SPEKTROSKOPI ANALITIK(UV, UV-VIS, IR, NMR) dan PADATAN MICROSKOPI

Oleh : Mushlihah (1406 201 703)Nur Komariyah (1406 201 705)Amin Makmun (1406 201 710)Edi Sutanto (1406 201 726)

PENDAHULUAN

� Spektrofotometer adalah alat untuk mengukur transmitans atau absorban suatu cuplikan sebagai fungsi dari panjang gelombang, digunakan untuk pengukuran serapan pada sinar UV/VIS

� Dalam spektrum elektronik yang penting adalah intensitas absorpsi atau emisi

� Intensitas absorpsi pada panjang gelombang tertentu dapat � Intensitas absorpsi pada panjang gelombang tertentu dapat ditentukan dengan melewatkan berkas cahaya monokromatis lewat cuplikan dengan tebal dan konsentrasi tertentu

� Transmitansi dapat ditentukan pada bermacam-macam panjang gelombang sehingga didapatkan suatu spektrum absorpsi

� Lambert mengembangkan teori yang menghubungkan berkas cahaya yang keluar dengan ketebalan medium homogen, Beer mengembangkan rumus untuk pengaruh konsentrasi

� Pada penyerapan sinar UV/VIS mengikuti hukum Lambert BeerA = ε b c

SPEKTROFOTOMETER

� Peralatan spektrofotometer dibedakan menjadi empat :� Spektrofotometer single Beam� Spektrofotometer Double BeamSpektrofotometer Double Beam� Spektrofotometer Multichannel� Spektrofotometer flourometer

SPEKTROFOTOMETER

SPEKTROFOTOMETER

SPEKTROFOTOMETER

SPEKTROFOTOMETER

SPEKTROFOTOMETER

SPEKTROFOTOMETER

SPEKTROFOTOMETER

SPEKTROFOTOMETER

Komponen-komponen penting dalam alat spektrofotometer

� Sumber sinar, menggunakan lampu awa muatan hidrogen atau deuterium

Komponen-komponen penting dalam alat spektrofotometer

� Pemilih panjang gelombang, , menggunakan monokromator

Komponen-komponen penting dalam alat spektrofotometer

� Sel/kuvet� Detektor

� recorder

ABSORBSI MOLEKULAR

Spesi absorbing

UV/Vis

- Terkait dengan transisi elektron- Karena besarnya jumlah bentuk vibrasi dan transisi maka spekra

muncul sebagai pita- Dasar teorinya adalah teori orbital Molekul- Orbital yang terlibat adalah orbital σ, σ*, π, π* dan n

Abrsobsi UV/Vis oleh senyawa organik terjadi bila energiterabsorbsi yang menyebabkan lompatan elektron dari orbitaldasar (populated orbital) ke orbital yang lebih tinggi (unpopulatedorbital)

Tidak teramati pada UV/Vis normal

Maxima absorbsi pada < 150 nmMaxima absorbsi pada < 150 nm

Energi terlalu besar

Tipe absorbsi ini terkait denganpemecahan ikatan C – C, C – H, C – O,C – X, …

Senyawa harus mempunyai atomdengan pasangan elektron bebas

Senyawa mengandung O, S, N danhalogen bisa mengabsorb melaluitransisi tipe ini

Absorbsi pada area 150 – 250 nm dansangat tidak intensif

Untuk orbital π* harus ada ketidakjenuhandengan beberapa ikatan rangkap yangterkonjugasiterkonjugasi

Merupakan absorbsi yang cukup intensif padaarea 200 – 700 nm)

Tingkat ketidakjenuhan meningkat akanmengakibatkan pergeseran ke λ yang lebihtinggi

- Solvent yang dipergunakan dapat mempengaruhi hasilspektrum dan bisa mengakibatkan pita melebar

- Solvent Polar menstabilkan transisi tingkat dasar π* ← n danmenyebabkan pergeseran biru, untuk transisi π* ← π tingkattereksitasi yang distabilkan dan terjadi pergeseran merah

Tidak ada solventdan interaksi antarmolekul minimal

Absorbsi oleh anorganikSama seperti organik- khususnya nitratDapat juga terlihat beberapa absorbansiuntuk spesi dengan orbital d yang terisisebagiansebagian

Banyak absorbsi dramatik yang teramatiuntuk kompleks logam transisi. Merupakanakibat interaksi ligan dengan orbital d darilogam

Absorbsi oleh anorganikLogam transisi pada umumnyamengandung orbital d yang terisi sebagian

Untuk ion bebas, orbital2 d pada tingkatUntuk ion bebas, orbital2 d pada tingkatenergi yang sama. Namun orbitalnya tidakidentik

Interaksi antar ligan akan menyebabkanpada beberapa orbital

Tipe dan tingkat splitting tergantung padaligan dan geometri kompleks yangterbentuk

Splitting dari orbital d mengakibatkantransisi d sampai >d yang berada padaarea UV/Vis

Charge transfer complexesKompleks terdiri dari spesi donor elektrondan spesi akseptor elektron

Menghasilkan kompleks yang membentukstruktur “resonansi-like” yang bisastruktur “resonansi-like” yang bisamengabsorbsi

Spesi ini cenderung memperlihatkanabsorbtifitas sangat besar (εmax > 10.000)sehingga banyak metoda analitik yangberdasarkan pada pembentukan komplektipe ini

Analisa kulitatif UV/VisSangat tidak berguna

Spektra cenderung merupakan pita lebarSpektra cenderung merupakan pita lebardengan struktur yang kecil

Spektra dengan gugus yang mempunyai dayaabsorbsi sama denderung sama

Analisa kuantitatif UV/Vis- Penggunaan umum untuk area spektra ini- Aplikasi luas

- Metodanya ribuan- Tipe yang umum untuk pengujian- Tipe yang umum untuk pengujian

- Sensitifitas tinggi- batasan deteksi 10-4 – 10-6 M

- Selektif- Akurasi baik : range 1 – 5 %- Relatif mudah dan tidak mahal

Langkah-langkah utama dalam analisa dengan sinar UV/Vis

� Pembentukan molekul yang dapat menyerap sinar UV/Vis� Harus dilakukan jika senyawa yang dianalisa tidak melakukan

penyerapan didaerah UV� Senyawa harus diubah menjadi bentuk lain yang dapat melakukan

penyerapan pada daerah yang dimaksud� Pemilihan panjang gelombang

� Bila tidak ada zat lain yang mengganggu, maka panjang gelombang yang digunakan biasanya adalah panjang gelombang Bila tidak ada zat lain yang mengganggu, maka panjang gelombang yang digunakan biasanya adalah panjang gelombang yang sesuai dengan absorbans maksimum

� Pembuatan kurva kalibrasi� Untuk keperluan ini dibuat sejumlah larutan standart dengan

berbagai konsentrasi yang diketahui� Absorbans larutan standart ini diukur kemudian dibuat grafik A

terhadap C� Hukum Lambert Beer terpenuhi , jika grafik berbentuk garis lurus

yang melalui titik nol� Pengukuran absorbans cuplikan

� Pembentukan warna pada cuplikan harus dilakukan pada kondisi yang sama seperti pada pembentukan warna standart

Pendahuluan

� Sinar IR ditemukan pertamakali oleh Sir William Herschel, tahun 1800

� Daerah IR���� λ : 0,75-300 µm

� Daerah serapan yang umum digunakan: 4000-667cm-1 (2,5-15µm)

� Spektrum IR seny organik/anorganik���� mempunyai sifat yang khas

� Spektrum IR suatu molekul����hasil transisi antara tingkat energi getaran (vibrasi) yg berlainan

� Inti-inti atom yang terikat ikatan kovalen mengalami vibrasi

� Bila molekul menyerap radiasi IR���� kenaikan dlm amplitudo getaran atom-atom yg terikat

MOLEKUL Vibrasi tereksitasi

Lanjutan Pendahuluan…

� Vibrasi dari ikatan, perbedaan pada:- Panjang gelombang�identifikasi gugus fungsi- Banyaknya energi yang diserap krn perub momen dipol (µ≠0)Misal : ikatan non polar (C-H atau C-C) : absorpsi lemah

ikatan polar (O-H, N-H dan C=O) : absorpsi kuat- Dapat menyerap energi pada lebih dari satu panjang gelombanggelombangMisal: Ikatan O-H menyerap energi pada frekuensi

� 3330 cm-1 : kenaikan vibrasi stretching�1250 cm-1 : kenaikan vibrasi bending

� Tipe vibrasi yang berlainan � vibrasi fundamental

Penggunaan Secara Umum

� Identifikasi senyawa organik maupun anorganik

� Penentuan gugus fungsi senyawa organik

� Penentuan komposisi molekul pada permukaan

� Penentuan kuantitas senyawa dalam campuran

� Metode � Nondestructive

Aplikasi

� Identifikasi senyawa dengan menjodohkan spektrum dari senyawa yang tidak diketahui dengan spektrum referensi (fingerprint)

� Identifikasi gugus fungsi dalam zat yang belum diketahui

� Identifikasi komponen-komponen reaksi dan untuk mempelajari kinetika � Identifikasi komponen-komponen reaksi dan untuk mempelajari kinetika reaksi

� Mendeteksi molecular impurities dalam jumlah 0,01- 0,1%

Samples

� State: solid, liquid or gas � sampling accessories.

� Amount: Solids 50 to 200 mg is desirable, but 10 µg ground with transparent matrix (such as KBr); 1 µg in suitable solvent. Liquids 0.5 µL neat, less if pure. Gases 50 ppb.

� KBr, suitable solvent (CCl and CS ). � KBr, suitable solvent (CCl4 and CS2).

� Many types of sample holders and cells are available.

� Water should be removed from sample if possible.

For For Non transparent sampleNon transparent sample

Range Frekuensi IR

� 13.000 sampai 10 cm–1, atau panjang gelombang dari 0,78 sampai 1000 µm.

� IR dekat , IR sedang, IR jauh� IR dekat , IR sedang, IR jauh

Teori

� Pada suhu absolut diatas nol, semua atom dalam molekul secara kontinyu mengalami vibrasi. Frekuensi dari spesifik vibrasi sama dengan frekuensi radiasi IR pada molekul �molekul menyerap radiasi

� Tipe utama dari vibrasi molekul adalah stretching dan bending

� Perubahan dalam panjang ikatan �stretching

� Perubahan dalam sudut ikatan �bending

� Spektrum infrared (IR) umumnya diperoleh dengan melewatkan radiasi infrared melalui sample dan menentukan apakah fraksi dari radiasi terabsorb pada partikel

Lanj teori….

� Energi pada puncak dalam spektrum absorbsi muncul sesuai dengan frekwensi vibrasi dari molekul sample

� Wavenumber (bilangan gelombang) �cm-1

� Peningkatan energi�peningkatan wavenumber� Peningkatan energi�peningkatan wavenumber

Hukum Hooke’s

� Suatu molekul dapat dianggap sebagai sistem massa yang tergabung oleh ikatan �bersifat spring like

� Kekuatan ikatan lebih besar �wavenumber lebih besar

m1 m2

Dua atom dihubungkan oleh ikatan kovalen ditunjukkan seperti 2 beban pada ujung-ujung pegas. Ketika beban dipindah dari posisi diamnya dan dilepaskan,vibrasinya hanya pada frekwensi tertentu yang tergantung pada massa beban dan konstanta berhubungan dengan kekakuan pegas.

Lanj Hukum Hooke‘s….

� Penetapan Frekuensi regang �hukum Hooke‘s

Dimana : ( )2/1

/2

1

+=

yxyx MMMM

f

cπν

v = frekuensi vibrasi (cm-1)c = kecepatan cahaya (cm/s)f = konstanta kekuatan ikatan (dyne/cm)

Faktor-faktor yang mempengaruhi frekuensi penyerapan

� Massa dari atom-atom yang berikatan.Massa meningkat �bilangan gelombang menurunC-H : 3000 cm-1 C-Cl : 750 cm-1

C-C : 1200 cm-1 C-Br : 600 cm-1

C-O : 1100 cm-1 C-I : 500 cm-1

� Kekuatan ikatan kimiaMakin kuat ikatan �bil.gelombang meningkatMakin kuat ikatan �bil.gelombang meningkatCΞC : 2150 cm-1 C=C : 1650 cm-1 C-C : 1200 cm-1

� HibridisasiIkatan makin kuat dalam susunan SP>SP2>SP3

C-H (SP): 3300 cm-1 C-H (SP2): 3100 cm-1 C-H (SP3): 2900 cm-1

� Resonansikonjugasi mengurangi energi untuk vibrasi ikatanketon terisolasi : 1715 cm-1 α,β keton tak jenuh : 1690 cm-1

α,β,γ keton tak jenuh : 1675 cm-1

Terjadinya Penyerapan Sinar IR

� Bila molekul menyerap sinar IR dari daerah 0,75-25 µm �terjadi perubahan tingkat energi vibrasi & energi rotasi

� Syarat molekul dpt menyerap energi sinar IR�vibrasi&rotasi molekul harus disertai perubahan momen dipol

� Perubahan momen dipol besar� pita serapan lebih kuat

� Adanya perbedaan elektronegativitas antara karbon & oksigen�gugus karbonil memberi serapan yang kuat

Vibrasi Fundamental

� Vibrasi ulur (stretching) �terjadi perubahan kontinyu dari jarak antara dua atom dalam suatu molekul

� Ada 2 macam stretching : simetris & tak simetris

� Vibrasi tekuk (bending) �terjadi perubahan sudut antara dua ikatan kimia

� Ada 4 macam bending,yaitu:

Scissoring - Bending di dalam bidang

Rocking

Wagging- Bending di luar bidang

Twisting

Peralatan

� Spektrometer IR umumnya �double-beam (berkas ganda)Terdiri dari: sumber radiasi, daerah cuplikan fotometer, kisi difraksi (monokromator), dan detektor

� Sumber radiasi � pemijar Nerst (batang Sirkonium&Ytrium oksida) atau Globar (batang Silikon karbida)

Monokromator terdiri dari : � Monokromator terdiri dari : celah masuk & keluar, alat pendispersi yang berupa kisi difraksi atau prisma dan cermin untuk memantulkan & memfokuskan sinar

� Detektor � menggunakan detektor panas

Characterization of Heterogeneous Catalysts

by Diffuse Reflectance Spectroscopy.

Titanium silicalite (TSTitanium silicalite (TS--1)1)

TS1TS1--11

TS1TS1--22

TS1TS1--33

TS1TS1--44

TSILTSIL

Ti - O - Si

TS1TS1--33

TSILTSIL970

970

1400 1200 1000 800 600 400 Wavenumber, cm-1

TSILTSIL

SILSIL

TIOTIO

TSILTSIL

SILSIL

TIOTIO

1230

1105

800550

452

Sample TO4 Stretching, Si–O–Ti T-O Bending

Asymmetric Symmetric Asymmetric

TS-1 (1%) 1229 1105 799 978 548 453

TS-1 (2%) 1230 1105 804 971 549 452

TS-1 (3%) 1231 1102 803 971 548 452

TS-1 (4%) 1228 1107 799 968 549 544

SIL 1231 1106 799 - 551 452

Ti/SIL 1231 1109 799 - 551 452

ZSM-5 1227 1104 798 547 453

Titanium MCMTitanium MCM--41 (Ti41 (Ti--MCMMCM--41)41)

TM4

TM3

TM2

1400 1200 1000 800 600 400 Wavenumber, cm-1

TM2

SM

Ti - O - SiH - O - Si

Bifunctional catalyst (Nb/TS1)Bifunctional catalyst (Nb/TS1)

TS1TS1

NTS1 NTS1

1400 1200 1000 800 600 400 Wavenumber, cm-1

Nb=O

Nb-O-Nb

NBA NBA

NBO NBO

Tube Furnace

CellCaF2 window

Vacuum Pump(Rotary and Diffusion)

Sample holder

Experimental setup for hydroxyl groups and acidity analysis

H-ZSM-5

SIL

3743

3609

3660

3742

3733

3726

352835

TS-1 (1%)

TS-1 (2%)

TS-1 (3%)

TS-1 (4%)

3800 3600 3400 3200 Wavenumber, cm-1

3730

526

3526

Infrared spectra of the silicalite, ZSM-5 and TS-1 samples in the hydroxyl groups region, after evacuation at 400oC in vacuum.

3526

3736

Absorbance, a.u.

TS-1

4000 3800 3600 3400 3200 3000Wavenumber, cm-1

Absorbance, a.u.

SO42-/TS-1

SO42--Ti/TS-1

Figure 4.5: FTIR spectra of the TS-1, SO42-/TS-1 and SO4

2-Ti/TS-1 samples after heated at 400oC for 4 h in vacuum.

HZSM-5

SIL

TS-1 (1%)

TS-1 (2%)

Sample Brønsted, µµµµmol/g Lewis, µµµµmol/g

TS-1 (1%) - 30

TS-1 (2%) - 52

TS-1 (3%) - 83

TS-1 (3%)

TS-1 (4%)

1700 1600 1500 1400Wavenumber, cm-1

Infrared spectra of the silicalite, ZSM-5 and TS-1 samples after evacuation at 400oC under vacuum followed by pyridine adsorption at room temperature and desorption at 150oC for one hour.

TS-1 (3%) - 83

TS-1 (4%) - 48

SIL - 11

HZSM-5 162 78

0.3

0.4

0.5

0.6

0.7

0.8

ABS

3000.03100.03200.03300.03400.03500.03600.03700.03800.03900.04000.01/cmTestscan Shimadzu FTIR 8000 series

3608.6

3659.73742.6

-0.2

0.0

0.2

0.4

0.6

0.8

ABS

1400.01425.01450.01475.01500.01525.01550.01575.01600.01625.01650.01675.01700.01/cm

0.35

0.4

0.45

0.5

0.55

0.6

ABS

3000.03100.03200.03300.03400.03500.03600.03700.03800.03900.04000.01/cmTestscan Shimadzu FTIR 8000 series

3609.5

3664.5

3744.5

0.25

0.5

0.75

1.0

1.25

1.5

ABS

1300.01400.01500.01600.01700.01800.01900.02000.01/cmTestscan Shimadzu FTIR 8000 series

1452.3

1489.9

1545.8

1624.01635.5

1869.9

sample 1870 1545 1444 gr sampleper 10

mg k B k L Luas

tzo 13.4928 2.88398 1.75824 13 0.00592 3.03 3.8 0.7857

tzht 11.50901 3.08807 1.39229 13 0.00592 3.03 3.8 0.7857

tzcu 8.429 1.169 7.7813 13 0.00592 3.03 3.8 0.7857

tbo 5.404 2.0926 2.904 13 0.00592 3.03 3.8 0.7857

tbcu 7.18748 0.0563 10.76245 13 0.00592 3.03 3.8 0.7857

t-zsm5 8.10955 2.2025 1.2672 13 0.00592 3.03 3.8 0.7857

tbea 6.09805 2.48797 2.2744 13 0.00592 3.03 3.8 0.7857

tzcuht 8.5891 1.4065 7.1721 13 0.00592 3.03 3.8 0.7857

sample 1870 1545 1444 1870 1545 1444sample 1870 1545 1444 1870 1545 1444

tzo 13.4928 2.88398 1.75824 13.4928 2.88398

tzht 11.50901 3.08807 1.39229 13.4928 3.620356

tzcu 8.429 1.169 7.7813 13.4928 1.871288

tbo 5.404 2.0926 2.904 13.4928 5.22484

tbcu 7.18748 0.0563 10.76245 13.4928 0.10569

t-zsm5 8.10955 2.2025 1.2672 13.4928 3.664555

tbea 6.09805 2.48797 2.2744 13.4928 5.504986

tzcuht 8.5891 1.4065 7.1721 13.4928 2.209501

13 1

1074 996

1390

SZ500

SZ600

Absorbance / a.u.

400oC 1446

1390

1357

Absorbance / a.u.

1373

1358

1315

1400 1300 1200 1100 1000 900Wavenumber, cm-1

SZ7001276

Absorbance / a.u. 300oC

150oC

1700 1600 1500 1400 1300 1200Wavenumber, cm-1

1541

1308

Absorbance / a.u.

NMR NMR

nmr

� Liquid - state� Solid - state

Solid-State NMR

Impact of Structural Order on NMR Spectrum• Factors that average to zero in solution due to

random motion are now factors in solid state NMR• dipole-dipole interaction• mutual spin flips occurring between pairs of spins

� Each nucleus is “fixed” in the crystal lattice� Each nucleus produces a rotating magnetic field

as it precesses in the applied magnetic field �lifetime of spin state is reduced

� Each spin has a static field component that influences frequency of neighbors-- Spin directions vary randomlySpin directions vary randomly-- Range of frequencies that add to lineRange of frequencies that add to line--widthwidth

� Chemical shift anisotropy-- Chemical shift varies with orientation relative to BChemical shift varies with orientation relative to B00-- Contributes to line broadeningContributes to line broadening

Static & dynamic disorder

Diffraction-based methods are most suited to “rigid solids”

Because NMR probes local environment, it is local environment, it is applicable to any system

But “inversion” to structural information may be non-trivial

Solid-State NMR

BBoo

Solid-state(ordered structure)

Solution-state(random-orientation)

Solid-State NMR

Broad Structureless Resonances• Requires Different Approaches Compared to Solution

State NMR• Contains Unique Information Relative to Solution

State NMRPeak width is caused by dipole-dipole interaction � Peak width is caused by dipole-dipole interaction which is distance related -- Solid state NMR spectrum can be used to obtain Solid state NMR spectrum can be used to obtain

internuclear distancesinternuclear distances� Peak width can monitor motion within the crystal

lattice-- Slowly increase temperatureSlowly increase temperature-- LineLine--width transactions indicates introduction of width transactions indicates introduction of

motion motion

13C NMR of glycine

H2N

O

OH

glycine

solution-state solid-state

Angew. Chem. Int. Ed. 2002, 41, 3096-3129

Solid-State NMRPowder vs. Crystal

• Crystal – regular uniform and repeat lattice structure

• Powder – consists of very many crystals all with different orientations

Powder Pattern• Dipolar coupling

� Interaction of nuclear magnetic moments of two different nuclear spins (I & S)

� The local magnetic field at spin S will be affected by spin I-- Changes resonance frequency of spin SChanges resonance frequency of spin S

� The degree by which spin I affects the magnetic field at spin S is determined by the dipolar coupling constant (d):

�� where where θθθθθθθθ is the angle betweenis the angle between BoBo and the internuclear and the internuclear distance (r)distance (r)

Solid-State NMR

( ) zzIS SIdH 1cos3 2 −−= θ

distance (r)distance (r)� The dipolar constant is dependant on the distance

between the nuclear spins and their gyromagnetic ratios

• Through space interaction � structural information• In solution, random motion averages dipolar coupling to

zero• In solids, orientations are static � defined by crystal

lattice

z

y

x

11HH

1313CC

θθθθBB00

r34 IS

SIo

rd

γγπ

µ h

=

Angew. Chem. Int. Ed. 2002, 41, 3096-3129

34 IS

SIo

rd

γγπ

µ h

=

Solid-State NMR

Powder Pattern• Dipolar coupling

� Contains structural information ( r, θ)

Dipolar coupling provides distance informationDipolar coupling provides distance information

IS

( ) zzIS SIdH 1cos3 2 −−= θ

Orientation relative to BOrientation relative to B 00

Angew. Chem. Int. Ed. 2002, 41, 3096-3129

Solid-State NMRPowder Pattern

• Chemical Shift Anisotropy� Chemical shift is dependent on orientation of nuclei in the solid

-- Distribution of chemical shiftsDistribution of chemical shifts-- Averaged to zero for isotropic tumblingAveraged to zero for isotropic tumbling-- Leads to extensive lineLeads to extensive line--width broadening in solidwidth broadening in solid--state NMR state NMR

Progress in Nuclear Magnetic Resonance Spectroscopy 6 46 (2005) 1Progress in Nuclear Magnetic Resonance Spectroscopy 6 46 (2005) 1––2121

Solid-State NMR

Temperature Dependence• Crystal Lattice Mobility Changes with Temperature

� Changes in bond rotations� Large changes in line-shape depending on mobility in lattice

Rotation about CRotation about C--N bondN bond

Rotation of NMeRotation of NMe 33

Whole molecule rotates Whole molecule rotates and diffuse within crystaland diffuse within crystal

Solid-State NMR

Magic Angle Spinning (MAS)• Nucleus with magnetic moment (µ) will create a field at a second nucleus at a

distance r away� Magnetic field will have a z component (Bz) in direction of Bo direction

-- Influences the frequency of the second nucleusInfluences the frequency of the second nucleus-- Couples the two spinsCouples the two spins

� Magnitude of Bz will depend on the angle of the magnetic moment relative to B0

( )1cos3 23

−= θµr

KBZ ( )

3rZ

z

y

x

11HH

1313CC

θθθθBB00

r

Solid-State NMR

Magic Angle Spinning (MAS)• Zero z component (Bz) if the angle (θ) relative to B0 is 54.44o

� All dipolar interactions disappear at this angle� All chemical shift anisotropy disappear at this angle� Quadrupole broadening is also reduced

BB zz = 0= 0

� Simulate a uniform distribution of magnetic moments in a powder by spinning the sample very fast at 54.44o

Solid-State NMR

Magic Angle Spinning (MAS)• Spin Samples at 54.44o to reduce line-width

� Spinning speed must be greater than static line-width to be studied (powder pattern width)-- Normal speed limit is 35 kHzNormal speed limit is 35 kHz

Sample holderSample holder rotorrotor

rotor at MASrotor at MAS

Sample holder at MASSample holder at MAS MAS probeMAS probe

Solid-State NMR

Magic Angle Spinning (MAS)• Impact of Spinning Speeds at MAS

Incr

easi

ng S

pinn

ing

Spe

ed13C NMR of glycine powder

Similar to Solution SpectrumH2N

O

OH

glycine

Angew. Chem. Int. Ed. 2002, 41, 3096-3129

Incr

easi

ng S

pinn

ing

Spe

ed

Powder Pattern

Lines are separated by spinning speed

Number of lines are reduced with increase in spinning speed as it approaches static line-width

Solid-State NMR

MAS reduces linewidth MAS reduces linewidth from 5000 Hz to 200 Hzfrom 5000 Hz to 200 Hz

Spin ½ Nuclei with Low Magnetogyric ratios (13C, 15N, 29Si, 31P, 113Cd)• Combine MAS with high power 1H decoupling

� Double resonance technique� High power is required because of very large 1H line-widths

-- Long TLong T 1 1 requires slow pulse rates to avoid saturation of si gnalrequires slow pulse rates to avoid saturation of si gnal-- Low sensitivity of nuclei requires long acquisition times Low sensitivity of nuclei requires long acquisition times

High power decoupling High power decoupling reduces linewidth from reduces linewidth from 5000 Hz to 450 Hz5000 Hz to 450 Hz

Increase in sensitivity Increase in sensitivity (NOE, spin(NOE, spin--splitting)splitting)

MAS & high power decoupling MAS & high power decoupling reduces linewidth from 5000 reduces linewidth from 5000 Hz to 2 HzHz to 2 Hz

Similar to liquid state sampleSimilar to liquid state sample

Si

SiO2

◇◇◇◇ External reference:

Tetramethysilane (TMS)

◇◇◇◇ Spinning rate: 7kHz

NMR spectraNMR spectraNMR spectraNMR spectra

0 -20 -40 -60 -80 -100 -120 -140 -160 -180 -200

Chemical Shift (ppm)

SiO

◇◇◇◇ Pulse length: 5 µs

◇◇◇◇ Delay time: 10 s

29Si MAS NMR spectra for Si, SiO 2 and SiO powders.

NMR spectraNMR spectraNMR spectraNMR spectra

0.14 V on charge

pristine

0.21 V on charge

50 0 -50 -100 -150 -200

2.0 V on discharge

0.0 V on charge

Chemical Shift (ppm)

29Si MAS NMR spectra for the SiO electrodes

Contributions from the siliconnuclei show Gaussian peaksat approximately -109 ppm(Q4), -101 ppm (Q3), -92 ppm(Q2), -84 ppm (Q1). Therelative contributions of thesestructural sites werecalculated from deconvoluted,integrated areas. The NMRintegrated areas. The NMRdata show that with the K/Momolar ratio the nature of thesilica surface changes. Thechange in the silica surfacearises from the increasinginteraction of MoOx with thesurface hydroxyl groups.

Solid-State NMR

Cross-polarization combined with MAS (CP-MAS)• Exchange polarization from 1H to 13C

� Similar in concept to INEPT experiment

2 ms 50 ms

•• 11H 90H 90oo pulse generates xy magnetization (Bpulse generates xy magnetization (B 1H1H))•• SpinSpin--lock pulse keeps magnetization in xy planelock pulse keeps magnetization in xy plane

precessing atprecessing at ::γγγγγγγγHHBB1H1H/2/2ππππππππ Hz Hz

•• 1313C pulse generates xy magnetization that precesses C pulse generates xy magnetization that precesses at:at:

γγγγγγγγCCBB1C1C/2/2ππππππππ HzHz2 ms 50 ms γγγγγγγγCCBB1C1C/2/2ππππππππ HzHz•• Polarization transfer occurs if:Polarization transfer occurs if:

γγγγγγγγHHBB1H1H//2π2π2π2π2π2π2π2π HzHz = γγγγγγγγCCBB1C1C/2/2ππππππππ HzHzHartmann Hahn matching conditionHartmann Hahn matching condition

∆∆∆∆E = γγγγ h Bo / 2ππππ

1111ΗαΗαΗαΗα

1111ΗβΗβΗβΗβ

13131313Cαααα

13131313Cββββ

γγγγγγγγHHBB1H1H//22ππππππππ γγγγγγγγCCBB1C1C//22ππππππππ

Polarization transferPolarization transfer

-101

.4

-109

.4

29Si CP MAS NMR (solid state) spectrum of

material X3-SH

δ ppm

I I II0 -50 -100 -150

Solid-State NMR

Cross-polarization combined with MAS (CP-MAS)• Simultaneously pulse 1H to 13C

� Use RF energy to equilibrate energy states

The increase in the 13C signal depends on the strength of the dipolar

γγγγγγγγHHBB1H1H//2π2π2π2π2π2π2π2π HzHz = γγγγγγγγCCBB1C1C/2/2ππππππππ HzHz

� The increase in the 13C signal depends on the strength of the dipolar interaction and the duration of the mixing or contact time

� Maximum enhancement is γH/γC

Solid-State NMR

Cross-polarization combined with MAS (CP-MAS)• Example of CP-MAS 13C spectrum

� Cross-polarization increases the 13C population difference by the factor γH/γC� Increases signal sensitivity

Solid-State NMR

Spin ½ Nuclei with High Magnetogyric ratios (1H, 19F)• Homonuclear interactions are very strong

� Difficult to remove by MAS� Highest field strength and spinning rates can reduce a 10 kHz line-width to

1500 Hz• Static line-widths are very large and chemical shifts are small

� Obtaining resolution is challenging • Simulate MAS spinning by a series of RF pulses (MREV-8)

� Shift magnetization quickly between the three orhogonal axes� Hop around magic angle and reduce dipole-dipole interaction� Does not affect CSA or heteronuclear interactions

• MAS can be used to remove CSA• CRAMPS – combines MAS with MREV-8

Solid-State NMR

CRAMPSCRAMPS

1H NMR of aspartic acid powder

Spin ½ Nuclei with High Magnetogyric ratios (1H, 19F)• Example of CRAMPS

� Resolution on the order of 180 Hz is possible

NH2 O

OH

O

HO

aspartic acid

Static Spectrum with Static Spectrum with Broad LineBroad Line--widthswidths

MAS with increasing MAS with increasing spinning ratesspinning rates

aspartic acid

Surface morphology

(Microscopy)

Scanning Electron MicroscopeSEM

is an incredible tool for seeing the unseen worlds of microspace.

Conventional light microscopes use a series of glass lenses to bend light waves and create a magnified image.

The Scanning Electron Microscope creates the

magnified images by using electrons instead of light waves.

The SEM shows very detailed 3-dimensional images at much higher magnifications than is possible with a light microscope. The images created

without light waves are rendered black and white.

Samples have to be prepared carefully to withstand the vacuum inside the microscope.

Biological specimens are dried in a special way that prevents them from shriveling. Because the SEM illuminates them with

electrons, they also have to be made to conduct electricity .

How do you make a mosquito conductive ? Our SEM samples are coated with a very thin layer of gold by a machine called a sputter coater.

Now the prepared specimen is ready.

The sample is placed inside the microscope's vacuum column through an air-tight door.

After the air is pumped out of the column, an electron gun [at the top] emits a beam of high energy electrons. This beam travels downward through a series of

magnetic lenses designed to focus the electrons to a very fine spot.

Near the bottom, a set of scanning coils moves the focused beam back and forth across the specimen, row by row.

As the electron beam hits each spot on the sample, secondary electrons are knocked loose from its surface. A detector counts these electrons and sends

the signals to an amplifier.

The final image is built up from the number of electrons emitted from each spot on the sample.

The Scanning Electron Microscope is revealing new levels of detail and complexity in the amazing world of micro-organisms and

miniature structures.

Here is a small picture of the whole system

Field EmissionScanning Electron Microscopy (FESEM)

Principle of OperationA field-emission cathode in the electron gun of a s canning electron microscope provides narrower probing beams at low as well as h igh electron energy, resulting in both improved spatial resolution and minimized sample ch arging and damage .

For applications which demand the highest magnifica tion possible

Applications include•Semiconductor device cross section analyses for gat e widths, gate oxides, film

thicknesses, and construction details•Advanced coating thickness and structure uniformity determination•Small contamination feature geometry and elemental composition measurement

Why Field Emission SEM?FESEM produces clearer, less electrostatically dist orted images with spatial resolution down to 1 1/2 nm. That's 3 to 6 times better than conventional SEM.Smaller-area contamination spots can be examined at electron accelerating voltages compatible with Energy Disper sive X-ray Spectroscopy.Reduced penetration of low kinetic energy electrons probes closer to the immediate material surface.High quality, low voltage images are obtained with negligible electrical charging of samples. (Accelerating volta ges range from 0.5 to 30 kV.)from 0.5 to 30 kV.)Need for placing conducting coatings on insulating materials is virtually eliminated.

Cross-section of a laser window showing multiple th in layers at 50,000x. (in the original photo)

Energy Dispersive X-Ray Spectroscopy (EDS)

EDS identifies the elemental composition of materia ls imaged in a Scanning Electron Microscope (SEM) for all elements with an atomic number greater than boron. Most elements are an atomic number greater than boron. Most elements are detected at concentrations of order 0.1%.

Applications include

•Materials evaluation and identification•Contaminants •Elemental diffusion profiles •Glassivation phosphorus content •Multiple spot analysis of areas from 1 micron to 10 cm in diameter

•Failure analysis•Failure analysis•Contamination identification •Unknowns identification •Stringer location and identification

•Quality control screening•Material verification •Plating specification and certification

Principle of OperationAs the electron beam of the SEM is scanned across the sample surface, it generates X-ray fluorescence from the atoms in its path. The energy of each X-ray photon is characteristic of the element which produced it. The EDS microanalysis system collects the X-rays, sorts and plots them by energy, and automatically identifies and labels the elements responsible for the peaks in this energy labels the elements responsible for the peaks in this energy distribution. The EDS data are typically compared with either known or computer-generated standards to produce a full quantitative analysis showing the sample composition. Data output is either this element analysis, the original spectrum showing the number of X-rays collected at each energy, or maps of distributions of elements over areas of interest.

Wavelength Dispersive X-Ray Spectrometry (WDS)

WDS identifies the elemental composition of materia ls imaged in the SEM with an order of magnitude better spectral resolution, sensitivity and ability to det ermine concentratins of light elements than is achievable with EDS. Most elements are detected below 0.1% and some as low as a few ppm.

Applications include

•Identification of spectrally overlapped elements, such as•S in the presence of Pb or Mo •W or Ta in Si, or N in Ti •Br in Al, common in semiconductor device failure

•Detection of low concentration species (down to 100 or even 10 ppm)•P or S in metals •Contaminants in precious metal catalysts •Trace heavy metal contamination •Trace heavy metal contamination •Performance-degrading impurities in high temperature solder alloys

•Analysis of low atomic number elements•Composition of advanced ceramics and composites •B in BPSG films (sensitivity to 2000 ppm) •Oxidation and corrosion of metals •Characterization of biomedical and organically modified materials

Principle of OperationThe characteristic X-ray photons excited by the electron beam are sorted using a diffracting crystal, whose angular placement relative to the sample and photodetector is a unique measure of their wavelengths. As with EDS, the resulting spectral distribution is automatically compared with those from actual standards or synthetic X-ray fluorescence spectra of material formulations.

WDS vs. EDSX-ray microanalysis in the scanning electron microscope is X-ray microanalysis in the scanning electron microscope is accomplished using EDS and/or WDS. EDS is more commonly applied due to its simplicity and speed, while WDS offers an important and often critical refinement of EDS data by providing Analysis for light elements with at least an order of magnitude higher sensitivity than available (ultrathin X-ray window) EDS instruments Resolution of severely overlapped spectrum peaks for improved element specificity Lowered detection limits over the entire periodic table More accurate quantitative analyses.

Atomic Force Microscope/Scanning Probe Microscopy

Atomic Force Microscopy and Scanning Probe Microsco py (AFM/SPM) provide topographic information down to t he Angstrom level. Additional properties of the sample, such as thermal and electrical conductivity, magnetic and e lectric field strength, and sample compliance can simultaneously be strength, and sample compliance can simultaneously be obtained using a specialty probe. Many applications require little or no sample preparation.

Applications include

Materials Evaluation:Surface roughness on implanted silicon wafers

Thermal properties such as thermal conductivity, glass transition temperature (Tg), and melting temperature of various phases of a blended polymer measured down to the nanometer scale Surface profiles and magnetic field mapping of recording media or reading heads Nanomechanical testing

Failure AnalysisRapid hot-spot analysis of powered electronic devices

Defect analysis of compact disk stampers

Quality ControlSurface profiles of thin film and coatings

Metrology of semiconductor devices and compact disks Surface finish of substrates for thin film deposition

Principle of OperationThe Atomic Force Microcope uses a physical probe raster scanning across the sample using piezoelectric ceramics. A feedback loop is used to maintain a constant interaction between the probe and the sample. The position of the probe and the feedback signal are electronically recorded to produce a three dimensional map of the surface or other information depending on the specialty probe used. Data Output is either a three dimensional image of the surface or a line Data Output is either a three dimensional image of the surface or a line profile with height measurements. The surface roughness parameters of Ra or RMS are also available with either of the above outputs. Other types of feature analysis include Partical Grain Size Analysis, Bearing Ratio, Fractal Dimension, Power Spectrum, and Fast Fourier Transform.

Atomic Force Microscope/Scanning Probe Microscopy

Scanning Auger Microanalysis (SAM)

SAM provides elemental and chemical composition for all elements with an atomic number greater than helium. Its samp ling depth of 2-3 nm allows films as thin as a few monolayers to be a nalyzed. Auger also produces images of the distributions of elemen ts along the surface and produces profiles of composition vs. de pth from 1 to 2000 surface and produces profiles of composition vs. de pth from 1 to 2000 nm.