量子ドット、ナノシートを用いた色変換素子の開発
東京工業大学・物質理工学院 宮内雅浩
① 多色・高速変換が可能なリモートフォトクロミック
 Miyauchi et al. Adv. Funct. Mater. 20, 4162, 2010.
 Miyauchi et al. Nanoscale 7, 12510, 2015.
② 水溶液がインク、酸素が消しゴムとして働く色変換素子
 Miyauchi et al. Chem. Commun. 47, 8596, 2011.
 Miyauchi et al. J. Mater. Chem. C 2, 3732, 2014.

①

Quantum Dot②H+e-Nanosheet

AluminumNanosheet

Limitation of Photochromism andElectrochromism in WO3
O2

C. B.

2.8 eV

V. B.

W5+, W4+

Limitation of WO3 for chromic device

1.

Color Limitation (Yellow ↔ Blue)

2.

Excitation Wavelength (λ < 450 nm)

3.

Slow decoloration rate

Quantum dots (QDs):

tunable color!

Nano-size (Nanosheet):quick response!

Materials in the present study
Nanosheet (Cs4W11O362-) and QD (CdS)
200.0

pyrochlore structure

200.0
8cycles

TiO2

CdS

4cycles

160.0

Exfoliation

1cycle(αhv)25 nm

40.0

Cs4W11O362nanosheet

QDs

80.0

40.0

TiO2

0.0

0.0
2.0

 transparent
 electron trapping large surface area, quick response
Fukuda et al. ACS Nano 2, 1689, 2008.

120.00cycle(αhv)1/2

120.0

80.0

Cs6W11O36
bulk

160.02cycles

2.5

3.0
3.5
Photon E nerg y / eV4.0

 color tunable facile wet synthesis(SILAR method)

Miyauchi et al. Appl. Catal. B Environ. 179, 113, 2015.

Fabrication of QDs/ Nanosheet Film
Quantum Dots: SILAR

Nanosheets: Exfoliation
Cs2CO3
Solid phasereactionProtonexchange
Exfoliation

WO3
900℃ 5h

Cs6W11O36

Thin Film:
Spin or Dip
coating

Successive Ionic Layer
Adsorption and Reaction
substrate

12M HCl 2days

H2Cs4W11O36

TBAOH 10days

substrateColloidal nanosheets
suspension

visible light

substrate① Remote
photochromism

water,oxygen

 Color change Kelvin probe forced
microscope (KFM)
glass substrate

Aluminum② Color change
in water Color change Comparison withparticles film
 pH dependenceStructure of Cs4W11O362- Nanosheets

200 nmTEM

FE-SEM：Surface

AFM

500 nmFE-SEM： Cross Section

Tunable Color by QDs Size
SILAR method
LayeredNanosheet

SILAR回数0cycle

QDs size
Bandgap
EnergyLayeredNanosheet＋QDs

4cycle1cycle2cycles4cyclesQDs8cycles

3.7 nm 5.0 nm 5.9 nm 6.4 nm
3.6 eV

2.8 eV

2.6 eV

Tunable2.4 eV

2.3 eV
Quantum Size effects

Empirical dependence of QDs size:

D=(-6.6521×10-8)λ3+(1.9557×10-4) λ2 -(9.2352×10-2) λ+13.29

Remote Photochromism under Visible Light

Color

UV-visExcite only QDs

DecolorXPSAction Spectra for Remote Photochromism

KPFM Analysis of QDs/ Nanosheet
(i)

CdS
QD

trapped

(a)
(ii)
(iii)

Cs4W11O36- nanosheet

Mapping of work
functionQDs
Cs4W11O362mica

(i)

(b)

(i)

(c)

(ii)

(ii)(iii)(iii)

before light irradiation

after light irradiation

positiveDecoloration Process
Nanosheet Vs. Conventional WO3 Particles

 Oxygen is accepter
 Fast decoloration

FastSlowRepeated Property

Quantum Dot

visible lightdark
Excitation light: Xe lamp
 TON≧8000(生成した正孔/担持CdS量)

Nanosheet 量子ドットのサイズによって色制御可能
 高速・可逆色変換

量子ドット、ナノシートを用いた色変換素子の開発
東京工業大学・物質理工学院 宮内雅浩
① 多色・高速変換が可能なリモートフォトクロミック
 Miyauchi et al. Adv. Funct. Mater. 20, 4162, 2010.
 Miyauchi et al. Nanoscale 7, 12510, 2015.
② 水溶液がインク、酸素が消しゴムとして働く色変換素子
 Miyauchi et al. Chem. Commun. 47, 8596, 2011.
 Miyauchi et al. J. Mater. Chem. C 2, 3732, 2014.

①Quantum Dot②O2H+ O2e-Nanosheet

AluminumNanosheet

Novel Chromic WO3/Al Device
WO3+e-+H+→H+W5+O3

WO3
Alin aq.

Al → Al3++3e-in airAqueous acid solution: Ink
Oxygen molecules in air: Eraser

Electroless Galvanic Inks on
Inorganic WO3/Al Boards

Miyauchi et al. Chem. Commun. 47, 8596, 2011.

Working Principle
着色 (酸性溶液）+H
空間電荷層の𝑑𝑑 =e2𝜀𝜀𝜀𝜀0 Δ𝐸𝐸𝑒𝑒𝑒𝑒eeeeeeeeeeee- Al

WO3の場合~2000 nm消色(空気中）O2-O2eeeeeeeeee

Al

Al3+

Al → Al3++3e-Dissolutionee

Al3+Al3+/Al: -1.662 V
Al

Potential (V) vs NHE

厚み d∆E WO +e-+H+↔
0 V (H+ / H2)

3

H+W5+O3
W6+/W5+: +0.3V

O2
RecoveryO2-Al

WO3eeee

WO3粒子を使って原理検証➝ ナノシートによる高性能化

XRD and XPS for WO3/Al(ii)Intensity (a. u.)(i)

O-2p(i)
(iii)

(i)
(ii)
(iii)

H0.5WO35045(ii)4035
Binding energy (eV)Al-2p(iii)102030405060

7080

3025(ii)
(iii)

9590

540

535
530
Binding energy (eV)

525

520

(i) Initial(ii) Dipping in water (pH=3)(iii) Exposure to air

2 theta (degree)(i) Initial(ii) Dipping in water (pH=3)(iii) Exposure to air

545

(i)

Al-2p
Intensity (a. u.)

Intensity (a. u.)

W-4f

Intensity (a. u.)

Al

Monoclinic WO3

858075
Binding energy (eV)7065

Repeatability of the Reversible Color
Change in WO3/Al
1.8

Absorbance at 550 nm

1.6
1.4

Initial1.210.80.60.4

After repeatedevaluation

0.200100200300400Time (min)500600WO3/Al Structures by Various Processes
in acidin air(a) Polycrystalline WO3 coated on Al foilin acidin air(b) Polycrystalline WO3 coated on Al coated glass substrate(Al was deposited on glass substrate by sputtering)in acidin air(c) Amorphous WO3 coated on Al plate by pulsed
layer deposition method.

From Particles To Nanosheets
2nm

20 nm

Aluminum

WO3 Particles

200nm

To achieve
good properties

AluminumCs4W11O362- Nanosheets

Advantages of NansheetsColoration: Better junction between nanosheets

Decoloration: Short length for electron transfer

Transparency: Large bandgap by quantum size effectTEM Images of Particles and Nanosheets
WO3 nanoparticle (比較例)• Cs4W11O362- nanosheet

Color Change of Nanosheet/ Al Board
0.5

Absorbance at 600nm

 Fast decoloration rate
t1/2= 630 s⇒ t1/2=25s

Coloration：inacid solution
Decoloration：in
airBlue
Cs4W11O3620.4
WO3 particle

0.3

0.2

0.1

Cs4W11O362- nanosheet
Transparent Cs4W11O3620

1000

2000

time /s3000

量子ドットの元素戦略
量子ドットとして硫化物（クラーク数15）を利用する。
8910111213141516AlSiP

SFeCo

NiCuZnGaGeAsSe

TcRh

PdAgCdInSnSbTe

太陽電池や量子ドットに使われる多くの既往の化合物：
毒性・希少金属を含む（CIGS、CdTe）

安価、安全な元素からなり、可視光を吸収する化合物：● SnS (BG= 1.3 eV)● Cu2ZnSnS4 (CZTS) (BG= 1.2 eV)

Future Work 1: Ubiquitous QDselemental strategy
ubiquitousSSn
theorydeviceH2

Miyauchi et al. Chem. Commun. 52, 7470, 2016.

Miyauchi et al. J. Phys. Chem. C 122, 21695, 2018.

Future Work 2: Surface Modification
For more stable: PEDOT coating
PEDOT
QD

TiO2oxide
metal
Miyauchi et al. Appl. Catal. B Environ. 179, 113, 2015.

For more efficient: SiO2 coating
SiO2
TiO2QD
Miyauchi et al. Appl. Phys. Lett. 96, 233107, 2011.

Acknowledgement
本研究は公益財団法人日本板硝子材料工学助成会の支援のもと、おこないました。ここに感謝の意を表します。積水樹
脂技術研究所様にも深く御礼申し上げます。

近藤彰彦 （卒業生）
現 日本特殊陶業（株）