What absorbs at 1520 cm⁻¹ in an FTIR spectrum?
A band near 1520 cm⁻¹ can point to several functional groups. Below are the most likely assignments, ranked by how much published evidence supports each — every one traceable to literature (DOI) and cross-validated against our 130,000+ reference spectra and knowledge graph.
Backed by 8 cited sources
Quick answer
A band near 1520 cm⁻¹ is usually interpreted by checking which functional groups repeatedly co-occur there in the literature, then confirming at least one or two additional peaks in the same sample. This page ranks those assignments by accumulated evidence rather than by a single fixed textbook rule.
Possible functional-group assignments
| Functional group | Supporting facts | Cited sources | Top confidence |
|---|---|---|---|
| Amide | 14 | 13 | 1.0 |
| Aromatic ring | 9 | 8 | 1.0 |
| N h | 5 | 5 | 1.0 |
| Ring structure | 4 | 4 | 1.0 |
| Carboxyl (COOH) | 4 | 3 | 1.0 |
| C-O single bond | 2 | 2 | 1.0 |
| Urethane | 2 | 2 | 1.0 |
| Water (H2O) | 2 | 2 | 1.0 |
| Secondary amine | 2 | 2 | 1.0 |
| C c single bond | 2 | 2 | 1.0 |
| Protein beta sheet | 2 | 2 | 1.0 |
| Carbon dioxide | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| Protein | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
| Alkyl C-H | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Protein alpha helix | 1 | 1 | 1.0 |
| Nitrogen heterocycle | 1 | 1 | 0.8 |
Ranking reflects accumulated literature evidence, not a single fixed rule. Always confirm against your sample context.
Possible materials
| Material | Supporting peaks | Overlapping groups | Cited sources |
|---|---|---|---|
| Polyaniline | 1520, 1565, 1570 | Aromatic ring, Amide, Ring structure | 1 |
| composite | 1520, 1703, 1295 | Aromatic ring | 1 |
Materials are shown only when the same literature pool supports this band and at least one additional characteristic peak.
Spectrum logic
This band becomes meaningful only when read with its neighboring peaks. In practice, analysts first look at the assignments above, then check whether the same sample also shows other peaks expected for the same structural motif. A lone band near 1520 cm⁻¹ is usually not enough for material identification by itself.
Real-world usage
This type of query is common in polymer identification, unknown plastic screening, QC troubleshooting, recycled-material verification, and literature-backed peak assignment review.
Common mistakes
- Treating one isolated band as proof of a material without checking at least one or two supporting peaks.
- Ignoring overlap: multiple functional groups can contribute near the same wavenumber.
- Skipping validation when additives, blends, oxidation, or contamination may distort the spectrum.
Verification advice
When ambiguity remains, validate the hypothesis with DSC, GC-MS, or TGA, especially for blends, degraded samples, and filled polymers.
Literature behind these assignments
-
Aromatic ring confidence 1.0
“The absorption at 1520 is usually ascribed to the aromatic CAC ring-stretching vibration of benzenoid rings whereas the feature Initial stage of leucoemeraldine oxidation.”
Revisiting the Redox Transitions of Polyaniline. Semiquantitative Interpretation of Electrochemically Induced IR Bands DOI: 10.1016/j.jelechem.2021.115593 -
Amide confidence 1.0
“LLM confirmed rule peak-group candidate”
Dual delivery of platelet‐derived growth factor and bone morphogenetic factor‐6 on titanium surface to enhance the early period of implant osseointegration DOI: 10.1111/jre.12756 -
Amide confidence 1.0
“Nevertheless, Nevertheless, the the peaks peaks at at 1540, 1540, 1545, 1545, and and 1551 1551 cm-1 α-helical β-sheet usually assigned to structure, while the peaks at 1520 to 1525 are assigned to conformational sensitivity compared with a”
Sadat 和 Joye - 2020 - Peak Fitting Applied to Fourier Transform Infrared DOI: 10.3390/app10175918 -
Ring structure confidence 1.0
“LLM confirmed rule peak-group candidate”
Sandomierski 等 - 2016 - Reactive Diazonium-Modified Silica Fillers for Hig DOI: 10.1021/acs.langmuir.6b02891 -
confidence 1.0
“be assigned to -NH stretching and the signal at 1520 could be due to N-H bending.”
Shoaib 和 Bahadur - 2016 - Synthesis of thermally and mechanically improved p DOI: 10.1515/epoly-2016-0134 -
Amide confidence 1.0
“1690cm(cid:3)1), and turn structure (1610 and followed by CH asym3 (1440cm(cid:3)1) metric bending vibration and amide II band in ranAcknowledgement (1520cm(cid:3)1).”
Two-dimensional infrared spectroscopic study on the thermally induced structural changes of glutaraldehyde-crosslinked collagen DOI: 10.1016/j.saa.2015.01.003 -
Water (H2O) confidence 1.0
“tungstenlamp and CaF 2 1520cm-1 beamsplitterforNIR;andglobarlightsourceandKBrbeamsplitterfor is partly superimposed by the band of molecular water at”
Vetere 等 - 2011 - Solubility of H2O and CO2 in shoshonitic melts at DOI: 10.1016/j.jvolgeores.2011.03.002 -
confidence 1.0
“This peak sharply increased in intensity and shifted to 1462 In addition, a cm-1 new peak appeared at 1520 due to an increase in the oxygen-containing functionalities cm-1, cm-1, cm-1) on the surface of NASIF.”
Adsorption of Methylene Blue by Biosorption on Alkali-Treated Solanum incanum: Isotherms, Equilibrium and Mechanism DOI: 10.3390/su14052644
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