Faculty of Engineering

Metallurgical Engineering and Materials Science

Graduate Studies

Hana jamhuoer

MME 662

"Reporter about IR and Glasses studies "

Introduction

The light our eyes see is but a small part of a broad spectrum of electromagnetic

radiation. On the immediate high energy side of the visible spectrum lies the

ultraviolet, and on the low energy side is the infrared. The wavelength range

for infrared from 2,500 to 16,000 nm, with a corresponding frequency range

from 1.9*1013 to 1.2*1014 Hz. The infrared portion of the electromagnetic

spectrum is divided into three regions; the near-, mid- and far- infrared, named

for their relation to the visible spectrum. The far-infrared, approximately 400-

10 cm-1 (1000–30 μm), lying adjacent to the microwave region, has low energy

and may be used for rotational spectroscopy. The mid-infrared, approximately

4000-400 cm-1 (30–1.4 μm) may be used to study the fundamental vibrations

and associated rotational-vibrational structure. The higher energy near-IR,

approximately 14000-4000 cm-1 (1.4–0.8 μm) can excite overtone or harmonic

vibrations.

IR radiation supplies sufficient energy to produce translational, rotational, and

vibrational motion in molecules. The measurement of the characteristic IR

energies (photons) that correspond to these transitions results in a spectrum.

Based on its atomic structure, each molecule produces a unique and

characteristic IR spectrum. The specific number and position of absorption

bands for any molecule are governed by its degrees of freedom, its functional

groups, and the IR selection rules. A spectral pattern, sometimes called a

fingerprint, is used to identify an unknown material when the absorptions in

its spectrum are matched with the absorptions in the spectrum of a known

material. Infrared spectroscopy is the measurement of the wavelength and

intensity of the absorption of mid-infrared light by a sample. Mid-infrared is

energetic enough to excite molecular vibrations to higher energy levels. The

wavelength of infrared absorption bands is characteristic of specific types of

chemical bonds, and infrared spectroscopy finds its greatest utility for

identification of organic and organ metallic molecules.

IR Spectroscopy Definition

IR spectroscopy can be defined as a method for the identification of substances

based on their absorption of IR wavelength.

Applications of IR spectroscopy

Identification of all types of organic & many types of inorganic compounds.

Determination of functional groups.

Identification of chromatographic effluents.

Quantitative determination of compounds in mixtures.

Determination of molecular composition & stereochemistry.

Determination of molecular orientation (Polymers & Solutions) .

Theory of Infrared Absorption

For a molecule to absorb IR, the vibrations or rotations within a molecule

must cause a net change in the dipole moment of the molecule. The

alternating electrical field of the radiation (remember that electromagnetic

radiation consists of an oscillating electrical field and an oscillating magnetic

field, perpendicular to each other) interacts with fluctuations in the dipole

moment of the molecule.

If the frequency of the radiation matches the vibrational frequency of the

molecule then radiation will be absorbed, causing a change in the amplitude

of molecular vibration.

Molecular Rotations

Rotational transitions are of little use to the spectroscopist. Rotational levels are

quantized, and absorption of IR by gases yields line spectra.

However, in liquids or solids, these lines broaden into a continuum due to

molecular collisions and other interactions.

Molecular Rotations (cont)

L ≈ I w rot=M a02 wrot

I ≈ M a02

Vibrational-Rotational Transitions

In general, a molecule which is an excited vibrational state will have rotational

energy and can lose energy in a transition which alters both the vibrational and

rotational energy content of the molecule. The total energy content of the

molecule is given by the sum of the vibrational and rotational energies. For a

molecule in a specific vibrational and rotational state, denoted by the pair of

quantum numbers (v, J), we can write its energy as:

E(v, J)=Evib(v) + Erot(J)

Transitions (cont)

The energies of these three transitions form a very distinctive pattern. If we

consider the lower vibrational state to be the initial state, then we can label the

absorption lines as follows. Transitions for which the J quantum number

decreases by 1 are called P-branch transitions, those which increase by 1 are

called R-branch transitions and those which are unchanged are called Q-

branch transitions.

Vibrational Motion

Subdivided into so-called normal modes of vibration which rapidly increase

with the number of atoms in the molecule. Each of these normal vibrational

modes contributes RT to the average molar energy of the substance and is a

primary reason why heat capacities increase with molecular complexity. If there

are Xvib modes of vibration, then the vibrational energy contributes Xvib(RT) to

the average molar energy of the substance.

Stretching and Bending

Stretching Vibrations

Quantum Treatment of Vibrations

Transitions in vibrational energy levels can be brought about by absorption of

radiation, provided the energy of the radiation exactly matches the difference in

energy levels between the vibrational quantum states and provided also that the

vibration causes a fluctuation in dipole. Infrared measurements permit the

evaluation of the force constants for various types of chemical bonds.

Infrared Spectra

An IR spectrum displays detector response as percent transmittance ( % T)

on the y-axis, and IR frequency in terms of wave number (cm-1 ) on the x-axis,

as shown in Figure 2. The detector response indicates the extent of interaction

of the IR electromagnetic radiation with the sample as it is proportional to the

resultant intensity of IR radiation that reaches the detector after passing through

the sample. Tw o types of interactions-absorption and transmission are

important in the typical IR experiment. When the molecule in the sample

compartment of the spectrometer is exposed to a source of continuous IR

radiation, the photons of discrete energy units that are absorbed by the molecule

do not reach the detector. The IR spectrum reveals these missing photons, or

absorptions, as a series of well-defined, characteristic, and reproducible

absorption bands. Photons that are not absorbed by the sample are transmitted to

the detector essentially unaltered. For a given wavelength or frequency of IR

radiation striking a sample, these two interactions are inversely related through

the following equation:

A=log 1/T

Or A = log(I0 / I1)

Where A=absorbance, T=transmittance (% T/100) And I0 and I are the

intensities of radiation beforeand after transmission through the sample.

Figure 1 . I R spectrum of gelatin plotted as percent transmittance (% T)

on the y-axis, and IR frequency in terms o f wave number(CM-1 ) on t h e x-

axis..

Infrared Instruments

An infrared spectrophotometer is an instrument that passes infrared light

through an organic molecule and produces a spectrum that contains a plot of the

amount of light transmitted on the vertical axis against the wavelength of

infrared radiation on the horizontal axis. In infrared spectra the absorption peaks

point downward because the vertical axis is the percentage transmittance of the

radiation through the sample. Absorption of radiation lowers the percentage

transmittance value. Since all bonds in an organic molecule interact with

infrared radiation, IR spectra provide a considerable amount of structural data.

Fourier transform infrared (FTIR) spectroscopy

Is a measurement technique that allows one to record infrared spectra. Infrared

light is guided through an interferometer and then through the sample (or vice

versa). A moving mirror inside the apparatus alters the distribution of infrared

light that passes through the interferometer. The signal directly recorded, called

an "interferogram", represents light output as a function of mirror position. A

data-processing technique called Fourier transform turns this raw data into the

desired result (the sample's spectrum): Light output as a function of infrared

wavelength (or equivalently, wave number). As described above, the sample's

spectrum is always compared to a reference. There is an alternate method for

taking spectra (the "dispersive" or "scanning monochromator" method), where

one wavelength at a time passes through the sample. The dispersive method is

more common in UV-Vis spectroscopy, but is less practical in the infrared than

the FTIR method. One reason that FTIR is favored is called "Fellgett's

advantage" or the "multiplex advantage": The information at all frequencies is

collected simultaneously, improving both speed and signal to noise ratio.

Another is called "Jacqui not's Throughput Advantage": A dispersive

measurement requires detecting much lower light levels than an FTIR

measurement. There are other advantages, as well as some disadvantages, but

virtually all modern infrared spectrometers are FTIR instruments.

Case study

"STUDIES OF BORATE VANADATE GLASSES USING IR

SPECTROSCOPY"

ABSTRACT

IR spectra of xV2O5.(1-x)B2O3 glasses (with 0.05 x 0.8) have been measured

and analyzed ; IR reveal changes in spectra .The samples having x 0.6 a peak

characteristic to V2O5 appears ;This is an indication that vanadate structure was

forming and The vanadium oxide acts as network modifier in these glasses for 0.05

x 0.5 wile at 0.6 x 0.8 vanadium oxide acts as glass forming.

Introduction

IR spectroscopy become effective tools for resolving the structure of local

arrangement in glasses. The transition metal (TM) oxide glasses have been

extensively studied by several authors during the last twenty years. These

glasses are of importance due to their semiconducting properties and the

electrical conduction is due to electron hopping on account of the available

reduced states of the TM ions. Some authors have studied the effect of single

and multiple TM ions as dopants in alkali or alkaline earth oxide glasses. On the

other hand some have reported the effect of glass formers on these TM oxides

as regards the glass formation and have examined the electrical behavior and

performed spectroscopic studies. In this case we report the structure study of

borate vanadate glasses using IR spectroscopy.

Experimental

Glasses of xV2O5(1-x)B2O3 system with 0.05 x 0.8 were prepared by

mixing H3BO3 and V2O5 having reagent grade purity in suitable proportions and

melting this admixtures in sintered corundum crucibles at T = 1523 K for 0.5

hour. Vitrification was achieved by rapid cooling of the melts on stainless steel

plates at room temperature and atmospheric pressure. The IR spectra were

recorded in 4000-400 cm-1 spectral range with a Brucker IFS 120 spectrometer

using the KBr pellet technique.

IR spectra Results and discussion

IR spectra of xV2O5(1-x)B2O3 glasses with various contents of copper

oxide(0.05 x 0.8) are shown in Fig.2. The following bands are present in

these spectra: 642 cm-1, 796 cm-1, 883 cm-1, 1023 cm-1, 1195 cm-1, 1384 cm-1,

1465 cm-1, 1630 cm-1, 2260 cm-1, 2360 cm-1, 2520 cm-1, 3220 cm-1, and 3443 cm-

1.

Fig. 2. IR spectra of xV

Samples having up to 0.5 V2O5 show a water band at 3220 cm-1 and -OH

stretching peaks at 2520 cm-1, 2360 cm-1 and 2260 cm-1. These are intense for

low V2O5 content as shown in fig 2. these bands and peaks are due to the

hygroscopic character of the powdered glass samples. Hence, it can be safely

concluded that the samples are quite hygroscopic in nature at low x content. An

absorption peak was observed at 1630 cm-1. The origin of this peak is not

obvious, but the H-O-H bending mode gives rise to an absorption in this region

and the possibility of some adsorbed water giving rise to this peak cannot be

ruled out. A broad band at around 1450 cm-1 as observed in crystalline B2O3 is

present in low composition V2O5 glasses, but its character changes in samples

above 0.5 V2O5. As already reported in Na2O-B2O3 glasses the characteristic

>B-O- stretching band in the B2O3 glass network is assigned to a broad band

from 1428 cm-1 to 1333 cm-1. This band appears in our IR spectra, confirming

the amorphous nature of studied glasses. The low V2O5 content glasses show a

very sharp absorption peak at 1195 cm-1. This peak may be attributed to

triangular B-O stretching vibrations .This peak disappears when V2O5 content

increases. The spectra corresponding to x >0.6 present a band at 1250 cm -1 and

do not exhibit the 1195 cm-1 peak. The disappearance of the 1195 cm-1 peak and

the progressively appearance of the band centered at 1250 cm-1 corresponds to a

change from triangular to tetrahedral boron structure when the system goes to

higher V2O5 content . An absorption band at 1023 cm-1 was observed in all the

samples, also at highest V2O5 content. This peak in attributed to V=O stretching

vibrations . The peak at 883 cm-1 which is observed for low V2O5 content

disappear for x > 0.5. This disappear might be due to the rupture of boron ring

structure when the V2O5 content increases. A broad absorption peak between

740 cm-1 and 800 cm-1 in crystalline B2O3 and at 825 cm-1 in crystalline V2O5 is

observed. For higher compositions, this band disappears completely. The

absence of this band indicates that either the structural units of V2O5 in V2O5-

B2O3 glasses is not the same as that in crystallineV2O5 or the intensity of the peak

becomes very weak and could not be detected. Below 800 cm-1 there are several

absorption peaks in crystalline B2O3 as well in V2O5 .Therefore, we can not

assume these bands to particular groups (borate or vanadate). For low V2O5

content IR spectra reveal the presence of triangular and tetrahedral borate units.

At high V2O5 content only IR bands corresponding to the tetrahedral borate

units appear, in agreement with Raman conclusions. This indicates a

modification of the structure of studied glasses, determined by the changes of

the vanadium oxide content. Both Raman and IR analyses show the presence of

vanadate groups at high concentration of vanadium oxide. Thus at high V2O5

content vanadium oxide starts to act as a glass former.

Conclusions

The IR spectra of studied glasses have been qualitatively interpreted in the

range of 4000 cm-1 to 500 cm-1. The main characteristic is the disappearance of

some bands when V2O5 content increases. For low vanadium oxide content,

specifically borate units with triangular and tetrahedral configuration are

present, while for high V2O5 content are present only borate units with

tetrahedral configuration. In the same time, the feature of IR spectra reveal

bands characteristic to vanadate structure. Therefore, we conclude that

vanadium oxide acts as network modifier in these glasses for 0.05 x 0.5.

For higher concentration, vanadium oxide starts to act as glass former.

Index

Title Page Number

Introduction 1-2

IR Spectroscopy Definition 2

Applications of IR spectroscopy 2

Theory of Infrared Absorption 2-5

IR Spectra 5-6

Infrared Instruments 7

Fourier transform infrared (FTIR)

spectroscopy 7-8

Case study

"IR studies of Borate Vanadate

Glasses using IR spectroscopy"8-12

Reference :-

1-power point" Introduction to Infrared Spectroscopy(Chapter 16 Instrumental

Analysis) used reference :-

http://www.acs.org http://www.chemcenter/org,http:

www.shu.ac.uk/schools/sci/chem/tutorials/molspec/irspec/.htm

http://www.kerouac.pharm.uky.edu/asrg/wave/wavehp.html

2- PDF . book name Infrared Spectroscopy in Convervation Science by Michele .R-Drrick.

Dusans Bulik James m.Landy . Loaded from www.scribd .com .

3 -Paper Studies of Borate Vanadate Glasses using Raman and IR Spectroscopy/ studia universitatis babeş-bolyai, physica, special issue, 2001/ d.maniu*1, t. Iliescu1, i. Ardelean1, i. Bratu2, c. Dem31babes bolyai university, faculty of physics, kog¾lniceanu 1, 3400 cluj-napoca, romania2 institute for isotopic molecular technology, p.o. box 700, 3400

cluj-napoca 5, Romania3institut für physicaliche chemie, universitat würzburg, am hubland, d-97074 würzburg, germany

4-Chapter 15"Infrared Spectroscopy"/C.-P. Sherman Hsu, Ph.D. Separation Sciences Research and Product Development Mallinckrodt, Inc. Mallinckrodt Baker Division.