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Related Concept Videos

IR Spectroscopy: Molecular Vibration Overview01:24

IR Spectroscopy: Molecular Vibration Overview

When Infrared (IR) radiation passes through a covalently bonded molecule, the bonds transition from lower to higher vibrational levels. The fundamental vibrational motions that result in infrared absorption can be classified as stretching or bending vibrations.
Stretching vibrations are vibrational motions that occur along the bond line, changing the bond length or distance between two bonded atoms. They are further distinguished as symmetric or asymmetric. In symmetric stretching, the...
Ultraviolet and Visible (UV–Vis) Spectroscopy: Overview01:02

Ultraviolet and Visible (UV–Vis) Spectroscopy: Overview

Ultraviolet–visible (UV–visible or UV–Vis) spectroscopy is an analytical technique that investigates the interaction between matter and UV–Vis light within the electromagnetic spectrum. This method is widely used for its versatility, simplicity, and relatively quick data acquisition, making it valuable for both qualitative and quantitative analysis. When UV–Vis radiation passes through a material,  molecules absorb light depending on the energy required for electronic transitions. As a result...
IR Frequency Region: Fingerprint Region01:03

IR Frequency Region: Fingerprint Region

IR spectra are divided into two main regions: the diagnostic region and the fingerprint region. The diagnostic region of the spectrum lies above 1500 cm−1. The absorptions resulting from single-bond vibrations of the N–H, C–H, and O–H stretch at higher wavenumbers and appear on the left side of the spectrum. The stretching absorptions of the C≡C and C≡N occur between 2100–2300 cm−1. In contrast, those arising from stretching absorptions of the C=O, C=N, and C=C occur between 1600–1850 cm−1.
The...
IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations01:08

IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations

Identical bonds within a polyatomic group can stretch symmetrically (in-phase) or asymmetrically (out-of-phase). Similar to hydrogen bonding, these vibrations also influence the shape of the IR peak. Generally, asymmetric stretching frequencies are higher than symmetric stretching frequencies. For example, primary amines exhibit two distinct IR peaks between 3300–3500 cm−1 corresponding to the symmetric and asymmetric N-H stretching, while secondary amines exhibit a single stretching vibration...
UV–Vis Spectrometers01:14

UV–Vis Spectrometers

The absorbance of UV and visible (UV–visible) radiations is measured using a UV–visible spectrophotometer. Deuterium lamps, which emit UV radiation, and tungsten lamps, which produce radiation in the visible region, are used as light sources in UV–visible spectrophotometers. A monochromator or prism is used for diffraction grating, i.e., to split the incoming radiation into different wavelengths. A system of slits is used to focus the desired wavelength on the sample cell. Samples for...
Infrared (IR) Spectroscopy: Overview01:09

Infrared (IR) Spectroscopy: Overview

When electromagnetic radiation passes through a material, atoms or molecules transition from a lower to a higher energy state by absorbing radiation corresponding to the energy difference between the two states. The absorption of infrared (IR) radiation causes transitions between vibrational energy levels in a molecule. Therefore, IR spectroscopy is a useful analytical tool for determining the molecular structure of molecules.
Different compounds display unique properties due to their...

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Updated: Jun 23, 2026

Interfacial Molecular-level Structures of Polymers and Biomacromolecules Revealed via Sum Frequency Generation Vibrational Spectroscopy
09:43

Interfacial Molecular-level Structures of Polymers and Biomacromolecules Revealed via Sum Frequency Generation Vibrational Spectroscopy

Published on: August 13, 2019

Surface-enhanced IR-visible sum frequency generation vibrational spectroscopy.

Qifeng Li1, Chiung Wen Kuo, Zheng Yang

  • 1Department of Chemistry, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1.

Physical Chemistry Chemical Physics : PCCP
|May 8, 2009
PubMed
Summary

Surface-enhanced infrared-visible sum frequency generation (SFG) using silver and gold nanospheres achieved significant vibrational spectral enhancement. Optimal sphere size and localized surface plasmon resonance maximized SFG signals for molecular analysis.

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Multimodal Nonlinear Hyperspectral Chemical Imaging Using Line-Scanning Vibrational Sum-Frequency Generation Microscopy
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Ultrafast Time-resolved Near-IR Stimulated Raman Measurements of Functional π-conjugate Systems
09:57

Ultrafast Time-resolved Near-IR Stimulated Raman Measurements of Functional π-conjugate Systems

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Interfacial Molecular-level Structures of Polymers and Biomacromolecules Revealed via Sum Frequency Generation Vibrational Spectroscopy
09:43

Interfacial Molecular-level Structures of Polymers and Biomacromolecules Revealed via Sum Frequency Generation Vibrational Spectroscopy

Published on: August 13, 2019

Multimodal Nonlinear Hyperspectral Chemical Imaging Using Line-Scanning Vibrational Sum-Frequency Generation Microscopy
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Ultrafast Time-resolved Near-IR Stimulated Raman Measurements of Functional π-conjugate Systems
09:57

Ultrafast Time-resolved Near-IR Stimulated Raman Measurements of Functional π-conjugate Systems

Published on: February 10, 2020

Area of Science:

  • Surface-enhanced spectroscopy
  • Plasmonics
  • Nanomaterials

Background:

  • Sum frequency generation (SFG) spectroscopy probes interfacial molecular vibrations.
  • Nanostructured metal films offer potential for signal enhancement.
  • Controlling nanostructure morphology is key for reproducible enhancement.

Purpose of the Study:

  • To investigate surface-enhanced SFG (SE-SFG) using silver and gold films over nanospheres (AgFON and AuFON).
  • To correlate SE-SFG enhancement with nanosphere size and localized surface plasmon resonance (LSPR).
  • To determine the enhancement factors for different molecular vibrational modes.

Main Methods:

  • Fabrication of AgFON and AuFON with controlled sphere diameters (300-620 nm).
  • Measurement of SFG vibrational spectra of octadecanethiol self-assembled monolayers.
  • Analysis of spectral enhancement relative to sphere diameter and LSPR.
  • Polarization-dependent SFG measurements.

Main Results:

  • Maximum SFG enhancement observed for sphere diameters near 360 nm, matching LSPR.
  • AgFON showed an SFG enhancement factor of ~730 for the asymmetric CH3 stretch.
  • AuFON provided a quarter of the enhancement seen with AgFON.
  • The symmetric CH3 mode enhancement was ~10 times lower than the asymmetric mode.

Conclusions:

  • AgFON and AuFON enable reproducible, large-area SE-SFG with significant enhancement.
  • Optimal enhancement is achieved when the input wavelength matches the LSPR of the nanospheres.
  • Surface-parallel electric fields are primarily responsible for the observed SE-SFG enhancement.