Synthesis of uniform cube shape CuFe₂O₄ nanoparticles by a hydrothermal method

Nghiên cứu khoa học công nghệ

SYNTHESIS OF UNIFORM CUBE SHAPE CuFe₂O₄

NANOPARTICLES BY A HYDROTHERMAL METHOD

LÊ XUÂN DƯƠNG ⁽¹⁾, NGÔ THỊ LAN ⁽¹⁾, NGUYỄN VĂN DUY ⁽¹⁾

1. INTRODUCTION

Magnetic nanoparticles (NPs) have been of great interest because of its

attractive features and wide range of extensive applications in catalyst, adsorption,

and as a supercapacitor electrode [1-3]. The size and shape of NPs determine their

physical and chemical features, which may funtion as a foundation for the

development of new product [4, 5]. As a conventional magnetic material, magnetite

Fe₃O₄and ferrites MFe₂O₄have yielded a great deal of paper featuring mumerous

techniques and nanoparticle morphologies [6, 7].

In a previous report, solvothermal strategy has been widely used to synthesize

many kinds of NPs with uniform size and shape, including monodisperse

nanocrystals and microspheres MFe₂O₄. Controling the shape of NPs is also an

equally improtant aspect of nano synthesis. However, the challenge to synthetically

control the morphology of MFe₂O₄nanostructures with a simple method still remain

up to date [8, 9]. Compared with other ferrites, CuFe₂O₄NPs has attracted more

attention due to its property and application in catalysis for it is inexpensive and

environmental friendly [10, 11]. Additional, CuFe₂O₄NPs can be recovered

conveniently after the reaction by a magnet [12-14].

In this study, monodisperse NPs cube shape CuFe₂O₄were successfully

synthesized through a hydrothermal method. The CuFe₂O₄NPs has a

superparamagnetic and an uniform cube shape structure.

2. EXPERIMENTAL

2.1. Material

Iron(II) sulfate heptahydrate (FeSO₄.7H₂O), oleic acid (OA), ethanol (EtOH),

sodium hydroxide (NaOH), copper sulphate pentahydrate (CuSO₄.5H₂O) were

purchased from Aladdin Chemical Co., Ltd. All the reagents were of analytical

grade and used without further purification, and solution were prepared using de-

ionized water.

2.2. Synthesis of cube shape CuFe₂O₄NPs

In a typical synthesis, 1.5 g NaOH, 15 mL H₂O, 9 ml ethanol, and 15 mL oleic

acid (OA) were mixed together to form an even solution. After stirring for 30 min,

an aqueous solution of 2 mmol FeSO₄.7H₂O (0.56 g) and 1 mmol CuSO₄.5H₂O

(0.25 g) (in 21 mL de-inozed water) was the added. After further stirring for 30 min,

the solution was transferred into an autoclave and kept at 160^oC, 180^oC, 200^oC for

10h, respectively. The system was then allowed to cool to room temperature. The

CuFe₂O₄products were isolated by strong magnetic suction, and washed with

ethanol and deionized water several times [3].

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2.3. Characterization

Powder X-ray diffraction (XRD) spectra were obtained by a Rigaku D/max-

2400 diffractometer using Cu-K radiation in the 2 range of 10-90°. Transmission

electron microscopy (TEM) images were obtained on a Tecnai G2 F30, FEI, USA.

SEM images was collected on a Hitachi S-4800 field emission scanning electron

microscope equipped with a Horiba EMAX energy-dispersive X-ray analyser.

Magnetic measurements of CuFe₂O₄NPs were investigated with a quantum design

vibrating sample magnetometer (VSM) at room temperature in an applied magnetic

field sweeping from -15 to 15 kOe.

3. RESULTS AND DISCUSSION

The morphologies and structural of the synthesized CuFe₂O₄NPs were

analyzed by SEM. As is illustrated in Fig. 1 (a,b and c) with a uniform cube shape,

resulting from a minimized surface energy.

Fig. 1. SEM image of the CuFe₂O₄NPs formed at different temperatures;

(a) 160^oC, (b) 180^oC and (c) 200^oC

We can draw from Fig. 1 that the size of CuFe₂O₄NPs increased with the

increase of reaction temperature.

Fig. 2. TEM image of the CuFe₂O₄NPs formed at different temperatures;

(a) 160^oC, (b) 180^oC and (c) 200^oC

TEM image (Fig. 2) confirms the CuFe₂O₄NPs shape is cube structure. The

particles were well dispersed with a mean particle size of about 50 nm.

The XRD patterns of the CuFe₂O₄NPs is shown in Fig. 3. The XRD pattern

of the CuFe₂O₄NPs shows the characteristic peaks of magnetite NPs. The sharp and

strong peaks confirm that the products are well crystallized. The CuFe₂O₄NPs show

five characteristic diffraction peaks at 2 theta = 30.3^o, 35.6^o, 43.2^o, 57.2^oand 63.0^o

corresponding to (220), (311), (400), (511), and (440), respectively [15].

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From the SEM, TEM and XRD, we can draw conclusions. The reaction

temperature at 180°C is the best condition for synthesized unifrom cube shape

CuFe₂O₄NPs.

Fig. 3. XRD of CuFe₂O₄NPs formed at different temperatures;

(a) 160^oC, (b) 180^oC and (c) 200^oC

Fig. 4 shows the FT-IR spectra of CuFe₂O₄NPs. The IR spectra show main

absorption bands at ∼580 cm⁻¹, corresponding to the the metal oxygen stretching

vibrations of octahedral and tetrahedral ions [15]. The absorption broad band at

∼3400 cm⁻¹represents the stretching mode of H₂O molecules and OH groups. The

band around 1600 cm⁻¹is corresponds to the bending mode of H₂O molecules.

Fig. 4. FT-IR spectra of CuFe₂O₄NPs with reaction temperatures 180^oC

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Fig. 5. Room temperature magnetization curves of the CuFe₂O₄NPs

with reaction temperatures 180^oC

The magnetic measurements were carried out by VSM at room temperature.

The magnetization curves measured for CuFe₂O₄is shown in Fig. 5. The magnetic

saturation values of CuFe₂O₄is 20.5 emu/g. The abovementioned results indicated

an easy and efficient way to separate and recycle the CuFe₂O₄from the solution by

an external magnetic field.

4. CONCLUSION

In summary, CuFe₂O₄NPs which features with superparamagnetic, and cube

shape structure was synthesized by a hydrothermal method. It can also be valuable in

catalyst, medicine, and as supercapacitor electrode, and in nano composite materials.

Acknowledgement: This research is funded by Le Quy Don Technical

University in the regular research projects 2019-2020 under Grant No. 19.1.004.

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SUMMARY

In this study, CuFe₂O₄nanoparticles (NPs) which features with

superparamagnetic, and uniform cube shape structure was synthesized by a

hydrothermal method. The prepared samples were characterized by scanning

electron microscope (SEM), transmission electron microscopy (TEM), vibrating

sample magnetometer (VSM), X-ray powder diffraction (XRD). The CuFe₂O₄NPs

were well dispersed with a mean particle size of about 50 nm. The CuFe₂O₄NPs is

extremely useful for support catalyst in heterogeneous catalysis applications and

adsorption.

Keywords: Cube shape CuFe₂O₄, superparamagnetic, nanoparticles.

Nhận bài ngày 21 tháng 8 năm 2020

Phản biện xong ngày 25 tháng 9 năm 2020

Hoàn thiện ngày 29 tháng 9 năm 2020

⁽¹⁾Faculty of Technical Physics and Chemistry, Le Quy Don Technical University

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