Synthesis and sensing properties of triphenylamine based dye sensor

Article abstract of DOI:10.1166/jnn.2010.2810

We have designed and synthesized a triphenylamine-based new dye sensor and corresponding selective and sensitive detection functions for heavy metal ions were investigated. The complex potentials for heavy metal ions were characterized by the measurements

Full text of DOI:10.1166/jnn.2010.2810

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Journal of
Nanoscience and Nanotechnology
Vol. 10, 7730–7734, 2010
Synthesis and Sensing Properties of
Triphenylamine Based Dye Sensor
Byung-Soon Kim1ꢀ2, Young-Sung Kim1, Sung-Hoon Kim3ꢀ∗, and Young-A Son1ꢀ∗
1School of Chemical and Biological Engineering, Chungnam National University, Yuseong-gu, Daejeon 305-764, S. Korea
2Department of Environmental Sciences, Faculty of Education and Human Sciences,
Yokohama National University, Hodogaya-ku, Yokohama 240-8501, Japan
3Department of Textile System Engineering, Kyungpook National University, Daegu, 702-701, S. Korea
We have designed and synthesized a triphenylamine-based new dye sensor and corresponding
selective and sensitive detection functions for heavy metal ions were investigated. The complex
potentials for heavy metal ions were characterized by the measurements of optical properties using
UV-Vis spectrophotometer and spectrofluorophotometer. Furthermore, the molecular energy levels
of the designed dye sensors were also computationally optimized and calculated by the density
function theory (DFT) with exchange correction functional of local density approximation (LDA)
based on the Perdew-Wang (PWC) set and cyclic voltammetry.
Keywords: Dye Sensor, Triphenylamine Derivatives, Mercury Ion, Complex Ability, Molecular
Energy Levels.
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1. INTRODUCTION
The levels of metal ion detection were discussed with
UV-Vis absorption and fluorescent emission measurements
in details. In addition to metal ion detection properties, the
molecular energy potentials (HOMO and LUMO energy
levels) of the dye chemosensor based on triphenylamine
derivatives were also calculated and determined.
The research development of selective, sensitive and sim-
ple chemosensor using dye chromophores toward heavy
metal ions is an important topic in dye molecular chem-
istry due to its fundamental roles in chemical, biological,
and environmental systems.1–4 Since the initial findings
was reported in chemosensors such as crown ether, many
research efforts have been focused on the design, synthe-
sis and detection of heavy metal ions due to their toxic
impacts.5
2. EXPERIMENTAL DETAILS
2.1. Materials and Measurements
All reagents and solvents used for synthesis of
triphenylamine-based dye chemosensor were purchased
from Aldrich and used without further purification. The
spectroscopic characteristics and the fluorescent proper-
ties of these dyes were examined and determined using
Agilent 8453 UV-Vis spectrophotometer and Shimadzu
Thus, the concerns over highly noxious heavy and tran-
sition metal ions such as mercury (Hg2+ꢀ, copper (Cu2+
ꢀ
and zinc (Zn2+ꢀ are of topical interests because they are
considered as highly toxic environmental pollutants. As
well known, mercury and copper are considered to be
highly dangerous heavy metals in the human body and
play an important role in the physiologic process due to
their severe toxic effects. In addition, zinc is reported to
be related to the etiology of Alzheimer’s disease because
of the formation of ꢁ-amyloid.1ꢂ6ꢂ7
1
RF-5301 spectrofluorophotometer, respectively. H NMR
spectra and elemental analyses were recorded with a JNM-
AL400 spectrometer operated at 400 MHz NMR and a
Carlo Elba Model 1106 analyzer, respectively. The elec-
trochemistry properties of these dyes were examined with
a VersaSTAT3 using a platinum wire served as a working
electrode, an Ag/Ag+ electrode served as a reference elec-
trode and a carbon served as a counter electrode. The scan
rate was 100 mV/s. The optimized geometry structure and
molecular energy potentials were calculated with Materials
studio 4.2.
In this context, we have designed and synthesized the
dye chromophores based on triphenylamine derivative as a
chemosensor for heavy metal ions. The metal ion detection
properties of these dyes were examined and determined.
∗Authors to whom correspondence should be addressed.
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J. Nanosci. Nanotechnol. 2010, Vol. 10, No. 11
1533-4880/2010/10/7730/005
doi:10.1166/jnn.2010.2810

Kim et al.
Synthesis and Sensing Properties of Triphenylamine Based Dye Sensor
2.2. Synthesis and Characterization of
stirring. After 3 h, the reaction was quenched into the
ice water and being stirred for 24 h. The formed pre-
cipitate solution was adjusted to the neutral pH condi-
tion using 1% sodium carbonate solution. After 3 h, the
mixture was filtrated with ꢀdistilled water at several times
and dried in oven at 40 C.10–12 Dye 3, Yield: 23.03%
(0.34 g); Anal. Calcd for C13H10N2O2: C, 69.02; H, 4.46;
Triphenylamine-Based Dye Sensor (Scheme 1)
To the mixture of 4 g (16.3 mmol) triphenylamine and 8 ml
N,N-dimethylformamide, 7.6 ml phosphorus oxychloride
ꢀ
was added at 0 C and the mixture was then refluxed for
ꢀ
ꢀ
2 h at 45 C (dye 1) and 4 hrs at 95 C (dye 2). The reac-
tion was cooled to room temperature and the mixture was
quenched into 150 ml ice water. The formed precipitate
solution was adjusted to the neutral pH condition using
4 M sodium hydroxide solution. The solid was filtered
and purified by column chromatography by eluting with
hexane/ethyl acetate.8ꢂ9 Dye 1, Yield: 61.07% (2.72 g);
Anal. Calcd for C19H15NO: C, 83.49; H, 5.532; N, 5.12.
1
N, 12.38: found; C, 69.16; H, 4.16; N, 12.81. H NMR
(400 MHz, CDCl3ꢀ: ꢃ 4.00 (s, 2H), 6.24 (d, 1H), 6.28
(d, 1H), 7.18–7.32 (m, 2H), 7.42–7.50 (m, 1H), 7.52–7.62
(m, 1H), 7.30 (d, 1H), 11.47 (s, 1H).
For next step synthesis, the chemosensor dyes 4 and 5
were obtained from the prepared intermediates 2 and 3.
0.045 g and 0.090 g (0.2 mmol, 0.4 mmol) of Dye 1 were
mixed with dyes 2 and 3 (0.2 mmol, 0.054 g, 0.06 g),
respectively. The reaction mixture was dissolved in 15 ml
of benzene. 5∼6 drops of piperidine was added dropwise
during the reaction and the mixture was then refluxed for
48 h. The reaction product was filtered using benzene and
dried (dyes 4 and 5).13 Dye 4, Yield: 53.37% (0.052 g);
Anal. Calcd for C32H23N3O2: C, 79.81; H, 4.81; N, 8.73.
1
Found: C, 83.42; H, 5.50; N, 4.995. H NMR (400 MHz,
CDCl3ꢀ: ꢃ 7.06 (d, 2H), 7.19–7.25 (m, 6H), 7.38 (t, 4H),
7.7.2 (d, 2H), 9.85 (s, 1H). Dye 2, Yield: 68.27% (2.52 g);
Anal. Calcd for C20H15NO2: C, 79.72; H, 5.02; N, 4.65.
1
Found: C, 79.65; H, 5.07; N, 4.65. H NMR (400 MHz,
CDCl3ꢀ: ꢃ 7.19 (m, 6H), 7.40 (t, 2H), 7.76–7.78 (d, 4H),
9.89 (s, 2H).
The signal unit dye 3 was prepared by condens-
ing p-aminosalicylic acid 0.998 g (6.52 mmol) and
o-aminophenol 0.711 g (6.52 mmol). 20 g of polyphos-
1
Found: C, 79.26; H, 4.56; N, 8.25. H NMR (400 MHz,
DMSO-d6ꢀ: ꢃ 6.07 (s, 4H), 6.26–6.29 (m, 2H), 6.86–6.88
(m, 2H), 7.07–7.19 (m, 1H), 7.32–7.33 (m, 5H), 7.69–7.70
(m, 7H), 9.75 (s, 1H). Dye 5, Yield: 35.81% (0.052 g);
ꢀ
phoric acid was added and heated at 200 C with constant
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POCl3
DMF
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N
N
CHO
CHO
OHC
(Dye 1)
(Dye 2)
O
OH
HOOC
NH2
C
NH2
N
NH2
HO
OH
HO
(Dye 3)
N
N
OH
N
O
O
N
O
C
H
C
N
C
H
N
C
C
H
C
N
N
HO
(Dye 4)
(Dye 5)
Metal ions
Metal ions
Metal ions
N
N
O
N
C
O
O
N
C
O
O
C
N
C
H
C
H
N
C
H
N
N
O
Metal ions
Scheme 1. Synthesic routes for designed dye sensor.
J. Nanosci. Nanotechnol. 10, 7730–7734, 2010
7731

Synthesis and Sensing Properties of Triphenylamine Based Dye Sensor
Anal. Calcd for C46H31N5O4: C, 76.97; H, 4.35; N, 9.76.
Kim et al.
0.3
0.2
0.1
(a)
Dye 5
1
Found: C, 76.94; H, 4.70; N, 10.31. H NMR (400 MHz,
Dye 5+Zn2+
Dye 5+Cu2+
Dye 5+Hg2+
CDCl3ꢀ: ꢃ 6.29–6.34 (t, 4H), 6.29 (s, 4H), 7.52–7.54
(d, 1H), 7.60–7.64 (m, 4H), 7.71–7.78 (m, 8H), 7.86 (s,
2H), 8.03–8.05 (d, 2H), 8.43 (s, 2H), 9.87–9.89 (d, 2H),
11.58 (s, 2H).
2.3. Absorption and Fluorescence Measurements
Dye 5+Hg2+
UV-Vis absorption and fluorescence spectra were per-
formed by the addition from 0 to 2 equiv of different
metal ions (Hg2+, Cu2+ and Zn2+ꢀ in 3 ml dye solution
(1ꢄ0×10−4 M).
0.0
0.3
300
400
500
600
Wavelength (nm)
(b)
0.2
0.1
0.0
2.4. Composition of the Metal Complex
0.2
0.1
0.0
The dyes 4, 5 and Hg2+ ion solution were mixed in dif-
ferent volume ratio (1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2,
9:1, 10:0) using a total concentration of 1ꢄ0×10−4 M. The
mixture solutions were characterized at maximum absorp-
tion value using spectrophotometer.
300
350
400
450
Wavelength (nm)
3. RESULTS AND DISCUSSION
300
400
500
600
Wavelength (nm)
In this work, the aldehydes of triphenylamine (dyes 1,
2) and benzoxazole intermediate (dye 3) were reacted to
Fig. 2. (a) Absorption spectra of dye 5 (1ꢄ0 × 10−4 M, chloroform) in
2+, Hg2+, Cu2+ꢀ and (b) dye 5
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2+
titrated selectively with Hg
.
Copyright: American Scientific Publishers
0.6
0.4
0.2
(a)
Dye 4
(a)
Dye 4+Zn2+
Hg2+/equiv
Dye 4+Hg2+
Dye 4+CU2+
Dye 4+Hg2+
0.0
0.6
300
400
500
600
400
450
500
550
600
Wavelength (nm)
Wavelength (nm)
0.6
0.5
(b)
(b)
0.4
0.3
0.2
0.0
Hg2+/equiv
0.4
0.2
0.0
320 340 360 380 400
Wavelength (nm)
300
400
500
600
Wavelength (nm)
400
450
500
550
600
Wavelength (nm)
Fig. 3. Fluorescence emission spectra of dye 4 (a) and dye 5 (b) (1ꢄ0×
10−4 M, chloroform) titrated with Hg2+
Fig. 1. (a) Absorption spectra of dye 4 (1ꢄ0 × 10−4 M, chloroform) in
the addition of 2 equiv. of metal ions (Zn2+, Hg2+, Cu2+ꢀ and (b) dye 4
titrated selectively with Hg2+
.
.
7732
J. Nanosci. Nanotechnol. 10, 7730–7734, 2010

Kim et al.
Synthesis and Sensing Properties of Triphenylamine Based Dye Sensor
0.3
(a)
(a)
0.2
0.1
0.0
0.0
0.2
0.4
0.6
0.8
1.0
Mole fraction of Hg2+
(b)
0.4
0.3
0.2
0.1
0.0
(b)
0.0
0.2
0.4
0.6
0.8
1.0
Fig. 6.
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tonitrile (0.05 M TBAPF6, Ag/Ag+ reference electrode and scan rate
Mole fraction of Hg2+
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100 mV/s).
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Fig. 4. Job’s method for the addition of Hg2+: dye 4 complex (a) and
dye 5 complex (b).
ions. The optical characteristics of dyes 4 and 5 dis-
played the increased behavior around 320 nm and the
decreased behavior around 400 nm with increasing con-
centration of Hg2+. The isobestic point at 350 nm was
clearly observed. This sensing behavior occurred by the
metal binding reaction. Figure 3 shows that fluorescence
spectra of dyes 4 and 5 with addition of Hg2+ ions. With
addition of Hg2+ to dye 4, the maximum emission band
at 500 nm was decreased with increasing concentration
produce the aimed dyes 4 and 5. Absorption and fluo-
rescence emission spectra were measured to monitor the
sensing functions of the designed dyes 4 and 5 toward
heavy metal ions (Hg2+, Cu2+ and Zn2+ꢀ. Absorption
spectra of dyes 4 and 5 with three metal ions in chlo-
roform are shown in Figures 1 and 2, respectively. The
detection properties of dyes 4 and 5 toward three metal
ions showed the selective functions, especially to Hg2+
LUMO
(–4.61 eV)
LUMO
(–4.74 eV)
HOMO-LUMO gap (∆E) 1.92 eV
HOMO-LUMO gap (∆E) 2.1 eV
HOMO
HOMO
(–2.82 eV)
(–2.51 eV)
Fig. 5. Geometrical optimization of dyes 4, 5 and HOMO and LUMO energy levels.
J. Nanosci. Nanotechnol. 10, 7730–7734, 2010
7733

Synthesis and Sensing Properties of Triphenylamine Based Dye Sensor
Kim et al.
Table I. HOMO/LUMO values of dye sensor 4 and 5.
where, Epeak potential and E1/2ꢆFerroceneꢀ is the maximum, min-
imum peak potential and half-wave potential of Ferrocene
(0.42 V).
Computationally
calculated
Determined with
cyclic voltammograms
Dye sensor
HOMO
LUMO
ꢅE
HOMO
LUMO
ꢅE
4. CONCLUSIONS
4
5
−4.61
−4.74
−2.51
−2.82
2.1
1.92
−4.88
−4.98
−2.58
−2.78
2.3
2.2
In this work, we have developed new dye chemosensor
4 and 5 based on triphenylamine. The dye chemosensor
clearly showed the selective detection properties of absorp-
of Hg2+. However, in the case of dye 5, the maximum
emission band at 500 nm was increased with increasing
concentration of Hg2+. This optical changing behavior was
explained by MLCT, namely “metal to ligand charge trans-
fer.” When the metal binding reaction occurred, it shows
the clear optical emission property changes. These sensing
properties provide the easy way to determine the metal ion
detection properties with naked eyes.
The Job’s method is widely used to determine the com-
plex composition of the host-guest interaction. The rela-
tionship of maximum absorption peak versus mole fraction
of the metal ion is shown in Figure 4. From the results of
dyes 4 and 5, it is showed that the mole fraction was close
to 50% and 65%. This finding confirms that dyes 4 and 5
make a formation of 1:1 and 1:2 binding complexes with
the added Hg2+ ion, respectively.
tion and fluorescence emission intensities toward Hg2+
.
A stable binding functions of dyes 4 and 5 formed 1:1 and
1:2 complexes with Hg2+ ion, which was determined by
Job’s method. The molecular energy levels were calculated
using computational optimization and cyclic voltammetry.
The synthesized dye sensor 4 and 5 could be utilized as
selective good chemosensors for Hg2+ ions in chemical,
environmental and biological systems.
Acknowledgments: This research was supported by
research grant of the National Archives of Korea. This
work was supported by the Korean Science and Engineer-
ing Foundation (KOSEF) grant funded by the Korea gov-
ernment (MEST) (No. 2009-0063408).
The optimization of the molecular geometrical struc-
ture and the molecular energy potential of dye sensor 4
References and Notes
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and 5 were computationally calculated with the DFT with
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IP: 91.242.217.159 On: Wed, 15 Jun 2016 07:24:02
exchange correction functional of LDA based on the PWC
Copyright: American Scientific Publishers
set employing Materials studio 4.2. Figure 5 shows that
electron density of dye sensor 4 and 5 was distributed
in triphenylamine moiety in HOMO states and was local-
ized in benzoxazole moiety in LUMO states after excited.
From the findings, HOMO and LUMO energy levels were
calculated by −4.61 eV and −2.51 eV (dye sensor 4)
and −4.74 eV and −2.82 eV (dye sensor 5). Cyclic-
voltammetry measurements of these dyes were also carried
out using a conventional three-electrode system. The oxi-
dation and reduction potential values were also used to
determine the potential of HOMO and LUMO energy lev-
els. Figure 6 shows the redox potential characteristics of
dye sensor 4 and 5, respectively. From the redox poten-
tials, HOMO and LUMO energy levels of dye sensors
were determined and compared (Table I). The HOMO and
LUMO energy levels were calculated using the following
formula,14
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(2007).
HOMO ꢆor LUMOꢀꢆeVꢀ = −4ꢄ8−ꢆEpeak potential
−E1/2ꢆFerroceneꢀ
ꢀ
Received: 4 September 2009. Accepted: 30 October 2009.
7734
J. Nanosci. Nanotechnol. 10, 7730–7734, 2010