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SUPPORTING INFORMATION

Synthesis of magnetic cobalt ferrite nanoparticles with controlled

morphology, monodispersity and composition: the influence of solvent,

surfactant, reductant and synthetic condition

Le T. Lua*, Ngo T. Dung

a, Le D. Tung

b, Cao T. Thanh

c, Ong K. Quy

d, Nguyen V. Chuc

c,

Shinya Maenosonoe and Nguyen T. K. Thanh

b*

aInstitute for Tropical Technology -Vietnam Academy of Science and Technology ,18 Hoang Quoc

Viet, Cau Giay, Hanoi, Vietnam. bBiophysics Group, Department of Physics and Astronomy,

University College London, Gower Street, London WC1E 6BT, UK. cInstitute of Materials Science,

Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam.

dInstitute of Materials, Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland.

eSchool of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai,

Nomi, Japan.

Electronic Supplementary Material (ESI) for Nanoscale.This journal is © The Royal Society of Chemistry 2015

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Figure S1: TEM images of the cobalt ferrite NPs synthesised in di-octyl ether with the

precursor ratio Co2+

: Fe3+

= 1 : 2 under equimolar amount of OA/OLA at total concentration

of 248 (a, b) and 620 mM (c,d); and different reaction times: 5 (a,c) and 120 min (b,d). Scale

bar: 200 nm.

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Co: Fe = 1: 1 1.5:1

Figure S2: TEM images of NPs synthesised in dioctyl ether with a total concentration of

equimolar amount of OA and OLA at 240 mM at ratio of Co: Fe = 1: 1 (left ) and 1.5: 1

(right) and different reaction times. Scale bar: 200 nm.

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Figure S3: TEM images of the cobalt ferrite NPs synthesised in the presence of equimolar

amount of OA/OLA at the total concentration of 2.4 M. The starting precursor ratio Co2+

: Fe3+

= 1 : 1.5 and the reaction time is 30 min. Scale bar: 200 nm.

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0 100 200 300 400 500 600 700

-12

-10

-8

-6

-4

-2

0

15 %

TG

(m

g)

T (oC)

Co(acac)2 + Fe(acac)3

52 %

a)

0

20

40

60

80

100

We

igh lo

ss (

%)

0 100 200 300 400 500 600 700

-7

-6

-5

-4

-3

-2

-1

0

+ 1

TG

(m

g)

T (oC)

Co(acac)2 + Fe(acac)3 + OA + OLA

38 %

27 %

b)

0

20

40

60

80

100

We

ight

loss (

%)

Figure S4: TGA measurements: a) metal acetylacetonate compounds (1 Co(acac)2 + 2

Fe(acac)3 and b) metal-acac compounds in the presence of OA and OLA (1 Co (acac)2 + 2

Fe(acac)3 + OA + OLA). [OA] = [OLA] = 310 mM. TGA plots were recorded at a constant

heating rate of 10 oC/min under nitrogen atmosphere.

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Figure S5: TEM images of the cobalt ferrite NPs synthesised in the presence of equimolar

amount of OA/OLA concentration of 372 mM (186 mM each) at different starting precursor

Co2+

: Fe3+

ratios: a) 1: 2, b) 1: 1.5 and 1.5: 1. The reaction time is 60 min. Scale bar: 20 nm.

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a)

0 2 4 6 8 10 12 14 16 18 200

20

40

60

Fre

quency

Particle size (nm)

d = 8.3 nm

stdv = 0.8 nm

n = 241

b)

c)

0 2 4 6 8 10 12 14 16 18 200

20

40

60

Fre

quency

Particle size (nm)

d = 7.5 nm

stdv = 0.8 nm

n = 241

d)

0 5 10 15 20 25 30 350

20

40

60

Fre

qency

Particle size (nm)

d = 18.6 nm

stdv = 1.8

n = 290

e) f)

0 5 10 15 20 25 30 350

20

40

60

Fre

quency

Particles size (nm)

d = 18 nm

stdev = 5.6 nm

n = 247

g) h)

Figure S6: TEM images and size distribution histograms of the NPs synthesised in the

presence of 496 mM OA/OLA (248 mM each) with HDD (a-d) and without (e-h) for 60 min

(a,b,e,f) and 120 min (c,d,g,h). Scale bar: 20 nm.

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0 5 10 15 20 25 30 350

10

20

30

40

50

60

70

80

Fre

quency

Particle size (nm)

d = 10.6 nm

stdev = 2.3 nm

n = 241

a) b)

0 5 10 15 20 25 30 350

10

20

30

40

50

Fre

qu

en

cy

Particle size (nm)

d = 13.5 nm

stdev = 2.6 nm

n = 211

c) d)

Figure S7: TEM images and size distribution histograms of the NPs synthesised in the

absence of HDD and at 372mM OA/OLA (186 mM ecah) (a,b) and 744 mM (372 mM (c,d)

for 60 min. Scale bar: 20 nm.

Figure S8: TEM image of cobalt ferrite NPs synthesised in the presence of sole 620 mM OA

for 30 min. Scale bar: 100 nm

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10 20 30 40 50 60 70

0

20

40

60

80

100

120

2 theta

A2

B2

c2

D2

with OCD-ol

without HDD/OCD-ol

with HDD

with HDD a)

b)

c)

d)

Figure S9: XRD patterns of some cobalt ferrite nanoparticles synthesised under different

synthetic conditions: a,b) in the presence of HDD with 248 mM equimlar OA/OLA for 60

min (a) and 120 min (b); c) in the absence of HDD/OCD-ol and 744 mM OA/OLA (372 mM

each) for 60 min; d) in the presence of OCD-ol and 186 mM OLA for 30 min.

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500 1000 1500 2000 25000

50

100

150

Co: Fe

1: 1

1: 11: 1.51: 1.5

Tb(K

)

Vx 10-26

(m3)

1: 2

a)

500 1000 1500 2000 25000

2

4

6

8

Co: Fe

b)

1: 1

1: 1

1: 1.5

1: 1.5

1: 2

Vx 10-26

(m3)

Kx

10

4 (

J/m

3)

Figure S10: The plot of blocking temperature Tb (a) and magnetocrystalline anistrotropy

constant K of them samples prepared at different Co: Fe ratios (1: 2, 1: 1.5 and 1: 1) vs. the

average volume of the nanoparticles.

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-10000 -5000 0 5000 10000

-60

-40

-20

0

20

40

607.5 nm a)

8.5 nm b)

10.6 nm d)

8.5 nm c)M

s(e

mu

/g)

H (Oe)

Figure S11: Hysteresis curves of CoFe2O4 NPs with different size synthesized under different

reaction conditions: a,b) in the presence of OCD-ol in octadecene with 186 mM OA for 30

min (a) and 248 mM equimlar OA/OLA for 60 min (b); c) the presence of HDD and 124 mM

equimolar OA/OLA for 30 min in dioctyl ether; d) in the absence of HDD/OCD-ol and 248

mM equimolar OA/OLA for 60 min.

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Figure S12: High magnification SEM (a) and TEM images of CNTs grown on the 4.9 nm

cobalt ferrite NPs coated Si/SiO2.

NPs

NPs

NPs

a)

c)

b)