-Volmer constant (K_SV). This suggests that the spontaneous adduct formation equilibrium for the 'probe-picric acid' ensemble becomes stronger with the increase in temperature. A negative ΔH value of -81.77 kJ mol^-1 confirmed that the spontaneous adduct formation in equilibrium was exothermic in nature. Apart from the sensing of picric acid, PTC and the PTC + Cu²⁺ complex possess the ability to permeate cells and thus, they were explored for the imaging of living cells. Moreover, agreement between the theoretical and experimental findings on the PET-based sensing mechanism indicated that the extensive conjugation of the pyrene system attached to the adjacent imine along with the higher electric potential, encompassing the thiophene ring are very much instrumental in PTC acting as a PA sensor.

Full text of DOI:10.1039/c9nj02342a

View Article Online
View Journal
NJC
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: S. Mukhopadhyay,
B. K. Kundu, P. Porwal, R. Kyarikwal and S. M. Mobin, New J. Chem., 2019, DOI: 10.1039/C9NJ02342A.
Volume 40 Number
1
January 2016 Pages 1–846
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
NJC
New Journal of Chemistry
www.rsc.org/njc
A journal for new directions in chemistry
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
author guidelines.
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, outlined
in our author and reviewer resource centre, 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.
ISSN 1144-0546
PAPER
Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
diarylethene-based metal–organic frameworks
rsc.li/njc

Page 1 of 19
New Journal of Chemistry
1
2
3
1
4
View Article Online
Mechanistic and thermodynamical aspects of pyrene based fluo
D
r
O
e
I:
s
1
c
0.
e
10
n
39/C9NJ02342A
t
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
2
probe to detect picric acid
Bidyut Kumar Kundu, Pragti, Reena, Shaikh M. Mobin, Suman Mukhopadhyaya, b,*
a
a
a
a
3
a
4
5
Discipline of Chemistry, School of Basic Sciences, Indian Institute of Technology Indore,
Simrol, Khandwa Road, Indore 453552, India
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
b
6
7
Centre for Biosciences and Biomedical Engineering, School of Basic Sciences, Indian
Institute of Technology Indore, Khandwa Road, Simrol, Indore 453552, India.
8
*E-mail: suman@iiti.ac.in; Fax: +91 731 2361; Tel: +91 731 2438 735
9
ABSTRACT
1
1
0
1
A remarkable PL based Schiff base probe [(2E/Z)-2-(9-Pyrenylmethylene)hydrazide-2-
ThiopheneCarboxylic acid or PTC] has been employed for the rapid analytical detection of
2
+
12
Cu and picric acid (PA) up to nM level. Although, there are several literature reports on
utilization of fluorescent probe for efficient explosives sensing in the last few years, however,
there is no such report on the reaction spontaneity between ‘probe-explosive’ ensemble in
equilibrium. Herewith, in this report for the first time, a detailed thermodynamic investigation
has been included. Temperature dependent thermodynamic study reveals high negative Gibbs
free energy as G values of –120.3 to –123.0 kJ/mol have been obtained for PTC-PA adduct.
Interestingly, there is a steady decrease of G values with increase in temperature along with
1
1
1
3
4
5
16
1
1
1
7
8
9
a consecutive increment in Stern-Volmer constant (K ). This suggests that the spontaneous
SV
20
21
adduct formation equilibrium for ‘probe-picric acid’ ensemble becomes stronger with rise in
temperature. A negative H value of -81.77 kJ/ mol confirms that the spontaneous adduct
formation in equilibrium is exothermic in nature. Apart from picric acid sensing, PTC and
2
2
2
3
2+
PTC + Cu complex possesses cell permeable ability, and thus, they have been explored for
24
the living cell imaging. Moreover, theoretical and experimental agreement on the PET based
sensing mechanism correlates that the extensive conjugation of pyrene system attached to the
adjacent imine along with the higher electric potential encompassing thiophene ring are very
much instrumental for PTC to act as PA sensor.
2
2
2
5
6
7
2
8
INTRODUCTION
29
In last few years, enormous focus has been given to detect and quantify various chemical
entities in environment and biological systems. Developing new probes for efficient and cost
effective methodology for sensing a particular entity has taken the forefront of chemical
research. Though, massive number of molecular probes have been introduced for sensing
different molecules or groups, the mechanistic and thermodynamical aspects of sensing
3
3
3
0
1
2
33
1

New Journal of Chemistry
Page 2 of 19
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
View Article Online
1
2
largely remains in backseat. One of such area is the detection of common explosives which
DOI: 10.1039/C9NJ02342A
are based on nitro-aromatic compounds (NACs), such as trinitrophenol/ picric acid (TNP/
PA), trinitrotoluene (TNT). The importance of the detection of such molecules like TNT and
cyclotrimethylenetrinitramine (RDX) lies in the fact that they are the potential chemicals
which are quite capable to explode and bring out considerable damages in terms of life and
property if utilized with evil intentions.1 On the other hand PA with easily dissociable
phenolic proton has been found to be more corrosive than that of RDX and TNT.2-6 Having
incredible water solubility, PA is responsible for several diseases or symptoms associated to
groundwater poisoning, viz anaemia, nausea, vomiting, asphyxiation, sycosis, skin/ eye
itching, abdominal pain, and liver or kidney damage.3, 7 Furthermore, picric acid is widely
3
4
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
5
6
7
8
9
10
1
1
1
2
used in fireworks, pharmaceuticals, rocket fuels, leather and dye industries but also it has
been accepted as an environmental pollutant and is quite dangerous to humans and wildlife.8-
1
0
The acceptable tolerance concentration of picric acid in groundwater is 0.001 mg/L.11
13
1
4
Thus, the trace detection of PA has an unmet need to reduce environmental pollution as well.
1
5
Though, there are numerous analytical techniques to detect NACs, but the most
widely used methodology is the utilization of fluorescent probes.12, 13 There are already
several reports where change in fluorescent pattern has been introduced to detect NACs.14, 15
However, to the best of our knowledge, there is no report where the thermodynamical
aspects, which is a key to understand the mechanistic pathways have been explored for
detection of PA. Among the different kinds of probes quantum dots, nanoparticles, COFs/
MOFs, oligomers, or conjugated polymers, micro or nano aggregates, etc. found to be
common.8, 16-20 Various mechanistic approaches (such as PET, ESIPT, FRET, RET,
chemodosimeters, AIE etc.) have been proposed to explain the probable cause behind FL
quenching during explosive sensing.2, 19, 21, 22 Among them donor-acceptor theory is the most
common explanation, which involves the charge or energy transfer from the sensor’s
photoexcited state to the ground state of NACs.23
16
1
1
7
8
19
2
2
2
0
1
2
23
2
2
2
4
5
6
2
2
7
8
To investigate the mechanistic and thermodynamical aspects of sensing of NACs, herein, we
have designed and developed a pyrene based small molecule chemosensor, PTC (where, PTC
= (2E/Z)-2-(9-Pyrenylmethylene)hydrazide-2-ThiopheneCarboxylic acid) (Scheme 1) for the
efficient detection of PA which has been found to be effective with a limit of detection
(LOD) value of 19 nM in acetonitrile (ACN) via FL spectroscopy. LOD value in nM range
suggest that PTC can act as ultrasensitive fluorescent sensor for PA. The pyrene as well as
thiophene based system has been selected because of (a) π-electron rich, planar, aromatic
29
3
3
3
0
1
2
33
2

Page 3 of 19
New Journal of Chemistry
1
2
3
View Article Online
1
conjugated nature, which enables the 1D π-π stacking to support the exciton migration, (b) H-
DOI: 10.1039/C9NJ02342A
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
2
3
bonding, π-π stacking and van der Waal forces based supramolecular interactions which
2
4
helps the chemosensor to form the stronger self-assembly, and (c) thiophene accelerates
electron transfer to NACs due to its higher electric potential.25-27 Although PTC possesses
considerable FL emission, however, a low concentration of PA solution can be sufficient to
4
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
5
2
+
6
quench it. Furthermore, selective addition of copper ion (Cu ) can enhance the FL intensity
2
+
2+
7
of PTC by ten folds because of PTC-Cu complex formation. In turn, this Cu complex can
2
+
8
also act as a fluorescent probe towards PA. The fluorescence of PTC and its Cu complex
can be easily visible in naked eyes under UV chamber. Detailed reaction spontaneity for
PTC-PA adduct was fully illustrated by temperature variable thermodynamical study, and
corresponding H, S, and G parameters have been determined.
9
10
1
1
H
O
H
O
MeOH
H SO
Reflux, 8-12 h
H2N NH2 . H2O
O
N NH2
S
2
4
S
EtOH
Reflux, 8-12 h
S
OH
O
O
H
H
N
EtOH Reflux, 3-4 h
O
N
H
OH
H
H
O N
NO2
2
N
S
O
N
O
NO2
S
N
O
O N
PA
2
O
NO2
PTC
1
2
13
Scheme 1. Synthesis of PTC and corresponding sensing representation with PA.
1
4
Several reports of Schiff base probes as PA sensor have been reported in the past few years
but mechanistic pathways are unknown for many of such cases. In this circumstances, we
have investigated the probable mechanistic pathway by correlating the experimental
overviews with that of theoretical calculations. The corresponding DFT and TDDFT
calculations has been carried out by Gaussian 09 software using B3LYP (6-31G) and
CAMB3LYP basis sets respectively.
15
1
1
1
6
7
8
19
2
2
0
1
EXPERIMENTAL SECTION
General Remarks
3

New Journal of Chemistry
Page 4 of 19
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
View Article Online
1
2
3
4
The analytical grade solvents and reagents were acquired from Aldrich, Merck, and TCI, and
DOI: 10.1039/C9NJ02342A
used without purification. Thiophene-2-carboxylic hydrazide was prepared according to the
2
8
previous report. Please check ESI† for all the characterization data of PTC, viz. Fig. S1-
S3†.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
5
6
Instrumentation
Kindly consult ESI† for detailed instrument specifications.
7
8
Synthesis of PTC [(2E/Z)-2-(9-Pyrenylmethylene)hydrazide-2-ThiopheneCarboxylic
acid)]
9
0
1
Thiophene carboxylic acid was first refluxed in methanol for 8-12 h to get the corresponding
ester. Now, hydrazine hydrate was added and refluxed further for 8-12 h. to produce the
white residue of thiophene-2-carboxylic hydrazide.
1
1
1
1
1
1
1
1
2
3
4
5
6
7
The solution of thiophene-2-carboxylic hydrazide (2 mmol = 284 mg) in MeOH (10 mL) was
added to a methanolic solution (30 mL) of pyrene-1-carboxaldehyde (2 mmol = 460 mg). The
ο
mixture was then refluxed for 8 h at 70 C followed by the filtration ad washed through
MeOH and diethylether. The solid crystalline residue was dried over vacuum and collected
for further characterization. X-ray diffraction suitable deep yellow colored single crystals
were obtained after 9 days by slow evaporation in DMF solvent at room temperature.
ο
1
1
1
2
2
2
2
8
9
0
1
2
3
Yield: 92% (orange solid), M.p. 265-268 C. H NMR (400.13 MHz, 298K, D -DMSO, δ
6
ppm, E:Z = 1.4:1) : δ (E-isomer) = 7.29 (1H, t, Py-H), 7.99 (1H, d, Th-CH), 8.14 (2H, d, Py-
H), 8.28 (2H, d, Py-H), 8.37 (4H, d, Py-H), 8.56 (1H, t, Th-CH), 8.83 (1H, d, Th-CH), 9.48
(1H, s, Py-CH=N), 12.07 (1H, s, exchangeable C=O-NH) ppm; (Z-isomer) = 7.27 (1H, t, Th-
Py-H), 7.92 (1H, d, Th-CH), 8.10 (2H, d, Py-H), 8.21 (2H, d, Py-H), 8.36 (4H, d, Py-H), 8.55
(1H, t, Th-CH), 8.73 (1H, d, Th-CH), 9.27 (1H, s, Py-CH=N), 11.96 (1H, s, exchangeable
1
3
24
C=O-NH) ppm (Fig. S1a); C NMR (100.61 MHz, 298 K, D -DMSO, δ ppm): (E/Z-isomer)
6
2
2
2
5
6
7
= δ 124, 126, 127, 128, 129, 130, 131, 132, 135, 142, 146, 158, 161 (Fig. S1b). FT-IR (KBr,
-1
cm ): 3220 and 3063 (N-H), 1635 (C=O), 1560 (C=N) (Fig. S2). Anal. Calcd (%) for
C H N OS: C, 74.55; H, 3.98; N, 7.90; O, 4.51; S, 9.05. Found: C, 74.29; H, 3.57; N, 7.94;
2
2
14
2
+
28
S, 8.93 %. HRMS in HPLC MeOH (+, m/z): (C H N OS + Na) : 377.0719 (100%) (Fig.
22 14 2
2
9
S3).
30
Preparation of stock for photo-physical studies
4

Page 5 of 19
New Journal of Chemistry
1
2
3
View Article Online
1
Please see the supporting information (Section S3†) for more details. In addition, Section S5†
DOI: 10.1039/C9NJ02342A
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
2
3
4
describes the crystallographic information about PTC probe.
RESULTS AND DISCUSSION
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Synthesis and characterization of PTC
5
6
PTC was isolated as yellow solid by Schiff base condensation and further dark yellowish
single crystals were grown in DMF medium in 9 days (see ESI† for details). Chemosensor
was well characterized by NMR (Fig. S1), FTIR (Fig. S2), HRMS (Fig. S3) and single crystal
7
1
8
X-ray crystallography (Fig. 1a). H NMR data suggest that PTC is in E/Z isomeric form and
9
the corresponding ratio is 1.4:1. Prominent IR stretching modes are observed at 3220 and
-1
-1
-1
29, 30
10
3063 cm (N-H), 1635 cm (C=O), 1560 cm (C=N).
HRMS in HPLC MeOH having
+
1
1
1
2
chemical formula (C H N OS + Na) has been observed at 377.0719. Structural elucidation
2
2
14
2
of PTC indicates a monoclinic crystal system with P 21/c space group. The corresponding
bond lengths and bond angles are summarized in Table S1-2. Several supramolecular non-
covalent interactions such as H-bonding, π-π stacking, CH-π interaction etc. contribute
together to form a dimeric (Fig. S4a) and 1D/ 2D polymeric frameworks (Fig. 1b-c and Fig.
S4b-d).
13
1
1
1
4
5
6
1
7
Photo-physical studies
18
Solubility in numerous solvents help the chemosensor PTC to avail absorption or emission
spectroscopy as a sensing tool in a broader way (Fig. S5). Various wavelength maxima of
PTC in different solvents are summarized in Table S3 along with log ε values. This
solvatochromic behavior reveals that absorption spectra at ~370 nm in organic solvents are
having larger log ε values in comparison to those in 100% aqueous medium. This may be due
1
2
2
9
0
1
22
2
2
3
4
to the easy formation of intermolecular hydrogen bonds between PTC and H O in fully
2
aqueous or buffer medium. Although, no such considerable change was observed in the
25
position of λmax/ λ . The metal ions sensing response of PTC was explored via UV-Vis and
ex
2
+
2
2
2
6
7
8
FL experiments (Fig. S6). It shows that Cu ion can be selectively sensed among all essential
metals, which can be visualized even in naked eye under UV light through paper strip
experiment (Fig. S7). Sensor shows the absorption maximum at 274, 368, and 400 nm which
are assignable as the intra-ligand π-π* and n-π* transitions. Two isosbestic points generated
at 352 and 384 nm along with a new peak at 436 nm (LMCT) upon complexation with Cu2+
(Fig. S8).
29
3
3
0
1
5

New Journal of Chemistry
Page 6 of 19
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
View Article Online
DOI: 10.1039/C9NJ02342A
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
Fig. 1. (a) Single crystal x-ray diffracted structure of sensor PTC, (b) and (c) Several
supramolecular interactions (intermolecular hydrogen bonding, CH-π, and π-π interactions) to
2
+
form self-assembled 2D framework, (d) fluorescence titration of PTC by Cu ion, and (e)
titration profile of PTC (0.8 μM in acetonitrile, slit: 2) in presence of PA (10-100 nM;
λexcitation: 368 nm, and λemission: 425 nm).
7
8
Quantum yield (Φ) calculation
The fluorescence quantum yield (Φ) was calculated as per following equation:31
AbsR AreaS S
 


 R
s
AbsS
AreaR
R
9
1
1
0
1
Where ‘Φ’ denotes the fluorescence QY, ‘Abs’ denotes optical density, ‘Area’ terms denote
the integration under the fluorescence curve, and the refractive index as ‘η’ (η = 1.3284 for
MeOH solvent medium). Subscripts ‘R’ and ‘S’ stand for the respective parameters
belonging to the experimental reference as well as the sample.
12
1
3
2
+
14
Φ of PTC (0.007) increases more than 10 folds upon addition of Cu (Φ = 0.076) with
1
1
1
5
6
7
respect to Cumarin (ɸ = 0.09 in MeOH). However, increasing concentration of PTC (10-307
R
nM) shows a good FL response (Fig. S9). Moreover, with increasing concentration of Cu2+
ion emission intensity increases with a blue shift of ~16 nm (shift from 425 to 409 nm) (Fig.
1d and Fig. S10a).
18
2+
1
9
Binding studies of PTC towards Cu and PA
6

Page 7 of 19
New Journal of Chemistry
1
2
3
4
5
Fig. S10b represents the B-H plot of PTC-Cu2+ adduct. From which association constant
View Article Online
DOI: 10.1039/C9NJ02342A
1
4
-1
2
value was found to be 1.37  10 M . Moreover, the detection limit (LOD) of PTC towards
6
2
+
-7
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
3
4
Cu has been evaluated as 3.5  10 M (Fig. S10c). Apart from that, PTC possesses superior
activity up to nanomolar range to selectively detect PA among other NACs. Although, most
of the recent literatures are focused to detect PA from various nitro explosives, but
unfortunately specific sensing of PA among other similar substituted nitro phenols (NPs) are
uncommon. Herewith, we focus to find out (a) the exclusive binding motif of PTC towards
PA and / or (b) the importance of –OH group for the detection of PA with respect to rest of
the NPs. Fig. S11 shows the optical density (O.D) values of PTC in presence of different
NACs. Notably, no such change in O.D values were observed in the λmax range of PTC except
PA, which shows considerably high molar extinction coefficient in compared to PTC. The
detailed photophysical properties of PA sensing by PTC were investigated in ACN medium
at room temperature. Firstly, the large blue shift of 24 nm (from 368 to 344 nm) was
observed in UV-Vis titration with PA. Consequently, λmax at 274 nm of PTC disappears upon
gradual addition of PTC and generates a new peak at 237 nm (Fig. S12). Furthermore, a
bathochromic shift of 37 nm was observed when PTC was titrated with PA (from 425 to 462
nm) (Fig. 1e).
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
5
6
7
8
9
10
1
1
1
1
2
3
14
1
1
1
5
6
7
(a)
(b)
(c)
(d)
INPUT (X) INPUT (Y)
OUTPUT (Z)
PTC
0
PA
0
0
1
0
0
1
0
0
1
1
1
1
1
8
9
Fig. 2. (a) Lifetime decay diagram of PTC and PTC-PA (λ at 368 nm, and λ
at 425
collection
ex
20
nm, concentration: 1.0 μM). (b) Nonlinear Stern-Volmer (K ) plot of PTC in presence of
SV
2
2
2
1
2
3
quencher, PA. (c) INHIBIT gate for Logic responses (Inset); where X and Y are inputs and Z
is the output signal(s) having respective visual identification. (d) Truth table representation
using PTC and PA as inputs, and the current signals of the logic gate at 425 nm emission.
7

New Journal of Chemistry
Page 8 of 19
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
View Article Online
1
2
3
4
5
Fluorescence response of PA was drastically changed upon introduction of various NACs and
DOI: 10.1039/C9NJ02342A
were summarized in Fig. S13a. Colorimetric histogram of PTC (Fig. S13b) can distinguish
PA among other NACs, which can be also visualized in naked eye under UV chamber.
Excited-state lifetimes of probe and sensor adduct(s) have been calculated according to the
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
following equations:31, 32
2

t 
F(t)  a exp 

i




i1

i
6
7
8
The above equation has been used for the determination of time-resolved emission decays,
where, F(t) is the FL decay at normalized condition, α is the pre-exponential factor,
i
9
and a and a denotes
the
normalized
amplitude
having
decay
1
2
10
component τ and τ respectively. The equation below gives the value of average lifetime (in
1
2
1
1
ns):
2
  aii

i1
1
1
2
3
th
where, a is the contribution of the i decay component, and a = α /Σα .
i
i
i
i
1
1
1
4
5
6
Lifetime decay dynamics of PTC and PTC-PA are shown in Fig. 2a and the corresponding
parameters are summarized in Table S4. PTC shows three exponential fitting with small
2+
contribution from faster (˂ 1 nS) nonradiative decays. Upon treatment of PTC with Cu , the
17
lifetime considerably increases to restrict the nonradiative decay, therefore enhancing
emission intensity. However, addition of PA shows a huge contribution from faster
nonradiative decay (0.074 nS).
1
1
8
9
6
-1
2
2
2
0
1
2
The host-guest PTC-PA ensemble exhibits association constant of 6.814 × 10 M (by using
B-H plot: K = intercept : slope ratio, when plotted (A /A -A) vs 1/[PA] following linear
a
0
0
equation, where A is the O.D. value in absence of PA), which further fitted with online
0
23
‘BindFit v0.5- Supramolecular’ server (Fig. S14a-b).31 As displayed in Fig. 2b, the Stern-
3
3
2
2
2
4
5
6
Volmer (S-V) quenching constant (K ) was calculated by S-V equation: I0/I = 1 +
SV
K [PA], where I and I are the fluorescence intensities of PTC before and after the addition
SV
0
of PA, and [PA] is the molar concentration of PA during fluorescence titration at 425 nm.
Two distinct regions in S-V plots (Fig. 2b and Fig. S15a) suggest: (a) static quenching in the
lower concentration of PA, and (b) H-bonding energy transfer process or self-absorbance of
27
2
2
8
9
3
PA to facilitate the dynamic quenching in the higher range of [PA]. Moreover, this higher
8

Page 9 of 19
New Journal of Chemistry
1
2
3
View Article Online
1
linear concentrations range of S-V plot provides a signature of ultrasensitive detection ability
DOI: 10.1039/C9NJ02342A
4
7
-1
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
2
3
of PTC towards PA. KSV was estimated as 2.29 × 10 M having an excellent detection limit
of 19 nM (Fig. S15b) and the high KSV value make PTC a potential candidate to act as a
sensor with respect to other reported molecular probes. Furthermore, fluorescence “off-on”
4
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2+
5
switching of PTC and PTC + Cu with PA encouraged us to explore the field of molecular
6
switches and logic gates. As described in Fig. 2c, green output signal was only observed
2
+
7
when X = 1 and Y = 0, where, X is the input for PTC or PTC + Cu and Y defined the same
3
4
8
for PA. Output, Z behaves like an INHIBIT logic gate (Fig. 2d), when both the inputs are its
“on” state (= 1). Interestingly liquid phase FL response was further employed for the naked
eye visualization of PA through paper strip method.
9
10
(a)
(b)
PTC
PTC + PA
1
1
1
1
1
1
2
3
4
Fig. 3. Binding affinity studies through: (a) sequential H NMR titration of PTC and PA
(400.13 MHz, D -DMSO, 0.5 mL, δ in ppm) at room temperature, (b) ESI-MS spectra in
6
CH CN solvent representing the formation of intermediate ‘PTC-PA’; Inset: same for the
3
15
chemosensor PTC in absence of PA.
1
6
1H NMR titration and ESI-MS were employed to have an insight into the binding affinity of
2
+
17
PTC with Cu or PA. As shown in Fig. S16, the slight peak shifting as well as decrement in
9

New Journal of Chemistry
Page 10 of 19
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
View Article Online
1
2
peak intensities in the aromatic zone (δ ~ 8.4 ppm) indicates the favoured metalation course.
DOI: 10.1039/C9NJ02342A
Furthermore, a consecutive peak broadening occurs upon increase in the equivalent ratio of
2
+
3
Cu ion in the aliphatic zone (δ ~ 3.3 ppm), which might be responsible for the interaction
4
with water. Apart from that, the interaction between PTC and PA are depicted in Fig. 3a and
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
5
Fig. S17. All the H NMR titration were conducted at room temperature in DMSO-d
6
6
medium. The proton signal at δ ~ 12.07 ppm surprisingly vanishes upon gradual increase in
the concentration of PA. This might be attributed to the formation of hydrogen bonds
between -NH proton of PTC and PA. A slight up field shift belongs to pyrene ring protons at
δ ~ 7.29 ppm was observed under similar condition. A new singlet peak at δ ~ 8.78 ppm
appears during the course of titration, which is associated with the aromatic protons of PA.
7
8
9
10
1
1
1
2
So,
we may conclude that the formation of strong intermolecular H-bonds between sensor
and PA initiates the effective fluorescence quenching process. Furthermore, ESI mass
spectral analysis shows the peaks at 417.0 and 492.8 (Fig. S18 and Fig. 3b) for 1:1 binding of
13
2
+
1
1
1
4
5
6
PTC with Cu and PA, which is also corroborated with the theoretical calculations. In
addition, the 1:1 stoichiometric coefficient was confirmed by Jobs plot measurement having
mole fraction 0.5 with respect to the sensor (Fig. 4a) for detection of PA. An abrupt FL
quenching of chemosensor PTC has been observed within a few seconds upon interference of
PA as shown in Fig. 4b. There was no further change in fluorescence intensity has been
observed upon standing.
17
1
1
8
9
(a)
(b)
20
21
Fig. 4. (a) Jobs plot to better understand the stoichiometric coefficient during binding
experiment between PTC and PA. (b) Time dependent FL intensity during the course of PTC
titration with PA in acetonitrile solution.
2
2
2
3
24
Thermodynamical aspects
1
0

Page 11 of 19
New Journal of Chemistry
1
2
3
1
4
View Article Online
DOI: 10.1039/C9NJ02342A
Thermodynamic parameters such as H, S, and G have been evaluated using van’t Hoff
5
6
2
equation: [lnK = (S/ R) - (H/ RT)], and Gibbs free energy equation: G = H - TS,
b
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
3
4
5
6
7
8
9
0
1
where K , R, H, S, and G defines binding constant, real gas constant, enthalpy change,
b
entropy change, and standard Gibbs free energy change (Fig. 5). It gives an overview about
extent of PTC-PA adduct formation in equilibrium and the corresponding thermodynamic
parameters have been summarized in Table S5. As depicted in Fig. 6A, the high negative
value of G (–120.3 to –123.0 kJ/ mol) suggests the favoured the adduct formation. A
negative H value of -81.77 kJ/ mol has been found for the similar reaction profile,
confirming that the adduct formation is exothermic in nature. Fig. 6B depicts the decreasing
trend of the intensity of dark spots by decreasing the concentration of PA (10 to 0.0001 μM)
in a fixed concentration of PTC immersed test paper. The spot detection technique for PA can
be also utilized for the solid phase detection (Fig. S19).
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
1
12
1
3
14
Fig. 5. (a-c) Temperature dependent fluorescence quenching of PTC in presence of picric
acid (solvent: acetone, temperature range: 288-308 K, [PTC] = 0.5 μM, [PA] = 10-70 nM).
(d) Scatchard plots of the PTC–PA ensemble. (e) Steady-state Stern–Volmer plots of PTC at
three different temperatures (288 K, 298 K, and 308 K) as a function of PA concentrations.
1
1
5
6
17
1
1

New Journal of Chemistry
Page 12 of 19
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
View Article Online
DOI: 10.1039/C9NJ02342A
(
A)
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(B)
1
2
3
4
5
Fig. 6. (A) van’t Hoff plot for PTC-PA adduct (solvent: acetone, temperature range: 288-308
K). (B) PTC immersed ‘paper strip experiment’ on the basis of different concentration ratio
of PTC : PA; where [PA in μM] are (a) 10 μM, (b) 1.0 μM, (c) 0.1 μM, (d) 0.01 μM, (e)
0.008 μM, (f) 0.004 μM, (g) 0.001 μM, (h) 0.0005 μM, (i) 0.0001 μM, (j) 0 μM.
6
7
Theoretical calculations
Despite of several experimental evidences, it is worthy to investigate it further by theoretical
approach. For better understanding, the correlation between the experimental and theoretical
agreement of sensing mechanism as well as optical responses has been established by density
functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations.
8
9
10
1
1
1
2
Probable sensing mechanism
-
The introduction of donor-acceptor e transfer theory can explain the FL quenching
13
phenomenon. The electron densities of HOMO (-5.33 eV) of PTC are delocalized only on
-
1
1
4
5
pyrene moiety (donor part), not on the thiophene ring (acceptor part), however e density
spread over both the pyrene and thiophene in case of LUMO (-2.12 eV). The band gap (ΔE =
LUMO-HOMO) is 3.20 eV for the sensor PTC (Fig. 7a). The deprotonation process of picric
acid is favored when added to PTC in polar medium. This statement was previously
16
1
7
1
2

Page 13 of 19
New Journal of Chemistry
1
2
3
1
View Article Online
1
supported by H NMR titration also. In fact, HOMO (-3.26 eV) of picrate situated above the
DOI: 10.1039/C9NJ02342A
4
-
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
2
3
4
5
6
7
8
LUMO of PTC-PA adduct (-3.73 eV) to favor the e migration process as shown in Fig. S20.
However, HOMO energy level of the chemosensor resides below to the LUMO of PA
(HOMO-LUMO gap is higher in PA in comparison to PTC; ΔE = 4.65 eV) causing the lower
probability of GS charge transfer from chemosensor to PA. This phenomenon may be
attributed to the static fluorescence quenching of fluorophore.35 Similar kind of DFT
mediated sensing mechanism has been also reported for anthracene and some other π-
conjugated systems.2, 3, 19
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
-
9
0
1
Apart from that, in case of PTC-PA adduct, the HOMO (-6.35 eV) e density is located on the
-
1
1
most e deficient picrate and that of LUMO (-3.73 eV) is occupied by sensor. Despite being
stabilized in terms of HOMO as well as LUMO, PTC-PA adduct possesses lower band gap
(ΔE = 2.62 eV) in compared to PTC. Therefore, the charge transfer process form HOMO to
LUMO is preferred during the adduct formation between sensor and PA. As a result,
considerable FL quenching was observed due to the decrement in ΔE value. The optical
energy gaps (ΔE) of sensor and the corresponding adduct are calculated as per previous
report, and are summarized in Table S6.
12
1
1
1
3
4
5
16
1
1
7
8
Fig. 7. (a) Pictorial representation of HOMO-LUMO molecular orbitals of chemosensor PTC
and that of PTC-PA adduct, (b) and (c) compares the UV-Vis band gaps (ΔE) with those of
theoretically calculated values.
19
2
0
2
1
As depicted in Fig. 7, the optical band gaps for the sensor and PTC-PA are 3.04 and 2.77 eV,
respectively, which are in good agreement with those of theoretical values.
22
1
3

New Journal of Chemistry
Page 14 of 19
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
View Article Online
1
2
TDDFT calculations were performed to explain the UV-Vis and FTIR spectra. Fig. 8a-b
DOI: 10.1039/C9NJ02342A
shows a good correlation between the experimental and calculated absorbance and infrared
spectra. Upon photon excitation, the donor to acceptor intramolecular charge transfer (ICT) is
taking place to the extremely π-conjugated system of PTC. The ICT process prohibited when
3
4
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2+
5
PTC is being coordinate to the Cu ion, resulting in a sharp decrease in O.D. value at 368
6
nm. Spectral overlap theory can help to deeply understand the charge transfer process.
Notably, the region covered by the absorption and emission spectral overlap of Cu-complex
is very large with respect to PTC, leading to a preferable ICT process (Fig. 8c). In addition,
as represented in Fig. 8d, the spectral overlap with the emission spectrum of sensor PTC is
exceptionally low for PA in compared to picrate. Therefore, considerable spectral overlap can
favor the energy transfer process from sensor to picrate, which could be another pathway for
7
8
9
10
1
1
1
2
21
the FL quenching of PTC in solution phase. In contrast, solid phase fluorescence quenching
13
14
efficiency is quite small and less sensitive as PA to picrate conversion (deprotonation ability)
in solid state during contact with sensor is very less.
(a)
(b)
υC=O
560 & C=N
1
1635
υN-H
220
3
3063
(C)
(d)
1
5
16
Fig. 8. (a) The experimental (black), and theoretical (red) normalized UV-visible spectra. (b)
The calculated (pink) and experimental (green) stretching frequencies in FTIR spectrum. (c)
Spectral overlap between absorption and emission spectra of PTC and its Cu-complex. (d)
Spectral overlap between UV-visible spectra of PA and picrate with the emission spectra of
sensor PTC.
1
1
1
7
8
9
20
1
4

Page 15 of 19
New Journal of Chemistry
1
2
3
View Article Online
DOI: 10.1039/C9NJ02342A
1
Cell imaging study
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
2
3
4
5
6
Apart from the explosive sensing, fluorescence properties of the chemosensor PTC as well as
2
+
PTC + Cu adduct were used for confocal imaging. A549 cell lines were incubated with
2
+
Cu followed by treatment of PTC (10 μg/mL) for 1h at 37 °C. As depicted in Fig. 9, the
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2+
control experiment with only Cu ion never shows any imaging capabilities, whereas, that of
2
+
PTC and PTC + Cu complex can clearly discriminate the binding motif inside the cells.
7
2
+
8
9
Fig. 9. Fluorescence images of A549 cancer cells with DAPI control (100 ng/mL), Cu ,
2+
PTC, and corresponding PTC + Cu complex (10 μg/mL). Blue laser filter of wavelength
10
405 nm has been used during confocal microscopy.
1
1
1
2
DAPI has been used as a positive control in the similar emission range. Result shows that the
2+
intensity of fluorescence imaging enhances for PTC + Cu complex with respect to blank
1
5

New Journal of Chemistry
Page 16 of 19
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
2+
View Article Online
1
2
PTC. Hence, PTC and PTC + Cu complex possesses cell permeable nature, and can be used
DOI: 10.1039/C9NJ02342A
for the living cell imaging.
3
4
5
6
7
8
9
0
1
CONCLUSION
In conclusion, we have demonstrated a new pyrene based fluorescent chemosensor to detect
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2
+
Cu and picric acid in CH CN and many other polar solvents. The probe has been found to
3
be a potential candidate to act as copper(II) ion and nitro-explosive (PA) detector even by
naked eyes. It is also suitable for environmental monitoring of those species and the efficacy
of the probe has been found to be comparable to other existing NAC sensors (Table S7).
Theoretical calculations strongly support the experimental results which includes
spectroscopic reliability and, mechanistic pathways of explosive sensing. Additionally, PTC
1
1
2+
can also be useful to detect Cu inside the living cells. Apart from that, the thermodynamical
12
aspect, which is a key to understand about the reaction spontaneity of PTC-PA adduct, has
been explored. More importantly, this is the first report of detailed temperature dependent
thermodynamic investigation for picric acid sensing, which we have established in this
literature.
1
1
1
3
4
5
1
6
ASSOCIATED CONTENT
17
Supporting Information.
1
8
This material is available free of charge via the Internet at http://pubs.acs.org. Synthetic
1
19
procedures, instrumentation, and analytical characterization data. Fig. S1-S20† including H,
2
2
2
0
1
2
13C NMR, FTIR, UV-Vis, Fluorescence, Hand-held camera pictures for colorimetric
detection, X-ray crystallography, DFT calculated energy gaps, sensing applications. Table
S1-S7†. CCDC 1861748 is for PTC.
2
3
AUTHOR INFORMATION
Corresponding Author
*E-mail: suman@iiti.ac.in.
Author Contributions
24
2
2
2
5
6
7
The manuscript was written through contributions of all authors. All authors have given
approval to the final version of the manuscript.
28
2
9
Funding Sources
1
6

Page 17 of 19
New Journal of Chemistry
1
2
3
View Article Online
1
This work is supported by DST India under Indo-Portuguese joint collaborative project
DOI: 10.1039/C9NJ02342A
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
2
scheme (Grant Number INT/PORTUGAL/P-04/2013).
3
4
Notes
The authors declare no competing financial interests.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
5
ACKNOWLEDGMENT
6
7
8
Thankful to IIT Indore for the doctoral fellowships. The analytical supports received from
SIC, IIT Indore, are gratefully acknowledged. Support by SERB, DST India
(INT/PORTUGAL/P-04/2013) is gratefully acknowledged.
9
0
ABBREVIATIONS
1
NMR, nuclear magnetic resonance; ESI-MS, electrospray ionization mass spectrometry;
PL/FL, photo-luminescence/ fluorescence; PET, photo-induced electron transfers; DFT,
density functional theory.
11
1
2
13
REFERENCES
1
1
1
4
5
6
1.
N. Ular, A. Üzer, S. Durmazel, E. Erçağ and R. Apak, ACS Sensors, 2018, 3, 2335-
2342.
2.
3.
Z.-H. Fu, Y.-W. Wang and Y. Peng, Chem. Commun., 2017, 53, 10524-10527.
K. Maiti, A. K. Mahapatra, A. Gangopadhyay, R. Maji, S. Mondal, S. S. Ali, S. Das,
R. Sarkar, P. Datta and D. Mandal, ACS Omega, 2017, 2, 1583-1593.
S. Shanmugaraju and P. S. Mukherjee, Chem. Commun., 2015, 51, 16014-16032.
M. Rong, L. Lin, X. Song, T. Zhao, Y. Zhong, J. Yan, Y. Wang and X. Chen, Anal.
Chem., 2015, 87, 1288-1296.
17
18
1
2
2
2
2
9
0
1
2
3
4.
5.
6.
7.
8.
X. Sun, J. He, Y. Meng, L. Zhang, S. Zhang, X. Ma, S. Dey, J. Zhao and Y. Lei, J.
Mater. Chem. A, 2016, 4, 4161-4171.
T.-P. Huynh, A. Wojnarowicz, A. Kelm, P. Woznicki, P. Borowicz, A. Majka, F.
D’Souza and W. Kutner, ACS Sensors, 2016, 1, 636-639.
S. Mukherjee, A. V. Desai, A. I. Inamdar, B. Manna and S. K. Ghosh, Cryst. Growth
Des., 2015, 15, 3493-3497.
24
25
2
2
2
2
3
6
7
8
9
0
9.
10.
S. Huang, Q. He, S. Xu and L. Wang, Anal. Chem., 2015, 87, 5451-5456.
B. Naskar, A. Bauzá, A. Frontera, D. K. Maiti, C. Das Mukhopadhyay and S.
Goswami, Dalton Trans., 2018, 47, 15907-15916.
31
11.
12.
13.
S. Senapati and K. K. Nanda, ACS Sustain. Chem. Eng., 2018, 6, 13719-13729.
K. Ponnuvel, G. Banuppriya and V. Padmini, Sens. Actuators, B, 2016, 234, 34-45.
S. Kumari, S. Joshi, T. C. Cordova-Sintjago, D. D. Pant and R. Sakhuja, Sens.
Actuators, B, 2016, 229, 599-608.
3
3
3
3
3
2
3
4
5
6
14.
15.
T. Luo, Y. Li, Y. Xu, S. Zhang, Y. Wang, X. Kou and D. Xiao, Sens. Actuators, B,
2017, 253, 231-238.
A. F. Khasanov, D. S. Kopchuk, I. S. Kovalev, O. S. Taniya, K. Giri, P. A. Slepukhin,
S. Santra, M. Rahman, A. Majee, V. N. Charushin and O. N. Chupakhin, New J.
Chem., 2017, 41, 2309-2320.
37
38
3
4
9
0
16.
H. Lu, S. Quan and S. Xu, J. Agric. Food. Chem., 2017, 65, 9807-9814.
1
7

New Journal of Chemistry
Page 18 of 19
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
View Article Online
DOI: 10.1039/C9NJ02342A
1
2
3
4
5
6
7
8
9
0
1
17.
X. Qi, Y. Jin, N. Li, Z. Wang, K. Wang and Q. Zhang, Chem. Commun., 2017, 53,
10318-10321.
18.
19.
S. Xu and H. Lu, Chem. Commun., 2015, 51, 3200-3203.
A. H. Malik, S. Hussain, A. Kalita and P. K. Iyer, ACS Appl. Mater. Interfaces, 2015,
7, 26968-26976.
20.
A. S. Tanwar, S. Hussain, A. H. Malik, M. A. Afroz and P. K. Iyer, ACS Sensors,
2016, 1, 1070-1077.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
21.
22.
A. Chowdhury and P. S. Mukherjee, J. Org. Chem., 2015, 80, 4064-4075.
A. S. Tanwar, L. R. Adil, M. A. Afroz and P. K. Iyer, ACS Sensors, 2018, 3, 1451-
1461.
P. Taya, B. Maiti, V. Kumar, P. De and S. Satapathi, Sens. Actuators, B, 2018, 255,
2628-2634.
A. K. Bar, S. Shanmugaraju, K.-W. Chi and P. S. Mukherjee, Dalton Trans., 2011,
40, 2257-2267.
A. Senthamizhan, A. Celebioglu, S. Bayir, M. Gorur, E. Doganci, F. Yilmaz and T.
Uyar, ACS Appl. Mater. Interfaces, 2015, 7, 21038-21046.
X. Wang, J. Bian, L. Xu, H. Wang and S. Feng, Phys. Chem. Chem. Phys., 2015, 17,
32472-32478.
Y. Upadhyay, T. Anand, L. T. Babu, P. Paira, G. Crisponi, A. K. Sk, R. Kumar and S.
K. Sahoo, Dalton Trans., 2018, 47, 742-749.
J. Laborde, C. Deraeve, L. Lecoq, A. Sournia-Saquet, J.-L. Stigliani, B. S. Orena, G.
Mori, G. Pratviel and V. Bernardes-Génisson, ChemistrySelect, 2016, 1, 172-179.
B. K. Kundu, R. Singh, R. Tiwari, D. Nayak and S. Mukhopadhyay, New J. Chem.,
2019, 43, 4867-4877.
B. K. Kundu, V. Chhabra, N. Malviya, R. Ganguly, G. S. Mishra and S.
Mukhopadhyay, Micropor. Mesopor. Mat., 2018, 271, 100-117.
B. K. Kundu, P. Mandal, B. G. Mukhopadhyay, R. Tiwari, D. Nayak, R. Ganguly and
S. Mukhopadhyay, Sens. Actuators, B, 2019, 282, 347-358.
M. S. Mathew and K. Joseph, ACS Sustain. Chem. Eng., 2017, 5, 4837-4845.
J. Keizer, J. Am. Chem. Soc., 1983, 105, 1494-1498.
1
1
23.
24.
25.
26.
27.
28.
29.
30.
31.
12
1
1
1
1
1
3
4
5
6
7
18
19
2
2
2
2
2
0
1
2
3
4
25
26
2
2
2
3
3
7
8
9
0
1
32.
33.
34.
A. Saghatelian, N. H. Völcker, K. M. Guckian, V. S. Y. Lin and M. R. Ghadiri, J. Am.
Chem. Soc., 2003, 125, 346-347.
32
3
3
35.
K. Acharyya and P. S. Mukherjee, Chem. Commun., 2014, 50, 15788-15791.
3
4
1
8

Page 19 of 19
New Journal of Chemistry
1
2
3
4
5
6
7
8
9
View Article Online
: 10.1039/C9NJ02342A
Mechanistic and thermodynamical aspects of pyrene b
D
a
OI
s
e
d
fluorescent probe to detect picric acid
a
a
a
a
a,b
Bidyut Kumar Kundu, Pragti, Reena, Shaikh M. Mobin and Suman Mukhopadhyay*
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
aDiscipline of Chemistry, School of Basic Sciences, Indian Institute of Technology Indore,
Khandwa Road, Simrol, Indore 453552, India. Tel: +91 731 2438 735 Fax: +91 731 2361
4
82
bDiscipline of Biosciences and Biomedical Engineering, School of Engineering, Indian
Institute of Technology Indore, Khandwa Road, Simrol, Indore 453552, India.
*
Contact E-mail: suman@iiti.ac.in; Fax: +91 731 2361; Tel: +91 731 2438 735
Graphical Abstract
Thermodynamical investigation of picric acid sensing by a pyrene based fluorescent probe.