Raman Spectroscopy with Practical Applications · Raman spectroscopy and laser excited...

© 2019 HORIBA, Ltd. All rights reserved. 2© 2019 HORIBA, Ltd. All rights reserved. 2

Raman Spectroscopy with Practical Applications

David Tuschel

May 29, 2019

© 2019 HORIBA, Ltd. All rights reserved. 3

Raman spectroscopy and photoluminescence Polymorphism Liquid and head space Raman spectroscopy Raman spectroscopy of polymers Particle size characterization with chemical

identification

Presentation Topics


Vibrational spectroscopy studies vibrations in a system using light. IR and Raman spectroscopy are the most common and

complementary to each other. IR spectroscopy is absorption (or reflection) spectroscopy Raman spectroscopy is scattering spectroscopy

Applications of vibrational spectroscopy Molecular spectroscopy

- Vibrations of atoms within molecules- Gas, liquid and solid

Solid state and material science- Vibrations of atoms within molecules (e.g. molecular crystals, amorphous

materials)- Vibrations between atoms and molecules (e.g. amorphous materials)- Vibrations of crystalline lattice- From liquid to solid (e.g. gel, crystal)

Vibrational Spectroscopy


Raman Scattering

RayleighStokes Anti-Stokes

E0

E1

Virtual States

v0

v1

v2

v3

hνex

hνex hνex hνex

h(νex – νv)h(νex + νv)


Raman Spectra of Polystyrene at 532, 638 and 785 nm Excitation

Raman Shift (cm-1)

Inte

nsity

/ A

rbitr

ary

Uni

ts

λex: 532 nm

λex: 638 nm

λex: 785 nm


Raman Spectra of Polystyrene at 532, 638 and 785 nm Excitation

Wavelength (nm)

Inte

nsity

/ A

rbitr

ary

Uni

ts

λex: 532 nm

λex: 638 nm

λex: 785 nm


Raman Spectra of Glass Microscope Slide at 532, 638 and 785 nm Excitation

Raman Shift (cm-1)

Inte

nsity

/ A

rbitr

ary

Uni

ts

Photoluminescence

PhotoluminescenceRaman Scattering

λex: 532 nm

λex: 638 nm

λex: 785 nm


Raman Spectra of Fused Quartz at 532, 638 and 785 nm Excitation

Raman Shift (cm-1)

Inte

nsity

/ A

rbitr

ary

Uni

ts

λex: 532 nm

λex: 638 nm

λex: 785 nm


Photoluminescence of Few-Layer MoS2

Wavelength (nm)

Inte

nsity

(arb

itrar

y un

its)

691

Raman bands

930λex: 633 nm

λex: 532 nm

Same location


Raman Spectra of Al2O3:Cr at 532 and 633 nm Excitation

Raman Shift (cm-1)

Inte

nsity

(Arb

itrar

y U

nits

)

144 417

568

734

λex: 532 nm

λex: 633 nm

PL

PL


Photoluminescence Spectra of Al2O3:Cr at 405, 532 and 633 nm Excitation

Wavelength (nm)

Inte

nsity

(Arb

itrar

y U

nits

)

810

λex: 532 nm

λex: 633 nm

λex: 405 nm

692.8 694.2R1R2


Raman Spectra of Methanol and Ethanol

20000

15000

10000

5000

0

500 1000 1500 2000 2500 3000 3500

OHstretching

CHstretching

CO stretching

CH3deformation

Raman Shift (cm-1)

Ram

an In

tens

ity (a

rbitr

ary

unit) CO

stretching

CH3 and CH2deformation

13


Spectral Analysis: Comparison

The same chemical composition C6H12O6but different molecular structures

Inte

nsity

(a.u

)

1 000 2 000 3 000Wavnumbers (cm-1)

glucose

fructose


Similar Molecular Structures3,4-Methylenedioxymethamphetamine (MDMA) Methamphetamine

500 1000 1500 2000 2500 3000 3500Raman Shift (cm-1)

Ram

an Intensity (arbitrary unit)


DiastereomersPseudoephedrineEphedrine

500 1000 1500 2000 2500 3000 3500Raman Shift (cm-1)

Ram

an Intensity (arbitrary unit)


1000

800

600

400

200

Inte

nsity

(cou

nts/

s)

Wavenumber (cm-1)

MgSO4

Substitution

Na2SO4


Carbon Nanotubes

200

400

600

800

1 000

1 200

1 400

1 600

1 800

2 000

2 200

2 400

2 600

2 800

3 000

Inte

nsity

(cnt

)

200 400 600 800 1 000 1 200 1 400 1 600 1 800 2 000Raman Shift (cm-1)

Radial breathing mode (RBM) Nanotube diameter

Tangential modes (G band) Electronic properties

D band Info on defects


Raman Spectroscopy and Polymorphism

Monoclinic and Tetragonal ZrO2

Anatase and Rutile TiO2

Acetaminophen Forms I and II


200

300

400

500

600

700

Inte

nsity

(cnt

/sec

)

200 300 400 500 600 700 800 900 1 000

MZrO2TZrO2

635

.9

177

.7 1

90.2

221

.2

265

.7

306

.0 3

32.9

346

.3

380

.5

475

.6 5

02.5

536

.6 5

57.3

613

.2

642

.1

145

.7

176

.7 1

88.1

261

.5

322

.5

465

.3

608

.0

At ambient conditions the monoclinic phase is stable. The high T tetragonal phasecan be stabilized by alloying with oxides such as Y2O3, Al2O3, CaO. There is a thirdphase which is cubic, and stable at even higher temperatures.

ZrO2 : Monoclinic and Tetragonal

Tetragonal

Monoclinic


Anatase and Rutile TiO2 with 532 nm Excitation

Raman Shift (cm-1)

Inte

nsity

(Arb

itrar

y U

nits

)

516

445610

397197

143

241

638

Rutile

Anatase

Both Anatase and Rutile are TiO2 but of different polymorphic forms - identical chemical composition, different crystalline structures.


Rutile with Anatase TiO2 Impurity, Green Spectrum

Raman Shift (cm-1)

Inte

nsity

(Arb

itrar

y U

nits

)

516

445 610

397197

143

241638

Rutile

Anatase


Acetaminophen Form I (Red) and Form II (Blue)

Raman Shift (cm-1)

Inte

nsity

(Arb

itrar

y U

nits

)

Form I

Form II



Raman Shift (cm-1)

Inte

nsity

(Arb

itrar

y U

nits

)

1447

1324

1619

1649

1221

1169

1237

1561

1279 1611Form I

Form II

1258 1372

11691245

1265

1327

13751452 1508

1576

16091625

1650


Raman Shift (cm-1)

Inte

nsity

(Arb

itrar

y U

nits

)

505413

466

652

332

330

340628

392605

Form I

Form II

345389

394

419454

508

651

624

605



Raman Shift (cm-1)

Inte

nsity

(Arb

itrar

y U

nits

)

215

90

109

51

25

3342

152

56

130

Form I

Form II45

76122

140

206



Liquid and Head Space Raman Spectroscopy

Hydrogen Bonding and Molecular Interactions


Macro-Raman Sampling from a Cuvette


Macro-Raman Sampling from a Bottle


Head Space of Beer – CO2

Raman Shift / cm-1

Inte

nsity

/ co

unts

Head Space

1408.8

1284.8

O2

1387.5

1264.4

fwhm: 0.9 cm-1

1369.3

ν1

2ν2

2ν21 hotν1

1/ν1(13C)

2ν2(13C)

ν1 should be at 1330 cm-1

2ν2 should be at 1334 cm-1

Fermi splitting = 103 cm-1


Sparkling Water – CO2

Raman Shift / cm-1

Inte

nsity

/ ar

bitr

ary

units

Head Space

Liquid

1633.6

1379.6

1285.0

O2

1387.7

1272.7

fwhm: 0.9 cm-1

fwhm: 9.9 cm-1


Ammonia – Hydrogen Bonding

Raman Shift / cm-1

Inte

nsity

/ ar

bitr

ary

units

Head Space

Liquid3424O-H

3314N-H

3340N-H

3659O-H

Note the relative strengths of hydrogen bonding between NH3 and H20.


Methanol – Hydrogen Bonding

Raman Shift / cm-1

Inte

nsity

/ ar

bitr

ary

units

Head Space

Liquid

2832 2941

3340O-H

3684, 3697O-H

28462956


Raman Spectroscopy of Polymers

Aromatic PolymersPET

Stretched Polypropylene


Polymers• Very long chain of (usually) organic repeating unit. Extensive flexibility is

possible:– Non-oriented “spaghetti” form (amorphous), or oriented chains, as a

result of extrusion, which can be amorphous or crystalline– Orientation is a requirement for crystallinity (but not visa versa)– Often there are lamellae, regions where the chains fold back and forth

over each other


Raman Characterization of Polymers

• Types of Information– Chemical Identification– Tacticity (side group positioning)– Morphology

• Orientation• Crystallinity

• Applications– Contaminant ID– Composition of copolymer or blend– Engineering strength, elasticity, dyeability, etc.– Drug delivery (API solvent)– Barrier films (food, biomedical, etc.)


Raman Spectra of Aromatic PolymersThe strong band near 1000 cm-1 that is characteristic of a ring mode in PS is never observed in any aromatic with 1,4 substitutions on the ring, as in Kevlar and PET.

x10 3

0

5

10

15

20

25

30

35

40

45

500 1 000 1 500 2 000 2 500 3 000 3 500Raman Shift (cm-1)

Kevlar

PET

Polystyrene

Aromatic CH stretches

Saturated CH stretches

Carbonyl band

Aromatic band

Amide band

Aromatic band


Raman Studies of PET: Polarization and Crystallinity

C=O stretchingWidth=>crystallinity

glycol modes:Indicators of conformation

Raman Shift / cm-1

Inte

nsity

/ ar

bitr

ary

units


Raman Shift (cm-1)

Inte

nsity

(Cou

nts) 835

Unperturbed

Stretched

315

992

Stretched and Unperturbed Polypropylene


Raman Shift (cm-1)

Inte

nsity

(Cou

nts)

169

315

Unperturbed

Stretched

522

449


393391


Raman Shift (cm-1)

Inte

nsity

(Cou

nts)

803835

Unperturbed

Stretched836

968


992 993


Raman Shift (cm-1)

Inte

nsity

(Cou

nts)

11461148

Unperturbed

Stretched

1213

1325


1324

1354 14311430

1454


Introducing ParticleFinder• ParticleFinder offers

automated – Particle location on

optical images– Particle size/shape

characterization– Particle analysis using

Raman spectroscopy– Particle chemical

identification

• ParticleFinder includes:– Morphological analysis

• Thresholding• Morphological filtering• Size and shape

parameters– Chemical analysis

• Automated Raman acquisition

• Fast analysis with high throughput systems

• Flexible capabilities* for different sample types

– Multiple laser wavelengths (UV, visible, NIR)

– High spectral resolution– Ultra-low frequency


Step-by-Step

Acquire video

Single image, or montagedwide field of view image

Threshold

Locate dark particles on bright background, or

bright particles on dark background

Process

Erode/dilate/open/ close/majority, fill holes,

remove edge particles


Characterize

Position, size, shape

Acquire Raman

Automatically analyze each particle

Select

Screen particles based on position, size or shape

Step-by-Step


Application Example• Pharmaceutical crystals on glass slide• 1 × 1 mm2 area imaged with video montage (12

images)• Image thresholds locate 44 particles

– Exclude edge particles– Exclude particles with area < 50 μm2

STATISTICS (mean)DIAMETER 19.7 μmPERIMETER 109.7 µm AREA 386.0 µm2

MAJOR AXIS 33.6 μmMINOR AXIS 14.8 μmELLIPSE RATIO 0.50CIRCULARITY 0.64

Video image

Binary image


ParticleFinder Workspace – Paracetamol and PMMA


ParticleFinder Tabulated Results


Raman spectroscopy and laser excited photoluminescence can be performed using the same instrument.

Raman spectroscopy can be used to differentiate polymorphs and characterize polymers.

Vapor phase and liquid molecular interactions are manifest in Raman spectra.

Particle size characterization with chemical specificity

Conclusions

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