SUPPLEMENTARY INFORMATION

Highly efficient catalytic reductive degradation of various organic dyes by

Au/CeO2-TiO2 nano-hybrid

PRANJAL SAIKIA,*,a ABU T MIAHa and PARTHA P DASb

a Department of Applied Sciences (Chemical Science Division), GUIST, Gauhati University, Guwahati 781 014, Assam, India

b Department of Physics, NIT Karnataka, Surathkal, Mangalore 575 025, Karnataka, India

Email: psjorhat@gmail.com; pranjalsaikia@gauhati.ac.in

*For correspondence

Table of contents

Table S1. Comparison of metal nanoparticles catalyzed reduction of MB by NaBH4 with the

present work.

Figure S1. (a) Ce 3d, (b) Ti 2p, and (c) O1s XP spectrum of Au/CeO2-TiO2 nano-hybrid.

Figure S2. UV-Vis absorption spectra for aqueous MB (30 mL, 48.14 × 10−6 M) with 2 mL, 0.2

M NaBH4 and 0.433g/L of (a) Au/CeO2 and (b) Au/CeO2-ZrO2 nano-hybrid.

Figure S3. Plausible mechanism for Au/CeO2-TiO2 nano-hybrid catalyzed reductive degradation

of MB.

Figure S4. UV-Vis absorption spectra for degradation of MB (48.14 × 10−6 M, 30 mL) with

different catalyst loading: (a) 0.183 g/L, (b) 0.233 g/L, (c) 0.333 g/L, and (d) 0.433 g/L.

Figure S5. UV-Vis absorption spectra for Au/CeO2-TiO2 nano-hybrid catalyzed degradation of

MB with different MB concentration: (a) 48.14 × 10−6 M, (b) 58.84 × 10−6 M, (c) 66.86 × 10−6 M,

and (d) 74.89 × 10−6 M.

Figure S6. UV-Vis absorption spectra for Au/CeO2-TiO2 nano-hybrid catalyzed degradation of

MB with different NaBH4 concentration: (a) 0.125 M, (b) 0.150 M, (c) 0.175 M, and (d) 0.200

M. (e) ln(At/Ao) vs. time plot of pseudo-first-order reaction kinetics for degradation of MB with

2 mL of different NaBH4 concentrations with Au/CeO2-TiO2 nano-hybrid.

Figure S7. ln(At/Ao) vs. time plot for degradation of MB with 0.2 M, 2 mL of NaBH4 (a) and

with 13 mg of Au/CeO2-TiO2 nano-hybrid (b).

Figure S8. UV-Vis absorption spectra of (a) MO (61.10 × 10−6 M, 30 mL) and NaBH4 (0.2 M, 2

mL), (b) Congo red (28.71 × 10−6 M, 30 mL) and NaBH4 (0.2 M, 2 mL), (c) RhB (10.44 × 10−6

M, 30 mL) and NaBH4 (0.2 M, 2 mL), and (d) MG (54.81 × 10−6 M, 30 mL) and NaBH4 (0.01 M,

0.3 mL).

Figure S9. UV-Vis absorption spectra for the reduction of (a) MO, (b) CR, (c) RhB, and (d) MG,

catalyzed by Au/CeO2-TiO2 nano-hybrid in the presence of NaBH4.

Figure S10. (a) % degradation of MB obtained after successive cycles for reuse of Au/CeO2-

TiO2 nano-hybrid. Reaction conditions: 30°C, 13 mg Au/CeO2-TiO2 nano-hybrid, 30 mL of

48.14 x 10−6 M aqueous MB solution, 2 mL, 0.2 mol/L NaBH4. (b) & (c) are, respectively, the

XRD and TEM patterns of recovered Au/CeO2-TiO2 nano-hybrid after performing 5th cycle.

Calculation of particle size: Debye Scherrer’s equation

Table S1. Comparison of metal nanoparticles catalyzed reduction of MB by NaBH4 with the

present work.

Catalysta Reductant/Template used for catalyst

synthesisb

MB concentration

Catalyst loadingc

(mg)

MNP loadingd (wt

%)

Amount of NaBH4

kapp

(10−3

min−1)

Ref.

Au/CT Urea (48.14 ×10−6

M) × 30 ml13.0 mg 1.00 0.2 M × 2

ml333.6 Our

workCoO NWs

2,7-DHN/CTAB, MW

heating

(8 × 10−6 M)

× 8 mL

0.25 mL n.a. 0.1 M × 1.75 mL

38.3 51

Au NPs SMG (1 mM + 7.5

mL H2O) ×

1.5 mL

n.m. n.a. 10 mM × 1 mL

241 52

Au/LCG Laser ablation

10−5 M × 2.5

mL

50 μL 9.06 0.1 M × 0.5 mL

384 x 102

53

Au/sa-GH

TETA, hydrothermal

treatment(180 ̊ C)

0.1 mM ×

2.8 mL

0.1 mg 2.26 0.1 M ×

0.20 mL

237 54

Au/TiO2 UV light/Sodium

citrate

(34.76 × 10−6

M) × 20 mL2 mg 123.24 0.1 M × 2

mL

156 8

Ag/PEI-SiO2

PEI (9.4 × 10-5

M) × 1 mL1/10.5

(MB/Ag, molar ratio)

1.33 1/1700 (MB/NaBH4, molar

ratio)x 2 ml

46 x 102

55

Cu/SBA-15

NaBH4/Pluronic P-

123

22.5 mL of 9 x 10−2 mM MB + 12.5 mL H2O

1 mg 12.5 0.2 M × 5 mL

510 2

Ag/GO PQBAE 1 μM × 1.50 mL

0.50 mL 41.35 0.01 M × 1.00 mL

38 46

Au@PPy

/Fe3O4

PDDA/NH3.H2O/

THF

(64.18 x 10−6

M) × 2.5 mL0.1 mg 4.6 15 mg/mL

× 1.0 mL266 56

Ag NPs D-maltose/PAA

(1 × 10−5 M) × 1 mL

3 × 10−8 M Ag n.a.

0.01 M ×

1 mL

141.4 57

Ag/PAGs Amidodiol/

PAA

160 mg/L ×

20 mL

20 mg n.m. 10 mM ×

2 mL

222 58

Pd/

Fe3O4-

PEI-

RGO

NaBH4/PEI 50 μM 0.8 mg/mL 1.90 1μM 441.5 50

Au/

F

e3O4@C

K2CO3/

NaBH4/

PDDA

0.01 mM ×

15 mL

5 mg 1 5 mM 331 45

aCT = ceria-titania, NWs = nanowires, LCG = laser converted graphene, sa-GH = self-assembled

graphene hydrogel, PEI = polyethyleneimine, GO = graphene oxide, PPy = polypyrrole, PAGs =

polyacrylic acid-amidodiol hydrogels (amidodiol = 1,6-bis(hydroxy butyramido) hexane), rGO =

reduced graphene oxide,

b2,7-DHN = 2,7-dihydroxy naphthalene, CTAB = cetyl trimethylammonium bromide, MW =

microwave, TETA = Triethylenetetramine, SMG = salmalia malabarica gum, PQBAE=Picrasma

quassioides bark aqueous extract, PDDA = poly(diallyldimethylammonium chloride), THF =

Tetrahydrofuran, PAA = Poly(acrylic acid), PEI = polyethyleneimine.

cn.m. = not mentioned,

dMNP = Metal nanoparticle, n.a. = not applicable, n.m. = not mentioned.

Figure S1. (a) Ce 3d, (b) Ti 2p, and (c) O1s XP spectrum of Au/CeO2-TiO2 nano-hybrid.

920 910 900 890 880

898.

94

884.

91

903.

56

917.

04

907.

80

901.

65 889.

53

883.

37

Inte

nsity

(a.u

.)

Binding Energy (eV)

(a) Ce 3d

466 464 462 460 458 456 454

Ti 2p1/2

Ti 2p3/2

Inte

nsity

(a.u

.)

Binding Energy (eV)

(b) Ti 2p

534 532 530 528 526

(c) O 1s

Inte

nsity

(a.u

.)

Binding energy (eV)

Figure S2. UV-Vis absorption spectra for aqueous MB (30 mL, 48.14 × 10−6 M) with 2 mL,

0.2 M NaBH4 and 0.433g/L of (a) Au/CeO2 and (b) Au/CeO2-ZrO2 nano-hybrid.

500 550 600 650 700

max (MB) = 664 nm(a)

Wavelength (nm)

Abs

orba

nce

(a.u

.)

10.5 min

0 min

500 550 600 650 700

(b)

10.5 min

0 min max (MB) = 664 nm

Wavelength (nm)

Abs

orba

nce

(a.u

.)

Figure S3. Plausible mechanism for Au/CeO2-TiO2 nano-hybrid catalyzed reductive

degradation of MB.

Figure S4. UV-Vis absorption spectra for degradation of MB (48.14 × 10−6 M, 30 mL) with

different catalyst loading: (a) 0.183 g/L, (b) 0.233 g/L, (c) 0.333 g/L, and (d) 0.433 g/L.

500 550 600 650 700

max (MB) = 664 nm

(a)

Wavelength (nm)

Abs

orba

nce

(a.u

.)

0 min1.5 min3 min4.5 min6 min7.5 min9 min10.5 min

500 550 600 650 700

(b) max (MB) = 664 nm

Wavelength (nm)A

bsor

banc

e (a

.u.)

0 min1.5 min3 min4.5 min6 min7.5 min9 min10.5 min

500 550 600 650 700

(c) max (MB) = 664 nm

Wavelength (nm)

Abs

orba

nce

(a.u

.)

0 min1.5 min3 min4.5 min6 min7.5 min9 min10.5 min

550 600 650 700

max (MB) = 664 nm

0 min1.5 min3 min4.5 min6 min7.5 min9 min10.5 min

(d)

Abs

orba

nce

(a.u

.)

Wavelength (nm)

Figure S5. UV-Vis absorption spectra for Au/CeO2-TiO2 nano-hybrid catalyzed degradation

of MB with different MB concentration: (a) 48.14 × 10−6 M, (b) 58.84 × 10−6 M, (c) 66.86 × 10−6

M, and (d) 74.89 × 10−6 M.

550 600 650 700

max (MB) = 664 nm

0 min 1.5 min 3 min 4.5 min 6 min 7.5 min 9 min 10.5 min

(a)

Abs

orba

nce

(a.u

.)

Wavelength (nm) 500 550 600 650 700 750

max (MB) = 664 nm(b)

0 min2.5 min3.5 min4.5 min5.5 min7 min9 min17 min

Abs

orba

nce

(a.u

.)Wavelength (nm)

500 550 600 650 700 750

Wavelength (nm)

Abs

orba

nce

(a.u

.)

(c) max (MB) = 664 nm

0 min 3 min 13 min 15 min 20 min

500 550 600 650 700 750

max (MB) = 664 nm

Wavelength (nm)

Abs

orba

nce

(a.u

.)

(d)

0 min 4 min 14 min 24 min

Figure S6. UV-Vis absorption spectra for Au/CeO2-TiO2 nano-hybrid catalyzed degradation

of MB with different NaBH4 concentration: (a) 0.125 M, (b) 0.150 M, (c) 0.175 M, and (d) 0.200

M. (e) ln(At/Ao) vs. time plot of pseudo-first-order reaction kinetics for degradation of MB with

2 mL of different NaBH4 concentrations with Au/CeO2-TiO2 nano-hybrid.

500 550 600 650 700

max (MB) = 664 nm(a)

Wavelength (nm)

Abs

orba

nce

(a.u

.)

0 min1.5 min3 min4.5 min6 min7.5 min9 min10.5 min

500 550 600 650 700 750

(b) max (MB) = 664 nm

Wavelength (nm)

Abs

orba

nce

(a.u

.)

0 min1.5 min3 min4.5 min6 min7.5 min9 min10.5 min

500 550 600 650 700 750

Wavelength (nm)

Abs

orba

nce

(a.u

.)

(c) max (MB) = 664 nm0 min1.5 min3 min4.5 min6 min7.5 min9 min10.5 min

500 550 600 650 700

max (MB) = 664 nm

0 min1.5 min3 min4.5 min6 min7.5 min9 min10.5 min

(d)

Abs

orba

nce

(a.u

.)

Wavelength (nm)

0 2 4 6 8 10 12

-4

-3

-2

-1

0(e)

ln(A

t/Ao)

Time (min)

(a) 0.125 M(b) 0.150 M(c) 0.175 M(d) 0.200 M

Figure S7. ln(At/Ao) vs. time plot for degradation of MB with 0.2 M, 2 mL of NaBH4 (a) and

with 13 mg of Au/CeO2-TiO2 nano-hybrid (b).

0 20 40 60 80 100-0.375

-0.300

-0.225

-0.150

-0.075

0.000

(a)

ln(A

t/Ao)

Time (min) 0 40 80 120 160 200

-0.6

-0.4

-0.2

0.0 (b)

Time (min)

ln(A

t/Ao)

Figure S8. UV-Vis absorption spectra of (a) MO (61.10 × 10−6 M, 30 mL) and NaBH4 (0.2

M, 2 mL), (b) Congo red (28.71 × 10−6 M, 30 mL) and NaBH4 (0.2 M, 2 mL), (c) RhB (10.44 ×

10−6 M, 30 mL) and NaBH4 (0.2 M, 2 mL), and (d) MG (54.81 × 10−6 M, 30 mL) and NaBH4

(0.01 M, 0.3 mL).

400 450 500 550 600

Wavelength (nm)

Abs

orba

nce

(a.u

.)

(a)

90 min

0 min

400 450 500 550 600 650

(b)

1.5 h

0 min

Abs

orba

nce

(a.u

.)

Wavelength (nm)

500 550 600

1 h

0 min

(c)

Wavelength (nm)

Abs

orba

nce

(a.u

.)

400 450 500 550 600 650 700

1.5 h

0 min

(d)

Abs

orba

nce

(a.u

.)

Wavelength (nm)

Figure S9. UV-Vis absorption spectra for the reduction of (a) MO, (b) CR, (c) RhB, and (d)

MG, catalyzed by Au/CeO2-TiO2 nano-hybrid in the presence of NaBH4.

400 450 500 550

(a) max (MO) = 464 nm

Abs

oban

ce (a

.u.)

Wavelength (nm)

0 min 1.5 min 3 min 4.5 min 6 min 7.5 min

400 450 500 550 600 650

(b)

max (CR) = 498 nm

0 min 2 min 4 min 6 min 8 min 10 min

Abs

orba

nce

(a.u

.)

Wavelength (nm)

450 500 550 600

max (RhB) = 553 nm(c)

Abs

orba

nce

(a.u

.)

Wavelength (nm)

0 min 2 min 4 min 6 min 8 min 10 min 12 min 14 min

500 550 600 650 700

A

bsor

banc

e (a

.u.)

Wavelength (nm)

(d) max (MG) = 616 nm

0 min 3 min 6 min 9 min 12 min 15 min

Figure S10. (a) % degradation of MB obtained after successive cycles for reuse of Au/CeO2-

TiO2 nano-hybrid. Reaction conditions: 30 °C, 13 mg Au/CeO2-TiO2 nano-hybrid, 30 mL of

48.14 x 10−6 M aqueous MB solution, 2 mL, 0.2 mol/L NaBH4. (b) & (c) are, respectively, the

XRD and TEM patterns of recovered Au/CeO2-TiO2 nano-hybrid after performing 5th cycle.

1 2 3 4 5

a

MB

deg

rada

tion

(%)

Cycle number

30 40 50 60 70 80

Inte

nsity

(a.u

.)

b

Calculation of particle size: The average particle size of CeO2 nano-crystals were calculated

with the help of Debye Scherrer’s equation: d = kλ/βcosθ, where d is the crystal size, k is a

constant whose value is often taken as 1, λ is X-ray wavelength (0.15406 nm for Cu Kα

radiation), β is the full width at half maximum of the (111) peak of the cubic CeO2 and θ is the

diffraction angle.