electronic supplementary information (esi) · arun 2kumar sinha1, p.k. manna , mukul pradhan 1,...

Electronic Supplementary Information (ESI)

Tin Oxide with Tunable p-n Heterojunction for UV and Visible

Light Photocatalytic Activity Arun Kumar Sinha

1, P.K. Manna

2, Mukul Pradhan

1, Chanchal Mondal

1, S. M. Yusuf

2 and

Tarasankar Pal1

1Department of Chemistry

Indian Institute of Technology, Kharagpur-721302, India

2 Solid State Physics Division, Bhabha Atomic Research Centre,

Mumbai 400 085, India

*E-mail: [email protected]

ESI 1:

1. Materials:

All the reagents were of AR grade. Triple distilled water was used throughout the

experiment. SnCl2.2H2O was obtained from E Merck. NaOH was purchased from BDH

Company, Mumbai.

2. Preparation of SnO nanoplate:

Pure SnCl2.2H2O was finely powdered by using an agate motor & pestle and a

measured amount (10 gm) was mixed with 30 mL NaOH (5.0 M) solution. Within 60

minutes of ultrasonication the white powder changes to a blue-black mass. The blue-

black SnO sample was obtained at the solid–liquid interface i.e. the interface between

powder SnCl2.2H2O and NaOH solution. The hydrolysis and dehydration steps occured

simultaneously.

Hydrolysis step SnCl2.2H2O + NaOH (5 M) → Sn6O4(OH)4 (white color) + 2NaCl

Dehydration step Sn6O4(OH)4 → SnO (Blue-black) + 3H2O

The blue-black SnO sample was produced slowly from the surface layer of SnCl2 powder

at the interface. The blue-black SnO was formed and washed with copious amount of

Electronic Supplementary Material (ESI) for RSC AdvancesThis journal is © The Royal Society of Chemistry 2013

water until pH of the washings lowered down to distilled water pH. The blue-black

sample was air dried and stored for further characterization.

3. Characterization Instruments:

1.1. UV-Visible study:

All absorption spectra for the degradation reaction were recorded in a chemito

spectrophotometer (India) and taking the solutions in a 1 cm quartz cuvette.

1.2. DRS study:

Reflectance spectra were measured using DRS (Diffuse Reflectance Spectra)

mode with a Cary model 5000 UV-vis-NIR spectrophotometer.

1.2. XRD-study:

XRD was done in a PW1710 diffractometer, Philips, Holland, instrument. The

XRD data were analyzed using JCPDS software.

1.3. Structural computational study:

The analysis of the X-ray diffraction pattern of SnO was done using the FullProf

program. This is free software and it is available in internet.

1.4. Raman-study:

Raman spectra were obtained with a Renishaw Raman Microscope, equipped with

a He–Ne laser excitation source emitting at a wavelength of 633 nm, and a Peltier cooled

(-70 °C) charge coupled device (CCD) camera.

1.5. XPS-study:

The chemical state of the element on the surface was analyzed by a VG Scientific

ESCALAB MK II spectrometer (UK) equipped with a Mg Kα excitation source (1253.6

eV) and a five-channeltron detection system.

1.6. FTIR-study:

FTIR studies were performed with a Thermo-Nicolet continuum FTIR

microscope.

1.7. BET-study:

Nitrogen adsorption-desorption measurements were performed at 77.3 K using a

Quantachrome Instruments utilizing the BET model for the calculation of surface areas.

The pore size distribution was calculated from the adsorption isotherm curves using the

Barrett-Joyner-Halenda (BJH) method.


1.8. FESEM and EDS analysis:

FESEM analysis was performed with a supra 40, Carl-Zeiss Pvt. Ltd instrument

and an EDS machine (Oxford, Link, ISIS 300) attached to the instrument was used to

obtain the material morphology and composition.

1.9. TEM and HRTEM analysis:

TEM analysis was performed with an instrument H-9000 NAR, Hitachi, using an

accelerating voltage of 200 kV.

1.10. Thermo gravimetric analysis:

A differential scanning calorimetry tester (DSC131, Setaram Labsys, France) was

used to measure the phase change of SnO nanomaterial. During the test, nanopowders

were heated at a rate of 5 °C/min under an O2 atmosphere.


ESI 2.

DR spectra of SnO nanocrystals and heat treated SnO samples

200 400 600 8000.0

0.3

0.6

0.9

1.2

1.5

1.8SnO (Room Temperature)

SnO (at 4000C)

SnO (at 8000C)

Ab

so

rban

ce (

a.u

.)

Wavelength (nm)


ESI 3:

ESI 3a. XRD pattern of SnO nanoplates showing temperature dependent phase

transformation from SnO to SnO2 (a) and XRD spectrum of rutile phase of SnO2 obtained

after 800°C heat treatment (b).

10 20 30 40 50 60 7010 20 30 40 50 60 7010 20 30 40 50 60 70-1x10

3

0

1x103

2x103

3x103

a

2

8000C

7000C

4000C

2000C

RT

SnO2

SnO (room temperature)

Inte

nsit

y (

a.u

.)

6000C

20 30 40 50 60 70 80

0

50

100

150

200

250(3

21)

(202)

(301)

(112)

(310)

(002)

(220)

(211)

(200)

(101)

(110) SnO

2 at 800

0C b

Inte

nsit

y (

a.u

.)

2


ESI 3b. Rietveld refined, observed (open circle) and calculated (solid line) XRD patterns

of (a) as prepared SnO, and SnO annealed at different temperatures (b) 200 C, (c) 400

C and (d) 800 C. The solid line at the bottom shows the difference between observed

and calculated patterns. Vertical lines show the positions of the Bragg peaks. The top,

middle and bottom layers of vertical lines in figure (c) indicate the Bragg peak positions

of SnO, SnO2 and Sn3O4, respectively.

0

1500

0

1500

10 20 30 40 50 60 70

0

200

0

700

Inte

nsity (

arb

. un

its)

As-prepared

200 C

800 C

2(deg.)

400 C

a

b

c

d


ESI 4:

ESI 4a. A comparative view of (a) SnO litharge structure and (b) SnO2 rutile

structure

ESI 4b. (a) SnO4 square pyramidal network in SnO; (b) SnO6 octahedral network

in SnO2.

c

ba

c

ba

a b

Sn

Sn

OO

c

ba

c

ba

a b

c

ba

c

ba

baa

c

ba

c

ba

baa

a b

Sn

Sn

OO

a

c

b

Sn

O

a

a

c

b

a

c

b

c

bb

Sn

O

a

b

a

c

b

a

c

b

a

c

a

cc

b


ESI 4c: Typical interatomic distances, and angles of SnO and SnO2, obtained from

the Rietveld refinement.

114.8(3)°Bond angles

Sn-O-Sn


O1-Sn-O2

3.187(2) ÅBond length O1-O4



2.04(2) ÅBond length Sn-O5


ValuesBond lengths and

bond angles of SnO2


Sn-O-Sn


O1-Sn-O2







bond angles of SnO2


Sn-O-Sn


O1-Sn-O2

3.799 (2) ÅBond length O1-O4




bond angles of

SnO


Sn-O-Sn


O1-Sn-O2

3.799 (2) ÅBond length O1-O4




bond angles of

SnO


ESI 4d: Structural parameters of SnO and SnO2, obtained from the Rietveld

refinement.

Inorganic Material SnO SnO2

Space Group P4/nmm P42/mnm

crystallographic unit

cell

a = b = 3.799(1) Å

c = 4.841(1) Å

a = b = 4.738(2) Å

c = 3.187(1) Å

Absolute position

And

Occupancy number

Sn (2c)

x = 1/4

y = 1/4

z = 0.238(1)

Occ = 1

Sn (2a)

x = 0

y = 0

z = 0

Occ = 1

Absolute position

And

Occupancy number

O (2a)

x = 3/4

y = 1/4

z = 0

Occ = 1

O (4f)

x = 0.304(5)

y = 0.304(5)

z = 0

Occ = 1

chi-square of the

pattern

χ2 = 2.13 χ2 = 1.97


ESI 5.

Raman spectra of heat treated SnO nanoplates examined under laser power 100% (20

mW) and laser exposure time 30 sec.

200 400 600 800 1000

1000C

2000C

4000C

6000C

8000C

479.27308.97 779.47

638.62

Inte

nsity (

a.u

.)

Raman shift (cm-1)


ESI 6.

Thermal analysis (TG-DTA) of SnO nameplates

The curve I represents the TG curve and the inflection region demonstrates the phase

change area of SnO material in relation with the temperature change. The significant

phase change from SnO to SnO2 via some intermediate (such as Sn3O4) took place at an

approximate temperature range of 300°-700°C and at 800°C the transformation of phase

becomes complete. In this case, DTA curves (black line) show exothermic peak because

there occurs one thermochemical reaction which is oxidative in nature.

200 400 600 8008200

8400

8600

8800

9000

9200

-100

-50

0

50

100

i=TG Curve

DT

G

g/m

inD

TA

mV

V

iii

ii

i

561.810C

TG

%

Temp ( 0C)

iii=DTA Curveii=DTG Curve)


ESI 7.

XPS analysis of SnO nanoplates at different temperature. Survey scan (a), Sn 3d (b) and

O 1s (c) core level XPS spectra of SnO (room temperature), SnO (200°C), SnO (400°C)

and SnO (800°C) samples.

484 488 492 496 500

1x104

2x104

3x104

4x104

b

495.04

495.26

495.29

495.363d

3/2

3d5/2

486.62 RT

486.77 2000C

486.82 4000C

486.87 8000C

Inte

nsit

y (

a.u

.)

Binding Energy (eV)

526 528 530 532 534 536

16000

20000

24000

C

531.12 8000C

530.99 4000C

530.95 2000C

530.75 RT

Inte

nsit

y (

a.u

.)

Binding energy (eV)

0 200 400 600 800 1000

Inte

nsit

y (

a.u

.)

8000C

4000C

2000C

RT

a

3P

1/2

3P

3/2

C 1

s

O 1

s

Sn

3d

5/2

Sn

3d

3/2

Binding Energy (eV)


ESI 8.

FTIR spectra of powder SnO sample at different temperature. (i) neat SnCl22H2O (ii) as

prepared SnO at RT (iii) SnO at 200° C (iv) SnO at 400° C (v) SnO at 600° C and (vi)

SnO at 800° C.

ESI 8 shows FTIR spectra SnO nanocrystals but at different temperatures. Thus FTIR

conclusively speaks for the non-hygroscopic behavior of SnO material. It is also observed

that as SnO is oxidized to SnO2 and the sample became hygroscopic. So a broad band at

3438.90 cm-1

appeared for SnO2 material at 600 and 800°C.

500 1000 1500 2000 2500 3000 3500 40000

50

100

150

200

250

300

500 1000 1500 2000 2500 3000 3500 40000

50

100

150

200

250

300

500 1000 1500 2000 2500 3000 3500 40000

50

100

150

200

250

300

500 1000 1500 2000 2500 3000 3500 40000

50

100

150

200

250

300

500 1000 1500 2000 2500 3000 3500 40000

50

100

150

200

250

300

500 1000 1500 2000 2500 3000 3500 40000

50

100

150

200

250

300

3438.90

% T

Wavelength (cm-1)

vi SnO NP (8000C)

v SnO NP (6000C)

iv SnO NP (4000C)

iii SnO NP (2000C)

ii SnO NP

i SnCl2.2H

2O


ESI 9.

Nitrogen adsorption–desorption isotherm and the BJH pore size distribution of SnO

nanoplates

The N2 adsorption–desorption isotherm and the pore size distribution of SnO nanoplates.

The BET specific surface area of the SnO plates is found to be 2.99 m2/g.


ESI 10.

HRTEM image of SnO sample annealed at 200°C. A polycrystalline SnO2

nanoparticles are formed on the surface of SnO.


ESI 11:

Morphplogy SnO nanoplates at different temperature


ESI 12:

Photodegradation experiment

To carry out the photoreaction, one 100 mL capacity photoreactor was used. The

photoreactor was kept at 30ºC circulating cold water during the photoreaction to avoid

heating effect on the reaction mixture. Reaction mixture was prepared in the photoreactor

using 0.025 g of the as prepared SnO powder and 50 mL aqueous solution of MB so that

the final concentration of MB becomes 3 × 10-5

M. The MB solution was allowed to

stand for 2 h for aging to reach an adsorption-desorption equilibrium on the surface of

SnO before light irradiation. We have used commercial visible light source (i.e. 200 W

and 500 W tugsten light) and commercial UV-light source (365 nm). The reaction

mixture was well stirred at 500 rpm during photoreaction due to passing of air O2 into the

reaction mixture.

The time dependent photocatalytic reaction was monitored spectrophotometrically.

During the absorption measurement of the reaction mixture containing the exposed dye

solution and SnO material, methylene blue solution was separated by centrifugation

(5000 rpm for 10 min) to avoid light scattering due to the dispersed SnO nanocrystals in

the aqueous phase. In the similar fashion, we have also used annealed tin oxide samples

for photodegradation of methylene blue by UV-light (365 nm)


ESI 13.

Photocatalytic degradation of MB on SnO nanoplates in presence of visible light

(tungsten light 200 W) (a), UVlight (365 nm) (b), and in the dark condition (c)

400 500 600 700 800 9000.0

0.5

1.0

1.5

2.0

2.5

max=662 nm

SnO

Visible light

a

Initial conc.

Adsorption

0 h

4

8

12

16

20 h

Ab

so

rpti

on

(a

.u.)

Wavelength (nm)

400 500 600 700 800 9000.0

0.5

1.0

1.5

2.0

max= 662 nm(b)

SnO

UV-Light

initial

0

4

6

9

12

15

18 h

Ab

so

rpti

on

(a.u

.)

Wavelength (nm)

400 500 600 700 800 9000.0

0.5

1.0

1.5

2.0

Dark condition Initial

adsorption (2 hr)

4 hr

8 hr

20 hr

c max

= 662 nm

Ab

so

rba

nc

e (

a.u

.)

Wavelength (nm)


ESI 14. Photocatalytic degradation of MB in presence of tin oxide

nanoplates under different visible lights

400 500 600 700 8000.0

0.5

1.0

1.5

2.0

2.5

Visible Light

Tugsten bulb 200 W

(a)

max= 662 nm

Initial conc.

Adsorption

0 h

4

8

12

16

20 hAb

so

rpti

on

(a.u

.)

Wavelength (nm)

400 500 600 700 800 9000.0

0.5

1.0

1.5

2.0

2.5

max= 662 nm(b)

Visible Light

(500 W tugsten bulb)Initial

2 hrs adsorption

0 hrs

3 hrs

6 hrs

9 hrs

12 hrs

15 hrs

18 hrs

Ab

so

rba

nc

e (

a.u

.)

Wavelength (nm)

400 500 600 700 800 9000.0

0.5

1.0

1.5

2.0

max= 662 nm

(c)

Visible Sun LightInitial

2 hrs adsorption

0 hrs

4 hrs

6 hrs

8 hrs

10 hrs

Ab

so

rban

ce (

a.u

.)

Wavelength (nm)


ESI 15. Photocatalytic degradation of MB (3 × 10-5

M) in presence of

annealed tin oxide samples (0.025 g) by UV-light (365 nm): SnO at 200°C

(a), SnO at 400°C (b), SnO at 600°C (c) and SnO at 800° C (d).

400 500 600 700 800 9000.0

0.5

1.0

1.5

2.0

max= 662 nm

(a)

Initail

Adsorption

3

6

9

12

15 hr

Ab

so

rpti

on

(a.u

.)

Wavelength (nm)

400 500 600 700 800 9000.0

0.5

1.0

1.5

2.0

Initail

Adsorption

3

6

9

12

15 hr

(c)

max= 662 nm

Ab

so

rpti

on

(a.u

.)

Wavelength (nm)

400 500 600 700 800 9000.0

0.5

1.0

1.5

2.0 (b)

Initail

Adsorption

3

6

9

12

15 hr

max

=622 nm

Ab

so

rpti

on

(a.u

.)Wavelength (nm)

400 500 600 700 800 9000.0

0.5

1.0

1.5

2.0 (d) max

= 662 nm

Initail

Adsorption

3

6

9

12

15 hr

Ab

so

rpti

on

(a.u

.)

Wavelength (nm)


ESI 16. Nitrogen adsorption–desorption isotherm for the SnO at 200°C (a),

SnO at 400°C (b), SnO at 600°C (c) and SnO at 800°C and their

comparative BET surface area and pore volume.

The BET surface area of the annealed SnO sample (at 200°C, 400°C, 600°C and 800°C)

is changed and the result is tabulated as bellow.

Annealed SnO

Sample

BET surface Area

(m2/g)

SnO (200°C) 2.85

SnO (400°C) 2.194

SnO (600°C) 3.816

SnO (800°C) 1.133

0.0 0.2 0.4 0.6 0.8 1.0

0

2

4

6

8

10

12

14

(b)

Desorption

Adsorption

Vo

lum

e [

cc/g

]

Relative Pressure, P/P0

0.0 0.2 0.4 0.6 0.8 1.0

0

5

10

15

20

25

(c)

Desorption

Adsorption

Vo

lum

e [

cc/g

]

Relative Pressure P/P0

0.0 0.2 0.4 0.6 0.8 1.0

0

1

2

3

4

5

6

7

8

Desorption

Adsorption

(d)V

olu

me [

cc/g

]


0.0 0.2 0.4 0.6 0.8 1.0

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Desorption

Adsorption

(a)

Vo

lum

e [

cc

/g]



ESI 17: Determination of VB position of SnO and SnO2 from the survey

scan of SnO and SnO2 material.

0 10 20 30 40500

1000

1500

2000

2500

3000

3500

4000

4500

SnO2

VB Position = 8.1 eV

(b)

Inte

nsit

y (

a.u

.)

Binding Energy (eV)

0 10 20 30 40

600

1200

1800

2400

3000

3600

4200 (a)

SnO

VB Position = 5.88 eV

Inte

nsit

y (

a.u

.)

Binding Energy (eV)


electronic supplementary information (esi) · arun 2kumar sinha1, p.k. manna , mukul pradhan 1,...

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