DSpace at VNU: Design and construction of a laser raman spectrometer to study hydrocarbon extracts from petroleum of Vietnam

12 Pham Van Ben, Nguyen The Binh, Nguyen Huy BinhA T F ig 1: The optical system scheme for sample excitation 3.

D E S IG N AND C O N STR U C TIO N O F A L A S E R RAMAN

S P E C T R O M E T E R TO STU D Y H YD R O C A R B O N E X T R A C T S FRO M

P E T R O L E U M O F V IE T N A M

P h a m V a n B e n , N g u y e n T h e B i n h , N g u y e n H u y B i n h

D e p a rtm en t o f P h ysic s, C ollege o f Science, V N U

A b s tr a c t W e stu d ie d to d e sig n a n d c o n s tru c t a la s e r R a m a n s p e c tro m e te r u sin g

o f th e la s e r R a m a n sc a tte rin g d e te c tio n s y s te m w a s e s tim a te d b y th e o b ta in e d

h y d ro c a rb o n e xtra cts fro m p e tro le u m o f V ie tn a m T h is re s u lt is a n im p o rta n t ste p

spe ctra o f p h o to -e le c tro n ic m a te ria ls

1 I n t r o d u c t i o n

L a s e r R a m a n spectroscopy h a s becom e a n e ffective m ethod to s tu d y the com position

an d c on stru ctio n o f m ate ria ls, e sp e cia lly to a n a ly s e h id ro c a rc b o n e x tra cts from petroleum and opto-electronic m aterials U s in g a n A rg o n la s e r a n d a dou b le g ra ttin g m onochrom ator

G D M - 1000 we h a ve d esign ed a n d con stru cte d a L a s e r R a m a n spectrom e te r in o u r laboratory B y t h is system we o bta in ed the R a m a n spectra o f som e s ta n d a rd so lu tio n such

as C6H u, CC14 a n d some h yd ro ca rb o ns e xtracted from p e tro leu m o f V ie tn a m

2 E x p e r i m e n t a l s e t u p

T h e b a n d in te n s it ie s in R a m a n s p e c tr u m m ay r a n g e fro m 1 02 to 10'6 % o f the

e x c ita tio n la s e r beam in te n s it y on th e s a m ple T h e re fo re , p o w e r fu l e x c ita tio n sources

a n d s e n s itiv e d e te ctio n sys te m s a re n e c e ss a ry to o b t a in a R a m a n s p ectru m T h e

s ch e m a tic d ia g ra m o f the b a s ic c o m p o n e n t o f th e la s e r R a m a n s p e c tr o m e te r syste m w a s

sh o w n in the F i g l T h e e x c ita tio n so u rce is a n A r g o n la s e r w h ic h can g iv e p o w e r o f 172m W a t 4 8 8 ,ln m w a v e le n g th a n d 60 m W a t 476,5 n m w a v e le n g th T h e la s e r b eam is

fo rcused on th e liq u id - s a m p le c e ll b y th e le n s o , (f|=7,7 cm ) a n d th e s c a t te r in g lig h t is

fo rcu sed o n th e m o n o ch ro m a to r e n tra n c e s lit h y th e le n s 02

M o u n t in g tw o p la n e m ir r o r s G , a n d G 2on tw o s id e s o f th e s a m p le c e ll in cre a s e the

in te n s it y o f th e sca tte re d r a d ia t io n B y th is w a y, th e la s e r b e a m is re fle c te d b a c k in to

th e s a m p le s ev era l tim es T h e con cave m ir r o r G a ( f 3 =16 cm , Ộ = 10,5 cm) b r in g s b ack

o nto th e m o n o ch ro m a to r s l i t the r a d ia t io n s ca tte re d b y th e s a m p le in th e reverse

d ire ctio n , T h e m a in fu n c tio n o f th e o p t ic a l syste m is to se c u re o p t im a l c o n d itio n s fo r

s a m p le illu m in a t io n a n d to fo cu s th e s c a tte re d r a d ia t io n o n th e m o n o ch ro m a to r

e n tra n ce s lit T h e R a m a n sp e c tr a is re co rd e re d b y a d o u b le g r a t tin g m o n o ch ro m a to r

G D M -1 0 0 0 a n d a p h o t o m u lt ip lie r tu b e M I 2 F C 5 1 T h i s s p e c tr u m re co rd e r system

o pe ra tes in th e ra n g e o f 2850 A0 + 66 5 0 A0 (23810 c m'1 -r 22727 cm ■') w it h the

d is p e rs io n o f 3 A0/mm

12 Pham Van Ben, Nguyen The Binh, Nguyen Huy Binh

A T

F ig 1: The optical system scheme for sample excitation

3 E x p e r im e n t a l r e s u lt s a n d d is c u s s io n

T o e x a m in e th e c a p a c ity a n d q u a lit y o f the R a m a n s p e c tro m e te r system w e f ir s t record ed the R a m a n s p ectra o f C C lj, C f,H 6 T h e n , w e re co rd e d R a m a n s p ectra o f some

h yd ro ca rb o n e x tra cts fro m p e tro le u m o f V ie tn a m T h e se sa m p le s h a v e d iffe r e n t b o ilin g - tem p eratu res: 110° c * 115° c fo r th e 5B110 s a m ple a n d 11 5 °c ■¥ 120° c fo r the 5B115 sam ple In the case o f C C lj, C6H6 w e recorded both R a m a n S to ke s a n d R a m a n a n ti-

S tokes s p ectra (as sh o w n in F ig 2) T h is re su lt in d ic a te d th e h ig h e ffic e n c y o f th e la s e r

R a m a n s c a tte rin g d e te ctio n system U s in g th is la s e r R a m a n s c a tte r in g d e te ction system

w e s tu d ie d to o b ta in s p ectra o f som e h yd rocarb on e x tra cts fro m p e tro le u m o f V ie tn a m ,

T h e sp ectra o f tw o sa m p le s o f V ie tn a m p e tro leu m e x tra cts w e re s h o w n in F ig 3

W e noted th a t in th e s p ectra o f both p e tro leu m sa m ple s, th e re is a double lin e

w it h stro n g in te n s it y in th e re g io n o f 2840 cm'1 -r 2930 cm'1 a n d a lin e o f w e a k er

in te n s ity a t 1444 cm'1 fo r th e ca se o f 5B110 s a m p le a n d a t 1454 cm'1 fo r the ca se o f 5B 1 15 s a m p le a n d som e lin e s o f ve ry w e a k e r in te n s ity in th e re g io n o f wave n um b e r

B a s in g on th e c h a r a c t e r is t ic o f b o ilin g -te m p e ra tu re , in te n s it y a n d fre q u e n cy s h ift

in R a m a n s p e c tr a o f th e tw o sa m p le s o f V ie tn a m p e tro leu m e x tra cts [2,3] w e cou ld

c o n c lu d e t h a t th e tw o s a m p le s con s is ted o f 2 -M e ty l p e ntane, X y c lo p e ntane, O ctane,

E ty x ic lo h e x a n , N o n a n p -X y le n a n d 2, 6 D im e ty l h eptanes A l l the se com p ou n d s b elong

to p a r a ffin , n a p h th a le n e a n d a ro m a tic h yd ro ca rb o n s fa m ily [5] T h is r e s u lt w a s in good

a g re e m e n t w it h s e v e ra l o th e r d ocu m en ts re p orte d on p e tro leu m o f V ie tn a m

Fig.3: The Raman spectra o f petroleum extract samples excited by 476,5nm wavelength

of Argon laser : a - for sample 5B110 , b - for sample 5B115

4 C o n c lu s io n s

A la s e r R a m a n sp ectrom etry system w ith an A rg on la s e r a n d a d ouble g ra ting

m onochrom ator G D M -1 0 0 0 h a s been developed a t o u r laboratory Severa l studies were carried o u t to design optica l system fo r o ptim a l sam ple excitation T h e o bta in ed R am a n spectra sho w ed th a t th is la s e r R a m a n spectrom etry system cou ld give h igh se n s itiv ity and resolution It is s u ita b le not o n ly to ana lyze hydrocarbon com pounds o f petroleum b ut also

to study sem icon d uctor m a te ria l structure

A c k n o w l e d g e m e n t s : T h i s w o r k w a s s u p p o rte d by the S c ie n tif ic R e s e a rch P ro g ra m

o f V N U

References

1 H B a ra tis k a , A L a b u d z in s k a , J.T e r p in s k i, A Laser Ram an Spectrom etry - E llis Howood

J W ile y & Sons 1987

2 F.R D ollish,W ,G Fateley, Characteristic R a m an Frequencies o f Organic compounds,

W il3ey-Interscience N e w Y o r k 1974

3 B e rn h a rd S chrader, Infrared a n d Ram an Spectroscopy W einh em -N ew Y o r k - 1994