The love for knowledge is the driving force for a good tomorrow.

1. By:
Abubakar Yakubu (PhD)
Wan Mahmud Mat Yunus
(PhD)

2. Outline
 Introduction
Why Photo-Thermal Technique
Principle of P.T Technique.
 Experimental (1), (2), (3)
 Theory
 Result and discussion
 Bibliography

3. Introduction
What is Optical methods
Radiometry: the measurement of optical radiation or
electromagnetic radiation in the frequency range of 3 x
1011 – 3 x 1016 Hz.
Photometry: is the measurement of light. Light in this
case is defined as the electromagnetic radiation
detectable by the human eye. The range visible to the
human eye falls between 360 nm to 830 nm.
Parameters
 Reflectance and Spectral reflectance
Transmittance and spectral transmittance
 Abdorptance, spectral absorptance and absorption
coefficient
Thermal diffusivity

4. Why Photo-Thermal Method
 Simple and reliable technique
 Non-destructive, it is fast and
simple
 Safe measurement
 Sensitivity is very high
 Inexpensive, very cost effective

5. Principle of P.T Technique
.
optical radiation usually starts from a source
Filtered to produce desired beam of light
Excitation reaches sample
Absorption, reflection, and transmission takes place
Signal is been amplified
Spectrum is displayed on the detector

6. Experimental 1
Measurement of thermal diffusivity of
gold nano-fluids
 Using Double beam thermal lens
technique
All samples were prepared using γ-
radiation method

7. Experimental Set-Up
Figure 1:Setup of Thermal Lens; C, Chopper; L1, L2, Lenses; S,
Sample; F, Filter; D, Detector (Shariari et al, 2013)

8. Theory
 Signal using a diffraction approximation for
Gaussian beams is given as (Shariari et al, 2013);
𝐼 𝑧, 𝑡
= 𝐼0(1
− 𝜃𝑡𝑎𝑛−1(
2𝑚𝑣
1 + 2𝑚)2 + 𝑉2 𝑡𝑐
2𝑡
+ 1 + 2𝑚 + 𝑉2
)2 (1)
Where 𝑉 =
𝑍1
𝑍2
, 𝑚 = (
𝑤 𝑝
𝑤 𝑒
)2, 𝑡𝑐 =
𝑤𝑒2
4𝐷
(2)
𝜃 =
𝑝 𝑒 𝛼𝑙
𝑘λ 𝑝
.
𝑑𝑠
𝑑𝑇
(3)

9. Result
Figure 2: UV-Vis Absorption
spectra of fluids
Figure 3: Time evolution of
the Thermal Lens

10. Result
TEM images and particles size
histograms of Au particles
Thermal diffusivity of Au nano-
fluid versus the particles size
Figure 4
Figure 5

11. Discussion 1
 Figure 2 shows an absorption peak at 525 nm
 Decrease in size of gold particles shifts absorption
peaks to higher wavelengths
TEM image in figure 4 shows a particles size
distribution of 20.5 nm
 The thermal lens signal in figure 3, shows agreement
between calculated and experimental data.
 Thermal diffusivity is calculated to be 2.51 x 10-3cm2/s
 Thermal diffusivity increases with increase in particle
size

12. Experimental 2
 Measurement of thermal
diffusivity of Polyaniline
 Using Photoflash technique
 Materials used in the study were
supplied by Zipperling Kessler &
Co.

13. Experimental set-up
Figure 6: Schematic diagram of Photoflash technique

14. Theory
 For an Opaque material, the temperature at the rear is
expressed as (Josephine et al, 2002);
𝑇 𝐿, 𝑡 =
𝑄
𝜌𝐶 𝑝 𝐿
1 + 2
𝑛=1
∞
−1 𝑛
𝑒𝑥𝑝 −
𝑛2
𝜋2
𝑎𝑡
𝐿2
(3)
Where Q is the energy of the light source, L is the
sample thickness, t is the transient response time and Cp,
p and n are the specific heat capacity, density and integer
(+).

15. THEORY
 The maximum temperature rise at the rear surface of
sample is expressed as;
𝑉 = 1 + 2
𝑛=1
∞
(−1) 𝑛
𝑒𝑥𝑝 −
𝑛2
𝜋2
𝑎𝑡
𝐿2
(4)
• The maximum temperature of the rear surface is
expressed as;
𝑇(𝐿, 𝑡) 𝑚𝑎𝑥=
𝑄
𝜌𝐶 𝑝 𝐿
(5)

16. • Parker et al, 1961 derived an analytical
solution that can be used to calculate
thermal diffusivity if conditions are ideal.
• Thermal diffusivity of material can be
calculated from the Parker solution, which is
given as;
∝=
𝟎. 𝟏𝟑𝟖𝟖𝑳 𝟐
𝒕 𝟏
𝟐
(𝟔)
Where t1/2 is the time when temp at the rear
surfaces reaches one half its final temperature

17. Result
Heat lost correction was calculated using Clark and
Taylor rise curve (Magic and Taylor, 1992). The
correction factor, K was calculated from the ratio of
t3/4/t1/4. the correction factor is thus calculated from;
𝐊 𝐑 = −𝟎. 𝟑𝟒𝟔𝟏𝟒𝟔𝟕 + 𝟎. 𝟑𝟔𝟏𝟓𝟕𝟖
𝐭 𝟎.𝟕𝟓
𝐭 𝟎.𝟐𝟓
− 𝟎. 𝟎𝟔𝟓𝟐𝟎𝟓𝟒𝟑
𝐭 𝟎.𝟕𝟓
𝐭 𝟎.𝟕𝟓
𝟕
The corrected value of thermal diffusivity at half time is
thus,
∝ 𝑐𝑜𝑟=
∝0.5 𝐾 𝑅
0.13885
(8)

18. Thermal diff vs Pressure
Figure 7: Graph of Thermal diff vs Pressure

19. X Ray Diffraction
Figure 8: Emerald Base Figure 9: Emerald salt

20. Discussion 2
 The measured thermal diffusivity of the emerald base
and salt were in the ranges of 1.52 – 1.79 cm/s and 1.37 -
1.56 cm/s respectively.
 Thermal diffusivity value for the emerald base and salt
increased in value as particle size of sample decreases.
 Thermal diffusivity value of the emerald base was
higher than the thermal diffusivity of the emerald salt.
 The XRD profile shown in figure 8 and 9 show that the
degree of crystallinity of the emerald base is higher
than that of the emerald salt.

21. Experimental 3
Measurement of thermal diffusivity of
Polypyrrole conducting polymer
composite films
 Using Photoacoustic technique
 Four series of Ppy-PEG films used
were prepared by Electrochemical
polymerisation method

22. Experimental set-up
Figure 10: Experiment setup for OPC detection technique (Lim
et al, 2009)

23. Theory
Photoacoustic technique was used to
measure thermal diffusivity of the
prepared conducting composite films.
Photoacoustic is the production of
acoustic waves by the absorption of
light.
In this experiment a heat transmission
configuration known as open
photoacoustic cell (OPC) was used.

24. Theory
 The photoacoustic signal for optical opaque samples at
low modulation frequency is given as (Lim, et al 2009);
𝑆 =
𝐴
𝑓
exp −𝑏 𝑓 9
Where, A is a constant and b is related to the thermal
diffusivity of sample with the expression;
𝑏 = 𝐼𝑠
𝜋
𝛼 10
Fitting the experimental data to equation (9), the
thermal diffusivity of the sample can be calculated.

25. Result
Figure 11: Signal fitting for PPy-
PEG Composite film
Figure 12: Thermal diffusivity vs
PEG concentration

26. Figure 13: Thermal diffusivity vs
pyrrole
Figure 14: Thermal diffusivity vs p-
toluene sulfonate concentration

27. Discussion 3
 Thermal diffusivity of PPy-PEG composite films
prepared by electropolymerization was
investigated using open photoacoustic
technique.
 The PPy-PEG composite films prepared at 0.20
M pyrrole monomer, 0.10 M p-toluene sulfonate
dopant and 1×10-3 M PEG at 1.20 volt gave the
highest thermal diffusivity of 7.88×10-7m2s-1.

28. Conclusion
 Three different photothermal techniques were used to
determine the thermal diffusivity of MUT.
 The three techniques used are;
Photothermal lens technique
Photoflash technique
Photoacoustic technique
All techniques were successfully used to calculate the
thermal diffusivity for materials under study. All three
techniques can be classified under photometry or
radiometry methods.

30. Bibliography
Josephine, L.Y.C, Wan Mahmood, M. Y, The, C.L,
(2003), Effect of particle size and compression
pressure on the thermal diffusivity of polyalinine
(Emerald base and Emerald salt) measured by a
photoflash method, Pertanika J. Sci. & Technol. 11(2):
219-228.
Lim, M.Y. Wan Mahmood, M.Y, Kassim, A and
Mahmud, H. N. (2009), Photoacoustic Measurement
of Thermal Diffusivity of Polypyrrole Conducting
Polymer Composite Films, American Journal of
Applied Sciences, 6 (2): 313-316

31. Shahriari E, Wan Mahmood, M.Y, Zamiri R. (2013),
the effect of nanoparticle size on thermal diffusivity
of gold nano-fluid measured using thermal lens
technique, J. Europ. Opt. Soc. Rap. Public. 8,
13026
Shen, J. Lowe, R. D and Snook, R. D. (1998), “Two-
beam Thermal Lens Spectrometer for Ultra-trace
Analysis,” Chem. Phys. 18, 403–408.
Turkevich, J. (1985), “Colloidal Gold Part II: Colour,
Coagulation, Adhesion, Alloying and Catalytic
Properties,” Gold Bull. 18, 125–131.

32. Almond D. P, Patel P. M, (1996), Photo-
thermal Science and Techniques en Physics
and its Application, 10 Dobbsand E. R and
Palmer S. B (Eds), Chapman and Hall,
London
Rosencwaig A, (1975), Physics Today 28 23
Angstrom A. J. Ann. (1861), Physik. Lpz. 114
513
Rontgen W. K. (1881), Ann Phys Lpz. 12 155
Bell A. G. (1880), Am. J. of Sci. 20 305

33. Cahill, D. G. Ford, W. K and Goodson, K. E
(2003), “Nanoscale thermal transport,” J. Appl.
Phys. 93, 793–818
James M. P (2010), “The measurement of
transmission, absorption, emission, and
reflection”. Handbook of Optics Third Edition,
Vol. I-V. Optical Sciences Center, University of
Arizona Tucson, Arizona
Parker, W. J, Jenkins, R.J, Butler, C.P, Abbot,
G.L, (1961), Photoflash method of determining
thermal diffusivity, heat capacity and thermal
conductivity. J. Appl. Phys. 32: 1679-1684