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M44_FTIR.html
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<html>
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<p class="head">Fourier Transform Infrared spectroscopy (FTIR)</p>
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<div id="Overview">
<p class="thema">Overview</p>
<p><a class="def">FTIR (Fourier Transform Infrared) spectroscopy</a> is a technique used to analyze the <a class="black" href="https://cvertan.github.io/physics4dh.github.io/32_Molecule.html" target="frameterms">molecular</a> composition of a sample by measuring the <a class="black" href="https://cvertan.github.io/physics4dh.github.io/7_Absorption.html" target="frameterms">absorption</a>, <a class="black" href="https://cvertan.github.io/physics4dh.github.io/23_Reflection.html" target="frameterms">reflection</a> or <a class="black" href="https://cvertan.github.io/physics4dh.github.io/31_Transmission.html" target="frameterms">transmission</a> of <a class="black" href="https://cvertan.github.io/physics4dh.github.io/10_infrared%20light.html" target="frameterms">infrared light</a>. Typically, FTIR utilizes near-infrared (NIR) or short-wavelength infrared light to examine the optical properties of an object as well as <a class="black" target="_blank" href="https://www.youtube.com/watch?v=mgXSevZmjPc">Fourier transform</a> of the <a class="black" href="https://cvertan.github.io/physics4dh.github.io/15_Wave.html" target="frameterms">spectra</a>.</p>
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<div id="Tasks">
<p class="thema">Research tasks & applications</p>
<p>It can be used to identify and verify known and unknown samples as well as characterize new materials allowing for determination functional groups, detect impurities, determine molecular structure, and assess sample purity or quality. An FTIR spectrum is like a chemical fingerprint. </p>
<p>FTIR spectroscopy is a versatile technique used in various fields, including chemistry, materials science, pharmaceuticals, forensic analysis, environmental monitoring, and more. It is commonly used in art conservation and restoration to study paintings, manuscripts, and other historical artifacts. It helps identify underlying sketches, pentimenti (artist's changes), and hidden text, aiding in the understanding of an artwork's creation process and revealing valuable information about its history. </p>
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<div id="P">
<p class="thema">Principle</p>
<p>The principle of FTIR (Fourier Transform Infrared) spectroscopy involves the measurement and analysis of the interaction between <a class="black" href="https://cvertan.github.io/physics4dh.github.io/20_Energy.html" target="frameterms">energy</a>infrared light and a sample. It is based on the fact that different <a class="black" href="https://cvertan.github.io/physics4dh.github.io/32_Molecule.html" target="frameterms">molecules</a> absorb infrared light at specific <a class="black" href="https://cvertan.github.io/physics4dh.github.io/15_Wave.html" target="frameterms">frequencies</a> corresponding to their <a class="black" href="https://cvertan.github.io/physics4dh.github.io/32_Molecule.html" target="frameterms">molecular</a> vibrations. </p>
<p>In FTIR spectroscopy, a broadband infrared light source is used to generate a range of infrared frequencies. The sample is exposed to this light, and the resulting <a class="black" href="https://cvertan.github.io/physics4dh.github.io/7_Absorption.html" target="frameterms">absorbed</a>, <a class="black" href="https://cvertan.github.io/physics4dh.github.io/31_Transmission.html" target="frameterms">transmitted</a> or <a class="black" href="https://cvertan.github.io/physics4dh.github.io/23_Reflection.html" target="frameterms">reflected</a> light is analyzed. </p>
<p>An <a class="black" href="https://cvertan.github.io/physics4dh.github.io/28_Interferometer.html" target="frameterms">interferometer</a> is used to modulate the infrared light, creating an interferogram that contains information about the sample's absorption, transmittance or reflectance characteristics at different frequencies. </p>
<p>By performing a <a class="def">Fourier transform</a> on the interferogram, a Fourier transform infrared <a class="black" href="https://cvertan.github.io/physics4dh.github.io/13_EM_spectrum.html" target="frameterms">spectrum</a> is obtained, which provides a detailed representation of the sample's molecular composition and structure based on the absorption peaks observed at specific frequencies. </p>
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<p>The <a class="def">procedure for performing FTIR spectroscopy</a> typically involves the following steps:</p>
<p>1) Before analyzing the sample, a background measurement is taken. This involves measuring the reference signal due to the sample holder or the surrounding environment without sample. </p>
<p>2) Sample measurement: the prepared sample is placed in the sample compartment of the FTIR instrument. The instrument is set to the desired measurement parameters, such as the wavelength range, resolution, and scan speed. The instrument then measures the infrared light <a class="black" href="https://cvertan.github.io/physics4dh.github.io/31_Transmission.html" target="frameterms">transmitted</a> through (in case of transmittance spectra) or <a class="black" href="https://cvertan.github.io/physics4dh.github.io/23_Reflection.html" target="frameterms">reflected</a> (in case of reflection spectra) from the sample. </p>
<p>3) Interferogram acquisition: the interferometer modulates the <a class="black" href="https://cvertan.github.io/physics4dh.github.io/10_infrared%20light.html" target="frameterms">infrared light</a> by splitting it into two beams, one of which travels through the sample and the other through the reference path. These beams are then recombined, creating an interference pattern called an interferogram. </p>
<p>4) Fourier transformation: the interferogram is subjected to a mathematical process called <a class="def">Fourier transform</a>. The output of the Fourier transformation is a frequency domain view of the original time domain function. This transformation generates a spectrum known as the Fourier transform infrared spectrum. The explanation of the Fourier series and Fourier transform is given <a class="ref" target="_blank" href="https://www.youtube.com/watch?v=mgXSevZmjPc">here</a> for ex. </p>
<p>5) Data analysis: the resulting infrared spectrum is analyzed to identify the molecular functional groups present in the sample. The spectrum is compared to reference spectra or spectral databases to interpret the absorption (or transmittance, or reflectance) peaks and determine the chemical composition or structure of the sample. </p>
<div class="gallery">
<img src="Figures/FTIR.jpg" width="400" height="100">
<div class="desc">FTIR spectroscopy procedure. Source: <a target="_blank" href="https://www.youtube.com/watch?v=tPoCh6Iff0Y">RedShiftBio</a>.</div>
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<div id="Equip">
<p class="thema">Equipment</p>
<p>The FTIR instrument is set up by aligning the optical components and calibrating the instrument. The system typically consists of a broadband <a class="black" href="https://cvertan.github.io/physics4dh.github.io/10_infrared%20light.html" target="frameterms">infrared light</a> <b>source</b>, an <b>interferometer</b>, a <b>sample compartment</b>, a <b>detector</b>, and a <b>computer</b> for data acquisition and analysis. </p>
<p>An FTIR spectrometer simultaneously collects high-resolution spectral data over a wide spectral range. This confers a significant advantage over a common <a class="black" href="https://cvertan.github.io/physics4dh.github.io/27_Spectrometer.html" target="frameterms">spectrometer</a>, which measures intensity over a narrow range of wavelengths at a time. </p>
<p>Determinative part of an FTIR spectrometer is the e.g. Michelson interferometer. During the measurement the IR-beam enters the interferometer and is directed at a beamsplitter. The beam is then split and directed at a fixed and moving mirror respectively. The beam is recombined (causing interference) and finally directed at the sample material. The spectral information of all <a class="black" href="https://cvertan.github.io/physics4dh.github.io/15_Wave.html" target="frameterms">wavelengths</a> is acquired simultaneously saving a lot of time. </p>
<div class="gallery">
<img src="Figures/FTIR_Eq.jpg" width="400" height="100">
<div class="desc">Configuration of FTIR spectroscopy system. Source: <a target="_blank" href="https://www.youtube.com/watch?v=KRoWMB3AR3s">Bruker corporation</a>.</div>
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<div id="Cases">
<p class="thema">Case Studies</p>
<table>
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<th>Object studied</th>
<!-- <th>Operating Range</th> -->
<th>Source</th>
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<td>Writing materials in Geniza Fragments </td>
<td>[<a target="_blank" href="bibliography.html#Cohen_2017">Cohen_2017</a>] </td>
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<td>Thirteenth-Century Ashkenazic Torah Scroll: Erfurt 7 (Staatsbibliothek zu Berlin, Ms. or. fol. 1216) </td>
<td>[<a target="_blank" href="bibliography.html#Gordon_2014">Gordon_2014</a>]</td>
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<td>15<a class ="super">th</a> century work of art "Christ with singing and music-making Angels" by Hans Memling (1430–1495) </td>
<td>[<a target="_blank" href="bibliography.html#Janssens_paint">Janssens_paint</a>]</td>
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<p class="acknow">Acknowledgements:
[<a class="ref" href=bibliography.html#Janke_2014>Janke_2014</a>],
[<a class="ref" href=bibliography.html#Knox_2020>Knox_2020</a>],
[<a class="ref" href=bibliography.html#Marshall_2012>Polder_2021</a>],
[<a class="ref" href=bibliography.html#wiki>wiki</a>],
[<a class="ref" href=bibliography.html#Porebski_2022>Porebski_2022</a>],
[<a class="ref" href=bibliography.html#Yao_2022>Yao_2022</a>],
[<a class="ref" href=bibliography.html#Peery_2020>Peery_2020</a>],
[<a class="ref" href=bibliography.html#Cohen_2017>Cohen_2017</a>],
[<a class="ref" href=bibliography.html#Gordon_2014>Gordon_2014</a>].</p>
<p class="important">More on subject: <a target="_blank" href="https://www.youtube.com/watch?v=tPoCh6Iff0Y">www.youtube.com</a>
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