DETERMINATION OF PHOTO ACOUSTIC SPECTRA OF DYES-I CONGO RED

(1)

HAL Id: jpa-00223185

https://hal.archives-ouvertes.fr/jpa-00223185

Submitted on 1 Jan 1983

HAL

is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire

HAL, est

destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

DETERMINATION OF PHOTO ACOUSTIC SPECTRA OF DYES-I CONGO RED

R. Mathur, G. Pandey

To cite this version:

R. Mathur, G. Pandey. DETERMINATION OF PHOTO ACOUSTIC SPECTRA OF DYES-I CONGO RED. Journal de Physique Colloques, 1983, 44 (C6), pp.C6-171-C6-175.

�10.1051/jphyscol:1983626�. �jpa-00223185�

(2)

JOURNAL DE PHYSIQUE

Colloque C6, suppIbment au nulO, Tome 44, octobre 1983 page C6- 171

DETERMINATION OF PHOTO ACOUSTIC SPECTRA OF DYES-I CONGO RED

R.N. Mathur and G . C . Pandey

University Service and Instrumentation Centre, JawaharZaZ Nehru University, New DeZhi 110067, India

msUME

Gn prgsente l e s spectres photo acoustiques du Rouge Congo qui e s t un materiau opaque. On canpare l e s spectres PA du solide, l e s spectres de transmission d'une solution dilu&, l e spectre PA du colorant dGpos6 sur un papier f i l t r e .

ABSTRACT

Photo acoustic (PA) spectra of one of the optically opaque material

-

dye Congc-Red has been reported. The PA spectra of solid dye have been compared with the transmission spectrum of the diluate aquous solution of the dye as well a s the PA spectrum of the air dried aquous solution of the dye on a f i l t e r paper.

PA spectroscopy i s one of t h e v e r y s t r o n g a n a l y t i c a l t o o l f o r i n v e s t i g a t i o n o f m a t e r i a l s n o t amenable t o

a n a l y s i s by t h e c o n v e n t i o n a l s p e c t r o s c o p y ( 1 ) S a t u r a t i o n e f f e c t s observed i n s u c h studies,however l i m i t i t s u t i l i t y i n t h e i n v e s t i g a t i o n of h i g h l y s b s e r b i n g compounds l i k e o r g a n i c dyes and semi-conductors(2).

L i n and ~ u d e k / 3 / have shown t h a t sample p r e p a r a t i o n t e c h n i q u e s c a n overcome t h e P.A. s a t u r a t i o n problem.

They developed t h r e e s e p a r a t e methods f o r d e t e r m i n a t i o n of P.A Spectrum of h i g h l y a b s o r b i n g compounds. These a r e :

( i ) D e p o s i t i o n of a t h i n l a y e r of t h e sample onto a q u a r t z p l a t e e i t h e r by vacuum d e p o s i t i o n o r by smearing w i t h a s u i t a b l e a p p l i c a t o r .

( i i ) Nolecular d i s p e r s i o n of t h e sample over t h e s u r f a c e of a non a b s o r b i n g medium such a s barium s u l p h a t e , magnesium oxide, n e u t r a l a l u n i n a and s i l i c a g e l , ( i i i ) The sample i s coground with a non a b s o r b i n g

s u b s t r a t e i n a v i b r a t i n g mill(mechanica1 d i s p e r s i o n technique) and t h e mixture used a s t h e sample

L i n and ~ u d e k / 3 / have s u c c e s s f u l l y used above methods f o r d e t e r m i n a t i o n of P A s p e c t r a of t e t r a phenyl- porphin a t d i f f e r e n t concentrations. However, t h e presence of d i l u e n t o r t h e s u b s t r a t e w i t h t h e sample may r e s u l t i n d e v i a t i o n s and d i s t o r t i o n s of t h e a c t u a l spectrum.

A n a t t e m p t w a s , t h e r e f o r e , made t o o b t a i n PA S p e c t r a of one of t h e h i g h l y a b s o r b i n g compolmds-Congo-Red i n s o l i d s t a t e ( w i t h o u t any s u b s t r a t e ) and i s r e p o r t e d i n t h e p r e s e n t paper.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1983626

(3)

JOURNAL DE PHYSIQUE

According t o Rosencwaig-Gersho t h e o r y a compound s h a l l be photo a c c o u s t i c a l l y opaque i f t h e t h e r ma1 d i f f u s i o n l e n g t h i s l e s s t h a n t h e o p t i c a l a b s o r p t i o n l e n g t h 1/B, S i n c e it r e q u i r e s modulation f r e q u e n c i e s i n excess o f ¹

o4

^HZ

t o b r i n g t h e s e p a r t i c l e s o u t of S a t u r a t i o n ( l / B ) , such samples w i l l appear t o be i n h e r e n t l y opaque, even from photo a c c o u s t i c p o i n t of view(4). I n s u c h c a s e s , t h e r e f o r e , P.A. S a t u r a t i o n s h a l l p r e v e n t r e c o r d i n g of a meaningful

spectrum.

SPECTROSCOPY

The PA spectrum o f t h e dye was o b t a i n e d u s i n g t h e normal s e t t i n g s of t h e i n s t r u m e n t as per d e t a i l s given below:

Modulation frequency : A s p e r d e t a i l s g i v e n i n f i g u r e s Scan r a n g e ; uv-vi s i b l e

Scan r a t e 100 nm/minute

S e n s i t i v i t y Phase

Lamp C u r r e n t

A s p e r d e t a i l s g i v e n i n f i g u r e s 90%

19 Am

The d i f f e r e n t s p e c t r a o f t h e dye recorded have been shown f i g u r e s 1-4.

WAVELENGTH

Figure-I: Photo Acoustic Spectrum of Congo Red.

Figure-1 shows t h e P.A S p e c t r a r e c o r d i n g w i t h normal ins'nrmental s e t t i n g s at a modulation frequency of 240 HZ A s m a l l hump a t 470-480m a l o n g - w i t h a r a p i d d e c r e a s e i n

P.A s i g n a l around 590 nm can be c l e a r l y d i l i n e a t e d from t h i s f i g u r e . A s no comparable spectrum was a v a i l a b l e i n t h e l i t e r a t u r e , it was very d i f f i c u l t t o a n a l y s e t h e

s p e c t m s p e c i a l l y t h e absence of any s t r o n g a b s o r p t i o n peak.

(4)

A s a l r e a d y mentioned even modulation frequency of 240 HL i s t o o low t o b r i n g t h e sample o u t of s a t u r a t i o n .

The P.8. s p e c t r a of t h e s o l i d d y e , t h e r e f o r e , were recorded a g a i n u s i n g s l i t widths f o u r times t h e normal used f o r r e c o r d i n g of t h e spectrum i n f i g u r e - I .

A t h i n l a y e r of t h e powdered sample Was spread on t h e bottom s u r f a c e of t h e c a v i t y i n t h e sample h o l d e r . The P.A.

s p e c t r a of t h e sample was t h e n recorded at d i f f e r e n t modulation f r e q u e n c i e s v i z . 10,20,40,80,160 and 240 1%

reproduced i n figure-2.

! 10 H z at 10mV 1100 n m l s e c 1 2 20 H Z at lorn" 1100 nm1s.cI I. '0 H Z 01 l a m " l , O o n m l r = c l

' ^{8 0 H Z}^{m t}¹^mV^1100nmf^S.c ¹

5. 20 H. .t 10 mv l l o o n m / s e ~ 2LoHz 1 m~ 1100om/..c 1 2i0 nZ I 1 2 0 nmf s * c 1 g smmpLa hold-r 100 P V I ~ ~ ~ ~ ' ~ '

(5111 w l t h L X ' ¹

WAVELENGTH

Figure-2: Photo Acoustic S p e c t r a of Congo-Eied(so1id s t a t e ) a t d i f f e r e n t modulation f r e q u e n c i e s ;

The P.A. s p e c t r a of t h e sample h o u e r has been i n c l u d e d i n t h e above f i g u r e . The spectmun a t 240 HZ recorded a t two d i f f e r e n t s c a n r a t e s ( 100 and 2C nm/rainute) t o l o c a t e any peak which might have been missed a t h i g h e r s c a n r a t e . I t ma be n o t i c e d from t h e above f i g u r e ( d p e c t r a N6s. 182fthat t h e two s p e c t r a a r e r e p r o d u c i b l e and t h u s excludes t h e p o s s i b i l i t y of any a d d i t i o n a l band/peak. The s p e c t r a a t o t h e r modulation f r e q u e n c i e s , t h e r e f o r e , were recorded a t 100 nm/minute s c a n r a t e only.

I t may a l s o be mentioned t h a t t h e s p e c t r a a t d i f f e r e n t moduiation f r e q u e n c i e s a r e s i m i l a r e x c e p t t h a t i n t e n s i t y of t h e bands(peak h e i g h t ) a r e reduced due t o s a t u r a t i o n e f f e c t s .

T h i s s t u d y t h u s shows t h a t t h e P.A. s p e c t r a of o p t i c a l l y opaque samples(without any s u b s t r a t e / d i l u e n t ) can a l s o be recorded b y a d j u s t m e n t of c e r t a i n i n s t r u m e n t a l s e t t i n g s , F u r t h e r work a l o n g t h i s l i n e i s i n progress.

A corn a r i s o n of t h e PA spectrum o f t h e dye i n s o l i d s t a t e y f i g u r e - 2 ) w i t h t h a t of t h e d i l u t e aquous s o l u t i o n

( t r a n s m i s s i o n spectrum reproduced i n f i g m e - 3 ) .

(5)

JOURNAL DE PHYSIQUE

C R = C o n g o r o d

Ftg 3. T r o n s m ~ s s i o n s p e c t r a of Dyes

Figure.5: Transmission Spectrum o f t h e aquous s o l u t i o n of t h e dye.

F i g u r e . 3 shows t h a t t h e broad band around 495 n m p r e s e n t i n t h e t r a n s m i s s i o n spectrum seems t o be a combination of t h e 2 bands a t 465 and 495 nm(weak) p r e s e n t i n t h e PA spectrum.

I ¹

2W 100 L 00 5W 600 700 800

WAVELENGTH

Figure-4: Photo Acoustic Spectrum of t h e f i l t e r paper w i t h and without dye.

The e f f e c t of s u b s t r a t e on t h e PA Spectrwn o f t h e dye was a l s o s t u d i e d . A p i e c e of 't!hatman(~o. 42) f i l t e r paper w a s soaked i n a d i l u t e aquous s o l u t i o n of t h e dye and d r i e d i n a i r , The s p e c t r a o f t h i s a s w e l l as

t h a t of t h e f i l t e r paper a s s u c h were r e c o r d e d ( f i g u r e - 4 ) . The E.A spectrum of

t h e dye soaked f i l t e r paper gave qnly one v e r y broad band between 420 and 600 nm. It may be mentioned t h a t t h i s spectrum, i s comparable t o t h a t of t h e t r a n s m i s s i o n spectrum(figure-3).

2

1 conpo r e d 2 F0II.r paper 3 *.lhyl=ne blue

Y e t h ~ I ~ ~ . blue o f f e r OIIosU,S

(6)

Conclusions : The above s t u d y i n d i c a t e s t h a t

( i ) t h e PA spectrum of h i g h l y a b s o r b i n g compounds can be recorded a t lower modulation f r e q u e n c i e s .

( i i ) The P.A. spectrum of t h e dye i n s o l i d s t a t e i s b e t t e r r e s o l v e d t h a n that of t h e t r a n s m i s s i o n spectrum of t h e dye s o l u t i o n .

( i i i ) ~ h e P.A. spectrum o f t h e aquous s o l u t i o n of t h e dye on a s u b s t r a t e ( f i 1 t e r paper) seems t o r e p l i c a t e i t s t r a n s m i s s i o n spectrwn. The d i l u e n t / s u b s t r a t e appear t o a f f e c t a change i n t h e P.A. spectrum of t h e dye.

T h i s work i s a p a r t of t h e p r o j e c t supported by Department of Environment, Government of I n d i a .

1

.

P&DhY G.C. ,Proc. 3 r d I n t e r n a t i o n a l Neeting o n Photo a c c o u s t i c and photo Thermal Spectroscopy, P a r i s 1983

2. BOBEITCWAIG A . , i n "Advances i n E l e c t r o n i c and E l e c t r o n P h y s i c s w Vol-46 ( e d . ~ . ~ o r t o n )

Academic p r e s s (N.Y.) 1978.

3. LIN J . W . and DUDEK L.P. Anal. Chem.

2

1627(1979]

4. ROSElhCWAIG A., "Photo Accoustics and Photo Accoustics Spectroscopyn John. ~ i l l e y ( l ~ . Y ) 1980 P . 170