Infrared Absorption
Infrared Absorption - Related Videos
08:11
Infrared Spectroscopy
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2023
Source: Vy M. Dong and Zhiwei Chen, Department of Chemistry, University of California, Irvine, CA This experiment will demonstrate the use of infrared (IR) spectroscopy (also known as vibrational spectroscopy) to elucidate the identity of an unknown compound by identifying the functional group(s) present. IR spectra will be obtained on an IR spectrometer using the attenuated total reflection (ATR) sampling technique with a neat sample of the unknown.
07:38
Characterization of Biological Absorption Spectra Spanning the Visible to the Short-Wave Infrared
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Cited by 8 •
2025
Biological samples have distinct optical characteristics in the short-wave infrared (SWIR) compared to the visible (VIS) and near-infrared (NIR) wavelength ranges. However, recording pure SWIR absorption spectra is challenging and rarely conducted for biological molecules. This article presents a method to characterize the VIS-SWIR absorption spectra of biological absorbers.
10:12
Near-infrared Fluorescence Imaging of Abdominal Aortic Aneurysms
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2023
Source: Arvin H. Soepriatna1, Kelsey A. Bullens2, and Craig J. Goergen1 1 Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana 2 Department of Biochemistry, Purdue University, West Lafayette, Indiana Near-infrared fluorescence (NIRF) imaging is an exciting optical technique that utilizes fluorescent probes to visualize complex biomolecular assemblies in tissues. NIRF imaging has many advantages over conventional imaging methods for noninvasive imaging of diseases.
03:04
A Fourier Transform Infrared Spectroscopy Technique to Study Peptide Self-Assembly
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2025
This video demonstrates the self-assembly of amyloid peptides into a beta sheet-rich supramolecular structure using Fourier transform infrared spectroscopy. An infrared beam is passed through a crystal with a high refractive index, and energy absorption across the interface of the crystal and the sample is recorded. The secondary structures of the sample proteins are identified by analyzing their characteristic absorption peaks at specific regions of the infrared spectrum, which aids in...
01:19
Drug Absorption: Factors Affecting GI Absorption
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2023
The process of oral drug absorption can be influenced by several factors. Weakly acidic drugs tend to be absorbed more readily from the stomach due to their nonionized state. However, absorption may be less efficient in the upper intestine, where drugs are often ionized. Interestingly, despite the stomach's apparent advantage for drug absorption, its mucous layer can hinder diffusion. Its surface area is also smaller than the intestine's, which can further slow down the absorption rate. In...
FAQs
A vibration becomes infrared-active only when it changes the molecule’s dipole moment, meaning the separation of electrical charge changes during the motion. This changing dipole interacts with the infrared radiation and permits energy uptake at a matching frequency. Vibrations that do not produce such a change do not create corresponding absorption bands in the spectrum.
Bond stretching, bending, and rotation produce transitions at frequencies determined by molecular structure. The position of a band reflects the associated molecular motion, while its intensity depends on how strongly that motion interacts with infrared radiation. Consequently, differences in structure can alter both the locations and strengths of observed absorption features.
The pattern of absorption bands can indicate functional groups and help identify a compound, providing qualitative information about molecular structure. Band intensity also depends on concentration, allowing infrared measurements to support quantitative analysis. Using both features lets chemists examine what substances are present and assess how much material is present or changing.
Related compounds may share some absorption features but differ in the overall pattern of band positions and intensities produced by their molecular structures. Examining the spectrum as a complete pattern, rather than relying on one band alone, helps reveal functional groups and supports compound identification. These structural differences also make spectra useful for comparing chemical samples.
A sample is examined with infrared radiation, and the resulting uptake is recorded across relevant infrared frequencies as a spectrum. Analysts then evaluate the locations and intensities of absorption bands, relating them to molecular vibrations, functional groups, structure, and concentration. This workflow converts radiation-response data into information about composition and chemical identity.
Infrared absorption can track chemical reactions by following changes in absorption bands as molecular structures and compositions change. The same approach supports materials characterization, where spectral patterns provide information about chemical components and structure. These applications extend beyond simple identification by using spectral changes or band intensities to assess evolving samples and material composition.