Synthesis of tetrakis(carboxyphenyl)porphyrin coated paramagnetic iron oxide nanoparticles via amino acid for photodegradation of methylene blue

Article abstract of DOI:10.3906/kim-1204-19

In this paper, synthesis of tetrakis(carboxyphenyl)porphyrin (TCPP) coated cadmium ferrite (CdFe₂O₄) nanoparticles by using L-lysine as an anchor is reported for the first time. The ferrimagnetic CdFe ₂O₄ nanoparticles were prepared via the facile self-assembly method of reflux followed by a heating treatment. The obtained magnetic nanoparticles were coated with TCPP in the presence of the amino acid L-lysine by sonication in ethanol and then refluxing for 12 h. The structural characteristics of the products were determined using FT-IR and XRD pattern. Scanning electron microscopy (SEM) images indicated uniform morphologies of the magnetic nanoparticles with an average size of 43 nm. The magnetic properties of the prepared samples were characterized on a vibrant sample magnetometer (VSM) with maximum saturation magnetization values of 65.09 and 46.80 emu/g for nanoparticles and nanoparticle/TCPP. The synthesized products were successfully employed to remove the methylene blue (MB) dye from aqueous solutions by using visible light irradiation. The magnetic CdFe₂O₄ nanoparticles indicated an enhancement of 13% for photodegradation of MB dye after being sensitized by TCPP. TUeBITAK.

Full text of DOI:10.3906/kim-1204-19

Turk J Chem
Turkish Journal of Chemistry
(2013) 37: 879 – 888
¨
http://journals.tubitak.gov.tr/chem/
˙
c
⃝ TUBITAK
doi:10.3906/kim-1204-19
Research Article
Synthesis of tetrakis(carboxyphenyl)porphyrin coated paramagnetic iron oxide
nanoparticles via amino acid for photodegradation of methylene blue
Rahmatolah RAHIMI,1,∗ Azadeh TADJARODI,1Mina IMANI,1 Mahboubeh RABBANI,1
Samaneh SAFALOU MOGHADDAM1, Hamed KERDARI2
1Department of Chemistry, Iran University of Science and Technology, Narmak, Tehran, Iran
2Department of Chemistry, Saveh Branch, Islamic Azad University, Saveh, Iran
Received: 08.04.2012
•
Accepted: 13.03.2013
•
Published Online: 04.11.2013
•
Printed: 29.11.2013
Abstract: In this paper, synthesis of tetrakis(carboxyphenyl)porphyrin (TCPP) coated cadmium ferrite (CdFe2 O4)
nanoparticles by using L-lysine as an anchor is reported for the first time. The ferrimagnetic CdFe2 O4 nanoparticles
were prepared via the facile self-assembly method of reflux followed by a heating treatment. The obtained magnetic
nanoparticles were coated with TCPP in the presence of the amino acid L-lysine by sonication in ethanol and then
refluxing for 12 h. The structural characteristics of the products were determined using FT-IR and XRD pattern.
Scanning electron microscopy (SEM) images indicated uniform morphologies of the magnetic nanoparticles with an
average size of 43 nm. The magnetic properties of the prepared samples were characterized on a vibrant sample
magnetometer (VSM) with maximum saturation magnetization values of 65.09 and 46.80 emu/g for nanoparticles and
nanoparticle/TCPP. The synthesized products were successfully employed to remove the methylene blue (MB) dye from
aqueous solutions by using visible light irradiation. The magnetic CdFe2 O4 nanoparticles indicated an enhancement of
13% for photodegradation of MB dye after being sensitized by TCPP.
Key words: Magnetic nanoparticles, cadmium ferrite, photodegradation, amino acid
1. Introduction
Most synthetic dyes are toxic or mutagenic and carcinogenic, and it is an important environmental challenge to
remove them from processing or waste effluents.1−3 In recent years, transition metal oxides of the type MFe2 O4
nanostructures have attracted scientific and technological attention due to the fact that they possess interesting
optical, magnetic, electrical, and heterogeneous catalytic properties.4−7 These magnetic nanomaterials with
excellent properties and cubic inverse spinel structure can be employed in the industrial photodegradation of
organic dye pollutants.8−12
Synthetic porphyrins have been extensively used as catalysts for hydroxylation of organic compounds
under mild conditions since 1979.13−15 However, their use in homogeneous systems is limited by drawbacks:
the porphyrin ring is liable to oxidative self-destruction and they are subject to aggregation through π − π
interaction.16,17
Immobilization of porphyrins on magnetic nanoparticles as supports can offer several advantages over
traditional solution-phase chemistry. For example, the solid-supported porphyrins have higher stability and
increased selectivity.17−20 In addition, electron transfers increase when they are adsorbed on nanomaterials.
∗Correspondence: rahimi rah@iust.ac.ir
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The greatest advantage of magnetic nanoparticle-supported porphyrin is that it can be simply recycled and
reused several times without significant loss of activity.21−30
The enhancement of accumulation of porphyrin photosynthesizers against biological substrates can be
achieved by conjugate formation with biomolecules (e.g., amino acids, proteins).8,31,32
In the present paper, we describe the facile synthesis of lysine conjugated porphyrin and its coating on
CdFe2 O4 nanoparticles. These nanoparticles were successfully synthesized by a self-assembly method of reflux
reaction. Ethylenediaminetetraacetic acid (EDTA), a powerful complexing agent that is widely commercially
available, was used as chelate agent during the reflux procedure. The phase structures, morphologies, particle
size, and chemical compositions of the nanoparticles were characterized by FT-IR, XRD, VSM, SEM, and
UV-Vis spectrophotometer. The photocatalytic activity of the as-prepared nanoparticles was measured by
photodegradation of methylene blue (MB) as the dye model under visible illumination. The impetus for this is
that the photocatalyst, utilized as a suspension, can be easily separated after the treatment. The photocatalyst,
once separated, can be reused due to its regenerative property under the photocatalytic reaction.
2. Experimental section
2.1. Materials of synthesis
Pure analytical iron(II) sulfate heptahydrate (FeSO4 .7H2 O), cadmium nitrate tetrahydrate (Cd(NO3)2 . 4H2 O),
EDTA, ammonia (NH3), L-lysine, and tetrakis(carboxyphenyl)porphyrin (TCPP) were supplied as initial
reagents to synthesize porphyrin coated paramagnetic CdFe2 O4 nanoparticles. MB (3,7-bis(Dimethylamino)-
phenothiazin-5-ium chloride) was used as the model dye. Absolute ethanol (CH3 CH2 OH) and N,N dimethyle-
formadie (DMF) were applied as solvents in all reactions. All of the chemicals used in this work were purchased
from Merck and used without further purification.
2.2. Synthesis of paramagnetic CdFe2 O4 nanoparticles
Magnetic cadmium ferrite (CdFe2 O4) nanoparticles were synthesized by self-assembly route. As a complexing
agent, 1.1 g of EDTA was dissolved in 30 mL of deionized water. Stoichiometric weights of FeSO4 .7H2 O and
Cd(NO3)2 .4H2 O as starting materials were dissolved in sufficient amounts of deionized water and poured into
the reflux flask. The solution was allowed to stir for 1.5 h at 90 ◦ C. Subsequently, 20 mL of ammonia solution
(5 M) was slowly dropped into the mixture of the reflux and the reaction continued at the same temperature
for 3 h. The reaction was completely performed under nitrogen atmosphere to prevent further oxidation of the
prepared nanoparticles. At the end, the obtained precipitation was collected, washed with distilled water, and
then dried at 70 ◦ C overnight. Following this step, the obtained precursor was heated at 550 ◦ C for 2 h at a
rate of 10 ◦ C/h under nitrogen atmosphere to prepare the paramagnetic nanoparticles.
2.3. Synthesis of lysine conjugated tetrakis(carboxyphenyl)porphyrin (LTCPP)
In order to prepare this product, LTCPP, a stoichiometric amount of TCPP dissolved in 100 mL of absolute
ethanol and DMF (1:1) mixture was slowly injected into 150 mL of solution of lysine in ethanol under continual
stirring and nitrogen atmosphere. The reflux reaction was performed at 70 ◦ C for 12 h. The synthesized
sample was collected and washed with distilled water and subsequently ethanol to remove the excess reagents.
The obtained precipitation was dried at 70 ◦ C overnight and then was employed for coating on the prepared
CdFe2 O4 nanoparticles.
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2.4. Preparation of porphyrin coated magnetic nanoparticles (LTCPPNP)
Some 300 mg of cadmium ferrite nanoparticles dispersed by ultrasonic wave energy was added to 50 mg of
LTCPP dissolved in 100 mL of ethanol. The mixture was sonicated for 1 h and then was transferred to a reflux
container and the reflux reaction was performed at 70 ◦ C for 12 h under continual stirring and N2 atmosphere.
Finally, the obtained product was collected and after washing with distilled water several times was dried at 70
◦ C overnight.
2.5. Photocatalytic activity
The photocatalytic activity of the synthesized paramagnetic CdFe2 O4 nanoparticles and TCPP coated CdFe2 O4
nanoparticles was measured by degradation of MB as a model dye in aqueous solution under visible light irra-
diation. In order to establish the adsorption–desorption equilibrium, each beaker containing magnetic products
and related dye solution was left in the dark and magnetically stirred for 15 min before starting the photocat-
alytic reaction. In the photocatalytic experiments, a certain amount (0.01 g) of photocatalyst was separately
poured into a 50-mL beaker containing 25 mL of related dye solution with an initial concentration (5 mg L−1
)
and magnetically stirred for 6 h under visible irradiation. At given intervals of irradiation (1 h), portions of
the suspension were taken out of the reaction vessel and easily separated using a permanent magnet and then
analyzed by UV-Vis spectrophotometer. Next, the remaining concentration of MB solution was studied by a
UV-Vis spectrophotometer at a wavelength of 668 nm.
2.6. Characterization
The powder X-ray diffraction (XRD) measurements were carried out using a Jeoljdx-8030 diffractometer with
˚
monochromatized Cu Kα radiation (λ = 1.5418 A, 40.0 kV, 30.0 mA). Fourier transform infrared (FT-IR)
spectra were recorded on a Shimadzu-8400S spectrometer in the range of 400–4000 cm−1 using KBr pellets.
The magnetic properties of the sample were recorded by using a vibrating sample magnetometer (VSM, MDK6,
Magnetis Daghigh Kavir Co., Iran). Scanning electron microscopy (SEM) images were obtained on a Philips
XL-30 with gold coating to prove the presence of elements. Diffuse reflectance spectra (DRS) were prepared via
a Shimadzu (MPC-2200) spectrophotometer to investigate the photocatalytic ability of magnetic nanoparticles.
The UV-Vis absorption study was performed at room temperature in the wavelength range of 190–800 nm on
a UV-Vis spectrometer (Shimadzu UV-1700).
3. Results and discussion
3.1. The study of FT-IR spectra
Figure 1 shows the FT-IR spectra of the prepared cadmium ferrite nanoparticles. The FT-IR spectrum of
cadmium ferrite before calcination obtained from the reflux reaction is indicated in Figure 1a. The observed
peaks in this spectrum are related to the organic groups of synthesized precursor. The broad peak observed
at 3442 cm−1 is attributed to the O-H stretching vibration bands of the EDTA compound overlapped with
the vibration bands of H2 O molecules. The signified peaks at 1620 and 1118 cm−1 belong to the ionized and
coordinated C=O and C-O stretching vibration bands of EDTA molecule, respectively, which were used in the
formation of precursor. These frequencies are less than those of the free functional group due to coordination
with the metal ions in the intermediate molecule. The observed frequency at 592 cm−1 is assigned to Fe-
O vibration, which is broadened due to overlapping with the Cd-O vibration band. The organic groups of
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synthesized precursor after heating at 550 ◦ C are completely removed and only the peak of Fe-O remains
(Figure 1b). Figure 2a indicates the FT-IR spectrum of LTCPP covered on CdFe2 O4 nanoparticles. The metal
oxygen vibration band is also observed at about 568 cm−1 . Figures 2b and 2c indicate the FT-IR spectra of pure
magnetic nanoparticles and pure TCPP, respectively, which are given for comparison. The FT-IR spectrum of
LTCPPNP (Figure 2a) revealed peaks at 1680 and 1527 cm−1 . These peaks were assigned to the C-O stretching
vibration of TCPP and the NH2 deformation of the amide group, respectively. The amide group is formed
when the carboxyl acid group of TCPP conjugates with the amino group of amino acid. The presence of these
peaks proves the LTCPP coated magnetic nanoparticles.
(b)
(b)
1620
(a)
(a)
(c)
3442
592
1118
4000 3400 2900
2400 1900 1400
900
400
4000
3500
3000
2500
2000
1500
1000
500
Wavenumber (cm–1)
Wavenumber (cm–1)
Figure 1. The FT-IR spectra of the prepared cadmium
ferrite nanoparticles (a) before calcinations and (b) after
calcinations at 550 ◦ C for 2 h.
Figure 2. The FT-IR spectra of (a) LTCPP coated
CdFe2 O4 nanoparticles, (b) pure CdFe2 O4 , and (c) pure
TCPP.
3.2. X-ray diffraction pattern
Figure 3 displays the XRD pattern of prepared magnetic nanoparticles calcined at 550 ◦ C for 2 h. The marked
peaks in the pattern reveal the spinal phase of CdFe2 O4 with identified peaks according to the JCPDS card
no. 22-1063. The major peaks at 2θ values of 29.00◦ , 34.12◦ , 35.68◦ , 41.46◦ , 45.37◦ , 51.39◦ , 54.76◦ , 60.06◦ ,
68.07◦ , 70.96◦ , 71.92◦ , and 78.44◦ are very compatible with the planes of 220, 311, 222, 400, 331, 422, 511,
˚
440, 620, 533, 622, and 551, respectively. The space group of Fd3m with lattice constant 8.699 A is also assigned
to cadmium ferrite. Although this pattern is compatible with the cadmium ferrite X-ray diffraction pattern,
there are partial diffraction signals at 2θ values of 12.74◦ , 33.95◦ , and 57.40◦ , which may belong to the slight
residual phase of Fe2 O3 (JCPDS card no. 025-1402).
3.3. Morphology study
The SEM images of the obtained cadmium ferrite nanoparticles are indicated in Figures 4a and b. The low
magnification image of SEM (Figure 4a) shows the accumulated magnetic particle shape. The high magnification
of SEM images (Figure 4b) clearly indicates the uniform morphology of nanoparticles with an average particle
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Fe2O3
250
200
150
100
50
0
0
10 20
30
40
50 60
70
80
2 eta (degree)
Figure 3. The XRD pattern of prepared magnetic CdFe2 O4 nanoparticles.
9
Mean 43.44
StDev 3.10
8
6
4
2
0
36
39
42
45
48
Particle size (nm)
Figure 4. (a, b) The SEM images and (c) the histogram of the particles size distribution of CdFe2 O4 nanoparticles.
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size of 43 nm and standard deviation of 3.10. A histogram of the particle size distribution for the obtained
product (shown in Figure 4c) was determined by microstructure measurement program and Minitab statistical
software. The observed agglomeration can be a result of high magnetization of samples. In fact, due to the
large surface area-to-volume ratio and magnetic dipole–dipole interactions between the synthesized particles,
these nanoparticles are prone to aggregate.33
3.4. Magnetic properties
Magnetic properties of the obtained samples were analyzed by vibrating sample magnetometer with an applied
field of −10 kOe ≤ H ≤ 10 kOe at room temperature; Figures 5a and 5b exhibit the magnetization (M)
versus the applied magnetic field (H) for synthesized CdFe2 O4 nanoparticles and TCPP coated nanoparticles,
respectively. The measured maximum values of saturation magnetization (Ms) for ferrite nanoparticles and
LTCPP/nanoparticles are 65.09 and 46.80 emu/g, respectively. The LTCPP/magnetic nanoparticles indicate
low saturation magnetization, which is attributed to the nonmagnetic contribution of the LTCPP shell covering
the cadmium ferrite nanoparticles. Moreover, the observed high saturation magnetizations of both prepared
samples can be assigned to the size of particles and well developed crystallinity of structures.34,35 Despite the
high saturation magnetization, all specimens indicated relatively small coercivity. The remnant magnetizations
(Mr) of mentioned samples are 4.2 and 4.5 emu/g, respectively. Spinel ferrites with the nanosized particles
indicate different magnetic properties from their bulk counterparts. Cadmium ferrite is a normal spinel having
an antiferromagnetic property in bulk form in which cadmium ions have occupied the tetrahedral sites. It has
been shown to be ferrimagnetically ordered when the grain size is reduced to nanometer size.
60
50
(a)
(b)
80
60
30
10
60
40
20
40
20
-1000
1000
-10
-30
40
-1000 -500
500 1000
-20
-40
-60
-50
20
0
0
0
-15,000 -10,000 -5000
5000 10,000 15,000
-10,000 -8000 -6000 -4000 -2000
0
2000 4000 6000 8000 10,000
-20
-20
-40
-60
-40
-60
-80
Applied !eld (Oe)
Applied !eld (Oe)
Figure 5. The magnetization (M) versus the applied magnetic field (H) for (a) synthesized CdFe2 O4 nanoparticles and
(b) TCPP coated nanoparticles.
Therefore, the as-prepared nanosized sample exhibits the ferrimagnetic characteristic. The hysteresis
loop of an S-shaped curve having the slight remanence effect can be indicative of the ferrimagnetical nature of
the product. Thus, the magnetization curves of the samples show strong magnetic behavior with high saturation
magnetization and slender hysteresis.34−36 The resulting values of saturation magnetization are considerable
in comparison with the reported values for this material so far.34,37−39 Substitution of cadmium ions into
crystalline structure causes the soft magnetic properties. It is found that the magnetic properties of samples
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RAHIMI et al./Turk J Chem
improve owing to reduction in particle size so that the sample of pure cadmium ferrite nanoparticles indicates
higher Ms than another one.
3.5. Photodegradation activity
The possibility of using CdFe2 O4 and LTCPP coated CdFe2 O4 nanoparticles for the photodegradation of
dyes such as MB was evaluated by examining the degradation efficiency of MB in the presence of visible
light irradiation. Photocatalytic efficiency was evaluated based on the absorption intensity of MB solutions at
different times. In addition, the decolorizing efficiency was inferred from Eq. (1):
C0 − Ci
Decolorozing efficiency =
× 100%,
(1)
C0
where C0 is the initial concentration of dye before the reaction happens, and Ci is the concentration of dye after
the treatment with prepared products at various illumination times. Figures 6 and 7 illustrate the changes in
MB absorbance versus wavelength (nm) in the presence of pure CdFe2 O4 nanoparticles and porphyrin coated
CdFe2 O4 nanoparticles, respectively, for 2 h at room temperature. In the absence of light irradiation, the
slight value of MB on both resulting samples is adsorbed. In fact, when no nanoparticles are present, the light
irradiation leads to negligible degradation of MB. It was found that the degradation values increased with the
introduction of prepared magnetic products into colored aqueous solution. Figure 8 represents the decolorizing
efficiency of MB by employing both products. It is observed that the photodegradation was increased from 76%
(Figure 8a) to 89% (Figure 8b) by replacing CdFe2 O4 nanoparticles with LTCPP/CdFe2 O4 nanoparticles.
This result revealed that such a modest enhancement can be attributed to the slight difference in the band
gap energies. Figure 9 shows the band gap energy curves of the pure nanoparticles (Figure 9a) and porphyrin
coated nanoparticles (Figure 9b) based on UV-Vis spectrum and using the Tauc equation as follows:
(αhϑ)n = B(hϑ − Eg),
(2)
where hν is the photon energy, α is the absorption coefficient, B is a constant value, Eg represents the band gap
energy, and n is related to direct and indirect transitions. By plotting of (αhν)2 vs. hν in eV and by determining
the extrapolation point, the band gap energies are calculated. However, the resulting nanomaterials have the
appropriate photocatalytic behavior, which can be explained by the injection of electrons to the conduction
band by porphyrin molecules coated nanoparticles. Likewise, it is concluded that the coating of nanoparticles
by porphyrin molecules leads to better dispersion of magnetic nanoparticles in the solution and to a higher
degradation of the pollutant.
A suggested mechanism of photodegradation behavior is shown in the Scheme. When the visible light is
irradiated on the surface of LTCPP coated CdFe2 O4 , the sum of the electrons is excited from valence band
(VB) to conduction band (CB). Subsequently, these electrons in the CB reduce O2 molecule adsorbed on the
surface of the catalyst and transform into singlet O2 and then H2 O2 and OH radical, which oxidize the dye
molecules to CO2 and H2 O.40
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1.2
1
Blank
In dark
1.2
1
Blank
In dark
1 h aer visible irradiation
1 h
2 h
0.8
2 h aer visible irradiation
0.8
0.6
0.4
0.6
0.4
0.2
0.2
0
0
200
300
400
Wavelength (nm)
500
600
700
800
200 300 400
500 600
Wavelength (nm)
700 800
Figure 6. The absorbance changes vs. wavelength (nm)
for MB on the surface of pure CdFe2 O4 nanoparticles for
2 h at room temperature.
Figure 7. The absorbance changes vs. wavelength (nm)
for MB on the surface of LTCPP/CdFe2 O4 nanoparticles
for 2 h at room temperature.
100
90
(b)
(a)
80
70
60
50
CdFe2O4
40
30
20
LTCPP/CdFe2O4
10
0
0
50
100
150
200
Time (min)
Figure 8. The photodegradation efficiency of dye solution (MB) using synthesized pure CdFe2 O4 and (b) LTCPP
coated CdFe2 O4 nanoparticles.
20
15
60
10
40
5
Eg = 1.67 eV
20
Eg = 1.7 eV
(a)
(b)
2.2
0
0
1.5
1.6
1.7
1.8
1.9
2.0
2.1
1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5
hv (eV)
hv(eV)
Figure 9. The plots of (αhν)2 vs. hν (eV) of (a) the pure CdFe2 O4 nanoparticles and (b) LTCPP/CdFe2 O4
nanoparticles.
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Scheme. The proposed mechanism of photodegradation of MB dye solution by using porphyrin coated CdFe2 O4
nanoparticles.
4. Conclusion
Uniform CdFe2 O4 nanoparticles with an average size of 43 nm and saturation magnetization (Ms) of 65.09
were synthesized by using a facile reflux reaction followed by heating treatment. Then the obtained magnetic
ferrimagnetic nanoparticles were successfully coated by lysine conjugated porphyrin to improve the photocat-
alytic activity in the visible domain. This process was evaluated using MB as a dye model. The dye removal
efficiency on the pure cadmium ferrite after 2 h of visible light was improved from 76% to 89% due to sensitizing
of the nanoparticles with porphyrin molecules. This performance is explained by improved flow of the excited
electrons to the conduction band and high dispersion of the particles by covering the surface of cadmium ferrite
nanoparticles with a thin layer of LTCPP molecules. The good efficiency and simple separation of catalyst after
photocatalytic treatment by a permanent magnet make these products suitable for many applications in this
field.
Acknowledgment
The financial support of this study by Iran University of Science and Technology is gratefully acknowledged.
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