What absorbs at 777 cm⁻¹ in an FTIR spectrum?
A band near 777 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 777 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 |
|---|---|---|---|
| Silicon (Si) | 6 | 6 | 1.0 |
| Silicon-oxygen (Si-O) | 5 | 5 | 1.0 |
| Alkyl C-H | 5 | 4 | 1.0 |
| Siloxane (Si-O-Si) | 3 | 3 | 1.0 |
| Aromatic ring | 3 | 3 | 1.0 |
| Silicon carbon | 2 | 2 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| Borate | 1 | 1 | 1.0 |
| Hydroxyl (O-H) | 1 | 1 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Carbonyl (C=O) | 1 | 1 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
| Silanol (Si-OH) | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Nitrogen heterocycle | 1 | 1 | 1.0 |
| Oxalate | 1 | 1 | 1.0 |
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 |
|---|---|---|---|
| SiO | 777, 800, 1745 | Silicon-oxygen (Si-O), Siloxane (Si-O-Si), Silicon (Si) | 1 |
| glass | 777, 1100, 1075 | Silicon-oxygen (Si-O), Siloxane (Si-O-Si), Silicon (Si) | 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 777 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
-
confidence 1.0
“Results show that after the heat treatment at 700°C, silicate bands cm-1 cm-1, cmfor Si-O-Si bending mode were observed at 452 and 521 Si-O-Si stretching (symmetric) mode at 777 1”
Fabrication of sol-gel derived new quaternary silicate Bioglass S55P4 DOI: 10.1063/1.5089369 -
Aromatic ring confidence 1.0
“of the characteristic functional groups of poly flavonoids moiety in proanthocyanidins, whereas those attributed to those of the characteristic functional groups of poly flavonoids moiety in cm-1 at 1520 and 777 were attributed to the skele”
Biao 等 - 2018 - Green Synthesis, Characterization and Application DOI: 10.3390/nano8010053 -
confidence 1.0
“The band around 777 has been Opuntia attributed to OCO deformations of calcium oxalate presents in the cladodes [60].”
Opuntia spp. Fibre Characterisation to Obtain Sustainable Materials in the Composites Field DOI: 10.3390/polym13132085 -
Alkyl C-H confidence 1.0
“vibration of ether bond 777 817 and aer fastness of silk fabrics mordanting with six metal ions article cm-1 C-H 872 are the absorption peaks of the bond on the were conducted, the results are shown in Table 2.”
Extraction of pigments from camellia seed husks and their application on silk fabrics DOI: 10.1039/d2ra06793e -
confidence 1.0
“The 270 cm-1 absorptions at 777 and 679 were assigned to deformation of the pyridine ring (Lin-Vien”
Franca 等 - 2020 - Monitoring diclofenac adsorption by organophilic a DOI: 10.1016/j.envpol.2013.04.012 -
Silanol (Si-OH) confidence 1.0
“3 (l) cm-1 Moreover, the latter exhibit specific peaks at 913 attributed to Si-OH bond stretching cm-1 vibrations, and at 777 related to the absorption bands of the stretching vibrations of”
Organic Bio-Based Aerogel from Food Waste: Preparation and Hydrophobization DOI: 10.3390/gels8110691 -
confidence 1.0
“In FTIR spectrum transmittance Electrochemical DNA biosensor was characterized at cm-1 peaks around 777, 1680 and 2512 indicative of aroeach step of fabrication using FE-SEM, FTIR and Raman matic C-H bending, C=O and O-H stretching.”
AuNPs/CNF-modified DNA biosensor for early and quick detection of O. tsutsugamushi in patients suffering from scrub typhus DOI: 10.1007/s13205-020-02432-w -
Borate confidence 1.0
“In Figures 3 and 4, which 700cm-1 777cm-1 the vibration signals of [BO is [BO 3] B-O-B vibration.”
Lan 等 - 2021 - The Relationship between the Structure and Thermal DOI: 10.1155/2021/2321558
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