1. Necessary Basics in Instrumental Analysis
Lokanathan Arcot
Department of Forest Products Technology
School of Chemical Technology
Aalto University

2. Analytical methods Infrared Spectroscopy Raman Spectroscopy
Nuclear Magnetic Resonance (NMR)
X-ray Photoelectron Spectroscopy (XPS)
Electron Microscopy
Atomic Force Microscopy (AFM)
Quartz Crystal Microbalance (QCM)
Surface Plasmon Resonance (SPR)
Dr. Lokanathan Arcot

3. Light and its interaction with matter
Dr. Lokanathan Arcot

4. Light – ElectroMagnetic wave
Red 694 nm
Ruby laser
Blue 450 nm
Gallium Arsenide
1964, 1971, 1981, 1997, 2000, 2014
Nobel prize for laser
Wavelength
λ (nm)
Light – ElectroMagnetic wave
Wavelength: Distance between two crests or troughs (nm)
Frequency: Number of vibrations per second (Hertz)
Further reading: Principles of Instrumental Analysis, by, Holler, Skoog, Crouch, Page
Dr. Lokanathan Arcot

5. Electromagnetic spectrum
Next : Basics of matter
Dr. Lokanathan Arcot

6. Basis of Infrared and Raman Spectroscopy
Atoms
Molecules
Bond
(e– density transfer)
Dipole Moment 𝛿0 𝛿+ 𝛿– + –
Non-Polar
’0’
Dipole moment
Highly Polar
’High’
The two atoms shown in zoomed in version of molecule is in fact NaCl
Delta EN (difference in electronegativity) Measure of Polarity
Dr. Lokanathan Arcot

7. Vibrational Spectroscopy: Infrared and Raman
Examples of Molecular Vibrations
Others
Rocking
Wagging
Twisting
In-plane Scissoring
Asymmetric
Stretching
Symmetric
Stretching
Effect of Vibrations
- Monopoles of dipole vibrate at a Freq.
- Oscillating elec. Field of same Freq.
Absorption of Light of wavelength λ or Frequency
Absorption occurs if the incident light wave has the same frequency as oscillating electric field of a molecule vibrating in a ’non-zero’ dipole moment mode
Dr. Lokanathan Arcot

8. Infrared Spectroscopy Absorption of Light of wavelength λ or Frequency
Absorption occurs if the incident light wave has the same frequency as oscillating electric field of a molecule vibrating in a ’non-zero’ dipole moment mode
Source of Light
A range of λ
Intensity IO
Sample
Molecules
Absorption
Transmitted I
Detector
IO - I
Spectrum
Absorption at λ
Presence of molecular vibration
Presence of a specific bond
QUALITATIVE
Intensity of Absorption at λ
QUANTITATIVE
Dr. Lokanathan Arcot

9. Light wave propagating
Raman Spectroscopy
Light wave propagating
Atom
’0’ Polarization
Atom
’Up’ Polarization
Atom
’Down’ Polarization
E = E0 + µE +αE2 + ……..
E0 – Initial energy
µ - Dipole moment
α - Polarizability
Energy of a Molecule in Electric Field E
Dr. Lokanathan Arcot

10. Interaction of Light and Polarizability
Neglegable
Significant
Neglegable
Significant
E = E0 + µE + αE2 + …
µ - Dipole moment
α - Polarizability
E = E0 + µE +αE2 + ……..
µ - Dipole moment
α - Polarizability
High Polarizability
Generally stronger coupling with E of light
Low Polarizability
Weak coupling with E of light, except for resonance freq.
IR active
pe(E) = pe(E = 0) + αE + ………. From (
ELECTRONIC JOURNAL OF THEORETICAL CHEMISTRY, VOL. 2, 325–336 (1997)
Dipole moment times electrif field =µE= Energy
Dr. Lokanathan Arcot

11. Scattering Phenomenon𝛿+ 𝛿–
Incident Light
Light wave couples for an instant
High Polarizability
Generally stronger coupling with E of light
Coupled light is randomly remitted in any direction
pe(E) = pe(E = 0) + αE + ………. From (
ELECTRONIC JOURNAL OF THEORETICAL CHEMISTRY, VOL. 2, 325–336 (1997)
Dipole moment times electrif field =µE= Energy
Dr. Lokanathan Arcot

12. Raman Scattering Types of Scattering E0 EV EJ Vex – VV Vex + VV
Loss of Energy
Anti-Stokes lines
Gain in Energy
Stokes lines
Rayleigh Scattering
Vex
Raman Scattering
Types of Scattering
Dr. Lokanathan Arcot

13. Intensity of scattered
Raman Spectroscopy
Source of Light
Laser λ
Sample
Molecules
Stokes/Anti-
Scattered
Detector
Intensity of scattered
Spectrum
Scattering peak at λ
Presence of molecular vibration
Presence of a specific bond
QUALITATIVE
Intensity of Peak at λ
QUANTITAIVE
Fluorescence – Quick (prompt) emission
Phosphorescence – Delayed emission
Dr. Lokanathan Arcot

14. Nuclear Magnetic Resonance
Nucleons – Protons and Neutrons
Have intrinsic property – Spin
Spin of Nucleus:
Pairs of Protons – cancel each other’s spin
Pairs of Neutrons – cancel each other’s spin
Nuclei with Non-Zero Spin
Odd number of Protons (Atomic number)
Odd number of Neutrons
Either or both: Example H1 , C13
Nucleus of Atoms
Protons
A spinning charged nucleus produces magnetic field, thus has a magnetic moment
Neutrons
Dr. Lokanathan Arcot

15. Nuclear Magnetic Resonance
A spinning charged nucleus produces magnetic field, thus has a magnetic moment
Energy hV BO
Radiofrequency
Electromagnetic radiation
Approx. 200MHz
Flip to
’Antiparallel’ Orientation
Randomly Oriented
BO - External
Magnetic Field BO
’Parallel’ Orientation
No – External
Magnetic Field
Dr. Lokanathan Arcot

16. Nuclear Magnetic Resonance
Radio Freq.
waves
Detector
Sample
External
Magnetic
Field
Absorption of Radiofrequency radiation
- Chemical information
(Nuclei in different chemical environments)
Dr. Lokanathan Arcot

17. Optical Spectroscopy Examples: Infrared Spectroscopy
Raman Spectroscopy
Nuclear Magnetic Resonance
SAMPLE
Light Source
Wavelength
Selector
Wavelength
Selector
Not needed for Absorption
Light
Sensor/
Detector
Further reading: Principles of Instrumental Analysis, by, Holler, Skoog, Crouch, Chapter 7
Dr. Lokanathan Arcot

18. Light Sources
Function: Highly reproducible source of light of specific wavelength or wavelength range
Types of Light Sources:
Continuous:
Uv – Deuterium lamp 190 – 370 nm
Visible – Tungsten lamp 350 – 2500 nm
* Effect of this during Uv-Vis measurements
Light Source
Line : (Most common are Lasers)
High intensity, Narrow bandwidth
Coherent nature
Dye and LED (Latest improvements)
Further reading: Principles of Instrumental Analysis, by, Holler, Skoog, Crouch, Chapter 7
Dr. Lokanathan Arcot

19. Wavelength Selectors SAMPLE Light Source Wavelength Selector
Sensor/
Detector
Function: Narrow down the width of radiation band being exposed to sample or being transmitted/emitted by sample
Dr. Lokanathan Arcot

20. Wavelength Selectors Refraction of Light Dispersion of Light
Light wave propagating
Chromatic
Dispersion
Index of Refraction is different for different wavelengths
Dr. Lokanathan Arcot

21. Destructive Interference of Light
Wavelength Selectors
Destructive Interference of Light
Light wave propagating
Phase
State of vibration
Wave 1
Wave 2
Light wave 1 and 2 ’out-of’ phase
Pathlength
Interference: Wave 1+2
Destructive interference
Dr. Lokanathan Arcot

22. Types Wavelength Selectors
Interference Filters:
Removes all the undesirable wavelengths
Destructive interference
Reinforces (intensifies) desired band of wavelengths
A dielectric film sandwitched between Two Metallic films
Metallic film- Partially Reflecting
1. Incident light – Partially reflected, partially passes through the first metallic film
2. The transmitted light passes through dielectric and is again partially reflected and transmitted by the second metallic film.
3. The partially reflected light reaches the first metallic film again (during which time it undergoes a path length shift)
4. The light reflected from second metallic film is again partially reflected/transmitted by first metallic film
5. Only the desired band of wavelengths are enhanced after interference with incoming light due to destructive interfence of all other wavelengths.
Further reading: Principles of Instrumental Analysis, by, Holler, Skoog, Crouch, Chapter 7, Page
Dr. Lokanathan Arcot

23. Types Wavelength Selectors
Interference Filters:
Interference phenomenon
Absorption Filters:
Absorption of range of undesired wavelengths
Transmitting the desired band of wavelengths
What if we wish to perform a wavelength absorption sweep ?
Absorption as a function of wavelength
We will need filters whose output can be varied from one wavelength to the other over a range of wavelengths
Monochromators: Greek: Mono – one, Chrom – Color
Continuously variable wavelength selector
Further reading: Principles of Instrumental Analysis, by, Holler, Skoog, Crouch, Chapter 7
Dr. Lokanathan Arcot

24. Wavelength Selectors: Monochromators
Example 1: Prism Monochromators (dispersion by refraction)
Changing wavelength passing through slit by
changing angle of Prism
Prism is the dispersing element
Image from:
Reading :
Dr. Lokanathan Arcot

25. Wavelength Selectors: Monochromators
Example 2: Grating Monochromators (dispersion by diffraction)
mλ=d (sin i + sinθ)
i – Angle of incidence
d – Groove spacing
θ – Diffraction angle
λ – Wavelength
Image from:
Diffraction Image from:
Dr. Lokanathan Arcot

26. Discussion Characteristics of Sample containers
Clue: Light of specific λ have to pass through
Should not interfere with measurement
No interaction with incoming light
No interaction with emitted light
Transparent to radiation in spectral region of interest
Dr. Lokanathan Arcot

27. Sample containers Examples Below 350 nm (UV)
Glass (Silicate), Plastic – not suitable
Fused Silica, Quartz – Good
350 – 2000 nm
Glass (Silicate) OK
Note: Fused Silica – Pure Silica
Glass or Silicate Glass – Silica + other salts Sodium Carbonate
Dr. Lokanathan Arcot

28. Light detectors/Sensors Radiation Transducers
Ideal Radiation Transducer
High sensitivity
Constant response over wide λ range
Fast response time
Dr. Lokanathan Arcot

29. Radiation Transducers
Types of Radiation Transducers
Photon Transducers
Photoelectric/Quantum detectors
Photocurrent: Photon causes emission of e– , Current flow
UV, Visible photons
Photoconductivity Transducers
Photon promotes e– into conduction band, Resistance
Near IR
Thermal Transducers
Photon transfers heat energy – raising temperature
IR and Near IR
Difference between Photon transducer and Thermal:
Dislodging of electron by photo where as in thermal electrons are not delocalized
Further reading: Principles of Instrumental Analysis, by, Holler, Skoog, Crouch, Chapter 7
Dr. Lokanathan Arcot

30. Summary of Part I Light Properties of Light
Interaction of Light with Matter
Absorption, Scattering
Vibrational Spectroscopy
IR, Raman
Radiofrequency absorption (NMR)
General setup for optical spectroscopy
Next after a break
X rays and electron spectroscopy
Dr. Lokanathan Arcot

31. Short Break
Dr. Lokanathan Arcot

32. Others: Electrons, Neutrons, Alpha particles
High energy probes
Light: Radiofrequency, IR, Visible, UV
X rays
Others: Electrons, Neutrons, Alpha particles
Dr. Lokanathan Arcot

33. X rays remove core electrons UV rays remove Valence electrons
Important Properties of Electrons
Photoelectric Effect
2 P
Photoelectron
energy KE
X ray photon
energy hn
2 S
UV photon
energy hn
1 S
X rays remove core electrons
Photoelectron
energy KE
2 P
2 S
Atom with electrons around it
UV rays remove Valence electrons
1 S
Atom with electrons around it
Dr. Lokanathan Arcot

34. H 285.0 eV C F 291.0 eV Chemical Information from Photoelectrons
Photoelectric law:
EKE= hn - EBE – ΦSp
Where, EKE –energy of photo-electron, hn – energy of incident photon, EBE – Binding energy, ΦSp – Work function
1 S
H eV
F eV
2 S
2 P C
B.E of 1s e-1
Chemical shift
H: 15, C: 285, O: 532, F: 685
C-C-M+n: 282 eV
C- C -C : 285 eV
O- C =O :
F- C -F : 292
Increasing
electronegativity
Conclusion: If one has to extract chemical information from Photoelectrons, then one should be able to quantify electrons as a function of K.E.
Dr. Lokanathan Arcot

35. – + Electron K.E. Analyser Effect of Electric Field on Tragetory of e–
High K.E.
Low K.E.
X-displacement
Entry of e–
Y–displ. +
Slit
Voltage across two plates
Higher K.E. means higher velocity
Along X direction: Force ’0’ ; Displacement x = vt  
Along Y direction: Force F = e.E ; Dispacement y = eEx2/2mv2
For a given time ’t’ X is higher for higher K.E. electron
Where along the Y direction will electrons at a given x value will be, is inversely dependent on the Velocity
So a higher K.E. will have lower Y displacement and hence will hit the anode at a much farther distance relative to lower K.E. electron
Deflection in Electric Field is the basis of Electron K.E. analysers
t – time, v – velocity of electron, m – mass of electron
e – charge of electron
Dr. Lokanathan Arcot

36. Effect of Electric Field on Tragetory of e–
Electron K.E. Analyser
Effect of Electric Field on Tragetory of e–
Setup for Electron Spectroscopy
Hemispherical Analyser + -
Dr. Lokanathan Arcot

37. Techniques using the electron deflection based dispersion
Spectroscopy:
X ray Photoelectron Spectroscopy (XPS)
Microscopy:
Scanning Electron Microscopy (SEM)
Transmission Electron Microscopy (TEM)
More about these techniques latter during the course
Dr. Lokanathan Arcot

38. Relevent Material Properties
Surface Plasmon Resonance
Piezoelectricity
Dr. Lokanathan Arcot

39. Surface Plasmon Resonance
Electrically neutral volume
Electric field
Plasma of Electrons
Collective oscillation
Dr. Lokanathan Arcot

40. Surface Plasmon Resonance Surface Plasmon and Resonance
Metal
Plasmon-Light coupling /Resonance
Surface Plasmon Polariton
Matching
Electron Freq and Light Freq
Depending on Electronic Properties
Surface and Surrounding Medium
Angle of Incidence
Dr. Lokanathan Arcot

41. Surface Plasmon Resonance
Application
Resonance conditions
Matching
Electron Freq and Light Freq
Depending on Electronic Properties
Surface and Surrounding Medium
Angle of Incidence
Dr. Lokanathan Arcot

42. Surface Plasmon Resonance
Application
Resonance conditions
Matching
Electron Freq and Light Freq
Depending on Electronic Properties
Surface and Surrounding Medium
Angle of Incidence
Good:
TIRF and SPR, different modes
Figure Good
Plasmon Polariton figure
Defenition of plasmon, polariton
Deeper Theoritical treatment
Dr. Lokanathan Arcot

43. Piezoelectricity
Mechanical stress on a material generates electric charge or vice versa
Dr. Lokanathan Arcot

44. How and why are Piezoelectric Materials, Piezoelectric ?
Piezoelectricity
Mechanical stress on a material generates electric charge or vice versa
How and why are Piezoelectric Materials, Piezoelectric ?
Crystalline Materials – Domains – Aligned Molecular Diople
Polycrystal
Polar axis of domains randomly oriented
Monocrystal
Polar axis of domains in same direction
POLARIZED
Dr. Lokanathan Arcot

45. A matrix of randomly oriented domains
Piezoelectricity
Poling Process – Formation of a Piezoelectric Material
After removal of applied potential, the matrix is permanently polarized
A matrix of randomly oriented domains
Apply a voltage to align the domains and temprerature > critical temperature
Dr. Lokanathan Arcot

46. A matrix of randomly oriented domains
Piezoelectricity
Example : Lead Titanate Zirconate
After removal of applied potential, the matrix is permanently polarized
A matrix of randomly oriented domains
Poling
Dr. Lokanathan Arcot

47. Mechanical deformation produces Potential
Piezoelectric Effect
Mechanical deformation produces Potential
Applied Compression
– along polar axis or
Applied Expansion
– Perpendi. to polar axis
Produced voltage with same polarity as poling voltage
Applied Elongation
– along polar axis or
Applied Compression
– Perpendi. to polar axis
Produced voltage with polarity opposing poling voltage
Dr. Lokanathan Arcot

48. Reverse Piezoelectric Effect
Potential produces Mechanical deformation
Applied voltage with same polarity as poling voltage
Causes Compression
– along polar axis
Causes Expansion
– Perpendi. to polar axis
Produced voltage with polarity opposing poling voltage
Applied Elongation
– along polar axis
Applied Compression
– Perpendi. to polar axis
Discuss: What happens if AC voltage is applied ?
Dr. Lokanathan Arcot

49. Reverse Piezoelectric Effect
Techniques which use
Reverse Piezoelectric Effect
Techniques covered in this course
Quartz Crystal Microbalance
Atomic Force Microscopy
Dr. Lokanathan Arcot

50. Quartz Crystal Microbalance
QCM
Quartz Crystal Microbalance
Dr. Lokanathan Arcot

51. QCM working principle AC voltage is applied – Vibration
Vibration at a Frequency
Sandwitched Piezo
Quartz crystal
Sauerbrey, G Z. Phys.155 (1958) 206
Dr. Lokanathan Arcot

52. QCM working principle Sauerbrey’s equation m-mass, f-frequency
Sauerbrey, G Z. Phys.155 (1958) 206
Dr. Lokanathan Arcot

53. AC voltage is applied – Vibration
QCM
Cross section of Setup
AC voltage is applied – Vibration
Moniter the Frequency
Dr. Lokanathan Arcot

54. Atomic force microscopy
Piezoelectric Vibrating Beam
AC voltage is applied – Vibration
Vibration
Frequency
Amplitude
Phase
Dr. Lokanathan Arcot

55. Atomic force microscopy
AFM Setup
Position Sensitive Photodiode
(PSPD)
Photodetector Quadrant Photodiode
Dr. Lokanathan Arcot

56. Atomic force microscopy
Tapping Mode - Setup
Dr. Lokanathan Arcot

57. Atomic force microscopy
Tapping Mode - Setup
Vibration
Amplitude
Phase
Feedback
Dr. Lokanathan Arcot

58. Summary of Part II Photoelectric Effect Electron in Electric Field
Surface Plasmon Resonance
Piezoelectric Effect
Quartz Crystal Microbalance
Atomic Force Microscopy
Dr. Lokanathan Arcot

59. Discuss about Wednesday
Now you all are ready with the basics to learn Instrumental Techniques in more detail
Discuss about Wednesday
Dr. Lokanathan Arcot