Supporting Information

Soft Template Induced Phase Selective Synthesis of Fe2O3 Nanomagnets: One Step

towards Peroxidase-Mimic Activity Rendering Colorimetric Sensing of Thioglycolic

Acid

Anindita Roy, Ramkrishna Sahoo, Chaiti Ray, Soumen Dutta and Tarasankar Pal*

Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, India

S1. Materials Used:

All chemicals used, are of analytical grade and no further purification has been done before

reaction. Mohr’s salt (Merck) [FeSO4, (NH4)2SO4, 6H2O] is used as precursor salt for the

preparation of Fe2O3 NPs. For the synthesis of Schiff bases; aldehydes used are glyoxal

(CHO-CHO) (40%, SRL) and glutaraldehyde [CHO-(CH2)3-CHO] (25%, Merck), and amines

used are ethylenediamine [(CH2NH2)2] and triethylenetetramine [H2N-C2H4-NH-C2H4-NH-

C2H4-NH2] (SRL). As hydrolysing agent, hydrazine, monohydrate [H2N-NH2, H2O] (80%,

Merck) is employed. Distilled water has been used for the entire procedure. Absolute ethanol

(99.9%, AR grade) has been used. 3,3׳5,5,׳-tetramethylbenzidine (TMB) (SRL), H2O2 (30%) ,

thioglycolic acid (TGA) (Merck) reagents are used of analytical grade.

S2. Instrumentation:

Powder X-Ray diffraction (XRD) was recorded with a SMART APEX II, BRUKER AXS X-

ray diffractometer (40kV, 20 mA) using Cu Kα radiation ((λ = 1.5418 Å) in the range of 5°-

90° at a scanning rate of 0.5° min-1. For analysing the XRD data, JCPDS software guided us.

Fourier transform infrared (FTIR) spectral studies were done in KBr pellets in reflectance

mode with PERKIN ELMER SPECTRUM RX1 (USA), (LASER HeNe nm < 0.4 mW) FTIR

microscope. For the analysis of liquid samples FTIR, NICOLET 6700, THERMOFISHER

Electronic Supplementary Material (ESI) for RSC Advances.This journal is © The Royal Society of Chemistry 2016

SCIENTIFIC INDIA PVT. LMT has been used. Surface morphology was analysed using

field emission scanning electron microscopy (FESEM) with a supra, Carl Zeiss Pvt. Ltd.

High resolution transmission electron microscopy (HRTEM) analysis was done with the help

of JEOL JEM 2100 (JAPAN), Resolution- 1.4 Å, Acceleration VOLT.: 200 kV, Filament:

LaB6. Superconducting quantum interference device (SQUID) magnetometry is carried out in

Evercool MPMS SQUID VSM DC magnetometer device. Dried powder samples (TemFe A,

TemFe B, TemFe C, TemFe D) were transformed into capsule made by Teflon tape and

inserted in a clear brass straw. Zero-field-cooled (ZFC) and field-cooled (FC) were carried

out by cooling the sample at 5-300 K by cycling the magnetic field under 100 Oe magnetic

field. Isothermal magnetisation as a function of field strength measurements has also been

carried out at low (5 K) and high (300 K) temperature within magnetic field sweep of + 2T

to -2T. UV-visible spectral analyses were done using SPECTRASCAN UV 2600 digital

spectrophotometer (Chemito, INDIA).

Figure S1.

Figure S1. PXRD pattern of TemFe B and TemFe C and product without template

corresponds to γ-Fe2O3.

20 40 60 808000

10000

12000

14000

16000

JCPDS no. - 04-0755

[440

]

[511

][4

22][4

00]

[311

]

[220

]

Inte

nsity

(a.u

.)

2( degree)

TemFe B

20 40 60 80

8000

10000

12000

14000

16000

18000

[440

]

[511

][4

22][4

00]

[311

][2

20]

JCPDS no. - 04-0755

Inte

nsity

(a.u

.)

2(degree)

TemFe C

20 40 60 803000

4000

5000

6000

7000

JCPDS no. - 04-0755

[440

][5

11]

[422

][400

]

[311

][2

20]

Inte

nsity

(a.u

.)

2(degree)

No template

Figure S2.

Figure S2. FTIR analysis of (a) four different Schiff bases (Tem A, B, C and D) and (b) α-

and γ-Fe2O3 nanoparticles (TemFe A, B, C, D) synthesised using those Schiff base templates.

500 1000 1500 2000 2500 3000 3500 4000 45000

20

40

60

80

b

% Transm

ittance

Wavenumber (cm-1)

TemFe A TemFe B TemFe C TemFe D

500 1000 1500 2000 2500 3000 3500 4000 4500-1012345678

% Transmitta

nce

Wavenumber (cm-1)

Tem A Tem B Tem C Tem D

a

Figure S3.

Figure S3. Surface morphology analysis using FESEM (a) TemFe A, (b) TemFe B, (c) TemFe C and (d) TemFe D at magnification of 200 nm and (e) without any template at

magnification of 300 nm.

Figure S4.

Figure S4: XPS spectra of Fe and O in Fe2O3 where reference material is carbon (1s- 284.0 eV).

Table S1: Deconvulated XPS peak analysis of Fe2p3/2 (Reference C 1s -284.0)B.E. (eV) Height FWHM AreaCatalyst

Fe+2 Fe+3 Fe+2 Fe+3 Fe+2 Fe+3 Fe+2 Fe+3

[Fe+2]/ [Fe+3]

TemFe A 708.9 710.86 8498 3879 2.25 2.77 21808 12510 1.74

TemFe B 709.39 711.29 7189 3800 2.09 2.77 16842 12257 1.374

TemFe C 709.88 711.39 7101 4471 1.94 2.77 16047 14420 1.112

TemFe D 710.0 711.86 3137 1652 2.21 2.77 7392 5329 1.37

700 705 710 715 720 725 730 735 7402

4

6

8

10

12

14

16Fe 2p3/2

Intensity

(a.u.

)

Binding Energy (eV)

Fe 2p1/2

524 526 528 530 532 534 536 5380

5

10

15

20

Intensity

(a.u.

)

Binding Energy (eV)

O 1s - 529 eV

Figure S5.

Figure S5: Saturation magnetisation (M-H) data of the sample without template at both 5 and

300 K.

-10000 0 10000-120

-80

-40

0

40

80

120

Mag

netis

atio

n (e

mu/

g)

Magnetic Field (Oe)

@ 5K @ 300K

No Template

Figure S6(a).

Figure S6(a). Close perception of hysteresis loop of M-H curve for all the TemFes (TemFe A, B, C and D) as well as without template Fe2O3 at 5 K.

-400 -200 0 200 400-2

0

2

Mag

netis

atio

n (e

mu/

g)

H (Oe)

TemFe 4 @ 5K

-400 -200 0 200 400-20

-10

0

10

20

Mag

netis

atio

n (e

mu/

g)

H (Oe)

TemFe C @ 5K

-400 -200 0 200 400

-20

-10

0

10

20

Mag

netis

atio

n (e

mu/

g)H (Oe)

TemFe B @ 5 K

-500 -250 0 250 500

-20

-10

0

10

20

H (Oe)

TemFe A @ 5K

Mag

netis

atio

n (e

mu/

g)

-400 -200 0 200 400-20

0

20

Mag

netis

atio

n (e

mu/

g)

H (Oe)

Template Free @5K

Figure S6(b).

Figure S6(b). Close perception of hysteresis loop of M-H curve for all the TemFes (TemFe A, B, C and D) as well as without template Fe2O3 at 300 K.

-400 -200 0 200 400

-40

-20

0

20

40

Mag

netis

atio

n (e

mu/

g)

H (Oe)

TemFe A @ 300 K

-400 -200 0 200 400

0

Mag

netis

atio

n (e

mu/

g)H (Oe)

TemFe B @ 300K

-400 -200 0 200 400-20

0

20

Mag

netis

atio

n (e

mu/

g)

H (Oe)

TemFe C @ 300 K

-400 -200 0 200 400

-1

0

1M

agne

tisat

ion

(em

u/g)

H (Oe)

TemFe D @ 300 K

-400 -200 0 200 400-20

0

20

Mag

netis

atio

n (e

mu/

g)

H (Oe)

No template @ 300K

Figure S7.

Figure S7. Temperature dependent ZFC-FC curves of TemFe A, B, C and D respectively under the magnetic field of 100 Oe.

0 50 100 150 200 250 3002

4

6

8

10

12M

agne

tisat

ion

(em

u/g)

Temperature (K)

ZFC FC

TemFe A

0 50 100 150 200 250 3002

4

6

8

10

12

TemFe BMag

netis

atio

n (e

mu/

g)

Temperature (K)

ZFC FC

0 50 100 150 200 250 3002

4

6

8

10

12

TemFe CMag

netis

atio

n (e

mu/

g)

Temperature (K)

ZFC FC

0 50 100 150 200 250 3000.100.150.200.250.300.350.400.450.500.55

TemFe DMag

netis

atio

n (e

mu/

g)

Temperature (K)

ZFC FC

Figure S8.

Figure S8: (a) UV-vis spectra of Ox-TMB using H2O2 as oxidising agent. Condition:

Catalysts are template assisted Fe2O3 (TemFe A, B, C, D) and Fe2O3 synthesised under

template free condition. (b) Control TMB oxidation using only SBs as catalysts. (c) pH-

dependent study of peroxidase-like catalytic activity of TemFe A.

4 5 6 7 8

0

20

40

60

80

100

Relat

ive Activity %

pH

c

550 600 650 700 750

0.0

0.1

0.2

0.3

0.4

0.5

Absorbance (a

.u.)

Wavelength (nm)

TemFe A TemFe B TemFe C TemFe D Template Free Blank

a

550 600 650 700 750-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

Intensity

(a.u.)

Wavelength (nm)

Tem A Tem B Tem C Tem D

b

Figure S9.

Figure S9: Emission spectra of terephthalic acid (TA) in the presence of H2O2 and TemFe A

(excitation at 320 nm). Here, 3 mL experimental solution is prepared from 0.1 M acetate

buffer solution (pH = 4.0), 0.1 ml (30%) H2O2, 2.5×10-5 M TA.

350 400 450 500 550

0

50

100

150

200 TA +H2O2

TA +H2O2 + 0.1 mg TemFe A

TA +H2O2 + 0.2 mg TemFeA

Fluoresence Intensit

y (a.

u.)

Wavelength (nm)

Figure S10.

a a

Figure S10. Steady state kinetic analyses using Michaelis-Menten model for TemFe A (a)

varying concentration of TMB with fixed amount of H2O2 and (b) varying concentration of

H2O2 with fixed amount of TMB.

Table S2: Comparison of different method of detection of TGASerial No. Method TGA detection

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-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5-1012345678

V 0 (M

s-1 )

(10-9

)

TMB concentration (mM)

a

40 50 60 70 80

2.0

2.5

3.0

3.5

4.0

4.5

5.0

V 0(M

s-1 )

(10-9

)

H2O2 concentration (mM)

b