1

Photothermal SpectroscopyLecture 2 - Applications

Aristides Marcano Olaizola (PhD)Research ProfessorDepartment of Physics and EngineeringDelaware State University, US

Outlook

1. Optical characterization of matter.2. The place of photothermal spectroscopy3. Achromatic character of the mode-

mismatched configuration.4. NIR Photothermal spectroscopy5. Photothermal-absorbance-fluorescence

spectrophotometer.6. Photothermal spectroscopy of

fluorescence and scattering samples.7. Perspectives.

Material samples exhibit generally more than one type of effect upon interaction with light

Transmitted lightIncident light

Reflected light

Scattered light

Absorption of lightPhotoacoustic effectsPhotothermal effectsPhotomechanical effectsPhotochemical effectsLuminescence

)()( RsThFTo PPPPPP

From the energy conservation law we obtain

sP

TP

oP Incident power

Transmitted power

FP Power used for fluorescence

Power degraded into heat ThPScattered power

RP Reflected power

)(

)(

o

T

PPT Transmittance

)(log)( TA Absorbance

)(

)(

o

F

PPF Fluorescence excitation

spectrum

)(

)(

o

R

PPR Reflectance

)(

)(

o

Th

PPPT Photothermal spectrum

-40 -20 0 20 40-0.15

-0.10

-0.05

0.00

0.05

Mode-mismatched

Mode-matchedT

L si

gnal

Sample position (cm)

o=-0.1, p=632 nm, e=750 nm, L=200 cm, D=0.001491 cm2/s,t=10 s, zp=0.2 cm for mode-matched scheme and zp=2000 cm formode-mismatched scheme.

D

Ampl.

Sample

Exc

itatio

n la

ser

M1M2

F

A

Osc.

L1

L2

L3

L4

Prob

ela

ser

B z

Ch

Marcano O. A. and N. Melikechi, App. Spectros. 61, 659-664 (2007).

-20 -10 0 10 20-0.06

-0.03

0.00

0.03

Mode-mismatched

Mode-matchedT

L si

gnal

Sample position (cm)

Experimental Z-scan of 1-cm cell containing distilled water measuredunder the mode-matched (open stars) and mode-mismatched (solidsquares) schemes.

p=632 nm, e=807 nm

700 800 900 10000.0

0.2

0.4 Mode-mismatched

Mode-matched

Abs

orpt

ion

(cm

-1)

Wavelength (nm)PTL spectra of distilled water measured using the mode-matched (large open stars) andmode-mismatched (large crossed circles) experimental configurations. Results ofprevious reports on water absorption of different authors have been included (smallsymbols).

Ultrasensitive spectroscopy of water

R. A. Cruz, A. Marcano O., C. Jacinto, and T. Catunda, “Ultra-sensitive Thermal Lens Spectroscopy of Water”, Opt. Lett. 34 (12), 1882-1884 (June 15, 2009).

High precision values of absorption of water in the 300-500 nm spectral region

700 800 900 10000.0

0.3

0.6 Comparison of TL spectrum with absorbance speof distilled water measured by other authors

TL spectrum

Pope and Fry

Palmer and Willians

Abs

orpt

ion

coef

ficie

nt (c

m-1)

Wavelength (nm)

700 800 9000.00

0.05

0.10

0.15A

bsor

banc

e

Wavelength (nm)

Ethanol TL

Cary absorbance measurement

NIR spectroscopy of Ethanol

700 750 800 850 900 9500.0

0.1

0.2

0.3

Abs

orba

nce

Wavelength (nm)

PTL Methanol cell 1 mm

Cary absorbance

NIR of Methanol

Nd:YAG OPO

He-Ne

M1

M2

D1 D2 D3

BS1

L1 Sample BS2

F1M3

L2

D4

Laser based PTL, absorbance ,and fluorescence excitation spectrophotometer.J. Hung, A. Marcano O., J. Castillo, J. Gonzalez, V. Piscitelli, A. Reyes and A. Fernandez, “Thermal lensing and absorbance spectra of a fluorescent dye”, Chem. Phys. Lett. 386, 206-210

A

L3

F2

Figure 2. Hung et al.

450 475 500 525 550 5750,00

0,01

0,02

0,03

Abs

olut

e va

lues

F(e)

1-T(e)

ATh(e)

Wavelength (nm)

. Absorbance (crossed circles), fluorescence excitation (crossed stars) and TL spectra (solidtriangles) of a 5 10-6 M ethanol solution of Rhodamine 6G. The solid line is the absorbancespectrum of the same sample obtained using a spectrophotometer.

Figure 3. Hung et al.

475 500 525 5500,000

0,006

0,012

F(e)

1-T(e)

ATh(e)

Abs

olut

e va

lues

Wavelength (nm)Absorbance (crossed circles), fluorescence excitation (crossed stars) and TL spectra (solid triangles) of the same sample of previous slide after adding of the quencher (KI).

475 500 525 5500,0

0,5

1,0

With quencher

No quencherFl

uore

scen

ce Q

uant

um Y

ield

Wavelength (nm)

Fluorescence quantum yield spectrum of the 5 10-6 M ethanol solution of Rhodamine 6G in presence of high fluorescence and in the presence of fluorescence quenching.

He-NeL1L2

M1

S

M2

D Ch

XeLamp

A

M3

IFSL3 L4

B

White light photothermal lens spectrophotometer

PTL spectrum of a non-fluorescent dye

400 500 600 7000

50

100

150

Wavelength (nm)

Mol

ar e

xtin

ctio

n co

effic

ient

(mM

-1 c

m-1)

0.0

0.4

0.8

ATL ()

PTL spectrum of 0.125 mM solution of Malachite green in ethanol. There is coincidence with the absorbance spectrum.A. Marcano O., J. Ojeda and N. Melikechi, “Absorption spectra of dye solutions measured using a white-light thermal lens spectrophotometer”, Appl. Spectros. 60 (5), 560-563 (2006).

PTL of a fluorescent dye

400 450 500 550 6000

50

100

Wavelength (nm)

Mol

ar e

xtin

ctio

n co

effic

ient

(mM

-1 c

m-1)

0.0

0.1

0.2

0.3

ATL ()

PTL and absorbance spectra of a 50 mM solution of R6G in ethanol.

Because of fluorescence both spectra are different. This property of PTL spectroscopy can be used for measuring the quantum yield of fluorescence

Quantum yield of fluorescence

450 500 550 6000.0

0.5

1.0

F

Wavelength (nm)

)L)(exp(1/)(A1 TLFF

L ︶︵

︶︵ATL

PTL absorbance

absorbance

FAverage wavelength of fluorescence

400 500 600 7000.0

5.0x104

1.0x105

1.5x105

Ext

inct

ion

(cm

-1/M

)Wavelength (nm)

Malachite Green Oxalate

400 500 600 7000.0

5.0x104

1.0x105

1.5x105

Ext

inct

ion

(cm

-1/M

)

Wavelength (nm)

Malachite Green Oxalatea b

a- PTL and extinction spectra of Malachite Green Oxalate with nopolystyrene microbeads added; b- PTL and extinction spectra of MalachiteGreen Oxalate containing polystyrene microbeads at concentration of0.005% by weight. The standard deviation is estimated averaging over 5different experiments.

PTL spectroscopy of scattering samplesA. Marcano O., S. Alvarado, J. Meng, D. Caballero, E. Marin and R. Edziah, Applied Spectroscopy, 68 (6), 680‐685, June  2014. DOI: 10.1366/13‐07385. 

a

500 600 7000.0

0.5

1.0N

orm

aliz

ed P

TL

Sig

nal

Wavelength (nm)

Methylene Blue

b

400 500 600 7000.0

0.5

1.0

0.0017 %

Nor

mal

ized

Ext

inct

ion

Wavelength (nm)

Methylene Blue

0

0.005 %

a - Normalized PTL spectra of Nile Blue with polystyrene microbeads added atconcentration of 0 (crossed circles), 0.0017% (stars) and 0.005% (crossed squares)by weight; b- Normalized extinction spectra of Nile Blue containing polystyrenemicrobeads at concentration of 0, 0.0017% and 0.005% by weight as indicated. Thestandard deviation is estimated averaging over 5 different experiments.

400 500 600 7000.0

0.5

1.0

Scat

teri

ng Q

uant

um Y

ield

Wavelength (nm)

Malachite Green

500 600 700

0.0

0.5

1.0

Scat

teri

ng Q

uant

um Y

ield

Wavelength (nm)

Methylene Blue

a b

a- Scattering quantum yield of the Malachite Green Oxalate sample with addedpolystyrene microparticles at 0.005 % concentration by weight; b- Scatteringquantum yield of the Nyle Blue sample with added polystyrene microparticles at0.005 % by weight. The standard deviation is estimated averaging over 5 differentexperiments.

400 500 600 700109

1010

1011

Ext

inct

ion

coef

ficie

nt (c

m-1

/M)

Wavelength (nm)

Au nanoparticles

Extinction (solid line) and PTL (crossed circles) spectra of a solution of 50-nmdiameter gold nanoparticles at concentration of 1 mg/mL. The standard deviationis estimated averaging over 5 different experiments.

400 500 600 7000.0

0.5

1.0

Scat

teri

ng Q

uant

um Y

ield

Wavelength (nm)

Malachite Green

500 600 700

0.0

0.5

1.0

Scat

teri

ng Q

uant

um Y

ield

Wavelength (nm)

Methylene Blue

a b

a- Scattering quantum yield of the Malachite Green Oxalate sample with addedpolystyrene microparticles at 0.005 % concentration by weight; b- Scatteringquantum yield of the Nyle Blue sample with added polystyrene microparticles at0.005 % by weight. The standard deviation is estimated averaging over 5 differentexperiments.

400 500 600 7000.01

0.1

1

10E

xtin

ctio

n co

effic

ient

(A.U

.)

Wavelength (nm)

Blood

a b

400 500 600 700

0.0

0.5

1.0

Scat

teri

ng Q

uant

um Y

ield

Wavelength (nm)

Blood

a- Extinction (solid line) and PTL (crossed circles) spectra of a blood sample; b-Scattering quantum yield of the same blood sample. The standard deviation is estimated averaging over 5 different experiments.

Photothermal mirror effect

Nanometric bump

Excitation light

Reflected light

Xe lamp

He-NeCoCh

D1

SF

L1 L2B

M1

M2

D2

A

Pre-AmplOsc.

White-light photothermal mirror spectrophotometer

The signal is defined as

o

o

TTTS

)()(

T() is the transmission through the aperture of the probe light in the presence of the pump beam.

To is the transmission through the aperture of the probe light in the absence of the pump beam.

)()()( PKS

A model based on the simultaneous resolution of the thermo-elastic deformation of the surface and thermal diffusivity equation predicts that

)( is the fraction of absorbed energy used to generate heat

)(P is the power of the pump light

K is a proportionality coefficient that does not depend on

)( PTM spectrum

PTM (black crossed squares) and absorbance (red crossed circles) of a glass plate

400 500 600 7000

3

6 AbsorbanceA

bsor

banc

e an

d PT

M

Wavelength (nm)

Small dark glass plate 2 mm

PTM

400 500 600 7000.0

0.2

0.4

0.6

0.8

PT

M

Wavelength (nm)

Ag plate no plasma

PTM spectra of a film made using the deposits from a silver nanoparticle solution

400 500 600 7000

2

4

6

8PT

M S

igna

l (A

rb. U

nits

)

Wavelength (nm)

Dy2TiO5

PTM spectrum of the dysprosium titanate sample

Conclusions

Photothermal spectroscopy (PT) is a new spectroscopic method that measures the ability of matter to produce heat following the absorption of light.

PT spectra and absorbance spectra coincide for samples with 100 % thermal yield.

Advantages

• High sensitive• Universality (any sample, any spectral region).• Scattering and fluorescence free• Only visible sensor technology required (no IR or UV sensors needed)• Remote sample analysis possible• Traditional and modern light source technology can be adapted.• Low cost.

Light Sources for PT Spectroscopy

Arc lamps

http://zeiss‐campus.magnet.fsu.edu/print/lightsources/xenonarc‐print.htm

High Intensity Tunable Light Source

22K$ www.newport.com

White Leds

10$ on ebay

The Argon laser

NIR lasers (MIRA 900)Fs and CW modes700-1050 nm

Vantage tunable diode

Spectra Physics Velocity™ Widely Tunable Lasers

Tunable diodes

Laser supercontinuum – good option for phototohermalspectroscopy

http://www.nktphotonics.com/