New sodium dodecyl sulfate-assisted preparation of Nd2O3 nanostructures via a simple route

Article abstract of DOI:10.1039/c5ra08394j

The effect of the anionic shape- and size-controller on the morphology and size of Nd₂O₃ prepared by a new simple approach was studied. Nanostructured Nd₂O₃ was synthesized by heat treatment in air at 900 °C for 5 h, employing powder, which was prepared by a solvent-free solid-state reaction from [NdL(NO₃)₂]NO₃ (L = bis-(2-hydroxy-1-naphthaldehyde)-ethanediamine Schiff base compound), as a new precursor, in the presence of sodium dodecyl sulfate (SDS) as shape- and size-controller. The structural, morphological and optical properties of the as-obtained nanostructured Nd₂O₃ were characterized by thermo-gravimetric analysis (TGA), X-ray diffraction (XRD), energy dispersive X-ray microanalysis (EDX), UV-vis diffuse reflectance spectroscopy, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR) spectroscopy. The obtained results demonstrated that the amount of SDS plays a key role in the morphology and particle size control of the neodymium oxide. Furthermore, the catalytic properties of the as-prepared nanostructures were evaluated by the photocatalytic degradation of the erythrosine (anionic dye) as water contaminant.

Full text of DOI:10.1039/c5ra08394j

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New sodium dodecyl sulfate-assisted preparation of Nd2O3
nanostrucrures via a simple route
Sobhan Mortazavi-Derazkola, Sahar Zinatloo-Ajabshir, Masoud Salavati-Niasari*
5
The effect of the anionic shapeꢀ and sizeꢀ controller on the morphology and size of Nd2O3 prepared by new simple approach was studied.
Nanostructured Nd2O3 was synthesized by heat treatment in air at 900 °C for 5 h., employing powder, which was prepared by a solventꢀ
free solidꢀstate reaction from [Nd L(NO3)2]NO3 (L = bisꢀ( 2ꢀhydroxyꢀ1ꢀnaphthaldehyde)ꢀethanediamine Schiff base compound), as new
precursor, in presence of sodium dodecyl sulfate (SDS) as shapeꢀ and sizeꢀ controller. The structural, morphological and optical
10 properties of asꢀobtained nanostructured Nd2O3 were characterized by thermoꢀgravimetric analysis (TGA), Xꢀray diffraction (XRD),
energy dispersive Xꢀray microanalysis (EDX), UV–vis diffuse reflectance spectroscopy, field emission scanning electron microscopy
(FESEM), transmission electron microscopy (TEM), Fourier transform infrared (FTꢀIR) spectroscopy. The obtained results demonstrated
that the amount of SDS play key role in the morphology and particle size controlling of the neodymium oxide. Furthermore, the catalytic
properties of the asꢀprepared nanostructures were evaluated by the photocatalytic degradation of the erythrosine (anionic dye) as water
15 contaminant.
Experimental
Introduction
55 Materials
In recent years, the preparation and characterization of the
nanostructured materials has drawn much attention owing to their
potential applications in various fields as well as excellent and
20 unique characteristics1ꢀ6. Neodymium oxide (Nd2O3) is well
known as one of the most interesting rare earth metal oxides
In this investigation, all the chemical reagents with analytical
grade including sodium dodecyl sulfate (SDS), methanol, ethyl
acetate, neodymium nitrate (Nd(NO3)3.6H2O), 2ꢀHydroxyꢀ1ꢀ
naphthaldehyde, ethylenediamine, and chloroform, were bought
because of its specific, excellent and unique optical and electrical 60 from Merck Co. and were employed as received.
properties as well as several applications in the thin films,
Preparation
ethanediamine Schiff base compound (L)
of
bis-(2-hydroxy-1-naphthaldehyde)-
luminescent and thermoluminescent materials, advanced
25 materials, protective coatings, photonic and catalysts7ꢀ12. So far,
neodymium oxide has been prepared by the gel combustion13,
microemulsion14, hydrothermal15, thermal decomposition16,
solutionꢀcoprecipitation17 and hydrogen plasmaꢀmetal reaction18.
The development of a reliable and simple way for preparation of
30 nanostructured Nd2O3 is of great importance to the potential
investigation of its characteristics. It has been reported that
particle size and shape have key impact on the characteristics of
nanoscale materials19,20. So, exploring desirable and appropriate
ways to produce nanostructured Nd2O3 and controlling its
35 morphology and particle size seems necessary and noteworthy.
In order to synthesize of Schiff base compound (L), 0.16 mol of
2ꢀhydroxyꢀ1ꢀnaphthaldehyde dissolved in methanol (80 ml) was
65 added dropꢀwise to an ethanediamine solution (0.08 mol) in 80
ml of methanol. The mixture was refluxed for 3 h. The yellow
precipitate was separated by filtration, washed and airꢀdried. It
was then recrystallized from methanol. The asꢀsynthesized
compound was characterized utilizing FTꢀIR and1HꢀNMR
70 techniques.
Preparation of the neodymium precursor
In order to synthesize of the neodymium precursor, 1 mmol
neodymium nitrate was dissolved in 20 ml ethyl acetate and then
was dropꢀwise to a solution of 1 mmol compound L in 20 ml
75 chloroform. The mixture was stirred for 2 h. Then, the yellow
precipitate was filtered, washed with ethyl acetate and chloroform
for three times, and after that airꢀdried for 24 h at room
temperature. The resulting neodymium precursor was
characterized utilizing FTꢀIR technique.
The thermal decomposition of the organometallic molecular
way is generally accepted as cost effective, versatile, convenient,
applicable, reliable and simple synthetic technique. This way
does not need special apparatus, complicated approaches and
40 severe reaction conditions, which can restrict the largeꢀscale
production of the nanomaterials. Furthermore, this procedure
provides effective and desirable method to the production of pure
nanostructured materials with uniform morphology.
Herein, we present a novel simple way for the synthesis of pure
45 nanostructured Nd2O3 via the thermal treatment of powder, which
is prepared by a solventꢀfree solidꢀstate reaction from [Nd
80
Preparation of Nd2O3 micro/nanostructures
Neodymium precursor (NP) and SDS were mixed and ground
for 15 min in an agate mortar at room temperature in a NP to SDS
molar ratio of 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5 and 1:6. The
85 identification of the resulting powders was based on Fourier
transform (FTꢀIR) spectrometer. Nd2O3 micro/nanostructures
were synthesized by subjecting 0.12 g of the asꢀobtained powders
L(NO3)2]NO3 (L
=
bisꢀ( 2ꢀhydroxyꢀ1ꢀnaphthaldehyde)ꢀ
ethanediamine Schiff base compound), as new precursor, in
presence of sodium dodecyl sulfate (SDS) as shapeꢀ and sizeꢀ
50 controller. Furthermore, the influence of the amount of the SDS
on the particle size and shape of Nd2O3 via a facile thermal
decomposition way is studied.
°
to heat treatment at (900 C) in the air. An average temperature
increase of 30 °C is recorded every minute, before the

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temperature reached 900 °C, and after keeping the thermal
treatment at 900 C for 5 h, it was allowed to cool to room
Table. 1 Preparation conditions of Nd2O3 micro/nanostructures.
°
Molar ratio
of
neodymium
source/SDS
Figure
of
FESEM
images
temperature. Schematic diagram of preparation of Nd2O3
micro/nanostructures is depicted in Scheme 1. To investigate the
influence of calcination temperature, the thermal treatment
process of the asꢀobtained powder (1:1 molar ratio of NP to SDS)
Calcination
temperature
(°C)
Sample
No.
Neodymium
source
5
1
2
3
4
5
6
7
8
Nd(III)complex
Nd(III)complex
Nd(III)complex
Nd(III)complex
Nd(III)complex
Nd(III)complex
Nd(III)complex
Nd(III)complex
1:1
1:1
700
800
900
900
900
900
900
900
ꢀ
°
was carried out in the 700, 800 and 900 C. In order to examine
the effect of SDS, a blank test was performed. In the blank test,
ꢀ
°
0.12 g of NP was subjected to heat treatment at (900 C) in the
10 air. To investigate the influence of L, one experiment was carried
out without L (blank test1). The preparation conditions of all
products were demonstrated in Table 1. The asꢀobtained
nanostructured Nd2O3 was characterized by TEM, XRD, EDS,
UV–vis, FESEM, FTꢀIR analyses.
1:1
6b
6a
6c
7a
7b
7c
1:0.5
1:2
1:3
1:4
1:5
9
Nd(III)complex
Nd(III)complex
Nd(NO3)3.6H2O
1:6
ꢀ
900
900
900
8a and b
10a
10a
11b
1:1
10b
a Blank test, in the absence of SDS
b Blank test 1
45
solution. A quartz photocatalytic reactor was employed to carry
out the photodegradation reaction. The photocatalytic degradation
was performed by employing 0.003 gr of erythrosine solution
including 0.05 g of asꢀobtained nanostructured Nd2O3 at room
50 temperature. For reaching adsorption equilibrium, this mixture
was aerated for 30 min. Later, the mixture was placed inside the
photoreactor in which the vessel was 40 cm away from the UV
source of 400 W mercury lamps. In order to hinder UV leakage,
the light source and quartz vessel were placed inside a black box
55 that equipped with a fan. Aliquots of the mixture were taken at
definite interval of times during the illumination, and after
centrifugation they were analyzed by a UV–vis spectrometer. The
erythrosine photocatalytic degradation percentage was calculated
as follow:
15
Scheme. 1 Schematic diagram of the preparation of neodymium oxide
micro/nanostructures.
Characterization
20 The electronic spectra of the nanostructured Nd2O3 were
obtained on a Scinco UV–vis scanning spectrometer (Model Sꢀ
4100). Powder Xꢀray diffraction (XRD) patterns of products were
60
collected with
a diffractometer of Philips Company with
X’PertPro monochromatized Cu Ka radiation (l = 1.54 Å). The
25 energy dispersive spectrometry (EDS) analysis was performed by
XL30, Philips microscope. Thermogravimetricꢀdifferential
thermal analysis (TGꢀDTA) was carried out by a thermal
gravimetric analysis instrument (Shimadzu TGAꢀ50H) with a
where Ct and C0 are the concentration of erythrosine at t and 0
min, respectively.
65 Results and discussion
°
flow rate of 20.0 ml minꢀ1 and a heating rate of 10 C minꢀ1.
As described before, in this study the bisꢀ(2ꢀhydroxyꢀ1ꢀ
naphthaldehyde)ꢀethanediamine Schiff base compound (L) was
firstly synthesized, to be employed in the preparation of
nanostructured Nd2O3. For ensuring an adequate purity of the
30 Fourier transform infrared spectra were recorded by utilizing a
MagnaꢀIR, spectrometer 550 Nicolet in KBr pellets in the range
of 400–4000 cmꢀ1. The microscopic morphology of Nd2O3 was
visualized by a Tescan mira3 field emission scanning electron
microscope (FESEM). Transmission electron microscope (TEM)
35 images of nanostructured Nd2O3 were taken by a JEMꢀ2100 with
an accelerating voltage of 200 kV equipped with a high resolution
CCD Camera.
1
70 obtained (L), FTꢀIR and HꢀNMR analyses were performed. The
FTꢀIR spectrum of the Schiff base compound is illustrated in Fig.
1a. Two absorption bands located at 1644 and 1359 cm−1 can be
ascribed to the ν(C=N) of the azomethines and ν(ArꢀO) of the
phenolic hydroxyl substituent, respectively. Fig. 2a reveals the
1
75 1HꢀNMR spectrum of the prepared (L) compound. HꢀNMR data
Photocatalytic test
The photocatalytic activity of asꢀprepared nanostructured
40 Nd2O3 (sample no.3) was studied by monitoring the
photodegradation of erythrosine as anionic dye in an aqueous
of the asꢀsynthesized Schiff base compound (DMSO, δ, ppm): 2.3
(s, 4H, 2 × CH2), 6.7 (s, 1H, CH aromatic), 7.4 (s, 1H, CH
aromatic), 7.6 (s, 1H, CH aromatic), 7.66 (s, 1H, CH aromatic),
2

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7.69 (s, 1H, CH aromatic), 8.29 (s, 1H, CH aromatic), 9.06 (s,
1H, CH), and 14.04 (s, 1H, OH). As observed, the results of the
FTꢀIR and 1HꢀNMR analyses illustrated the high purity of the asꢀ
prepared Schiff base compound.
5
Fig. 1bꢀd exhibits the infrared spectra of asꢀsynthesized NP, NP
in presence of SDS and nanostructured Nd2O3, respectively. Two
absorption bands seen at 1634 and 1353 cm−1 can be ascribed to
the ν(C=N) of the azomethines and ν(ArꢀO) of the phenolic
1
25 Fig. 2 HꢀNMR spectra of the (a) Schiff base compound (L), (b) NP and
(c) the UV–vis absorption spectra of the Schiff base compound (L) and
NP.
In comparison with the free (L) compound, the ν(C=N) band in
30 the NP shifted to 1634 cm−1. This seen blue shift (10 cm−1)
indicates a stronger double bond characteristic of the iminic
bonds as well as contribution of the azomethines nitrogen atoms
in the coordination16. This result was additional confirmed by
employing the absorption band seen at 500 cm−1 (Fig. 1b) which
35 might be related to ν(Nd–N) vibration. The different coordination
modes of the nitrate groups to the neodymium metal were
detected by the differences in the two seen bands |ν4 − ν1|. Several
peaks seen at 1479 cm−1 (ν1), 1032 cm−1 (ν2), 843 cm−1 (ν3) and
1311 cm−1 (ν4) in the FTꢀIR spectrum of the NP (Fig. 1b) can be
40 ascribed to the coordinated nitrate ions. The difference between
10
Fig. 1 FTꢀIR spectra of (a) Schiff base compound, (b) neodymium
precursor, (c) neodymium precursor in presence of SDS and (d)
nanostructured Nd2O3 obtained from 1:1 molar ratio of SDS to
neodymium precursor by thermal treatment at 900 °C for 5 h.
hydroxyl substituent, respectively. The FTꢀIR spectrum of NP
15 illustrates the (L) compound characteristic peaks with several
different shifts due to the complex formation. The FTꢀIR
spectrum of the NP reveals (Fig. 1b) an increase in the C–O
stretching frequency (10 cm−1) compared to the free (L) Schiff
base compound. This demonstrates that the coordination to the
20 neodymium ion happens via the oxygen atoms of the hydroxyl
benzene of the asꢀsynthesized (L) Schiff base compound. This
was additional indicated by employing the absorption band seen
at 470 cm−1 (Fig. 1b) which may be related to ν(Nd–O) vibration.
−
ν4 and ν1 is nearly 168 cm−1 illustrating that the coordinated NO3
ions in the asꢀprepared NP may play a bidentate compound role18.
In the spectrum of the asꢀobtained NP, the (νo) free nitrate seen at
1382 cm−1. In the spectrum of the asꢀobtained powder (NP in
3

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presence of SDS), the characteristic peaks of SDS seen at 2920,
preparation of Nd2O3.
2852, 1220 and 1076 cmꢀ1 (Fig. 1c). In the FTꢀIR spectrum of the
asꢀsynthesized nanostructured Nd2O3, the peaks observed at 3441
and 1645 cmꢀ1 ascribed to the v(OH) stretching and bending
vibrations, respectively, which illustrates the presence of
physisorbed water molecules linked to asꢀsynthesized
nanostructured Nd2O321. The characteristic bands of the Nd2O3
seen at 619 and 512 cmꢀ1 (Fig. 1d).22 1HꢀNMR analysis results
shown in Fig. 2a and b confirms the formation of the NP.
5
10 The UV–vis absorption spectra of the Schiff base compound
(L) and NP were performed in DMF solvent (Fig. 2c). The values
of the maximum absorption wavelength (λmax) and the absorbance
are listed in Table 2. The absorption spectrum of the Schiff base
compound (L) shows four absorption peaks located at λmax 361,
15 381, 400 and 426 nm. The two peaks locating at low energy side
can be ascribed to n→π* transitions of conjugation between the
lone pair of electrons of p orbital of Nꢀatom in C=N group and a
conjugated π bond of phenyl and naphthyl rings. The two peaks
locating at higher energy arise from π→π* transitions within the
20 phenyl and naphthyl rings and the π→π* of the C=N group. UV–
vis spectrum of the NP is different from that of Schiff base
compound (L) demonstrating the coordination of the Schiff base
compound (L) to the Nd(III) ions. Upon the coordination, the two
higher energy absorption peaks of the NP are shifted to longer
25 wavelength region (red shift) compared to those of the free Schiff
base compound (L). The two lower energy peaks in the free
Schiff base compound (L) are overlapped in a single peak and
shifted to shorter wavelength (blue shift). This shift can be
ascribed to the donation lone pair of electrons from the Schiff
30 base compound Nꢀatoms to the Nd(III) ions (Nd→Ln)23. As
demonstrated, FTꢀIR, 1HꢀNMR and UV–vis analysis results
confirm L and NP preparation.
50
Fig. 3 TGA of the neodymium precursor.
XRD technique, which is generally accepted as applicable
technique for determination of the crystal structure, was utilized
55 to investigate the composition and purity of the asꢀsynthesized
Nd2O3 (Fig. 4 and Table 3). The XRD pattern of products
°
obtained at 700, 800 and 900 C for 5 h (sample nos. 1ꢀ3) are
illustrated in Fig. 4aꢀc. XRD results demonstrate that the products
prepared through calcination at 700 and 800 C consist of the
°
60 cubic Nd2O3 that the pure hexagonal Nd2O3 has not been
synthesized (Fig. 4a and b). By increasing the temperature, pure
hexagonal Nd2O3 has been obtained. All diffraction peaks
observed in the Fig 4c can be readily indexed to the pure
hexagonal phase of Nd2O3 (JCPDS Card file no. 74ꢀ2139).
65 Utilizing Scherrer formula24, the crystallite size of the obtained
Nd2O3 from the XRD results was calculated to be about 32 nm.
Therefore, pure hexagonal Nd2O3 can be synthesized by calcining
the prepared powder (1:1 molar ratio of NP to SDS) at 900 °C.
The chemical composition and purity of the asꢀsynthesized
70 nanostructured Nd2O3 (sample no.3) were additional examined by
EDS technique. The illustrated bands in Fig. 5 related to Nd and
O. So, the prepared XRD and EDS results demonstrate that
hexagonal nanostructured Nd2O3 with high level of purity was
successfully produced by the present way.
Table. 2 The UV–vis absorption peaks (λmax) and absorbance (Abs.) of Schiff base
35 compound (L) and NP in DMF solution.
Band
assignments
Compound.
λmax (nm)
Abs.
361
400
426
381
1.529
1.933
1.687
1.873
π→π*
π→π*
π→π*
n→π*
π →π*
n→π*
π→π*
L
412
425
381
2.169
1.943
2.000
NP
75 As mentioned before, in this resaerch, nanostructured Nd2O3
was synthesized by employing [Nd L(NO3)2]NO3 (L = bisꢀ( 2ꢀ
…In order to study the thermal observation of the asꢀprepared
NP, thermal gravimetric technique (TGA) was employed. Fig. 3
40 reveals the TGA curve of the asꢀobtained NP. As illustrated in
Fig. 3, the weight loss steps are two. The first weight losses takes
place in the temperature range 200–380 °C, and displays 27.73 %
weight loss, which corresponds to the loss of two and one nitrate
species from the inner and the outer coordination sphere of the
45 asꢀsynthesized NP, respectively. The second step takes place at
the temperature range 380–850 °C (illustrating 42 % weight loss),
which may be attributed to the loss of the (L) compound from the
inner coordination sphere of the asꢀprepared NP, and the
hydroxyꢀ1ꢀnaphthaldehyde)ꢀethanediamine
Schiff
base
compound), as NP in presence of SDS as capping agent via a new
simple way. In order to examine the effect of the amount of SDS
80 on the size and morphology of the Nd2O3, FESEM images of
obtained Nd2O3 micro/nanostructures with SDS:NP molar ratio of
0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1 and 6:1 (Table 1) were taken and
illustrated in Fig. 6, 7 and 8, respectively. It can be seen that by
employing molar ratio of 0.5:1 (SDS to NP), the nanoparticles
85 were not form well (Fig. 6a). Therefore, in order to reduce the
amount of aggregate and contribute to the formation of
nanostructured Nd2O3 greater amount of SDS was added. Fig. 6b
4

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illustrated that uniform spherical nanoparticles are obtained in the
presence of 1 mmol of SDS. When 2:1, 3:1 and 4:1 molar ratio of
SDS:NP were employed, nanostructures composed of
nanobundles and rodꢀlike nanostructures as well as nanobundles
(Scheme 2a) and induce the nanoparticles to assemble in the
definite directions, and so rodꢀlike nanostructures, nanobundles,
nanorods, corrugatedꢀlike and scalesꢀlike nanostructures were
prepared, respectively. Therefore the molar ratio of SDS:NP has a
5
and nanorods were obtained (Fig. 6c and 7a and b). By increasing 30 significant impact on the morphology and particle size control of
the mmol of SDS from 2 to 3, the amount of the rodꢀlike
nanostructures increased.
the Nd2O3.
Fig. 5 EDS pattern of nanostructured Nd2O3 obtained from 1:1 molar ratio
35 of SDS to NP by thermal treatment at 900 °C for 5 h.
In order to investigate the detailed particle size and morphology
of the asꢀprepared nanostructured Nd2O3, TEM technique was
utilized. The typical TEM images of the nanostructured Nd2O3 in
40 a molar ratio 1:1 (SDS to NP) is illustrated in Fig. 9aꢀd. The TEM
images of the Nd2O3 demonstrate that nanoparticles with quasiꢀ
sphereꢀlike morphology are sintered together. Furthermore, the
images indicate that asꢀobtained Nd2O3 nanoparticles have
diameter in the range of 20ꢀ55 nm.
10 Fig. 4 XRD pattern of products obtained by thermal treatment of powder
in 1:1 molar ratio of SDS to NP at (a) 700, (b) 800 and (c) 900 °C for 5 h.
Table. 3 Preparation conditions and corresponding products.
45
To examine the effect of the SDS on the morphology of the
Nd2O3, sample no. 10 was synthesized as blank product
withoututilizing any SDS. Fig. 10a reveals FESEM image of
sample no. 10. It can be observed that in the absence of SDS,
50 high agglomerated particleꢀlike and bulk structures were
obtained. This result indicates that employing SDS with high
steric hindrance effect led to synthesize nanostructured Nd2O3.
SDS as capping agent limits the size of the Nd2O3 nanoparticles
and protects them from additional aggregation.
Calcination
temperature
(°C)
Composition of
the products
(XRD result)
Sample No.
1
Hexagonal
Nd2O3+ Cubic
Nd2O3
Hexagonal
Nd2O3+ Cubic
Nd2O3
700
2
3
800
900
Hexagonal
Nd2O3
55
In order to investigate the effect of the neodymium source on
the shape of the Nd2O3, sample no. 11 was prepared as blank 1
product with employing Nd(NO3)3.6H2O in the presence of the
SDS. FESEM image of the sample no. 9 is illustrated in Fig. 10 b
60 and c. It is noteworthy that bulk structures were formed. The bisꢀ
(2ꢀhydroxyꢀ1ꢀnaphthaldehyde)ꢀethanediamine compound with
high steric hindrance influence in [Nd L(NO3)2]NO3, can act as a
coꢀcapping agent. Obviously, employing [Nd L(NO3)2]NO3 as
neodymium source in the presence of the SDS results in
65 nanostructured Nd2O3 preparation (Fig. 6, 7 and 8). Therefore, a
privilege of employing [Nd L(NO3)2]NO3 in the presence of the
SDS is that it cause to formed nanostructured Nd2O3.
15 When 5 and 6 mmol of SDS were employed, corrugatedꢀlike and
scalesꢀlike nanostructures were obtained (Fig. 7c and 8a and b). It
seems that when the amount of SDS from 0.5 to 1 mmol
increases, the uniform and sphereꢀlike Nd2O3 nanoparticles forms
and also the particle size decreases with decreasing NP to SDS
20 molar ratio (Scheme 2b). It seems that when the amount of the
SDS increases, the aggregation between Nd2O3 nanoparticles
decreases and also nucleation to be taken place rather than the
particle growth owing to the steric hindrance influence of SDS.
By increasing the mmol of SDS from 2 to 6, the SDS as capping
25 agent can provide the different reaction interfaces for NP
5

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5
Fig. 7 FESEM images of the samples obtained from (a) 3:1, (b) 4:1, and
(c) 5:1 molar ratios of SDS to NP, by thermal treatment at 900 °C for 5 h.
Fig. 6 FESEM images of the products prepared from (a) 0.5:1, (b) 1:1,
and (c) 2:1 molar ratios of SDS to NP, by thermal treatment at 900 °C for
5 h.
6

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a blue shift compared with the reported band gap amount of
Nd2O3 in previous literatures29 which this blue shift is attributable
to decrease in the grain size which cause alteration in particle
25 energy levels and increase the band gap amount.
Fig. 8 FESEM images of the product prepared from 6:1 molar ratio of
SDS to NP, by thermal treatment at 900 °C for 5 h.
5
It has been reported that the band gap (Eg) has a main impact
on the determining the nanostructured materials characteristics
utilized in photocatalytic applications and is oftentimes calculated
from the UV–vis diffuse reflectance data. The UV–vis diffuse
reflectance spectrum of the nanostructured Nd2O3 in a molar ratio
10 1:1 (SDS to NP) demonstrated in Fig. 11a. In the UV–vis diffuse
reflectance spectrum of the asꢀprepared nanostructured Nd2O3
(Fig. 11a), the eight absorption bands (located at 434, 470, 532,
594, 612, 686, 756 and 800 nm) are ascribed to charge transition
4
from I9/2 to 2G9/2+2D3/2+4G11/2+2K15/2
,
4G9/2+4G7/2+2K13/2
,
,
15 G5/2+2G7/2
,
2H11/2
,
4F9/2
,
4F7/2+4S3/2
,
4F5/2+2H9/2 and F3/2
4
4
respectively22. The Eg can be determined based on the UV–vis
diffuse reflectance data employing Tauc’s equation25,26. The
energy gap of the nanostructured Nd2O3 has been calculated by
extrapolating the linear portion of the plot of (αhν)2 against hν to
20 the zero27,28 (Fig. 11b). The Eg amount of the asꢀsynthesized
nanostructured Nd2O3 calculated to be 5.12 eV, which illustrated
Scheme. 2 Schematic diagram showing (a) the effect of the amount of
30 SDS on the reaction interfaces for NP and (b) the formation of
neodymium oxideproducts at various conditions.
7

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RSC Advances
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DOI: 10.1039/C5RA08394J
.
.
ꢀ
20 OH + O2 + anionic dye → Photodegradation products
According to photocatalytic calculations by Eq. (1), the
erythrosine degradation was about 78 and 56 % over sample nos.
Fig. 9 TEM images of nanostructured Nd2O3 obtained from 1:1 molar
ratio of SDS to NP, by thermal treatment at 900 °C for 5 h.
5
The influence of morphology on photocatalytic activity was
studied by monitoring the photodegradation of the erythrosine as
anionic dye in an aqueous solution over asꢀprepared sample nos.
3 (Nd2O3 obtained from 1:1 molar ratio of SDS to NP) and 10
10 (prepared in the absence of Schiff base compound) with different
morphology under UV light illumination (Fig. 12, Scheme 3). No
erythrosine was practically broken down after 120 min without
using UV light illumination or Nd2O3. This observation indicated
that the contribution of selfꢀdegradation was insignificant. The
15 possible mechanism of the photodegradation of the anionic dye
may be summarized as follows:
25
Fig. 10 FESEM images of Nd2O3 prepared in the absence of (a) SDS and
(b and c) Schiff base compound.
Nd2O3 + hν → Nd2O3* + e− + h+
.
h+ + H2O → OH
.
ꢀ
e− + O2 →•O2
8

RSC Advances
Page 10 of 11
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DOI: 10.1039/C5RA08394J
Fig. 12 Photocatalytic erythrosine degradation of sample nos. 3 and 10
30 under UV light.
Fig. 11 UV–vis diffuse reflectance spectrum (a) and plot to determine the
band gap (b) of the nanostructured Nd2O3 obtained from 1:1 molar ratio
of SDS to NP, by thermal treatment at 900 °C for 5 h.
Scheme. 3 Reaction mechanism of erythrosine photodegradation over
Nd2O3 under UV light illumination.
35
5
3 and 10, respectively, after 120 min illumination of UV light,
and Nd2O3 with uniform spherical morphology demonstrated high
photocatalytic activity. It is well known that the heterogeneous
Table. 4 Characterization comparison of Nd2O3 with other works.
Calcination
Morphology,
Size (nm)
Method
Precursors
temperature
Ref.
(°C)
10 photocatalytic processes comprise the diffusion, adsorption and
reaction steps, and the desirable distribution of the pore is helpful
and advantageous to diffusion of reactants and products, which
prefer the photocatalytic reaction. In this research, the enhanced
photocatalytic activity of sample no. 3 with uniform spherical
15 morphology can be related to desirable distribution of the pore,
high hydroxyl amount and high separation rate of charge
carriers30.
[NdL(NO3)2]NO
3 (L = bisꢀ( 2ꢀ
hydroxyꢀ1ꢀ
naphthaldehyde)
ꢀethanediamine,
SDS
Thermal
treatment
Sphereꢀlike,
20ꢀ55 nm
900
This work
Nearly
spherical,
200ꢀ3000 nm
Irregular
shapes, 300ꢀ
1000 nm
Thermal
treatment
Neodymium
tartrate
800
950
[31]
[13]
Nd(NO3)3.5.2HO
, Na2C2O4,
Thermal
decomposition
PEG400
Nꢀbutanol, nꢀ
octane,
In this study, we described a new way to prepare nanostructured
20 Nd2O3 with the aid of [Nd L(NO3)2]NO3 (L = bisꢀ( 2ꢀhydroxyꢀ1ꢀ
naphthaldehyde)ꢀethanediamine Schiff base compound), as
neodymium source, in presence of sodium dodecyl sulfate (SDS)
as capping agent. The novelty of this research compared to other
reports is that for the preparation of Nd2O3, [Nd L(NO3)2]NO3 as
25 new neodymium source in presence of SDS were used. The bisꢀ
(2ꢀhydroxyꢀ1ꢀnaphthaldehyde)ꢀethanediamine compound with
high steric hindrance influence in [Nd L(NO3)2]NO3, can act as a
Nd(NO3)3,
Nd(NO3)3,
CTAB, (needed
stirring for 24
h)
Spherical,
40–80nm
Microemulsion
Combustion
900
900
[12]
[32]
Nd(NO3)3
oxalyl
,
Spherical,
20ꢀ100 nm.
dihydrazide
9

Page 11 of 11
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DOI: 10.1039/C5RA08394J
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smallest size and narrowest size distributions.
5
18 K. Binnemans, Y.G. Galyametdinov, R. Van Deun, D.W. Bruce,
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10 via the thermal treatment of the powder, which was obtained by a
solventꢀfree solidꢀstate reaction from [Nd L(NO3)2]NO3 (L = bisꢀ(
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dodecyl sulfate (SDS) as capping agent. Employing of [Nd
15 L(NO3)2]NO3 as a neodymium source in presence of SDS is the
novelty of this research. When asꢀsynthesized nanostructured
Nd2O3 was employed as photocatalyst, the percentage of
erythrosine photodegradation was about 78 after 120 min
illumination of UV light. This result suggests that asꢀobtained
20 nanostructured Nd2O3 as desirable material has high potential to
be employed for photocatalytic applications under UV light. High
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and FTꢀIR techniques. The optical characteristics of asꢀformed
Nd2O3 were also investigated.
80
90
25
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Acknowledgment
The authors are grateful to University of Kashan for supporting
this work by Grant No. (159271/20).
.
30
Notes and references
100
Institute of Nano Science and Nano Technology, University of Kashan,
Kashan, P.O. Box 87317ꢀ51167, I.R. Iran
35 *Corresponding author: Tel.: +98 31 5591 2383, Fax: +98 31 5555 29
30. Eꢀmail address: Salavati@kashanu.ac.ir
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