DPP based dual-sensing probe for the multi-color detection of toxic Co2+/Sn2+ and CN? ions in water: An electronic eye development

Article abstract of DOI:10.1016/j.dyepig.2021.109425

A dual-sensing mechanism probe for the multi-color detection of toxic Co²⁺/Sn²⁺ and CN^? ions in water based on a diketopyrrolopyrrole (DPP) moiety was designed and successfully synthesized. Colorimetric and fluorimetric methods were used to confirm the sensing performance of the probe. Different colors were achieved for the detecting ions Co²⁺, Sn²⁺, and CN^?. pink for Co²⁺, red for Sn²⁺, and colorless for CN^?, denoting high selectivity in the developed probe. A dual-sensing mechanism confirmed for the metal ion the sensing is via complexation resulting in color (different) change through metal to ligand charge-transfer transition (MLCT), and for anion (cyanide), it is through addition reaction with a disconnection in intramolecular charge-transfer transition (ICT). Pre-added selected ions to the different water samples effectively detect different colors. We developed an electronic eye (RGB - Arduino device) for the detection of toxic ions effectively.

Full text of DOI:10.1016/j.dyepig.2021.109425

Dyes and Pigments 192 (2021) 109425
Contents lists available at ScienceDirect
Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
DPP based dual-sensing probe for the multi-color detection of toxic Co2+/
Sn2+ and CNꢀ ions in water: An electronic eye development
Ramalingam Manivannan1, Jiwon Ryu1, Young-A Son*
Department of Advanced Organic Materials Engineering, Chungnam National University, 220 Gung-dong, Yuseong-gu, Daejeon, 305-764, South Korea
A R T I C L E I N F O
A B S T R A C T
A dual-sensing mechanism probe for the multi-color detection of toxic Co2+/Sn2+ and CNꢀ ions in water based on
a diketopyrrolopyrrole (DPP) moiety was designed and successfully synthesized. Colorimetric and fluorimetric
methods were used to confirm the sensing performance of the probe. Different colors were achieved for the
detecting ions Co2+, Sn2+, and CNꢀ . pink for Co2+, red for Sn2+, and colorless for CNꢀ , denoting high selectivity
in the developed probe. A dual-sensing mechanism confirmed for the metal ion the sensing is via complexation
resulting in color (different) change through metal to ligand charge-transfer transition (MLCT), and for anion
(cyanide), it is through addition reaction with a disconnection in intramolecular charge-transfer transition (ICT).
Pre-added selected ions to the different water samples effectively detect different colors. We developed an
electronic eye (RGB - Arduino device) for the detection of toxic ions effectively.
Keywords:
Electronic eye
DPP
Dual mechanism
Multi-color
Toxic ions
1. Introduction
accumulates in kidney and liver and can cause serious problem to
human health. The World Health Organization’s tolerable bounds for
Toxic ions, either anion or cations, have enormous effects in the bi-
otic environment. The presence of ions and their detection in water is of
primary importance from an industrial point of view and the environ-
mental and biological system and the detection to be fast, reliable, and
the presence of tin ion in tinned food is 0.25 g/kg [19].
Of the many anions, cyanide is the most toxic and is of specific
concern due to the daring poisonousness for the public and environment
[20,21]. The preoccupation of cyanide ions through the skin, gastroin-
testinal tract, and lungs injures human health by vomiting, loss of con-
sciousness, convulsion, and finally, death [22–24]. Nevertheless, the
mandatory usage of cyanide in various fields like electroplating, gold
mining, tanning, metallurgy, plastics manufacturing, and synthetic fi-
bers makes the essential for the quantification and recognition of cya-
nide [25–30]. The WHO permits an extreme allowable limit of cyanide
cost less [1–10]. The presence of metal ions (Al3+, Co2+, Cr2+, Cu2+
,
Sn2+, Hg2+, Fe2+, Fe3+, Mg2+, K+, Na+, Ni2+, etc.) in excess or defi-
ciency can lead to numerous physical complaints to the individual upon
exposure. Simple anions like acetate, bromide, chloride, cyanide, fluo-
ride, iodide, nitrate, and phosphate were well thought out as acute an-
ions due to their significance in drinking water and resulting in disease
onset when present in grater concentrations [11–13]. Co2+ is a necessary
element for life in trace amount and present in vitamin B12 [14,15].
However, cobalt ingestion causes severe health issues like skin, respi-
ratory problems, and even cancer, as per reports by the international
agency for research on cancer, cobalt poisoning [16]. Thus the detection
of even trace amounts of cobalt ion in water also significant. The
insufficiency of Co2+ ions in human beings leads to hypothyroidism,
anemia, and the chance to develop abnormalities in infants [17,18].
Amongst several cations, the detection of the Sn2+ ions is also equally
crucial as certain organotin compounds are toxic like cyanide, when
excess tin ion handled for a longer duration, which can quickly,
in drinking water is of 1.9 μM [31]. Therefore, metal ions toxic to bio-
logical system detection using a chemical probe is of great importance.
In past years, various approaches available in the literature for ion
detection like electrochemical detection methods, nanomaterials to
detect via fluorescence changes, high-performance liquid chromatog-
raphy, atomic absorption spectral technique, etc. Even though the result
obtained are reliable and reproducible the techniques have some dis-
advantages as if detection procedure is time-consuming and expensive
[32–37]. As a result, there exists a demand for the chemical sensor,
which can have the ability to sense the ions with high selectivity. The
colorimetric probe solves problems like expensive and time-consuming
* Corresponding author.
E-mail address: yason@cnu.ac.kr (Y.-A. Son).
1
These authors contributed equally to this work.
https://doi.org/10.1016/j.dyepig.2021.109425
Received 14 March 2021; Received in revised form 25 April 2021; Accepted 26 April 2021
Available online 4 May 2021
0143-7208/© 2021 Elsevier Ltd. All rights reserved.

R. Manivannan et al.
Dyes and Pigments 192 (2021) 109425
Scheme 1. Synthesis of the probe, DPPTPy.
Fig. 1. Visual response of DPPTPY [2 × 10ꢀ 5 M] in day and fluorescent lamp in the presence of various cations (A, B) [2 × 10ꢀ 5 M] and anions (C, D) [2 × 10ꢀ 5 M]
in 1:1 v/v DMF/H2O.
2

R. Manivannan et al.
Dyes and Pigments 192 (2021) 109425
Fig. 2. UV–Visible response of DPPTPY [2 × 10ꢀ 5 M] in the existence of different cations [2 × 10ꢀ 5 M] (A) and anions [2 × 10ꢀ 5 M] (B) in 1:1 v/v DMF/H2O.
and is used effectively for naked-eye detection of various ions present in
the water medium [38–41].
metal ion (Co2+, Sn2+) detection in water terpyridine (TPy) core
attached in the moiety, the two metal ions were detected with different
color changes.
Using these thoughts, herein we develop a diketopyrrolopyrrole
(DPP) and terpyridine (TPy) based probe DPPTPy for the recognition of
CNꢀ ions and metal cations (Co2+, Sn2+). The foremost objective was to
synthesize a probe with intramolecular charge transfer (ICT) for CNꢀ
ions in an aqueous media. The probe displays both fluorescent and ab-
sorption change with CNꢀ ion. As predicted, the probe, once treated by
CNꢀ ion, would be exploited as a discerning fluorimetric and colori-
metric probe for CNꢀ ions in aqueous media, diketopyrrolopyrrole
(DPP) core in moiety acts to serve the need of sensing cyanide ion. For
2. Experimental division
2.1. Materials and instruments
Compounds aimed at preparing DPPTPy: intermediate chemical,
solvents, and cations (chloride salts), anion (tetra butyl ammonium
salts) used for complete study acquired in sigma aldrich, tokyo chemical
3

R. Manivannan et al.
Dyes and Pigments 192 (2021) 109425
industries, used without any further refinement. Distilled water is used
for complete experiments. Proton and carbon-NMR of DPPTPy and its
intermediates measured and confirmed on a Bruker 600 instrument.
Mass analysis is done in JMS 700 JEOL spectrometer. Fluorescence and
UV–Visible data were obtained in a Varian Cary Eclipse spectropho-
tometer and Agilent 8453 device, respectively. Slit widths for excita-
tion/emission kept a constant of 3 nm throughout the experiment. The
complete study for detecting anions and cations in this work is done in
neutral pH conditions.
2.2. Synthesis and characterization of 3,6-Bis(4-bromophenyl)pyrrolo
[3,4-c]pyrrole-1,4(2H,5H)-dione (1)
4-bromobenzonitrile (5 g, 27.5 mmol) in 2-methyl-2-butanol (20 mL)
was added potassium t-butoxide (3.54 g, 31.5 mmol), the reaction
mixture stirred for 30 min at 120 ◦C. To the reaction mixture, added in
drops for 1 h a solution of diisopropyl succinate (2.22 g, 11 mmol) in 2-
methyl-2-butanol (10 mL) and stirred for another 2 h at 120 ◦C. Then the
reaction mixture cooled and added methanol (200 mL) and HCl (10 mL)
solution mixture to the reaction, and the precipitate was filtered and
washed with cold methanol (2 × 100 mL) and water (2 × 100 mL) to
obtain pure compound as red solid (Yield 4.0 g, 81.7%). The obtained
solid is insoluble; therefore, next step proceeded without
characterization.
2.3. Synthesis and characterization of 3,6-Bis(4-bromophenyl)-2,5-
diheptylpyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (2)
3,6-bis(4-bromophenyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (1
g, 2.25 mmol), potassium t-butoxide (0.5 g, 4.5 mmol) in DMF (25 mL)
were mixed. Maintained 1 h room temperature stirring under a nitrogen
atmosphere and then heated to 60 ◦C. 1-bromoheptane (excess about 10
equivalent) in DMF (10 mL) added in drops to the reaction mixture.
Stirring continued for another 24 h, and then the reaction mixture
cooled and added ethyl acetate to it and washed with water thrice (100
mL). The crude material was column purified using ethyl acetate and
hexane as eluent to obtain a bright orange solid powder (yield 0.38 g,
26.4%). Melting point: 134–136 ◦C; FT-IR (KBr) (νmax/cmꢀ 1): 2922,
2849, 1661, 1609, 1483, 1355, 1089, 1003, 843, 735, 672 (Fig. S1). 1H
NMR (600 MHz CDCl3): 0.75 (t, 3H, J = 6.6 Hz), 1.13 (m, 16H), 1.47 (s,
4H), 3.63 (t, 4H, 7.2 Hz), 7.57 (d, 8H, 7.2 Hz) (Fig. S2). 13C NMR (150
MHz CDCl3): δ 12.9, 21.4, 25.6, 27.6, 28.3, 30.5, 40.8, 108.9, 124.7,
125.9, 129.0, 131.2, 146.4, 161.3 (Fig. S3). HRMS (m/z) calcd. for
(Bromine isotope 81Br) C32H39BrN2O2 [M+H]+: 643.1358, found
643.1361 (Fig. S4).
2.4. Synthesis and characterization of 4’-(4-Bromophenyl)-2,2’:6′,2′′-
terpyridine (3)
4-bromobenzaldehyde (3 g, 16.2 mmol) in ethyl alcohol (60 mL)
solution was added 2-acetylpyridine (3.9 g, 32.4 mmol). To the stirred
reaction mixture, sodium hydroxide (1.3 g, 32.4 mmol) was added, and
the reaction mixture stirred at room temperature under a nitrogen at-
mosphere for 24 h and then added aqueous ammonia solution (28%, 60
mL) and refluxed for 24 h. After completing the reaction, cooled the
reaction mixture and washed with cold ethanol (3 × 50 mL) to obtain
pure product as a white solid (Yield 4.25 g, 67.5%). Melting point:
132–134 ◦C; FT-IR (KBr) (νmax/cmꢀ 1): 3249, 1581, 1471, 1377, 1073,
Fig. 3. UV–Visible spectra of DPPTPY [2 × 10ꢀ 5 M] in the presence of (A) Sn2+
[0-2x10ꢀ 5 M], (B) Co2+, and (C) CNꢀ [0-2x10ꢀ 5 M] in 1:1 v/v DMF/H2O.
1
823, 785, 734 (Fig. S5). H NMR (600 MHz DMSO‑d6): 7.52 (m, 2H),
7.77 (d, 2H, J = 8.4 Hz), 7.89 (d, 2H, J = 8.4 Hz), 8.02 (m, 2H), 8.66 (d,
2H, J = 7.8 Hz), 8.69 (s, 2H), 8.76 (d, 2H, J = 4.2 Hz) (Fig. S6). 13C NMR
(150 MHz DMSO‑d6): δ 118.2, 121.4, 123.5, 125.0, 129.5, 132.7, 137.1,
137.9, 148.7, 149.8, 155.2, 156.2 (Fig. S7). HRMS (m/z) calcd. for
(Bromine isotope 79Br) C21H15BrN3 [M+H]+: 388.0449, found
388.0451 (Fig. S8).
2.5. Synthesis and characterization of 4’-(4-(4,4,5,5-tetramethyl-1,3,2-
dioxaborolan-2-yl)phenyl)-2,2’:6′,2′′-terpyridine (4)
4’-(4-bromophenyl)-2,2’:6′,2′′-terpyridine (2.0 g, 5.15 mmol), bis
(pinacolato)diboron (1.376 g, 5.419 mmol) in DMSO (20 mL) was added
4

R. Manivannan et al.
Dyes and Pigments 192 (2021) 109425
Fig. 4. Fluorescence spectra of DPPTPY [2 × 10ꢀ 5 M] in the existence of different cations [2 × 10ꢀ 5 M] (A) and anions [2 × 10ꢀ 5 M] (B) in 1:1 v/v DMF/H2O.
potassium acetate (1.516 g, 15.44 mmol). Then the reaction mixture
degassed for 10 min under a nitrogen atmosphere and added Pd(dppf)
Cl2 (0.128 g, 0.18 mmol), then stirring continued at 80 ◦C for 8 h,
toluene added to the reaction mixture and extracted with water. The
process repeated twice, separated the organic layer, dried in sodium
sulfate, and evaporated to obtain pure compound as white solid (yield
0.94 g, 42%). Melting point: 198–200 ◦C; FT-IR (KBr) (νmax/cmꢀ 1):
3379, 1566, 1462, 1385, 1069, 790, 737 (Fig. S9). 1H NMR (600 MHz
CDCl3): 1.31 (s, 12H), 7.27 (m, 2H), 7.79 (m, 2H), 7.84 (m, 4H), 8.59 (d,
2H, J = 7.8 Hz), 8.66 (m, 4H) (Fig. S10). 13C NMR (150 MHz CDCl3): δ
23.8, 82.9, 117.9, 120.3, 122.8, 125.5, 134.3, 135.8, 139.9, 148.1,
149.1, 154.9, 155.2 (Fig. S11). HRMS (m/z) calcd. for C27H27BN3O2
[M+H]+: 436.2196, found 436.2160 (Fig. S12).
5

R. Manivannan et al.
Dyes and Pigments 192 (2021) 109425
2.6. Synthesis and characterization of 3,6-Bis(4’-([2,2’:6′,2′′-
terpyridin]-4′-yl)-[1,1′-biphenyl]-4-yl)-2,5-diheptylpyrrolo[3,4-c]pyrrole-
1,4(2H,5H)-dione (DPPTPy)
4’-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-
2,2’:6′,2′′-terpyridine (0.4 g, 0.92 mmol), 3,6-bis(4-bromophenyl)-2,5-
diheptylpyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (0.16 g, 0.25 mmol), in
toluene (20 mL) was added potassium carbonate (0.28 g, 2.68 mmol).
Then the reaction mixture degassed for 10 min under nitrogen atmo-
sphere. Added Pd(dppf)Cl2 (0.037 g, 0.05 mmol), then stirring
continued at 110 ◦C for 12 h. Then the reaction mixture cooled to room
temperature, added water (50 mL) to the reaction mixture extracted
with dichloromethane (3 × 100 mL) and dried over sodium sulfate and
recrystallized the crude material with methanol to obtain pure com-
pound as brown solid (yield 0.23 g, 81%) and the overall yield obtained
is 4.95%. Melting point: 296–298 C; FT-IR (KBr) (νmax/cmꢀ 1): 2920,
◦
1661, 1575, 1381, 1084, 791, 739, 624 (Fig. S13). 1H NMR (600 MHz
CDCl3) 0.76 (t, 6H, J = 7.2 Hz), 1.18 (m, 16H), 1.55 (m, 4H), 3.77 (bs,
4H), 7.27 (d, 4H, J = 5.4 Hz), 7.71 (m, 8H), 7.78 (m, 4H), 7.88 (d, 4H, J
= 7.2 Hz), 7.94 (d, 4H, 7.8 Hz), 8.58 (d, 4H, J = 7.2 Hz), 8.65 (s, 4H),
8.70 (s, 4H) (Fig. S14). 13C NMR (150 MHz CDCl3): δ 13.0, 21.5, 25.7,
27.7, 28.4, 28.6, 30.6, 41.0, 108.9, 117.6, 120.3, 122.8, 126.3, 126.5,
126.8, 128.3, 135.8, 135.8, 137.0, 139.4, 141.8, 146.9, 148.1, 148.1,
148.4, 154.9, 155.1, 161.7 (Fig. S15). HRMS (m/z) calcd. for
C
74H67N8O2 [M+H]+: 1099.5387, found 1099.5393 (Fig. S16).
3. Results and discussion
The probe DPPTPy preparation synthetic route is shown below
(Scheme 1). Colorimetric and fluorimetric methods were used to
confirm the sensing performance of the developed probe. A dual-sensing
mechanism established for the metal ion the sensing is via complexation
resulting in color change, and for anion (cyanide), it is through addition
reaction with a disconnection in intramolecular charge-transfer transi-
tion (ICT).
3.1. Visual detection
The sensing ability of the DPPTPy probe was studied for naked eye
recognition, changes obtained from the probe with various analyte
checked visually. In the primary attempt, we tried visible eye detection
to discover the sensing ability of DPPTPy (2 × 10ꢀ 5 M) towards different
cations/anions (2 × 10ꢀ 5 M) in a 1:1 DMF: H2O solution. The chosen
analyte (metal ions Al3+, Co2+, Cr2+, Cu2+, Sn2+, Hg2+, Fe2+, Fe3+
,
Mg2+, K+, Na+, Ni2+, etc.) and Simple anions like acetate, bromide,
chloride, cyanide, fluoride, iodide, nitrate, and phosphate. Selectivity is
the essential criterion for sensing. As depicted in Fig. 1, the DPPTPy
solution turned to pink for Co2+, red for Sn2+, and colorless for CNꢀ ,
from orange color, which denotes high selectivity in the developed
probe. Meanwhile, the other cations mentioned above/anions did not
yield any substantial color variations. Notably, DPPTPy changed its
fluorescence color from bright fluorescence yellowish orange to non-
fluorescent for Co2+; non-fluorescent red for Sn2+, and in the case of
cyanide ion addition, DPPTPy changed its fluorescence color from bright
fluorescence yellowish orange to fluorescent blue. Therefore, the
developed probe detects multiple ions by producing different colors for
each ion (Co2+, Sn2+, CNꢀ ), indicating the probe is selective. In addition,
the colorimetric response probes recognition towards anion/cation has
been verified and confirmed by a visual detection experiment. The
exceptional color change observed for each ion further been confirmed
by UV–Visible spectral measurement. The color change of the probe
associated with the addition of metal ions due to complexation with
pyridine core [42] and for cyanide ion color change occurs due to
addition reaction possibility in DPP core, and with the added cyanide
ion there exist a disconnection in ICT resulting in colored solution be-
comes colorless [43].
Fig. 5. Fluorescence spectra of DPPTPY [2 × 10ꢀ 5 M] in the presence of (A)
Sn2+ [0-2x10ꢀ 5 M], (B) Co2+, and (C) CNꢀ [0-2x10ꢀ 5 M] in 1:1 v/v DMF/H2O.
6

R. Manivannan et al.
Dyes and Pigments 192 (2021) 109425
Fig. 6. Binding mass spectra of DPPTPY in the presence of (A) Sn2+, and (B) CNꢀ .
3.2. UV–visible study
Fig. 2A, the electronic spectrum of DPPTPy (2 × 10ꢀ 5 M) in 1:1 DMF:
H2O solution exhibits an absorbance peak at 283, 322, and broad peak at
To confirm the changes observed in the visual detection experiment
and to agree the sensing ability of probe towards various anion and
cation, UV–Visible spectral measurement has been done. As shown in
491 nm which is because of the n-π* transition between TPy and DPP
core. However, the added Co2+ ions to a probe solution, the old peaks’
intensities enhanced with a shift towards the red region: a broad peak
Scheme 2. Possible binding site of the probe, DPPTPy with Sn2+ and CNꢀ ion.
7

R. Manivannan et al.
Dyes and Pigments 192 (2021) 109425
Fig. 7. Graphic illustration of RGB Arduino electronic device, the process takes place in detecting ions.
appeared between 500 and 580 nm. For Sn2+ ion, the original peak in-
tensities enhanced slightly with a little shift about 8 nm in the absorp-
tion spectrum (501 nm) with the color mentioned above change
322 nm decreased and disappeared with formation of a new peak at 297
nm (Fig. 3C). This result demonstrated that the probe DPPTPy effec-
tively detects Co2+, Sn2+, and CNꢀ ions.
observed in the visual detection experiment. Other cations (Al3+, Cr2+
,
Cu2+, Hg2+, Fe2+, Fe3+, Mg2+, K+, Na+, Ni2+, etc.) did not exhibit any
substantial absorption and color variations of the probe DPPTPy. Simi-
larly, the anions like acetate, bromide, chloride, fluoride, iodide, nitrate,
and phosphate did not yield any substantial absorption variations; only
cyanide ion interaction exhibits a disappearance of the original peak at
491 nm (Fig. 2B). The probe’s absorption change with added metal ion
due to the complexation of the metal ion with pyridine core and cyanide
ion, the absorption change due to disconnection in ICT resulting in a
colorless solution with no peak at 491 nm.
3.3. Fluorescence spectral response
The probe-based on diketopyrrolopyrrole (DPP)-Terpyridine (TPy)
derivative individually proved to be a well-known probe as TPy binds
effectively with metal ion and cyanide ion easily attacks DPP giving a
noticeable color change [42,43]. By combining these two units, the
response towards Co2+, Sn2+, CNꢀ , studied by fluorescence technique
and other added ion no fluorescence changes were observed (Fig. 4A and
B). The development of dual sensing mechanism holding probe is
The binding ability of DPPTPy towards Co2+, Sn2+, and CNꢀ was
investigated by absorption titration experiment. Upon adding the
gradual amount of Co2+, Sn2+, and CNꢀ individually to a DPPTPy (2 ×
10ꢀ 5 M) solution, the ion binding is studied. Three peaks appeared in the
probe solution in the 283, 322, and 493 nm regions. While adding Sn2+
ion (0-2x10ꢀ 5 M), to the probe solution, peak at 283 nm increased, and a
peak appeared in the region of 322 nm disappeared with the formation
of a new peak appeared at 349 nm and a shift of original peak at
493–501 nm (Fig. 3A), resulting in a color change of red color from
fluorescent orange. With the added cobalt ion (0-2x10ꢀ 5 M) to DPPTPy
solution, the peak at 283 and 322 nm decreased, and peak at 493 nm
increased gradually and shifted bathochromic with peak broadening in
the range of 520–580 nm (Fig. 3B), and the probe solution changes to
pink color. In case of detecting cyanide ion DPPTPy (2 × 10ꢀ 5 M) peak
appeared at 491 nm intensity reduced gradually with the gradual in-
crease in the cyanide ion (0-2x10ꢀ 5 M), to the probe resulting a com-
plete disappearance of peak at 491 nm simultaneously peak at 283 and
limited, and that too fluorescence quenching effect for metal ions (Co2+
,
Sn2+) and fluorescence enhancement for anions (CNꢀ ). In the present
work, we specially designed the probe DPPTPy for Co2+, Sn2+, which
has the co-ordination ability with terpyridine (N) as binding sites. With
the added metal ion (Co2+, Sn2+) to the DPPTPy (2 × 10ꢀ 5 M) solution,
fluorescence quenching occurs. To gain better insight into the sensing of
DPPTPy for Sn2+, a fluorescence titration experiment was employed.
DPPTPy reveals substantial peaks at 383 nm & 571 nm when excited at
322 nm (Fig. 5A–C) with stokes shift of 61 nm and 249 nm. With the
gradual amounts of Sn2+ (0-2x10ꢀ 5 M) addition to DPPTPy, the peak
gradually reduced at 383 nm and 571 nm. With the addition of 2
equivalents of Sn2+ into the DPPTPy solution, peaks seemed at 383 nm,
and 571 nm disappeared completely (Fig. 5A). But in the case of Co2+
,
the probes sensing effect via fluorescence technique is spontaneous with
even a very low concentration the original peak disappeared with no
time (Fig. 5B) such probes are very rare or not reported. In the case of
cyanide ion with the gradual amounts of CNꢀ ion (0-2x10ꢀ 5 M) addition
8

R. Manivannan et al.
Dyes and Pigments 192 (2021) 109425
Fig. 8. Response of RGB-Arduino device in detecting CNꢀ , Co2+ and Sn2+ ions.
to DPPTPy, the peak at 383 nm gradually grew, and at the same time, the
peak at 571 nm gradually reduced. With the 2 equivalents of CNꢀ into
the DPPTPy solution, peak seemed at 571 nm disappeared completely
and peak intensity enhanced at 383 nm (Fig. 5C). The data obtained
from the fluorescence spectra, the binding constant can be calculated
using the equation log [F0–F/F] = log KA + n log [Sn2+] (Fig. S17) [44]
and found the value as 4.43 × 108 M-1 for Sn2+ and for cyanide ion (Fα -
F0)/(Fx - F0) = 1/K[CNꢀ ] it is 3.08 × 104 M-1 (Fig. S18) [45]. The limit of
detection calculated by fluorescence emission spectra and was found to
be 2.21 × 10ꢀ 9 M for DPPTPy with Sn2+ and 1.44 × 10ꢀ 8 M for DPPTPy
DPPTPy and Sn2+ is approximately 1:2, similarly 1:2 ratio obtained for
CNꢀ [39]. Besides, the mass spectral data delivered added proof for the
1:2 compound of DPPTPy-Sn2+, DPPTPy-CN-.
3.4. Study of binding mechanism
With the identified stoichiometry from a jobs plot analysis, the
binding ability of the probe with the ions (Sn2+ and CNꢀ ) in the possible
binding site was identified further by mass analysis. To know the proper
sites of binding of DPPTPy towards Sn2+ and CNꢀ . A mass spectral
analysis experiment done by adding 2 equivalent of the ions mentioned
above. The obtained result from the HRMS spectrum of the DPPTPy-
with CNꢀ by means of 3
σ/k (Figs. S19 and S20). The quantum yield of
the probe DPPTPy before and after adding ions were calculated using
the following equation, using quinine sulfate as standard [46]:
(Sn2+
)
(found = 1408.2) complex indicates the expected result
(Fig. 62A) and agreed well with the proposed binding site mentioned in
Scheme 2. As predicted, the HRMS spectrum of the DPPTPy-(CNꢀ )2
(found = 1150.2) complex (Fig. 6B) also agreed well with the proposed
binding site. Therefore, from the obtained result, it is confirmed that the
DPPTPy dual-sensing mechanism probe for metal ion via complexation
and anion (cyanide) is through an addition reaction as illustrated in
Scheme 2. Further 1H NMR recorded for the probe with cyanide ion and
the NMR spectra, which herd the downfield shift of proton peaks cor-
responding to phenyl near DPP core and the obtained result is shown in
(Fig. S22).
/
/
2
2
ΦX = ΦST(GradX GradST)(ηX ηST
)
Where the subscripts ST and X denote standard and test, respectively,
Φ is the fluorescence quantum yield, Grad is the gradient from the plot of
fluorescence intensity vs absorbance, and
η is the refractive index of the
solvent. The quantum yield of DPPTPy was found to decrease from 0.49
to 0.09 for Sn2+ ion and the quantum yield is found to be 0.07 after the
addition of cyanide ion. To quantify the stoichiometric ratio between
DPPTPy and Sn2+, and CNꢀ ion a Job plot measurement was employed
(Fig. S21), and the molar fraction of [DPPTPY]/[DPPTPy + Sn2+] was
found to be 0.3, which indicates that the coordination ratio between
9

R. Manivannan et al.
Dyes and Pigments 192 (2021) 109425
Fig. 9. RGB-Arduino device coding data and algorithm in detecting CNꢀ , Co2+ and Sn2+ ions.
3.5. Practical application
Sn2+) and anions (CNꢀ ). Even though the different color obtained for
Co2+ (pink), Sn2+ (red), but for naked-eye detection, it is hard to
distinguish when lower concentration of ion present. To solve this issue
an electronic eye developed using RGB Arduino device using TCS3200
sensor module that can easily detect the RGB colors. The device is
consisting of an internal photodiode used to read the RGB values. The
statistical algorithm created for the developed device also coding data
generated for the sensor module. The probe solution (2 × 10ꢀ 5 M) was
placed in a sample holder; when 2 × 10ꢀ 5 M solution Co2+, Sn2+, or CNꢀ
has exposed the probe solution, the color change is determined the RGB
Arduino device the obtained result can be monitored and recorded
quickly. The obtained result for the ions mentioned above from the
device is shown in Fig. 8. The designed algorithm for the RGB - Arduino
device and coding data for ion detection given in Fig. 9.
3.5.1. An electronic eye (RGB - Arduino device) development and
application
RGB sensor kit containing RGB sensor TCS3200 module (Fig. 7):
when the metal ion was added to the sample holder vial containing
DPPTPY probe illuminates light based on color change and the inner
view of the box containing RGB sensor (TCS3200 sensor module,
Arduino board, breadboard and LED lamp). The sample (DPPTPY) in the
vial is placed in the RGB sensor TCS3200 module. When an ion is added
to the DPPTPY probe resulting in a change of color, the module gets
different reflection light where light to color scale conversion happens in
8 × 8 array photodiodes. Then, data transfer in USART format will be
sent to Arduino board (following coding algorithm) then this informa-
tion is then passed to the breadboard, and finally the signal is sent to the
LED lamp, illuminating light spontaneously. After the successful making
of the device, the efficiency of the probe in detection ions was checked.
3.5.2. Real sample application
A pre-added selected toxic ions Co2+/Sn2+ and CNꢀ 100 ppm to the
different water samples such as drinking, deionized, tap water (5 mL
The probe DPPTPy exhibited diverse colors for the cations (Co2+
,
10

R. Manivannan et al.
Dyes and Pigments 192 (2021) 109425
Fig. 10. Visual response of DPPTPY in the presence of Sn2+, Co2+, and CNꢀ ion in drinking, distilled and tap water.
approximately), and the ion containing water sample added to the 5 mL
of probe solution (2 × 10ꢀ 5 M) to each vial. The changes observed in the
probe solution are carefully monitored. An immediate color change was
observed in each vial indicates the probe DPPTPy effectively detects the
aforementioned ions with a different color: pink for Co2+, red for Sn2+
and colorless for CNꢀ , which is originally orange in color. The obtained
result is shown in Fig. 10.
CRediT authorship contribution statement
Ramalingam Manivannan: Conceptualization, Methodology,
Investigation, Formal analysis, Visualization, Writing – original draft.
Jiwon Ryu: Investigation, Formal analysis, Investigation, Chromatog-
raphy experiments, Analyzing data. Young-A Son: Conceptualization,
Methodology, Supervision, Writing – review & editing.
4. Conclusion
Declaration of competing interest
In summary, a dual sensing mechanism probe for the detection of
toxic Co2+/Sn2+ and CNꢀ ions in water based on a diketopyrrolopyrrole
(DPP) and terpyridine (TPy) fused moiety was designed and well syn-
thesized. Colorimetric response with different color was achieved for
Co2+/Sn2+ and CNꢀ . A dual-sensing mechanism is confirmed for anion
(cyanide), and it is through an addition reaction in the DPP unit with a
disconnection in intramolecular charge-transfer transition (ICT). For the
metal ion sensing via complexation in TPy unit resulting in color
(different) change. A pre-added selected ion to the different water
samples effectively detects a different color. In addition, we developed
an electronic eye (RGB - Arduino device) for the effective detection of
toxic ions.
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
Acknowledgements
This research was supported by Chungnam National University
(2020-2021).
Appendix A. Supplementary data
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.dyepig.2021.109425.
11

R. Manivannan et al.
Dyes and Pigments 192 (2021) 109425
[24] Li J, Qi X, Wei W, Zuo G, Dong W. A red-emitting fluorescent and colorimetric
dual-channel sensor for cyanide based on a hybrid naphthopyran-benzothiazol in
aqueous solution. Sens Actuators, B 2016;232:666–72.
References
[1] Ayangbenro S, Babalola OO. A new strategy for heavy metal polluted
environments: a review of microbial biosorbents. Int J Environ Res Publ Health
2017;14. 94-09.
[25] Wang ST, Sie YW, Wan CF, Wu AT. A reaction-based fluorescent sensor for
detection of cyanide in aqueous media. J Lumin 2016;173:25–9.
[26] Sun X, Wang Y, Zhang X, Zhang S, Zhang Z. A new coumarin based chromo-
fluorogenic probe for selective recognition of cyanide ions in an aqueous medium.
RSC Adv 2015;5:96905–10.
[2] Aron AT, Ramos-Torres KM, Cotruvo Jr JA, Chang CJ. Recognition- and reactivity-
based fluorescent probes for studying transition metal signaling in living systems.
Acc Chem Res 2015;48:2434–42.
[27] Young C, Tidwell L, Anderson C. Cyanide: social, industrial and economic aspects
minerals metals and material society Warrendale. 2001.
[3] Liu X, Lin Q, Wei TB, Zhang YM. A highly selective colorimetric chemosensor for
detection of nickel ions in aqueous solution. New J Chem 2014;38:1418–23.
[4] Cheah PW, Heng MP, Izati A, Ng CH, Tan KW. Rhodamine B conjugate for rapid
colorimetric and fluorimetric detection of aluminium and tin ions and its
application in aqueous media. Inorg Chim Acta 2020;512:119901.
[5] Vashisht D, Kaur K, Jukaria R, Vashist A, Sharma S, Mehta SK. Colorimetric
chemosensor based on coumarin skeleton for selective naked eye detection of
cobalt (II) ion in near aqueous medium. Sensor Actuator B Chem 2019;280:219–26.
[6] Wang L, Gong X, Bing Q, Wang G. A new oxadiazole-based dual-mode
chemosensor: colorimetric detection of Co2+ and fluorometric detection of Cu2+
with high selectivity and sensitivity. Microchem J 2018;142:279–87.
[7] Park JH, Manivannan R, Jayasudha P, Son YA. Selective detection of cyanide ion in
100% water by indolium based dual reactive binding site optical sensor.
J Photochem Photobiol Chem 2020;397:112571.
[28] Zhang Q, Zhang J, Zuo H, Wang C, Shen Y. A novel colorimetric and fluorescent
sensor for cyanide anions detection based on triphenylamine and benzothiadiazole.
Tetrahedron 2016;72:1244–8.
[29] Matsubara K, Akane A, Maseda C, Shiono H. “First pass phenomenon” of inhaled
gas in the fire victims. Forensic Sci Int 1990;46:203–8.
[30] Miller GC, Pritsos CA. Proc Symp Annu Meet TMS 2001;73.
[31] Guidelines for drinking-water quality. Geneva Switzerland: World Health
Organization; 1996.
[32] Destanoglu O, Ilmaz GGY, Apak R. Selective determination of free cyanide in
environmental water matrices by ion chromatography with suppressed
conductivity detection. J Liq Chromatogr RT 2015;38:1945–51.
[33] Minakata K, Nozawa H, Gonmori K, Yamagishi I, Suzuki M, Hasegawa K,
Watanabe K, Suzuki O. Determination of cyanide in blood by
[8] Park JH, Manivannan R, Jayasudha P, Son YA. Spontaneous optical response
towards cyanide ion in water by a reactive binding site probe. Spectrochim Acta A
2020;233:118190.
electrosprayionization tandem mass spectrometry after direct injection of
dicyanogold. Anal Bioanal Chem 2011;400:1945–51.
[34] Perring L, Dvorzak MB. Determination of total tin in canned food using inductively
coupled plasma atomic emission spectroscopy. Anal Bioanal Chem 2002;374:
235–43.
[9] Beer P, Gale P. Anion recognition and sensing: the state of the art and future
perspectives. Angew Chem Int Ed 2001;40:486–516.
[10] Cheng X, Li H, Zheng F, Lin Q, Zhang Y, Yao H, Wei T. A pillar[5]arene-based
cyanide sensor bearing on a novel cyanide-induced self-assemble mechanism. Dyes
Pigments 2016;127:59–66.
[35] Shi JX, Lu C, Yan D, Ma L. High selectivity sensing of cobalt in HepG2 cells based
on necklace model microenvironment-modulated carbon dot-improved
chemiluminescence in Fenton-like system. Biosens Bioelectron 2013;45:58–64.
[36] Tsoutsi D, Guerrini L, Ramon JMH, Giannini V, Marzan LML, Wei A, Puebla RAA.
Simultaneous SERS detection of copper and cobalt at ultratrace levels. Nanoscale
2013;5:5841–6.
[11] Ullmann encyclopedia of industrial chemistry. New York: Wiley-VCH; 1999.
[12] Bhattacharya R, Flora SJS. In: Gupta RC, editor. In handbook of toxicology of
chemical warfare agents. Academic Press Boston; 2009.
[13] Fawell JK. Guidelines for drinking water quality, vol. 1. Geneva: World Health
Organization; 1993.
[37] Khorrami AR, Fakhari AR, Shamsipur M, Naeimi H. Pre-concentration of ultra trace
amounts of copper, zinc, cobalt and nickel in environmental water samples using
modified C18 extraction disks and determination by inductively coupled plasma-
optical emission spectrometry. Environ Anal Chem 2009;89. 319-9.
[38] Kang SM, Jang SC, Kim GY, Lee CS, Huh YS, Roh C. A Rapid in situ colorimetric
assay for cobalt detection by the naked eye. Sensors 2016;16. 626-6.
[39] Mahapatra AK, Manna SK, Mandal D, Mukhopadhyay CD. Highly sensitive and
selective rhodamine-based “off-on” reversible chemosensor for tin and imaging in
living cells. Inorg Chem 2013;52:10825–34.
[14] Liu Z, Jia X, Bian P, Ma Z. A simple and novel system for colorimetric detection of
cobalt ions. Analyst 2014;139:585–8.
[15] Maiga A, Dlallo D, Bye R, Paulsen BS. Determination of some toxic and essential
metal ions in medicinal and edible plants from Mali. J Agric Food Chem 2005;53:
2316–21.
[16] Zhang Z, Zhang J, Lou T, Pan D, Chen L, Qu C, Chen Z. Label-free colorimetric
sensing of cobalt(II) based on inducing aggregation of thiosulfate stabilized gold
nanoparticles in the presence of ethylenediamine. Analyst 2012;137:400–5.
[17] Battaglia V, Compagnone A, Bandino A, Bragadin M, Rossi CA, Zanetti F,
Colombatto S, Grillo MA, Toninello A. Cobalt induces oxidative stress in isolated
liver mitochondria responsible for permeability transition and intrinsicapoptosis in
hepatocyte primary cultures. Int J Biochem Cell Biol 2009;41:586–94.
[18] Czarnek K, Terpiłowska S, Siwicki AK. Selected aspects of the action of cobalt ions
in the human body. Cent Eur J Immunol 2015;40:236–42.
[40] Dong ZM, Ren H, Wang JN, Chao JB, Wang Y. A new colorimetric and ratiometric
fluorescent probe for selective recognition of cyanide in aqueous media.
Spectrochim Acta A 2019;217:27–34.
[41] Li J, Chang Z, Pan X, Dong W, Jia AQ. A novel colorimetric and fluorescent probe
based on indolium salt for detection of cyanide in 100% aqueous solution. Dyes
Pigments 2019;168:175–9.
[42] Lopez MT, Munoz A, Ibeas S, Serna F, Garcia FC, Garcia JM. Colorimetric detection
and determination of Fe(III), Co(II), Cu(II) and Sn(II) in aqueous media by acrylic
polymers with pendant terpyridine motifs. Sens Actuators, B 2016;226:118–26.
[43] Yang C, Wang X, Xu Z, Wang M. Multi-responsive fluorescence sensing based on a
donor-acceptor-donor molecule for highly sensitive detection of water and cyanide.
Sens Actuators, B 2017;245:845–52.
[19] Fawell JK, Ohanian E, Giddings M, Toft P, Magara Y, Jackson P. Inorganic tin in
drinking-water. WHO guidelines for drinking-water quality. 2004.
[20] Wang S, Fei X, Guo J, Yang Q, Li Y, Song Y. A novel reaction-based colorimetric
and ratiometric fluorescent sensor for cyanide anion with a large emission shift and
high selectivity. Talanta 2016;148:229–36.
[21] Kulig KW. Cyanide toxicity. US Department of Health and Human Services Atlanta
GA; 1991.
[44] Kim IJ, Manivannan R, Son YA. A reaction based colorimetric chemosensor for the
detection of cyanide ion in aqueous solution. Sens Actuators, B 2017;246:319–26.
[45] Kim MJ, Manivannan R, Kim IJ, Son YA. A colorimetric and fluorometric
chemosensor for the selective detection of cyanide ion in both the aqueous and
solid phase. Sens Actuators, B 2017;253:942–8.
[22] Vennesaland B, Comm EE, Knownles CJ, Westly J, Wissing F. Cyanide in biology.
Academic Press London; 1981.
[23] Hu JW, Lin WC, Hsiao SY, Wu YH, Chen HW, Chen KY. An indanedione-based
chemodosimeter for selective naked-eye and fluorogenic detection of cyanide. Sens
Actuators, B 2016;233:510–9.
[46] Jonathan L, Marco L, Chiara M, Pierpaolo M, Fabio B, Andrea P. N-alkyl
diketopyrrolopyrrole-based fluorophores for luminescent solar concentrators:
effect of the alkyl chain on dye efficiency”. Dyes Pigments 2016;135:154–62.
12