Seminar Sakher

7/24/2019 Seminar Sakher

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ordan University Of Science and

ordan University Of Science and

Technology

echnology

Faculty of scienceFaculty of science

Department of physicsDepartment of physics

Seminar titleSeminar title

Raman scattering

aman scatteringPresented byPresented by::

Sakher Abed Al Razaq HayajnehSakher Abed Al Razaq HayajnehSuperiser nameSuperiser name::

Dr! Fedda AlzoubeDr! Fedda Alzoube

""stst semestersemester

#$$%#$$%&$$'#$$'


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..ABLE OF CONTENTS

ABLE OF CONTENTS::

!!(ntroduction(ntroduction

!!)ypes scatterin* of photon)ypes scatterin* of photon

!!Raman scatterin* e+planationRaman scatterin* e+planation

!!Application for Raman scatterin*Application for Raman scatterin* !!,ey feature of S-RS,ey feature of S-RS

!!.echanism of S-RS.echanism of S-RS

!!Application for S-RSApplication for S-RS

!!/onclusion/onclusion!!ReferencesReferences


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NTRO!UCTONNTRO!UCTON::

)he scatterin* of li*ht may be thou*ht of as)he scatterin* of li*ht may be thou*ht of asthe redirection of li*ht that takes placethe redirection of li*ht that takes place0hen an -lectroma*netic 1-.2 0ae 1i!e!0hen an -lectroma*netic 1-.2 0ae 1i!e!an incident li*ht ray2 encounters anan incident li*ht ray2 encounters an

obstacle or nonhomo*eneity3 (n our case3obstacle or nonhomo*eneity3 (n our case3the scatterin* material 1solid3 liquid or *as2the scatterin* material 1solid3 liquid or *as2!!

As the -. 0ae interacts 0ith the matter3As the -. 0ae interacts 0ith the matter3

the electron orbits 0ithin the constituentthe electron orbits 0ithin the constituentmolecules are perturbed periodically 0ithmolecules are perturbed periodically 0iththe same frequency 1no2 as the electricthe same frequency 1no2 as the electric

field of the incident 0aefield of the incident 0ae!!


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)he oscillation or perturbation of the)he oscillation or perturbation of the

electron cloud results in a periodicelectron cloud results in a periodicseparation of char*e 0ithin theseparation of char*e 0ithin themolecules3 0hich is called an inducedmolecules3 0hich is called an induceddipole momentdipole moment!!

)he oscillatin* induced dipole moment is)he oscillatin* induced dipole moment ismanifest as a source of -. radiationmanifest as a source of -. radiation33

thereby resultin* in scattered li*htthereby resultin* in scattered li*ht!!

)he majority of li*ht scattered is emitted)he majority of li*ht scattered is emittedat the identical frequency 1no2 of theat the identical frequency 1no2 of theincident li*ht3 a process referred to asincident li*ht3 a process referred to as

elastic scatterin*elastic scatterin*!!


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Ho0eer3 as e+plained belo03 additional li*htHo0eer3 as e+plained belo03 additional li*ht

is scattered at different frequencies3 ais scattered at different frequencies3 aprocess referred to as inelastic scatterin*process referred to as inelastic scatterin*!!

Raman scatterin* is one such e+ample ofRaman scatterin* is one such e+ample ofinelastic scatterin*inelastic scatterin*!!

(n summary3 the aboe comments describe(n summary3 the aboe comments describethe process of li*ht scatterin* asthe process of li*ht scatterin* as

a comple+ interaction bet0een the incidenta comple+ interaction bet0een the incident

-. 0ae and the material4s-. 0ae and the material4smolecular&atomic structure3 0hich is usefulmolecular&atomic structure3 0hich is useful

to study the microscopic structureto study the microscopic structure!!


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""55)homson scatterin*)homson scatterin*

##55/ompton scatterin*/ompton scatterin*

6655Raman scatterin*Raman scatterin*

)he last one 0ill be discussed in details)he last one 0ill be discussed in details!!

Three ty"es "hoton of

hree ty"es "hoton of

scatteringcattering


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Describe electroma*natic radiations inDescribe electroma*natic radiations in

a simple classical process scatter by thea simple classical process scatter by the

electron of ionized *as!0here thomsonelectron of ionized *as!0here thomsoncross5sectioncross5section

7 7eq 1"2eq 1"2

8here8here rroo9 classical radius of electron9 classical radius of electron

##$Thomson scattering%$Thomson scattering%

22921065.68 mrT

=


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(n )homson scatterin* the radiation is not(n )homson scatterin* the radiation is not

absorbed but reappears as radiationsabsorbed but reappears as radiations

traellin* in different directions !there is notraellin* in different directions !there is no

chan*e in frequency in quantum term thechan*e in frequency in quantum term the

photon collides elastically 0ith thephoton collides elastically 0ith theelectronselectrons!!

(n other 0ords! )he photon ener*y is mush(n other 0ords! )he photon ener*y is mush

less than the rest mass of the electronless than the rest mass of the electron ! !

h

h

2cm


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22..om"ton scattering

om"ton scattering::

/ompton scatterin* is obsered in +5rays/ompton scatterin* is obsered in +5rayspassin* throu*h a solid or *aspassin* throu*h a solid or *as!!

)he essential interaction is bet0een hi*her)he essential interaction is bet0een hi*her

photon ener*y and indiidual electrons!photon ener*y and indiidual electrons!0ether or not that electron is bond to0ether or not that electron is bond to

atomic nucleusatomic nucleus!!


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nder conseration of momentum and ener*y *iesnder conseration of momentum and ener*y *ies

compton scatterin* formulacompton scatterin* formula

7 7eq1#2eq1#2

8here8here ;


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66>>Raman scatteringRaman scattering:5:5

)he spentaneous raman effect 0as discoered by)he spentaneous raman effect 0as discoered by/ !? Raman "@#' 3he 0as a distin*uished/ !? Raman "@#' 3he 0as a distin*uished

indian physist 0ho 0as a0arded the noble prizeindian physist 0ho 0as a0arded the noble prize

in "@6$ for his 0ork on the scatterin* of li*ht andin "@6$ for his 0ork on the scatterin* of li*ht and

for the discoery of raman effectfor the discoery of raman effect!!

Raman scatterin* results from the interaction ofRaman scatterin* results from the interaction of

li*ht 0ith the ibrational modes of moleculesli*ht 0ith the ibrational modes of molecules

constitutin* the scatterin* medium ramanconstitutin* the scatterin* medium ramanscatterin* can equialently be described as thescatterin* can equialently be described as the

scatterin* of li*ht from optical phononsscatterin* of li*ht from optical phonons!!


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Raman scatterin* can occur by chan*eRaman scatterin* can occur by chan*eibrational 3 rotational or electronic ener*yibrational 3 rotational or electronic ener*y

of the moleculesof the molecules!!

)he difference ener*y bet0een the incident)he difference ener*y bet0een the incidentphoton and the raman scattered photon isphoton and the raman scattered photon is

equal to the ener*y of a ibrationequal to the ener*y of a ibration

Bf the scatterin* molecules and itsBf the scatterin* molecules and itsdescribed is inelastic scatterin*described is inelastic scatterin*!!


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(f there no chan*e in(f there no chan*e in

frequency bet0eenfrequency bet0een

incident andincident and

scattered photonscattered photon

)his scatterin* called)his scatterin* calledCCReylie*h scatterin*Reylie*h scatterin*4444

Figure 1Figure 1


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Raman scatterin* has small fraction of li*htRaman scatterin* has small fraction of li*ht

such as " from "$% photon 0ill besuch as " from "$% photon 0ill beinelastic scatter 3 the eent of scatterin*inelastic scatter 3 the eent of scatterin*

occurs in "$5"E seconds or lessoccurs in "$5"E seconds or less!!


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(n *eneral the(n *eneral thescattered li*htscattered li*htcontains frequenciescontains frequenciesdifferent from thosedifferent from thoseof e+citationof e+citationsource 3 thosesource 3 those

components shiftedcomponents shiftedto lo0er frequencyto lo0er frequencyare calledare called

CCStokes linesStokes lines ! !

Fi*ure #Fi*ure #


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and those shiftedand those shifted

to hi*herto hi*her

frequency arefrequency are

calledcalled

CAnti stokeCAnti stokelineslines ! !

Fi*ure 6Fi*ure 6


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)he stockes line are typically orders of)he stockes line are typically orders of

ma*nitude more intense than antima*nitude more intense than anti

stockes lines because at thermalstockes lines because at thermal

equilibrium and normal temperatures theequilibrium and normal temperatures the

population of electrons in leel n state ispopulation of electrons in leel n state issmaller than the population in *roundsmaller than the population in *round

state result from Goltzman ener*ystate result from Goltzman ener*y

distribution 1 proportionaldistribution 1 proportionaltoto 2 2kTw

e /


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Fi*ure EFi*ure E


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Stokes scatterin* result 0hen molecules areStokes scatterin* result 0hen molecules arein their *round state 0hen it is interact 0ithin their *round state 0hen it is interact 0ith

the beam of li*ht some of ener*y from thethe beam of li*ht some of ener*y from the

collidin* photon is channeled into thecollidin* photon is channeled into the

ibrational mode of the molecules thisibrational mode of the molecules this

causes the li*ht to absorbed and then re5causes the li*ht to absorbed and then re5

emitted at lo0er frequencyemitted at lo0er frequency!!


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Fi*ure IFi*ure I


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Anti stockes scatterin* occurs 0henAnti stockes scatterin* occurs 0hen

molecules is in aibrationally e+cited statemolecules is in aibrationally e+cited state0hen it interact 0ith the radiations the0hen it interact 0ith the radiations the

interaction can cause to drop to *roundinteraction can cause to drop to *round

state and lose some of it is ibrationalstate and lose some of it is ibrationalener*y to the re5emitted a hi*herener*y to the re5emitted a hi*her

frequency li*htfrequency li*ht!!


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Fi*ure JFi*ure J


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!!Dia*ram illustrate raman shiftDia*ram illustrate raman shift

Fi*ure %Fi*ure %


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Raman scattering e&"lanationRaman scattering e&"lanation::

Ki*ht is treated as a electroma*natic 0aeKi*ht is treated as a electroma*natic 0aeand the molecules is modeled as smalland the molecules is modeled as smallspheres connected by sprin*!spheres connected by sprin*!

)he incident li*ht can be described by)he incident li*ht can be described by

follo0in* equations :follo0in* equations :- 1+3 t2 9 -- 1+3 t2 9 -$$/os 10/os 10LL t 5 k4+23 7eq 162t 5 k4+23 7eq 162

)he induced dipole is)he induced dipole is

M 9M 9 NN ! - 3 7eq 1E2! - 3 7eq 1E2NN is the polarizability tensor 3 substitute is the polarizability tensor 3 substitute

in the electric field of li*htin the electric field of li*ht

M 9M 9 NN --$$/os 10/os 10LL t2 3 7eq 1I2t2 3 7eq 1I2


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)he polarizability tensor depend on)he polarizability tensor depend on

the conformation of the molecule3the conformation of the molecule3

it chan*es as the molecule ibrate !it chan*es as the molecule ibrate !

GutGut NN 99 NN1O 2 3 7eq 1J21O 2 3 7eq 1J2

O is the normal ibrational coordinates !O is the normal ibrational coordinates !

8e can e+pand8e can e+pand NN as tayler series 3as tayler series 3

NN 99 NNo Q 1o Q 1NN2& 1O 21O 5 $2 7 7eq 1%22& 1O 21O 5 $2 7 7eq 1%2 0here O 9 O0here O 9 O$$ /os 10/os 10mmt23 7eq 1'2t23 7eq 1'2

88mm is the frequency for the molecule ibrateis the frequency for the molecule ibrate


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Gy substituteGy substitute NN 0e calculate the induced0e calculate the induced

dipole 3dipole 3M 9M 9 NNoo--$$/os 10/os 10LLt2 t2 Q 1Q 1NN2& 1O 2! O2& 1O 2! O$$--$$

/os 10/os 10LLt2 !t2 !/os 10/os 10mmt2 3 7eq 1@2t2 3 7eq 1@2

M 9M 9 NNoo--$$/os 10/os 10LLt2 t2 Q 1Q 1NN2& 1O 2 !2& 1O 2 !OO$$--$$ Q/os 110Q/os 110LL55 00mm2t2 2t2

/os 110/os 110LL 00mm2t2 3 7eq 1"$22t2 3 7eq 1"$2


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""stst term Tterm T NNoo--$$/os 10/os 10LLt2 Ut2 U

mean the incident li*ht frequency is the samemean the incident li*ht frequency is the samefor the scattered li*ht frequency 0hich 0asfor the scattered li*ht frequency 0hich 0as

mentioned 1 Reylie*h scatterin* 2mentioned 1 Reylie*h scatterin* 2!!

##ndnd term K!H!Sterm K!H!S

])])NN(/ )(/ )QQ([.([.QQ00--$$ Q/os 110Q/os 110LL55 wwmm2t22t233

mean lo0er shift of frequency 0hich 0asmean lo0er shift of frequency 0hich 0asmentioned 1Raman stokes shift 2mentioned 1Raman stokes shift 2


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##ndnd term R!H!Sterm R!H!S

] )] )NN(/ )(/ )QQ([.([.QQ00--$$ Q/os 110Q/os 110LL wwmm2t2 3 mean2t2 3 meanhi*her shift of frequency 0hich 0ashi*her shift of frequency 0hich 0as

mentioned 1Raman anti stokes shift 2mentioned 1Raman anti stokes shift 2!!

ote that 3the Raman scatterin* intensityote that 3the Raman scatterin* intensityproportional toproportional to

QQ ) )NN(/ )(/ )QQ((## !!

55)he selection rule for raman scatterin* is)he selection rule for raman scatterin* is

) )NN(/ )(/ )QQ( ( 00


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A""lications for raman

""lications for raman

scatteringcattering::Surface enhanced raman scatteringSurface enhanced raman scatteringspectroscopy (SERS)spectroscopy (SERS)..

)his reie0 coers from the basic principles)his reie0 coers from the basic principlesof raman spectroscopy to the adancedof raman spectroscopy to the adancedtechnique of surface enhanced ramantechnique of surface enhanced ramanscatterin* 1S-RS2 spectroscopyscatterin* 1S-RS2 spectroscopy!!


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S-RS 0as accidentally discoered 0hile peopleS-RS 0as accidentally discoered 0hile people

tried to do raman on the electrode in "@%E !thetried to do raman on the electrode in "@%E !theori*inal idea to *enerate a hi*h surface area onori*inal idea to *enerate a hi*h surface area onthe rou*hed metalthe rou*hed metal!!

(n "@%% found the rou*h slier electrode produce(n "@%% found the rou*h slier electrode produceraman spectrum that is a million fold moreraman spectrum that is a million fold more

intense than 0as e+pectedintense than 0as e+pected!!

)his enormously stron* si*nal debuted surface)his enormously stron* si*nal debuted surfaceenhanced raman scatterin* 1S-RS2enhanced raman scatterin* 1S-RS2!!


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'ey feat(res of SERS'ey feat(res of SERS::

55S-RS occurs 0hen molecules are brou*ht to theS-RS occurs 0hen molecules are brou*ht to the

surface of metal in a ariety ofsurface of metal in a ariety of

morpholo*iesmorpholo*ies!!

55lar*e enhancement are obsered from siler 3*oldlar*e enhancement are obsered from siler 3*oldand copper 3the particles size forand copper 3the particles size for

enhancement raman to happen ran*es fromenhancement raman to happen ran*es from

#$#$nm 5 6$$nmnm 5 6$$nm!!55.olecules adsorbed in the first layer on the surface.olecules adsorbed in the first layer on the surface

sho0 lar*est enhancements 1lar*e ran*e effect "$sho0 lar*est enhancements 1lar*e ran*e effect "$

nanometer 2nanometer 2!!


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Fi*ure 'Fi*ure '


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)echanism of SERS)echanism of SERS::

55seeral years a*o fe0 0ere fully conincedseeral years a*o fe0 0ere fully coninced

that S-RS enhancement could be as hi*hthat S-RS enhancement could be as hi*h

as "I orders of ma*nitude and S-RSas "I orders of ma*nitude and S-RS

actie materials 0ould includeactie materials 0ould include

a ariety of transition metals and probablya ariety of transition metals and probably

semi5conductorssemi5conductors!!


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)he enhancement most probably comes)he enhancement most probably comes

from the increasin* of the electric fieldfrom the increasin* of the electric field!!8hen the shape of particle 0as sharp8hen the shape of particle 0as sharp

)he electric field near the sharp tip 0ould be)he electric field near the sharp tip 0ould be

*reatly enhanced 3 then if 0e collect t0o or*reatly enhanced 3 then if 0e collect t0o ormore particles *ather to*ether the electricmore particles *ather to*ether the electric

field could be collectie resonance of freefield could be collectie resonance of free

electron of the surface of the metalelectron of the surface of the metal

particles 0hich proides *reatparticles 0hich proides *reat

enhancementenhancement!!

A""lication for SERSA

""lication for SERS::


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A""lication for SERSA""lication for SERS::

S-RS used in detection of DA = RAS-RS used in detection of DA = RA

55ProcedureProcedure::

the *old particles 0ere desi*ned in specialthe *old particles 0ere desi*ned in special

0ay to make use of S-RS the dye /V6 0as0ay to make use of S-RS the dye /V6 0as

attached to the *old particles and the tar*etattached to the *old particles and the tar*et

0as attached to the /V6 then the *old0as attached to the /V6 then the *old

particle thro0n onto the DA chip After thatparticle thro0n onto the DA chip After that

add some siler particles to the solutionadd some siler particles to the solution

0hich *ather around the *old particles 0hich *ie0hich *ather around the *old particles 0hich *ieS-RS effectS-RS effect!!


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o0 0e are in a *ood shape to obtaino0 0e are in a *ood shape to obtain

Raman si*nals from the tar*et and locateRaman si*nals from the tar*et and locateit 0ith hi*h resolution and 0ill *etit 0ith hi*h resolution and 0ill *et

CCfin*erprint of the DA = RAfin*erprint of the DA = RA!!


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Concl(sionConcl(sionAs preious oerie0 the important factor for ramanAs preious oerie0 the important factor for raman

scatterin* that it is more sensitie to differentscatterin* that it is more sensitie to differentibrational modes this is the reason 0hy its calledibrational modes this is the reason 0hy its calledC fin*erprint of molecules after S-RS 0asC fin*erprint of molecules after S-RS 0as

discoereddiscoered!!

S-RS is amon* the most sensitie techniques aailableS-RS is amon* the most sensitie techniques aailable

to surface scienceto surface science!!its capability to delierin* specific chemical identificationits capability to delierin* specific chemical identificationand to couple this 0ith a 0ide ran*e of instruments3and to couple this 0ith a 0ide ran*e of instruments3has led to its continuin* use in both ne0 andhas led to its continuin* use in both ne0 and

traditional areas of surface sciencetraditional areas of surface science!!

!!


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such industrial fields related to surfacesuch industrial fields related to surface

o+idation 3adhesion3 corrosion ando+idation 3adhesion3 corrosion and

catalytic processes and in adancedcatalytic processes and in adanced

materials 3biolo*y and sensor researchmaterials 3biolo*y and sensor research!!

Finally 3 S-RS became a *ood tool in allFinally 3 S-RS became a *ood tool in all

adanced techniquesadanced techniques!!

Physicists study to increase surfacePhysicists study to increase surface

enhancement usin* nano 0iresenhancement usin* nano 0ires

technolo*ytechnolo*y!!


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REFERENCESREFERENCES:: 55.() course J!@%I handout 3,atrin ,neipp1#$$2.() course J!@%I handout 3,atrin ,neipp1#$$2

55(ntroductory Raman Spectroscopy3R!KFerraro3academic(ntroductory Raman Spectroscopy3R!KFerraro3academic

prees SA1"@@E2prees SA1"@@E2!!

55(ntroduction to modern optics3 Wrant R!Fo0les3#(ntroduction to modern optics3 Wrant R!Fo0les3#ndndeditionedition33

e0 8ork"@%Ie0 8ork"@%I

55)he ne0 interfacial ubiquity of surface enhanced Raman)he ne0 interfacial ubiquity of surface enhanced Raman spectroscopy3 . 3X!8eaer 1#$$$2spectroscopy3 . 3X!8eaer 1#$$$2

55Surface enhanced Raman spectroscopySurface enhanced Raman spectroscopy

3 3W3/!8eaer3,3orrod3X!/hem!%I3I3J#"1"@@'2W3/!8eaer3,3orrod3X!/hem!%I3I3J#"1"@@'2

55-lectroma*netic .echanism of surface enhanced-lectroma*netic .echanism of surface enhancedSpectroscopy 3W3/3Schatz3%I@5%%E 1#$$#2Spectroscopy 3W3/3Schatz3%I@5%%E 1#$$#2

55.!.oskoits 3D!P!Dilella3in surface enhanced Raman.!.oskoits 3D!P!Dilella3in surface enhanced Raman

Scatterin*3 R!,!/han* ne0 0ork3 #E65#%61"@'#2Scatterin*3 R!,!/han* ne0 0ork3 #E65#%61"@'#2


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Seminar Sakher