Literature Seminar–2D materials–
M2 T. Sawazaki
1901101

CONTENTS

2D materials
graphene (2004– )introduction
TMD (2005–)
MXene (2011–)…

Energy Environ. Sci., 2019, Advance Article. (IF 30.0)

beyond graphene
their application
hot reports
for future

ACS Photonics, 2017, 4, 407. (IF 6.9)
(virtual issue; http://pubs.acs.org/page/vi/ 2Dmaterials.htm)

practical using
hot reports2

INTRODUCTION (0)portablewearable

implantable“nanotechnology”
3INTRODUCTION (1)“The atom is the smallest unit of a substance.”

The atomic size is the theoretical smallest one.

·first isolation of atomic–size compind
Nobel Prize in Physics in 2010
"for groundbreaking experiments regarding the two-dimensional material graphene.”

Andre Geim

Konstantin Novoselov

Science, 2004, 306, 666.
4

ISOLATION OF GRAPHENE“access from 3D to 2D”
graphenegraphite

2D materials
van der Waals force(weak)atomic thin

3D (bulk) compound

semimetal
firmchanged properties

2D (layerd) compound

gapless semiconductor

flexible

5

PROBLEM OF GRAPHENE
the (practical) example
cf $695high costdifficulty of mass productiondifficulty of big–size production
no band gap

Ref. https://www.dezeen.com/2018/08/16/vollebakgraphene-jacket-radiator-conduct-power-clothing-design/
6BEYOND GRAPHENE (1)black phosphorus(phosphorene)

Metal Halide Perovskite

h–BN

J. Am. Chem. Soc. 2009, 131, 6050.
Nat. nanotech. 2014, 9, 372.

Appl. Phys. Lett. 2008, 92, 722.
Chem. Sci. 2017, 8, 2522.

7

BEYOND GRAPHENE (2)Transition Metal Dichalcogenide MX2

chalcogenTransition metal

8

COMBINAITON OF TMD

Nat. Chem., 2013, 5, 263.

a variety of combination9

EXAPMLE OF TMD

three–atom–thin layer
bulk crystal MoS2

Optical microscopy image
crystal structure
For lubrication
Ampere cop

Nat. Nanotechnol. 2012, 7, 699.
10

STRUCTURE OF TMD
MXbulk TMD

exfoliation

layerd TMD

X

precursor

H / T ...??

Nat. Nanotechnol. 2012, 7, 699.
11

STRUCTURE OF LAYERED TMD (1)trigonal prismaticoctahedral
Chem. Rev. 2018, 118, 6297.

1. What is trigonal prismatic / octahedral?
2. What makes H–phase / T–phase?
3. electronic properties

12

EXPLANATION (1)·crystal–field theory
ligandmetald orbital
egt2g“splitting d orbitals”

13

EXPLANATION (2)·spectrochemical series

small

big

[Co(NH3)5Br]3+[Co(NH3)5Cl]3+small[Co(NH3)5(NH3)]2+

big
14

EXPLANATION (3)·mono–lattice d orbital
trigonal prismaticoctahedrald orbitald orbital

e’’eg

e’t2g
a1 ’

15

BAND STRUCTURE OF LAYERED COMPOUND

trigonal prismaticEEoctahedral
e’’e’eg

t2g

a1 ’
band structure

band structure
16

STRUCTURE OF LAYERED TMD (2)trigonal prismaticoctahedral
Chem. Rev. 2018, 118, 6297.

1. What is trigonal prismatic / octahedral?
2. What makes H–phase / T–phase?
3. electronic properties

17

EXPLANATION (4)·Ketelaar triangle

ΔΧ

Χmean

d6–Ch: covalent
d4–Ch: metallic

The order of electronegativity (Χ)

4 <5 <6 <1618

TREMENDACE BETWEEN METAL AND PHASE

trigonal prismatic

Octahedral

interaction

Ionic repulsion

Not ionic (covalent)
d6 metal

d4 metal

19

STRUCTURE OF LAYERED TMD (3)trigonal prismatic
d6metal

1. What is trigonal prismatic / octahedral?
2. What makes H–phase / T–phase?
3. electronic properties

Octahedral
d4metalChem. Rev. 2018, 118, 6297.

20

EXPLANATION (5)·electronic properties
EEE

Band gap

insulator

Band gap

metal

semiconductor

21

EXAMPLE OF METALLIC TMD

Chem. Rev. 2018, 118, 6297.

NOTE

NbSe2 metal / MoSe2 not metal
22

EXPLANATION OF TMD PROPERTIESE

H–phaseNb4+ (d1)

NbSe2

metal

d5

MoSe2

H–phaseMo4+ (d2)insulator

d623

SHORT SUMMARY
3D materials(bulk)

graphiteTransition Metal Dichalcogenide

2D materials(layered)graphene

Transition Metal Dichalcogenide

1over 30constructing atoms

carbontransition metal and chalcogenstructure

1 typehexagonal

number of the example

material properties

gapless semiconductor

2 typestrigonal prismaticoctahedral
semiconducting TMDs (Nat. Nanotechnol. 2012, 7, 699.)
metallic TMDs (Chem. Rev. 2018, 118, 6297.)
24

SYNTHESIS METHOD (1)·mechanical exfoliation
top down approach–1
first report; Science, 2004, 306, 666.

·easy–to–access approach

3D
2D·not scalable·difficult to control the size·reaggregation
25

SYNTHESIS METHOD (2)·Chemical Vapor Deposition
bottom up approach–1often used for industrial method

MoO3 + x/2 S → Mo3–x + x/2 SO2
MoO3–x + (7–x)/2 S →MoS2 + (3–x)/2 SO2Adv. Mater. 2012, 24, 2320.

·large scale·difficult to control the number of the layer·poor quality

26

SYNTHESIS METHOD (3)·Metal–Organic Chemical Vapor Deposition
bottom up approach–2
first report; Nature 2015, 520, 656.

mass flow controllers·homogeneity·low decomposition
temperature of the precursor·limited examples (not yet for metal TMD)
·still relatively small (4–inch)·toxic gas27SYNTHESIS METHOD (4)·liquid phase exfoliation/mechanical approach
top down approach–2

sonication·stabilizing against the reaggreation
soluvent

organic
NMP or IPA (Science, 2011, 331, 568.)
ethanol/water (ACIE, 2011, 50, 10839.)
aqueous surfactant
a sodium cholate solution (Adv. Mater 2011, 23, 3944.)·few hundred nanometers in size

polymerJ. Phys. Chem. C, 2012, 116, 11393.
28

SYNTHESIS METHOD (5)·liquid phase exfoliation/chemical approach
top down approach–3
first report; Mater. Res. Bull. 1986, 21, 457.
Li–intercalation(topochemical reaction)
nBuLi

H2O–H2bulk MX2·effective in expanding the layers·high yield of monolayer

bulk LiMX2·expensiveness (Li+)·structurally and electronically different
for example; MoS2
trigonal prismatic(semiconducting)octahedral(metal)
29

BEYOND GRAPHENE (3)MXene
first example; Adv. Mater. 2011, 23, 4248.
–OH, –F, –O, –Cl

Ti
TiC
Al

sonication
DMSO intercalation

single layer MXene
etching

Ti3AlC2 + 3HF → AlF3 + 3/2H2 +Ti3C2
Ti3C2 + 2H2O → Ti3C2(OH)2 + H2
Ti3C2 +2HF → Ti3C2F2 + H2

Acc. Chem. Res. 2018, 51, 591.
30

CHARACTARISTICS OF MXene
1. metallic

high electronic conductivity (2.0×104 S cm–1)(cf. Cu, 5.8×105 S cm–1)

2. flexibility of composition
Ti2CTx, Ti3C2Tx, V2CTx, Nb2CTx, Mo2CTx,(Mo2Ti)C2Tx, Mo1.33CTx, Ti3(CN)Tx,Acc. Chem. Res. 2018, 51, 591.
31

HOT REPORT (1)·phase engineering
MoS2 semiconductor to metal transfermono–latticemono–latticee’’eg

e’t2g
3e casea1 ’
2e casesemiconductor transistor

metalNano Lett., 2015, 15, 5956.
32

HOT REPORT (2)·application of MXeneDAQACS Nano 2018, 12, 10419。

33

EXPECTED FUTURE

injection and release of the microneedle

freely moving mice

implantable LED

electrodewireless power system

Science 2013, 340, 211.
34

CONCLUSION

2D Mater., 2016, 3, 022002.

35

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https://www.nanophoton.jp/applications/30.html

37

PHYSICAL AND CHEMICAL TUNING (1)·z direction

calculated band structure
fluorescentAdv. Energy Mater., 2015, 5, 1402279.

E(k)Nano. Lett., 2010, 10, 1272.

k (electron wavenumber)
38

PHYSICAL AND CHEMICAL TUNING (2)·z direction
PtSe2

Nat. Commun., 2018, 9, 919.

39

PHYSICAL AND CHEMICAL TUNING·z direction

Nat. Commun., 2018, 9, 1545.

40

STRUCTURE PATTERMS OF BULK TMD

41

FIRST EXMAPLE OF TMD

PNAS, 2005, 102, 10451.

42