What absorbs at 505 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 505 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

Ranking reflects accumulated literature evidence, not a single authoritative rule. Always confirm against your sample context.

Possible materials

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 505 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

• Metal oxygen confidence 1.0

  “LLM confirmed rule peak-group candidate”

  Pascoal 等 - 2020 - Treatment by TiO2UV of wastewater generated in po DOI: 10.5004/dwt.2020.26390
• Aromatic ring confidence 1.0

  “nanocomposite shows that the origin of the vibrational bands is as FT-IR spectra of the Pani-TiO 2 cm-1 cm-1 follows: a band at 3454 is due to the NH stretching of aromatic amines, another at 2854 505cm-1 is due to aromatic CH-stretching, a”

  Rajakani 和 Vedhi - 2013 - Synthesis and electrochemical studies of TiO2 - Pa DOI: 10.4028/www.scientific.net/AMR.678.263
• Acetate confidence 1.0

  “Therewere three drastic decrement intensity peaks of C=O, C-OH, and C-O groups with the generation of new peaks at 576 cm-1, 505 cm-1 and 453 cm-1 corresponding to CuO stretching vibrations, that were explained by Gulati et al.”

  Effect of rGO wt.% on the Preparation of rGO/CuO Nanocomposites at Different Test Periods and Temperatures DOI: 10.3390/cryst12101325
• confidence 1.0

  “The spectra of samples 100Zn0Co and 100Zn0Co-T contained a peak at 505 cm-1, which can be attributed to zinc oxide with oxygen”

  Butova 等 - 2020 - Synthesis of ZnO Nanoparticles Doped with Cobalt U DOI: 10.3390/nano10071275
• Metal oxygen confidence 1.0

  “cm-1 551 in case of pure ZnO which corresponds to the Zn-O bond stretching 1 cm-1 1 vibration that shifted to about 505 for the polymeric hybrid [15].”

  Elkady 等 - 2015 - Formulation of Nano-zinc Oxide into Biocomposite B DOI: 10.1063/1.4914227
• Carboxyl (COOH) confidence 1.0

  “The band at 505 could be assigned to CoO.”

  Cobalt Oxide Catalysts in the Form of Thin Films Prepared by Magnetron Sputtering on Stainless-Steel Meshes: Performance in Ethanol Oxidation DOI: 10.3390/catal9100806
• confidence 1.0

  “bands at 1115 and 1025 can also indicate Si-O-Si cm-1 505 quartz bond and Si-O stretching of silicates/clays, and the 2515 peak could refer to thiol”

  Mineral and chemical changes of sediments after Cu sorption and then desorption induced by synthetic root exudate DOI: 10.1016/j.chemosphere.2019.124393
• Alkyl C-H confidence 1.0

  “Si-O-Si 1257 0.422 0.505 cm-1) gle bending peak of C-H (1510 observed in the freshly Si-O 3643”

  Khan 等 - 2021 - The Structural, Physical, and In Vitro Biological DOI: 10.14744/eej.2020.36349