Crystalline structure- Single crystal & Powder X-ray diffraction (XRD)- Electron crystallography

Oxidation state & Coordination- X-ray absorption spectra- X-ray photoelectron spectra (XPS & Auger)- Solid state NMR ( mainly coordination)- IR & Raman ( mainly coordination)- UV-Vis spectra

Elemental analysis- ICP-AES, XPS, EDXSurface area & Pore size

- N2 adsorption-desorption isotherm- Mercury Intrusion Porosimetry

Morphology- SEMPore structure- TEM

Techniques for characterization of nano-porous materials

X-ray Absorption Spectroscopy

x

I(0, ω)I(x, ω)

Beer’s Law: I(x, ω)=I(0, ω) e -µ(ω) x

−µtx = ln (I(x, ω) / I(0, ω))

8800 9000 9200 9400 9600 9800 10000 10200-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

Abs

orpt

ion

Energy (eV)

XANES EXAFS

Cu

Cu

constructive

destructive

Absorption edge

S K-edge XANES spectra of (a) MPTMS,(b) dipropyl disulfide, (c) S16-SO3H (10%) 2M HCl, (d) S16-SO3H (20%) 0.5M HCl, (e) S16-SO3H (20%) 1.0M HCl, (f) S16-SO3H (20%) 2.0M HCl and (g) S16-SO3H (30%) 2.0M HCl

Si-OH

Si-OH

Si-OH

H3COSiH3CO

H3CO

SHO

O

OSi SH

H2O2

O

O

OSi

SOH

O

O

2455 2460 2465 2470 2475 2480 2485 2490 2495 2500 2505

(g)

(f)

(e)

(d)

(c)

(b)

(a)

Nor

mal

ized

Inte

nsity

Energy/eV

MPTMS

d

Neighbor AtomAbsorbing Atom

Unoccupied ValenceStates

k = kc = 2π /d

k < kc

k > kc

EXAFS

XANES

E

EC

ER

E0

Continuum States

hv

de Broglie eq.

( )edgek Ehh

mE

hm

−

=

== ν

ππλπ

κ 2

221

2

2 88

2

2

21

mvEhE bk =−= ν

)(2 bEhm

hmvh

−==

νλ

photoelectron wave vector

EXAFS function

[ ] )()()()( 00 EEEE µµµχ −=

μ:measured absorption coeff.μ0: no EXAFS

( )edgek Ehh

mE

hm

−

=

== υ

ππλπ

κ 2

221

2

2 88

2

m = mass of electron

When the unit of Ek is eV, κ = [0.2625(E-E0)]1/2

In EXAFS region

Kronig structure – reflected the local structure surrounding the atom under study

Usually taking the spectra 50 – 1000 eV above adsorption edge, then subtract the background, and obtain the spectrum of χ(k) vs. K

( )

)2

exp(

)2exp()(22sin)( 222

κ

κσκφδκκ

κχ

ji

jjjjj

j

j

RV

fRR

N

−⋅

−⋅⋅++⋅⋅

= ∑

E2 a κ photoelectron wave vector

δ: phase shift of emitting atomφj: phase shift of back scattering atom in jth shellfj(K): amplitude of the back scattering factorσj

2: Debye-Waller factorvi: inelastic scattering of photo-electron waveNj: coordination no. of jth shellRj: interatomic distance of jth shell

the mean square fluctuation ofthe interaction distance

8800 9000 9200 9400 9600 9800 10000 10200 10400

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

expt bkg

Abs

orpt

ion

Energy (eV)

0 2 4 6 8 1 0 12 14 16 18 20-10

-8

-6

-4

-2

0

2

4

6

8

10

ok (A -1)

k3 χ

(k)

0 1 2 3 4 5 6 7 8 9 100

2

4

6

8

10

12

14

|χ(R)|data

|χ(R)|model

o

|FT[

k3 χ

(k)]

|=| χ

(R)|

R (A)

EXAFS

∑ −−+=

j

kR

jjj

jj j

j

eekkRkR

kFkSNk

2222

2

20 )](2sin[

)()()( σλδχ

原始實驗數據

去除不正常的數值點

扣除背景值及規一化

傅立葉轉換

r < 1 Å 之振幅

傅立葉濾波

在k空間進行曲線配適

在r空間進行曲線配適

EXAFS simulation provides informations on(i) Rj: accurcy ±0.01 ~ 0.05 Å for the 1st & 2nd shell(ii) Nj: ±20% for the 1st shell(iii) σj

2: as small as possible(iv) r: deviation factor (as small as possible)

Rh metal

Rh2O3

RhCl3

Coordination Number

Hydrogen Chemisorption and EXAFS Results of Rh, Ir and Pt Nano-Particles Supported on Alumina

Crystalline structure- Single crystal & Powder X-ray diffraction (XRD)- Electron crystallography

Oxidation state & Coordination- X-ray absorption spectra- X-ray photoelectron spectra (XPS & Auger)- Solid state NMR ( mainly coordination)- IR & Raman ( mainly coordination)- UV-Vis spectra

Elemental analysis- ICP-AES, XPS, EDXSurface area & Pore size

- N2 adsorption-desorption isotherm- Mercury Intrusion Porosimetry

Morphology- SEMPore structure- TEM

Techniques for characterization of nano-porous materials

• Electron Paramagnetic Resonance Spectroscopy

molecules, ions or atoms possess electron with unpaired spins magnetic moment of e-

HSg ee

vvvv ⋅=Η−= µβµ - ,

zSHg ˆˆ β=Η

2.0023193g .e free afor value,-g :g

operatorspin :ˆ2

magnetonBohr :

- =

=

Z

e

S

Cmeh

β

g value for an unpaired e- in a gaseous ion or atom

)1(2)1()1()1(

1+

+−++++=

JJLLSSJJ

g

HamiltonianMagnetic field

Zeeman Splitting for e- is ~700 times larger than for 1H

e.g. H0=10,000 gauses,

MHz 58.42

MHz 026,28

1 =∆

=∆ −

H

e

E

E

Sensitivity of EPR > NMR (because of ΔE)EPR lines broader than NMR

H g β=∆E

ms = +1/2, E = +1/2 gβH0

ms = -1/2, E = -1/2 gβH0

For electron of spin S= ½ ,

lα>, lβ>

lα>

lβ>

In magnetic field, H0

Two common freq. for EPR experiment (fixed frequeacy)micro-wave range

“X-band” H0=3,400 Gauss, ν~9500 MHz

“Q-band” H0=12,500 Gauss, ν~35,000 MHz

sensitivity α ν2

(free e- resonance freq.)

Water, alcohols, high dielectric constant solvents absorb microwave power, ⇒ not suitable solvent

Samples can be gases, solutions, powders, single crystals or frozen solutions

in NMR

in EPR

INN mHgE ∆−−=∆ 0)1( σβ

0HgE β=∆change in shielding constant

change in g value

For 1H, I=1/2

I=1

Zeeman interaction⇒ 2I+1 states

mI = +1/2, E = -1/2 gNβNH0

mI = -1/2, E = +1/2 gNβNH0

0NN H g β=∆E

mI = +1, E = -gNβNH0

mI = -1, E = +gNβNH0

mI = 00NN H g β=∆E

For H0 ˜ 14,000 Gauss, ν=60 MHz (60,000,000 sec-1) ~ 2x10-3 cm-1

Boltzmann Distribution

999995.01)2

1(

)21(

=∆

−≈=+

− ∆−

kTE

eN

NkT

E ΔE ~ 10-3 cm-1

kT ~ 200 cm-1

resolution ~ 0.1 Hz

If use higher field, e.g. 300 MHz ⇒ better resolution

0.999995

1.0

mI = -1/2

mI = +1/2

For 1H

I = 1/2

• High resolution NMR spectra of solids

ψψ E=Η

SRQCSJDRFZ Η+Η+Η+Η+Η+Η+Η=Η

external Hamiltonian internal Hamiltonian

HZ: Zeeman interaction of the nuclear magnetic moment with the applied field B0

HRF: interaction between nuclear spin & the time-dependent radio freq. field B1(t)

HD: dipolar interaction between nuclear magnetic dipole momentsHJ: e— mediacted nuclear spin-spin interactionHCS: chemical shift associated with electronic screening of nucleiHSR: spin-rotation interaction; I and molecular angular momentumHQ: nuclear spin & quadruple moment

not importantin solid

importantfor I > 1/2

A general Hamiltonian for the interactions experienced by a nucleus of spin I

HamiltonianWave function

eigenvalue

A general Hamiltonian for the interactions experienced by a nucleus of spin I in the solid state may be written as in equation (1.2)

H = HZ + HD + HCS + H SC + HQ (1.2)

0 ~ 109Quadrupolar

0 ~ 104Scalar Coupling

0 ~ 105Chemical Shift

0 ~ 105Dipolar

106 ~ 108Zeeman

Table 1.1 Approximate ranges of the different spin interactions (in Hz)

Zeeman interaction

ZNNzZ

ZZ

IHgIHH

HHHH

00

000 cos

βγ

µθµµ

−=−=

−=−=⋅−=

h

vv

=

==

Cme

g

IgI

PN

NN

2h

h βγµ

magnetogyric ratio

nuclear g factorBohr magneton of the particular nucleus

Dipolar interaction HD

IDIr

HHij

IIID

vvh⋅⋅== ˆ

3

22γ

internuclear distance

dipolar coupling tensor

magnetogyric ratio

For single type of spin, I

Chemical shift interaction

0ˆ HIH ICS

vvh ⋅⋅= σγ Proportional linearly to the applied field

Range of common isotropic chemical shift (ppm)

necleus

20031P

10019F

25013C

8029Si

35015N

201H

Table. Typical values of chemical shift

Spin-spin coupling interaction

SJIH SC

vv⋅⋅= ˆ

field independent and is usually smaller than the other interaction

Quadrupolar interaction

IQIHQ

vv⋅⋅= ˆ

nuclear electric quadrupole moment eQ

only when I > ½field independent

ν

ν

ν1

ν2

Dipolar Interaction

HD = 0, if 3cos2θij – 1 = 0

Magic Angle Spinning

(MAS)

Q4

Q3

Q2

Crystalline structure- Single crystal & Powder X-ray diffraction (XRD)- Electron crystallography

Oxidation state & Coordination- X-ray absorption spectra- X-ray photoelectron spectra (XPS & Auger)- Solid state NMR ( mainly coordination)- IR & Raman ( mainly coordination)- UV-Vis spectra

Elemental analysis- ICP-AES, XPS, EDXSurface area & Pore size

- N2 adsorption-desorption isotherm- Mercury Intrusion Porosimetry

Morphology- SEMPore structure- TEM

Techniques for characterization of nano-porous materials

△E = hνm

Vibrational Spectroscopy

IR Spectroscopy

IRstretching

bending

stretchingbending

stretchingbending

stretching

stretching

stretching

Faujasite

Ferrierite

ZSM-5

Raman Spectroscopy

Boltzman Distribution affects the intensity of Anti-Stocks

Anatase638

515 395

200400600800

Rutile445

608

200400600800

Fig. 3.2 FT-Raman spectra of TiO2 of anatase and rutile phases: (a) lab-made, and after calcination at (b) 400 ℃, (c) 700 ℃, in comparison to (d) ) commercially available.

(a)(a)

(b)(b)

(c) (c)

(d)

(d)

Conclusions

There are still a huge There are still a huge SPACESPACE in the research of in the research of nanonano--porous materials. porous materials.