Quantum dot self-decorated TiO 2 nanosheet

Quantum dot self-decorated TiO2 nanosheet

Feng-Min Zhao

Tianjin University, China

Sep. 24 2013

IUMRS-ICAM2013,Qingdao,Sep.22-28

2

3

4

1 Introduction

Experimental

Results and discussion

Conclusions

Contents

Chem. Soc. Rev., 2009, 38, 253-278.

Solar Energy

Introduction

<5%

Nature, 2008, 453, 638-641.

Faceted Anatase

Introduction

Faceted Anatase with Mesopores

Using MSC films, thefabricated all-solid-state, low-temperature sensitized solar cells that have 7.3 % efficiency, the highest efficiency yet reported.

Nature, 2013, 495, 215-219

truncated tetragonal bipyramid anatase

Science, 2001, 293, 269-271.

JACS, 2008, 130, 5018-5019.

Doping

Introduction

Science, 2011, 331, 746-750.

Experimental

TBOT + HF(40 wt%)

hydrothermally

treated at 180o

C

24h 72h 168h

A-t: NaOHA-tH: NaOH 100 oC 24hA-tC: NaOH 500 oC 2h

10 20 30 40 50 60 70 80

A-168C

A-168H

A-168

A-72

215

220

20421

110

5

200

004

Inte

ns

ity

(a

.u.)

2Theta (degree)

101

A-24

a

0 100 200 300 400 500 600 700 800

0.0

0.2

0.4

0.6

0.8

1.0

Eg

A1gB1g

No

rmal

ized

In

ten

sity

Raman shift ( cm-1)

A-24 A-72 A-168 A-168H A-168C

Egb

Results and discussion

24h

72h

168h

Results and discussion

24h

72h

168h

0 100 200 300 400 500 600 700 800

0.0

0.2

0.4

0.6

0.8

1.0

Eg

A1gB1g

No

rmal

ized

In

ten

sity

Raman shift ( cm-1)

A-24 A-72 A-168 A-168H A-168C

Egb

According to J. Phys. Chem. C 2012, 116, 7515 − 7519

SampleSide

length a/nm

Thickness

b/nm

Percentage of

{001} facets/%

SBET

/(m2 g–1)

A-24 55.2 5.4 83.7 69.4A-24H 55.1 5.6 83.1 68.5A-72 80.5 9.2 81.3 43.8

A-72H 79.8 9.1 81.4 44.1A-168 88.3 10.3 81.1 38.8

A-168H 89.0 10.1 81.6 36.8A-168C 88.8 10.3 81.2 17.4

%S{001}exp

=S{001}/(S{101}+S{001}) =2a2/{4ab+2a2]*100

350 400 450 500

3.0 3.2 3.4Photon energy (eV)

(ahv)

1/2 (e

V)1/

2

168h

24h

A-24 A-72 A-168 A-168H A-168C

Ab

sorp

tio

n (

a.u

.)

Wavelength (nm)

0.08 eV

UV-vis DRS

Results and discussion

-5 0 5 10 15 20 25

0.67 eV

c/s

Binding Energy (eV)

A-24 A-72 A-168 A-168H A-168C

O2s

XPS O2s

3200 3300 3400 3500 3600

g=1.961Inte

nsit

y (

a.u

.)

Magnetic Field (Gauss)

A-24 A-72 A-168 A-168C A-168H

g=1.989

EPR (110 K)

Results and discussion

468 466 464 462 460 458 456

468 466 464 462 460 458 456 454c/s

Binding Energy (eV)

A-24 A-72 A-168 A-168H A-168C

Ti4+Ti4+

Ti3+

Ti4+

XPS

0

2

4

6

8

10

P-25A-168A-72

k/S

BE

T (

10

-4 g

m-2 m

in-1)

Samples

Fresh sample

Hydrothermal sample at 100 oC

Calcined sample at 500 oC

A-24

Photodegradation of RhB

Post-hydrothermal Post-calcination

10 20 30 40 50 60 70 80

A-168C

A-168H

A-168

A-72

215

220

20421

110

5

200

004

Inte

ns

ity

(a

.u.)

2Theta (degree)

101

A-24

a

Results and discussion

A-168H: 3.4 times higher than A-24 2.7 times higher than P-25

Results and discussion

1

2

3

5

4

Ag photo-deposition on A-168H(d) and A-24(e)

0 2000 4000 6000 8000 10000

CuTi

AgO

Cu

Co

un

ts (

a.u

.)

C

Ag

Ag

Ag

1

2

3

4

5

Energy (KeV)

TEM-EDS

Conclusions

The long-time hydrothermal strategy and subsequent defect healing are the keys to obtain defect-free nanosheets decorated with TiO2 quantum dots.

The size of nanosheets progressively increases with t, but the {001} percentage almost remains unchanged (81–83%).

The surface Ti3+ defects suppress the photoactivity and could be removed by

hydrothermal treatment or calcination.

The quantum dots provide a new and more effective charge separation and transfer pathway over the nanosheet surfaces, and promote the photoactivity significantly.

Quantum dot self-decorated TiO2 nanosheet