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.
Quantum Dot
Nanosheet
Aluminume-
H+
Nanosheet
① ②
Limitation of Photochromism and Electrochromism in WO 3
V. B.
W5+, W4+
C. B. Limitation of WO3 for chromic device
1. Color Limitation (Yellow ↔ Blue) 2. Excitation Wavelength (λ < 450 nm) 3. Slow decoloration rate
2.8 eV
O2
Quantum dots (QDs): tunable color!
Nano-size (Nanosheet): quick response!
Materials in the present study
Nanosheet (Cs
4W
11O
362-) and QD (CdS)
Cs6W11O36
bulk Cs4W11O362- nanosheet
Exfoliation
Fukuda et al. ACS Nano 2, 1689, 2008.
transparent
electron trapping
large surface area, quick response
color tunable
facile wet synthesis (SILAR method)
0.0 40.0 80.0 120.0 160.0 200.0
0.0 40.0 80.0 120.0 160.0 200.0
2.0 2.5 3.0 3.5 4.0
(αhv)1/2
(αhv)2
Photon E nerg y / eV 8cycles 4cycles 2cycles 1cycle 0cycle
TiO2 CdS
5 nm
TiO2
QDs
Miyauchi et al. Appl. Catal. B Environ. 179, 113, 2015.
pyrochlore structure
Aluminum
Fabrication of QDs/ Nanosheet Film
Nanosheets: Exfoliation
Cs6W11O36 H2Cs4W11O36
Colloidal nanosheets suspension Cs2CO3 WO3
Exfoliation Proton exchange Solid phase
reaction 900℃5h
12M HCl 2days TBAOH 10days
Quantum Dots: SILAR
Successive Ionic Layer Adsorption and Reaction
Thin Film:
Spin or Dip coating
visible light ①photochromismRemote
Color change
Kelvin probe forced microscope (KFM)
② Color change in water
Color change
Comparison with particles film
pH dependence
water, oxygen
substrate
substrate
substrate
glass substrate
Structure of Cs
4W
11O
362-Nanosheets
200 nm
FE-SEM： Cross Section FE-SEM：Surface
TEM AFM
500 nm
Tunable Color by QDs Size
SILAR回数 0cycle 1cycle 2cycles 4cycles 8cycles QDs size 3.7 nm 5.0 nm 5.9 nm 6.4 nm
Bandgap
Energy 3.6 eV 2.8 eV 2.6 eV 2.4 eV 2.3 eV
Empirical dependence of QDs size:
D=(-6.6521×10-8)λ3+(1.9557×10-4) λ2 -(9.2352×10-2) λ+13.29
SILAR method 4cycle
Layered
Nanosheet Layered
Nanosheet＋QDs QDs
Tunable Quantum Size effects
Remote Photochromism under Visible Light
UV-vis XPS
Color Decolor Excite only QDs
Action Spectra for Remote Photochromism
KPFM Analysis of QDs/ Nanosheet
(a)
(b) (c)
(i)
(i) (i)
(ii)
(ii) (ii)
(iii)
(iii) (iii)
Cs4W11O36-nanosheet
CdSQD
trapped
before light irradiation after light irradiation Mapping of work
function
QDsCs4W11O362- mica
positive
Decoloration Process
Nanosheet Vs. Conventional WO
3Particles
Oxygen is accepter
Fast decoloration
Fast Slow
Repeated Property
TON≧8000(生成した正孔/担持CdS量)
Quantum Dot
Nanosheet
Excitation light: Xe lamp dark
visible light
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.
Quantum Dot
Nanosheet
Aluminume-
O2 H+ O2-
Nanosheet
① ②
Novel Chromic WO 3 /Al Device
Miyauchi et al. Chem. Commun. 47, 8596, 2011.
Aqueous acid solution: Ink
Oxygen molecules in air: Eraser
in aq.
WO3+e-+H+
→H+W5+O3 Al →Al3++3e- WO3
in air
Al
Electroless Galvanic Inks on Inorganic WO3/Al Boards
Working Principle
消色(空気中）
Al
e e e e e e e e e e e e e e
Al
e e e e e
e e e e
e e e e e
H+
e-
着色 (酸性溶液）
O2 O2- Al3+
WO3の場合
~2000 nm 𝑑𝑑 = 2𝜀𝜀𝜀𝜀0Δ𝐸𝐸
𝑒𝑒𝑒𝑒 空間電荷層の 厚み d
Potential (V) vsNHE
0 V (H+ / H2)
W6+/W5+: +0.3V Al → Al3++3e-
WO3+e-+H+↔ H+W5+O3
∆E
O2
O2- Recovery Al3+
Al Dissolution
Al WO3
Al3+/Al: -1.662 V
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 WO 3 /Al
(i) Initial
(ii) Dipping in water (pH=3) (iii) Exposure to air
10 20 30 40 50 60 70 80
2 theta (degree)
Intensity (a. u.) (i)
(ii) (iii)
Monoclinic WO3 Al
H0.5WO3
25 30
35 40
45 50
Binding energy (eV)
Intensity (a. u.)
(i) (ii) (iii)
W-4f
520 525 530 535 540 545
Binding energy (eV)
Intensity (a. u.)
(i) (ii) (iii)
O-2p
65 70 75 80 85 90 95
Binding energy (eV)
Intensity (a. u.)
(i) (ii) (iii) Al-2p
Al-2p
(i) Initial
(ii) Dipping in water (pH=3) (iii) Exposure to air
Repeatability of the Reversible Color Change in WO 3 /Al
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
0 100 200 300 400 500 600
Time (min)
Absorbance at 550 nm
Initial
After repeated evaluation
WO 3 /Al Structures by Various Processes
in acid in air
in acid in air
(a) Polycrystalline WO3coated on Al foil
(b) Polycrystalline WO3coated on Al coated glass substrate (Al was deposited on glass substrate by sputtering)
in acid
in air
(c) Amorphous WO3coated on Al plate by pulsed layer deposition method.
Aluminum
From Particles To Nanosheets
20 nm 2nm
200nm
To achieve
good properties
Advantages of Nansheets
Coloration: Better junction between nanosheets
Decoloration: Short length for electron transfer
Transparency: Large bandgap by quantum size effect Aluminum
Cs
4W
11O
362-Nanosheets
WO
3Particles
TEM Images of Particles and Nanosheets
• Cs4W11O362- nanosheet
WO3 nanoparticle (比較例)
Color Change of Nanosheet/ Al Board
Fast decoloration rate t1/2= 630 s⇒ t1/2=25s
0.1 0.2 0.3 0.4 0.5
0 1000 2000 3000
Absorbance at 600nm
time /s
Transparent Cs4W11O362- Blue
Cs4W11O362-
Cs4W11O362- nanosheet WO3 particle
Coloration：in acid solutionDecoloration：in air Coloration：in acid solutionDecoloration：in air
量子ドットの元素戦略
8 9 10 11 12 13 14 15 16
Al Si P S
Fe Co Ni Cu Zn Ga Ge As Se
Tc Rh Pd Ag Cd In Sn Sb Te
量子ドットとして硫化物（クラーク数15）を利用する。
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 QDs
elemental strategy
theory device
H2
Sn
ubiquitous S
Miyauchi et al. Chem. Commun. 52, 7470, 2016. Miyauchi et al. J. Phys. Chem. C 122, 21695, 2018.
Future Work 2: Surface Modification
QD PEDOT
TiO2
Miyauchi et al. Appl. Catal. B Environ. 179, 113, 2015.
For more stable: PEDOT coating
For more efficient: SiO
2coating
Miyauchi et al. Appl. Phys. Lett.96, 233107, 2011.
SiO2 QD TiO2
metal oxide
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）
