Raman Spectroscopy

and Chemical Imaging

2

Overview

• Fundamentals of Raman Spectroscopy

• Raman Microscopy

• Raman Imaging

• Raman-AFM

• Summary

Thermo ScientificTM

DXRTM SmartRaman

Thermo ScientificTM

DXRTM Raman Microscope

Thermo ScientificTM

DXRxiTM Raman

Imaging Microscope

3

Raman is a Complementary Technique to FT-IR

C=O C-O C=C

C=O

C=C C-O

C=C

FT

-IR

R

am

an

• Complementary information

• End functional groups dominant in IR spectrum

• Molecular backbone dominant in Raman spectrum

• Raman often useful for characterizing morphology

• Weak IR absorbers often strong Raman emitters and vice versa

• Aqueous solutions pose fewer challenges with Raman

trans-cinnamyl

acetate

4

Raman Spectroscopy – The Raman Effect

Rayleigh scattering (filtered out)

Raman scattering (Stokes shift)

LASER

200 400 600 800 1000 1200 1400 1600 1800 2000

Raman shift (cm-1)

Blo

ckin

g F

ilter

0 E

xc

itati

on

fre

qu

en

cy

V = 0

Rayle

igh s

ca

tte

rin

g

V = 1

Ram

an

sc

att

eri

ng

~~~~~~~~~~~~~~~ V = virtual state

5

Raman spectra Changes Information Examples

Characteristic

frequencies

Material

identification,

polymorphs

differentiation

rutile and anatase of

TiO2

PS, PET

Intensity

Quantity of material

analyte concentration

in aqueous solution;

thickness of

transparent coating

Change in

frequency

Stress/strain in

material

520 cm-1 peak shift in

Si upon strain

Change in width

Disorder or defects

crystalline 520 cm-1

and amorphous 480

cm-1 peak in Si;

D band in CM

Change in

frequencies,

intensities, widths

Thermal or

pressure

Impact

phase transformation,

melting, crystallization

Information from Raman Spectroscopy

6

Common Raman Microscopy Applications

Art Conservation and Archeology Identification and discrimination of paint pigments

using DXR microscopy and fiber optic analysis

Polymers and Packaging Subsurface analysis to identify inclusions and

verify layers without sample preparation

Geology and Gemstones Rapid non-destructive identification of fluid inclusions

in minerals using DXR confocal analysis

Photovoltaics Measurement of

silicon crystalline

fraction using

automated macros

for routine post

production analysis

7

Carbon Nanomaterials Determination of graphene layer thickness and

nanotube diameter populations

Common Raman Microscopy Applications

Life Science Applications Rapid high sensitivity detection of biomolecules

using the DXR SERS kit

Pharmaceuticals High speed polymorph screening and recrystallization studies Forensic Science

Identification of components in explosives residue

8

Dispersive Raman Instrument Fundamentals

• DXR System Basics:

• Laser

• 455 nm, 532 nm, 633 nm &

780 nm

• Rayleigh rejection filter

• 50 cm-1 cut-off

• Aperture

• Slit

• Pinhole (confocal mode)

• Grating

• Standard, 5 cm-1

• High Resolution, 2 cm-1

• Detector

• CCD, EMCCD

Sample

Grating

Aperture

Laser

Multichannel detector

Filter

50

2D

G

9

Sampling in Raman Spectroscopy

• Various Sample Types

• Solids, liquids, gases, powders, slurries, films,

etc.

• Aqueous samples

• Water has very weak Raman spectrum!

• Materials at high/low temperatures and

variable pressures

• Linkam and Harrick stages

• Bulk or microscopic samples even at

remote locations with little or no sample

preparation

• Analysis through many containers

• Glass bottles, Pyrex® reaction vessels, plastic

containers, blister packs, etc.

10

DXR Raman Microscope – High Spatial Resolution Capability

• Confocal Design

• High Spatial Resolution

• 0.5 µm (lateral), confocal depth

resolution – 2 µm (axial)

• Raman Mapping Capability

• Point, area (x,y) and depth (z)

• User Interchangeable

Components

• Laser, filter, gratings

• Proprietary Auto-Alignment

• Ocular or Video Image

Observation

• Class-I Laser Safety

Detector

Aperture

Objective

Focus

Plane

Sample

Lift sample

stage

11

NicoDerm CQ Transdermal Nicotine Patch

PET (~ 10 um)

Polyethylene (~ 25 um)

Ethylene/Vinyl acetate

copolymer (EVA) +

nicotine (~ 70 um)

Polyethylene (~ 20 um)

Polyisobutylene (PIB) (~ 20 um)

Poly(ethylene teraphthalate)

PET (~ 55 um)

Raman Z-map Video image of

the cross section

1

2

3

4

5

6

12

Ease of Use with Built-In Raman Expertise

• Point and shoot – results with a single push of a button

Start Measurement

Go Button

Autofocus Autoexposure Optimal Spectral

Quality

Collected Raman Spectrum Library Search Results Final Report

Real-Time

Fluorescence

Correction

Title:

GloboChem Corp.

Laser: 532 nm Grating: 900 lines/mm Spectrograph aperture: 25 µm pinhole Laser power level: 10.0 mW

-0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

6500

Ra

ma

n I

nte

nsity (

cp

s)

500 1000 1500 2000 2500 3000 3500

Raman shift (cm-1)

Tue May 27 13:58:26 2008 (GMT-05:00)

Sample #5-24-20081234A

*JC C07-3023 #1 RLL - run 1 - cocaine HCl

Matc h:95.98

Manufac tu re r: Sigma

Product #: C -5776

Lo t # : 83F-0562

Coc aine HC l

20

30

40

50

60

70

80

90

100

110

120

130

140

150

160

170

180

Int

500 1000 1500 2000 2500 3000

Raman sh ift (c m-1 )

Load sample Move to Target

13

Raman Images of Multi-Layer Solid Bead Dosage Form

Raman images of the split bead constructed as correlations with spectra of reference materials.

1 mm diameter bead with 5 μm mapping steps: 2500 high quality spectra for 7 hours!

14

Introducing DXRxi Raman Imaging Microscope

• Ultra fast data collection

• Hundreds of spectra per second

(600 spectra/sec max)

• Image-centric instrument platform

• Real-time chemical image

generation

• Parameter optimization on the fly

• Laser power, exposure time,

number of scans, etc.

A completely new approach to Raman imaging!

15

DXR versus DXRxi Sensitivity -Test Conditions

• Sample – Polystyrene Puck

• 100X Objective

• 532 nm laser – 0.5 mW

• 25 micron pinhole

• Exposure Times 0.020 – 8 seconds (50 – 0.125 spectra / s)

• S/N Calculations:

• Peak Height 1001 cm-1

• Noise RMS 2400-2300 cm-1

16

Collection Speed – 0.125 Spectra per Second

0.125 Spectra per Second - DXRxi

0.125 Spectra per Second - DXR

17

Compare Fastest DXR Result to Fastest DXRxi Result

50 Spectra per Second – DXRxi

(DXRxi could still go faster)

10 Spectra per Second – DXR

(instrument limit)

18

Video - Fast Imaging for a Full Tablet

19

Fast Surface Imaging of an Entire Headache Tablet

Acetaminophen Caffeine Titanium Dioxide Aspirin

• 226,000 spectra, 25 mm pixel size

• Acquisition parameters: 550 Hz

(1.8 ms/spectrum)

• 8 minute collect time!!

Determine:

• Size of each domain

• Distribution of domains

• Overall composition of tablet

11 x 11 mm surface area

20

Analysis of Pharmaceuticals

Acetaminophen Caffeine Titanium Dioxide Aspirin

11 x 11 mm surface area

532nm laser

5.4 million spectra!!! 0.5 mm pixel size

Acquisition parameters: 550 Hz (1.8

ms/spectrum)

~3 hour collect time!!

Component Calculated %

(Surface Area) Reported %

Aspirin 38.6 37

Acetaminophen 35.4 37

Caffeine 7.7 9.6

21

MCR Analysis of Headache Tablet

Acetaminophen Caffeine Starch Aspirin

1.6 x 1.7 mm surface area

532nm laser, 50X objective

116,000 spectra, 5 mm pixel size

Acquisition parameters: 200 Hz (5

ms/spectrum)

55 minute collect time

22

High Resolution MCR Analysis of Pharmaceuticals

Sodium Lauryl Sulfate Microcrystalline Cellulose

Acetaminophen Caffeine Starch Aspirin

225 x 250 mm surface area

532nm laser, 100X objective

229,000 spectra, 0.5 mm pixel size

Acquisition parameters: 100 Hz (10

ms/spectrum)

3 hour collect time!!

23

High Res Discrimination between Similar 1μm Particles

24

Raman Imaging of Tissue Samples

•17,000 spectra

• Acquisition parameters: 40 Hz (25 ms/spectrum), 100 scans, 2.0 mm pixel size

Collagen Glass Slide Cell Nuclei

*Sample provided by Ihtesham ur Rehman, University of Sheffield*

532 nm laser, 5.4 mW, 50X objective

25

Video - Fast Multi-Region Imaging for CVD Graphene

26

Characterizing Materials for Product Development

10 microns

Scale:

Single Layer Double Layer Triple Layer Multiple Layer

• Graphene Layer Thickness

• Graphene exhibits different properties

depending on how many layers are

present

• Simple application of a discriminant

analysis method quickly classifies the

number of layers.

27

MCR of Synthetic Volcanic Rock - Analysis of Volatiles

Chalcocite? Labradorite?

OH Glass CO2 Carbon

• The DXRxi maintains the same confocal

capability as the DXR

• Quantifying the volatiles in the sample

will provide clues about the nature of

volcanoes.

• 21,000 spectra

• Acquisition parameters: 40 Hz (25

ms/spectrum), 100 scans, 0.5 mm pixel

size

*Sample provided by Jenny Riker, University of Bristol*

28

Identification of Minerals and Carbonaceous Species in Oil Shale

*Sample provided by Prof Asish Basu, University of Texas, Arlington*

Pyrite Marcasite

Calcite Anatase

D-b

an

d

G-b

an

d

Video image showing the features of the oil

shale sample. Shown in red square is the

area where Raman imaging was performed.

Superimposed view of video and Raman

images, showing the kerogen in red.

Raman images

showing the locations

for Pyrite, Marcasite,

Calcite and Anatase.

Representative

Raman spectra.

Collection

parameters: 532

nm laser, 30

ms/spectrum, 30

scans

29

Imaging Thermal Maturity of Carbonaceous Species in Oil Shale

*Sample provided by Prof Asish Basu, University of Texas, Arlington*

Raman shift (cm-1)

Ra

ma

n in

ten

sit

y (

cp

s)

FWHM range

G-b

an

d

Representative spectra for the red,

orange and green regions, showing the

broadening the G-band from Green to

Red.

Raman image of CM maturity differences in G-

band FWHM values. Red is higher FWHM

value and lower maturity. Green is lower

FWHM and higher maturity. The orange

regions have intermediate value. The blue

regions mostly contain minerals and lack

kerogen.

30

High-Resolution Imaging of Stress in Silicon

• 50,000 spectra

• Acquisition parameters: 100 Hz (10

ms/spectrum), 25 scans, 0.5 mm pixel size

• Sample is a Si substrate with a

layer (41 nm) of Si/Ge deposited

followed by an additional layer of

Silicon

• The presence of the Ge causes

stress in the second layer (23

nm) of Si (Red imaging)

455 nm laser, 1.0 mW, 100X objective

31

Raman and AFM Integration

Co-Localized AFM Raman

• Simultaneous measurement two techniques

• Diffraction limited confocal Raman

• AFM topographical image

• Light confinement maintains focus on probe

tip

Tip Enhanced Raman Spectroscopy (TERS)

• Ag or Au-coated AFM tip acts as nano-

antenna

• Provide exceptional signal enhancement

• Spatial resolution beyond the diffraction limit • As high as 10 nm

X

Focused laser spot

AFM Probe

Focused laser spot

Enhanced

Raman signal

Nanoantenna

(Metal AFM probe)

~ λ / 2

32

Topography Adhesion Stiffness

dC/dZ

(dielectric constant) dC/dV

(differential capacitance )

Raman

(peak position) Raman

(peak intensity)

White Light

Image

Co-Localized AFM-Raman for a Polymer Blend

33

Complementary AFM and

Raman data provides rich

picture of sample

150 x 150 point scan

0.3 sec exposure time

Co-Localized AFM-Raman for CVD Graphene

Raman map:

2D-band

Raman map:

G-band

AFM height image Characteristic single point spectrum

2D-band

G-band

34

TERS maps of single layer CVD Graphene on

copper substrate • Green: pristine graphene (2D band intensity).

• Blue: CH-terminated graphene areas (CH-bands

intensity).

TERS map of mechanically

exfoliated single layer graphene

on Au substrate • Green: pristine graphene (2D band

intensity).

• Red: areas with strong defects (D-

band intensity)

Lateral resolution of Raman maps: <12 nm

TERS Mapping of Graphene

35

Summary

• Non-destructive

• Minimal sample preparation

• Sample through glass or plastic packaging

• Remote sampling capability

• Characterization of very small particles (sub-micron)

• Confocal sampling – looking below the surface of samples

• Fast and high-resolution imaging capability

• Integrated AFM – Raman and TERS solution – nano Raman imaging