TiO2/polymeric supported silver nanoparticles applied as superior nanocatalyst in reduction reactions

Article abstract of DOI:10.1016/j.materresbull.2017.02.004

A novel polymeric nanocomposites (TiO₂/poly(acrylamide-co-methylenbisacrylamide)) decorated with silver nanoparticles (Ag NPs) denoted as (Ag–TiO₂/poly(AM-co-MBAM)) was prepared and fully characterized. Initially, the surface of TiO<

Full text of DOI:10.1016/j.materresbull.2017.02.004

Accepted Manuscript
Title: TiO2/polymeric Supported Silver Nanoparticles Applied
as Superior Nanocatalyst in Reduction Reactions
Author: Roya Sedghi Shima Asadi Bahareh Heidari Majid M.
Heravi
PII:
S0025-5408(16)32397-2
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.materresbull.2017.02.004
MRB 9145
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Accepted date:
7-12-2016
29-1-2017
4-2-2017
Please cite this article as: R. Sedghi, S.A. B. Heidari, M.M. Heravi,
TiO2/polymeric Supported Silver Nanoparticles Applied as Superior
Nanocatalyst in Reduction Reactions, Materials Research Bulletin (2017),
http://dx.doi.org/10.1016/j.materresbull.2017.02.004
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Highlight
- This study focused on synthesis of tailored bi-magnetic clusters to induce unique magnetic
characteristics for self-bias magnetoelectric (ME) composites.
- The self-bias magentoelectric effect is very promising phenomenon, which can provide a
feasible ME voltage over 50 mV/cmOe under no-applied DC magnetic field.
- Two types of bi-magnetic materials were synthesized with magnetical combinations of
ferromagnetic[FM]/ferrimagnetic[FiM] and ferromagnetic[FM]/antiferromagnetic[AFM] to
induce built-in magnetic bias for large strain change at zero DC magnetic field.
- Size optimizations of clusters (over 100 nm) and primary particles (under 20 nm) were
successfully conducted to enhance effective strain transfer in ME composites and to improve
magnetic properties, respectively.
Page 1 of 18

Hydrothermal Synthesis of Bi-magnetic Clusters for Magnetoelectric Composites
Seon-Min Jang1, M. I. Bichurin2 and Su Chul Yang1,†
1Department of Chemical Engineering, Dong-A University, Hadan 840, Saha-Gu,
Busan 604-701, South Korea.
2Novgorod State University, 41 B.S.-Peterburgskaya, Veliky Novgorod 173003, Russia
Email.scyang@dau.ac.kr
Abstract
Bi-magnetic materials possess unique magnetic characteristics combining hysteretic
and built-in responses for self-bias magnetoelectric applications. In this work, two bi-
magnetic clusters of Co/MFe2O4(M=Co and Zn) were hydrothermally synthesized for relative
comparison of magnetic characteristics between ferromagnetic/ferrimagnetic (Co/CoFe2O4)
and ferromagnetic/antiferromagnetic (Co/ZnFe2O4) complexes. Both bi-magnetic clusters
were found to exhibit clear two-phases with random morphology and average cluster size of
110 nm via physical complexation. Magnetic characteristics of the Co/CoFe2O4 and Co/
ZnFe2O4 illustrated M-H slope of 0.02 emu/g〮Oe at Hdc = 0 Oe with different remanent
magnetization of 15.16 emu/g and 0.22 emu/g, respectively. As a magnetostritive phase in the
magnetoelectric composites, two bi-magnetic clusters were formed with uniform cluster size
for effective strain transfer between magnetostrictive-piezoelectric phases in the
magnetoelectric system.
Keywords: Bi-magnetic, Clusters, Magnetostriction, Self-bias, Magnetoelectric
Page 2 of 18

Introduction
Magnetoelectric effect is one candidate among several promising phenomena for
effective energy harvesting, which can induce an electrical voltage by applying a bias
magnetic field. The magnetoelectric responses were fundamentally obtained by applying a
small AC magnetic field (Hac = 1 Oe) under constant DC magnetic field, which can cause a
reliable electrical displacement with effective strain change in magnetoelectric materials.
Therefore, many research groups have attracted the magnetoelectric effect to develop
potential applications such as transducers, magnetic/electric sensors, memory storage devices
and even medical devices. [1, 2]
In recent, the magnetoelectric materials have been studied with two-phase composites
consisting piezoelectric and magentostrictive materials respectively due to strong
piezoelectricity and magentostriction given by each separated phase. The multi-phase
magnetoelectric composites (PZT/CoFe2O4, BaTiO2/LaxBa1-xMnO4, PZT/Ni/PZT) were
found to exhibit high magnetoelectric coefficients of ~ 500 mV/cm·Oe under a bias magnetic
fields by an optimum complexation of large strain change at magnetostrictive phase and high
piezoelectric property at piezoelectric phase. [2] Further, focused studies on effective strain
transfer at interface between magentostrictive and piezoelectric phases have been performed
for ME enhancement via microstructure investigation, post heat treatment and hardness
control of interfacial rooms respectively in each type of 3-0, 2-2 and 1-3 composite structures.
[3-6]
Even though magnetoelectric voltage improvement have been successfully conducted,
there is still a critical issue to be used in magnetoelectric applications, which is related with a
required driving force of DC magnetic field over 100 Oe. That means the magnetoelectric
responses cannot be obtained due to its non-effective strain change (∆λ/∆Hac) at low DC
Page 3 of 18

magnetic field under 100 Oe even if AC magnetic field was applied with constant magnitude
of Hac = 1 Oe, f = 1 kHz. Yang et al reported a feasible characteristic of self-bias
magnetoelectric effect, which is a remanent magnetoelectric responses under applying AC
magnetic field (Hac = 1 Oe, f = 1 kHz) at zero DC magnetic field. [7] They have revealed that
reliable magnetoelectric responses were existed with meaningful magnetoelectric magnitudes
of 20 mV/cm·Oe from an effective strain change (∆λ/∆Hac ) generated by coupling effect
between structural bending configuration and built-in magnetic bias field (Hbuilt-in). [7-9]
Herein, exchanging bias of adjusting magnetic hysteresis have been developed via applying
graded system between ferromagnetic and antiferromagnetic materials. [10, 11] Moreover,
impact researches on shift of optimum DC magnetic field have been investigated to obtain
feasible magnetoelectric voltage at low DC magnetic field under 100 Oe. [12, 13]
In this study, we have investigated magnetic properties of bi-magentic clusters for self-
bias magnetoelectric applications, which require effective strain changes under a limited
driving condition of small AC magnetic field (∆λ/∆Hac ). The bi-magnetic clusters consisting
antiferromagnetic (AFM), ferromagnetic (FM) and ferrimagnetic (FiM) complexations can
contribute variation of built-in magnetic bias field (Hbuilt-in). Further, particle size of magnetic
cluster with sub-micron (0.1 ~ 0.4 µm) provides an effective transfer of magentostriction into
piezoelectric phase. Therefore, we have hydrothermally synthesized and investigated tailored
bi-magnetic clusters through two compositional combinations of Co[FM]/CoFe2O4[FiM] and
Co[FM]/ZnFe2O4[AFM] as a magnetostrictive phase for self-bias magnetoelectric composites.
Experimental
Synthesis of cobalt nanoparticles: All reagents of Co(NO3)2·6H2O, Ni(NO3)2·6H2O,
Zn(NO3)2·6H2O, Fe(NO3)3·9H2O CoCl2·6H2O, NaBH4, NaOH were purchased from Sigma
Aldrich Inc. Cobalt nanopowders were synthesized at ambient condition via reduction
Page 4 of 18

method. [14] First, 2g CoCl2·6H2O was completely dissolved in 100 ml deionized water and
then 1g NaBH4 was added in the aqueous solution. NaBH4 was added over 5 times owing to
explosive reaction. After hydrogen emission stopped, a gray–black powders were collected
by strong magnet. The powders were washed with deionized water and ethanol for several
times to eliminate other impurities and then were collected by centrifuge at 15000 rpm for 2h.
Finally, the cobalt powders were obtained after drying at 80 for 48h.
Synthesis of bi-magnetic clusters: Bi-magnetic clusters of Co/CoFe2O4 were
synthesized by hydrothermal synthesis. [15] 1mmol Co(NO3)2 · 6H2O and 2mmol
Fe(NO3)3·9H2O were dissolved in 10ml deionized water (molar ratio, Co:Fe = 1:2). Then pH
of the solution was adjusted to pH~12 by drop-wise of 10M during virgours stirring. After
stirring for 1 h, prepared Co powders 0.1178g(2mmol) were added in viscous solution and the
mixed solution was sonicated for 10 min to prevent aggregation. The mixed solution was
sealed in 20ml Teflon lined stainless steel autoclave and heated at 200 for 8h. After
hydrothermal reaction, it was cooled at room temperature. Then the precipitates were washed
with deionized water and ethanol for several times to decrease pH~7. The washed precipitates
were centrifuged and dispersed in ethanol and dried at 80 for 48h. In the same process, bi-
magnetic clusters of Co/ZnFe2O4 were hydrothermally synthesized with molar ratio (Zn : Fe
= 1 : 2).
Characterizations: Crystallinity and crystal structure of the synthesized bi-magenetic
clusters were observed by X-Ray diffraction (XRD; Miniflex600(Cu Kα radiation =
1.5406Å), RIGAKU) analysis. Fe-O bonds in the bi-magenetic clusters were confirmed by
Fourier transform infrared spectra (FTIR; 4600 type A, JASCO) analysis. Primary particle
size andmorphology of the bi-magnetic clusters were investigated by Transmission electron
microscope (TEM; JEM 2010, 200kV, JEOL/Energy-dispersive X-ray spectroscopy, EDS;
Oxford instruments co.) analysis. Average size and size uniformity of the bi-magenetic
Page 5 of 18

clusters were investigated under deionized water as media by dynamic light scattering
measurement (Particle Size Analyzer; PSA, Multiscope, K-ONE). Magnetic properties of two
bi-magenetic clusters were determined at room temperature using vibration sample
magnetometer (VSM; 7404, Lake shore).
Results & Discussion
Crystal structures of Co, Co/CFO and Co/ZFO powders were identified by XRD
patterns shown in Figure 1. XRD peak of the Co particles were observed in a broad region
around 45°, which might be merged from two Co crystal structures confirmed by face
centered cubic (111) at 38o and hexagonal close packed (101) at 47o (fcc Co, PDF Card No.:
00-015-0806, JCPDS and hcp Co, PDF Card No.: 01-089-4308, JCPDS). [14] The two bi-
magnetic clusters of Co/CFO and Co/ZFO were found to exhibit 1st peak (311), 2nd peak
(440) and 3rd peak (220) (CoFe2O4, PDF Card No.: 01-079-1744, JCPDS and ZnFe2O4, PDF
Card No.: 01-077-0011, JCPDS) corresponding to spinel structure. Even though the bi-
magnetic clusters include Co particles, Co peak disappeared in Fig 1 (b) and (c) due to its low
crystallinity.
FT-IR analysis between 400 and 4000 cm-1 was conducted to confirm chemical or
physical bonding between magnetostrictive phases in the two clusters of Co/CFO and
Co/ZFO as shown in Figure 2. Since the spinel structure is normally composed of two site
with tetrahedral and octahedral site, it is unambiguously observed two peaks of divided into
Fe-O, Metal-O bands due to their different vibration bands. [16] The most important peaks
are strong Fe-O band of symmetrical stretching vibration at tetrahedral site 579cm-1 and
586cm-1 in Co/CFO(blue line) and Co/ZFO(green line), respectively. All broad peaks at 3396,
3401, 3423 cm-1 are O-H stretching vibrations. The peaks at 2921cm-1, 1631 cm-1, 1384 cm-
1and 1068 cm-1 indicate sp3C-H stretch, C=O stretch, C-H bend, C-O bonding, respectively.
Page 6 of 18

Primary particle size and morphology of the synthesized Co, Co/CFO and Co/ZFO
powders were investigated by TEM analysis. Figure 3 (a) and (b) illustrates that the as-
prepared Co particles were found to exhibit particle size of 20 ~ 80 nm with weak selected
area electron diffraction (SAED) image related to its low crystallinity. EDS analysis shown in
Figure 3 (c) exactly described that the as-prepared Co particles were consist of pure Co ions
without any impurities. The hydrothermally synthesized bi-magnetic clusters of Co/CFO and
Co/ZFO were found to exhibit no impurities, random morphology as a cluster and spinel
crystal structure with clear ring SAED patterns of (311), (440) and (220) as shown in Figure 3
(d) ~ (i). Table 1 illustrates that Co, CFO and ZFO after hydrothermal synthesis for bi-
magnetic clusters were found to exhibit average primary particle sizes of 45 nm (standard
deviation 19 nm), 16 nm (standard deviation 4 nm) and 9 nm (standard deviation 4 nm)
respectively but average cluster size cannot be measured due to its local scope region.
Dynamic light scattering measurement was performed under deionized water as media
to observe average cluster size of the synthesized Co/CFO and Co/ZFO clusters. It was
inferred that Co/CFO and Co/ZFO clusters have sufficient stability in deionized water
illustrating reliable results of average size and size distribution during dynamic light
scattering measurement for 30 minute. Figure 4 shows that average cluster sizes of Co/CFO
and Co/ZFO bi-magnetic clusters were found to exhibit cluster size of 110 nm, which is
smaller than 121 nm of Co particles. The reason might be that the Co particles have
aggregated form due to its stronger attraction of metallic natures in deionized water compared
with mixed bi-magnetic clusters of Co/CFO and Co/ZFO.As shown in figure 4 (b) and 4 (c),
it was described that the Co/ZFO bi-magnetic clusters have narrow size distribution with
suppressed particle aggregation over 1µm size compared with the Co/CFO clusters. That is
very important roles for effective magnetoelectric composites because micron-sized magnetic
particles disturb effective magnetoelectric coupling between piezoelectric and
Page 7 of 18

magnetostrictive phases. [17]
Magnetic properties of bi-magnetic clusters were investigated by VSM analysis. From
the Figure 5, highlight point for self-bias magnetoelectric effect is a sharp slope(∆M/∆H) at
Hdc = 0 Oe, which induces strong deformation from bi-magnetic materials under only
applying Hac = 1 Oe, f = 1 kHz.[18] That makes a large strain change transferring to
piezoelectric phase, which directly related to root ∆λ/∆H inducing self-bias magnetoelectric
effect. The Co/CFO [FM/FiM] and Co/ZFO [FM/AFM] bi-magnetic clusters possess M-H
slope of 0.02 emu/g∙Oe at Hdc = 0 Oe with remanent magnetization of 15.16 emu/g and 0.22
emu/g, respectively. In order to induce self-bias magnetostriction from magnetoelectric
composites, bending configuration will be required due to shifting strain-stress curve to make
asymmetric strain. Hence, the synthesized bi-magnetic clusters are very promising candidates
for self-bias magnetostriction for magnetoelectric applications.
Conclusion
In this study, two bi-magnetic clusters of Co/CFO [FM/FiM] and Co/ZFO [FM/AFM]
were hydrothermally synthesized as a magnetostrictive phase for self-bias magnetoelectric
composites. The bi-magnetic clusters were found to exhibit clear two-phases with random
morphology by physical complexation. The Co/CFO and Co/ZFO bi-magnetic clusters were
found to exhibit M-H slope of 0.02 emu/g·Oe at Hdc = 0 Oe and different remanent
magnetizations of 15.16 emu/g and 0.22 emu/g, respectively. Both bi-magnetic clusters with
uniform submicron cluster size can be used as magnetostrictive phase in magnetoelectric
composites by inducing effective strain transfer between magnetostrictive-piezoelectric
phases. In particular, high M-H slope at Hdc = 0 Oe in both bi-magnetic clusters can provide a
potential to generate self-bias magnetoelectric effect.
Page 8 of 18

Acknowledgements
This research was supported by Basic Science Research Program through the National
Research Foundation of Korea (NRF) funded by the Ministry of Education
(2016R1C1B1010884). The study of Bichurin M.I. was supported by the Ministry of
Education and Science of the Russian Federation in the framework of the State Order for
Higher Schools (Grant No. 3.1639.2014/K )". The author also would like to thank Dr.
Jungho Ryu at KIMS (Korea Institute of Materials Science) for VSM measurement.
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Fig. 1 X-ray diffraction patterns of (a) as-prepared Co particles, (b) Co/CFO clusters and (c)
Co/ZFO clusters.
Fig. 2 FT-IR spectra of as-prepared Co particles (red), Co/CFO clusters (blue) and Co/ZFO
clusters (green).
Fig. 3 TEM images, SAED patterns and EDS analysis of (a-c) as-prepared Co particles, (d-f)
Co/CFO clusters and (g-i) Co/ZFO clusters.
Fig. 4 Dynamic light scattering analysis of (a) as-prepared Co particles, (b) Co/CFO clusters
and (c) Co/ZFO clusters.
Fig. 5 M-H curves of (a) as-prepared Co particles, (b) Co/CFO clusters and (c) Co/ZFO
clusters.
Table 1 Average, minimum, maximum and standard deviation of crystalline size of as-
prepared Co particles, Co/CFO clusters and Co/ZFO clusters.
Co
CFO
ZFO
Avg. Crystalline Size (nm)
45
16
9
Page 10 of 18

Min. Crystalline Size (nm)
Max. Crystalline Size (nm)
Standard Deviation (nm)
24
77
19
12
17
4
5
10
4
Page 11 of 18

Page 12 of 18

Figure. 1│X-ray diffraction patterns of (a) as-prepared Co particles, (b) Co/CFO clusters and
(c) Co/ZFO clusters.
Figure. 2│FT-IR spectra of as-prepared Co particles (red), Co/CFO clusters (blue) and
Co/ZFO clusters (green).
Page 13 of 18

Figure. 3│TEM images, SAED patterns and EDS analysis of (a-c) as-prepared Co particles,
(d-f) Co/CFO clusters and (g-i) Co/ZFO clusters.
Page 14 of 18

Page 15 of 18

Figure. 4│ Dynamic light scattering analysis of (a) as-prepared Co particles, (b) Co/CFO
clusters and (c) Co/ZFO clusters.
Page 16 of 18

Figure. 5│M-H curves of (a) as-prepared Co particles, (b) Co/CFO clusters and (c) Co/ZFO
clusters.
Page 17 of 18

Page 18 of 18