What absorbs at 3435 cm⁻¹ in an FTIR spectrum?
A band near 3435 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 3435 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 |
|---|---|---|---|
| Hydroxyl (O-H) | 25 | 25 | 1.0 |
| N h | 12 | 11 | 1.0 |
| Water (H2O) | 5 | 5 | 1.0 |
| Secondary amine | 4 | 4 | 1.0 |
| Carbonyl (C=O) | 3 | 3 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| Ester | 2 | 2 | 1.0 |
| Silanol (Si-OH) | 2 | 2 | 1.0 |
| Carboxyl (COOH) | 2 | 2 | 1.0 |
| Amide | 2 | 2 | 1.0 |
| Alkyl C-H | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Phosphate (PO4) | 1 | 1 | 1.0 |
| Thiol | 1 | 1 | 1.0 |
| C-S single bond | 1 | 1 | 1.0 |
| Chitosan | 1 | 1 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| C=n | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Metal oxygen | 1 | 1 | 0.9 |
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 |
|---|---|---|---|
| silver nanoparticles | 3435, 1636, 1631 | Hydroxyl (O-H), N h | 2 |
| AgNPs | 3435, 1232, 1048 | N h, Hydroxyl (O-H) | 1 |
| polypyrrole | 3435, 1700, 400 | Secondary amine, N h | 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 3435 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
“In addition, the N-H stretching vibration is supported by peaks that appear cm-1, at 3435.48 and 3435.97 respectively.”
Antibacterial efficacy of synthesized silver nanoparticles of Microbacterium proteolyticum LA2(R) and Streptomyces rochei LA2(O) against biofilm forming meningitis causing microbes DOI: 10.1038/s41598-023-30215-9 -
Hydroxyl (O-H) confidence 1.0
“The band at 3435 indicates OH stretching as free OH groups absorb in”
Structural analysis and antioxidative properties of mutan (water-insoluble glucan) and carboxymethyl mutan from Streptococcus mutans DOI: 10.1016/j.procbio.2020.07.006 -
N h confidence 1.0
“The main absorption bands of such biomolecules appeared cm-1, cm-1 1631 and More details about the synthesized AgNPs were obtained at average wave numbers of 3435 cm-1, 1396 which are assigned for ν(N-H) of amide A from both TEM photographs”
Multi-bioactive silver nanoparticles synthesized using mosquitocidal Bacilli and their characterization DOI: 10.1007/s00203-019-01718-9 -
confidence 1.0
“The peaks at 3435 and 1632 the N-H stretching of secondary amides and C=O stretching were accomplished under a UV lamp set at 254nm (Germicidal vibrations in wool proteins based on their chemical environment, UV lamp from Keosan Enterprise”
Gashti 等 - 2015 - Electromagnetic Shielding Response of UV-induced P DOI: 10.1007/s12221-015-0585-9 -
Silanol (Si-OH) confidence 1.0
“The charage heat release rate (HRR), the peak HRR, total heat release cm-1 acteristic band at 3435 (THR), total smoke release (TSR), time to ignition (TTI), mass refers to the silanol (Si-OH) loss rate (MLR), and burning rate (BR) were cond”
Effect of Surface Functionalization of SiO2 Nanoparticles on the Dynamic Mechanical, Thermal and Fire Properties of Wheat Straw/LDPE Composites DOI: 10.1007/s10924-019-01576-y -
confidence 1.0
“The peaks at 3435 and 3410 assigned N-H stretching frequency were obtained for 2 M H 2SO modified and unmodified bentonite clay types, respectively.”
Preparation and characterization of adsorbents derived from bentonite and kaolin clays DOI: 10.1007/s13201-018-0827-2 -
Hydroxyl (O-H) confidence 1.0
“The absorption band at wave number Fe2+ tion of ions leads to the enhancement of interfacial polarization as 3435cm-1 is due to H-O-H (water) stretching vibration.”
Preparation and characterization of doubly substituted microwave absorbing material by sol-gel technique for super high frequency applications DOI: 10.1016/j.pnsc.2017.11.001 -
confidence 1.0
“FT-IR analysis of Ag NPs showed a peak at 3435 presence of N-H group (primary, secondary amines, and amides) on the surface of Ag NPs.”
Sable 等 - 2020 - Bioreduction mechanism of silver nanoparticles DOI: 10.1016/j.msec.2019.110299
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