The Fundamentals of Surface-Enhanced Raman

By manipulating the plasmonic features of nanomaterials, surface-enhanced Raman provides a significant improvement in sensitivity compared to traditional Raman spectroscopy, enabling the detection of analytes down to parts-per-billion (ppb) levels.

Nikalyte has used its advanced nanoparticle deposition technology to create high-performance, economical substrates for surface-enhanced Raman, allowing laboratories of any size to achieve inexpensive, versatile, and ultrasensitive analyte detection.

The Fundamentals of Surface-Enhanced Raman

Image Credit: Nikalyte Ltd

Surface-Enhanced Raman Fundamentals

When matter and light interact, some of the light waves will disperse inelastically, meaning that a light wave (photon) loses a portion of its energy to the chemical bonds of the molecule it interacts with before being re-emitted in another direction. This is called Raman scattering.

The volume of energy a photon gives to a molecule during Raman scattering relies on the exact nature of the molecule’s chemical bonds. The loss in photon energy can be detected as a frequency shift in the emitted and absorbed photon, which corresponds to a particular vibrational mode of the molecule it interacted with.

Raman spectroscopy uses this phenomenon to examine a sample’s chemical composition. Examining a sample with a monochromatic light source and assessing the frequency that shifts occur because of Raman scattering makes it possible to detect the sample's chemical bonds and particular molecules.

In 1973, scientists at the University of Southampton made a landmark discovery while studying the Raman spectrum of pyridine. They discovered that letting a sample adsorb to specific surfaces (in their case, a coarsened silver electrode) could considerably improve the intensity of Raman scattering and, therefore, the sensitivity of Raman spectroscopy. This became the foundation of surface-enhanced Raman spectroscopy.

Currently, surface-enhanced Raman is achieved by using nanotextured surfaces that present plasmon resonance, such as silver or gold nanoparticles. Surface-enhanced Raman spectroscopy can provide an improvement factor of up to 1012 (1,000,000,000,000) over traditional Raman spectroscopy, rendering it one of the most sensitive analytical spectroscopy methods on earth. 

Applications and Benefits of Surface-Enhanced Raman

The key benefits of surface-enhanced Raman are its selectivity and sensitivity, enabling the identification of less-than-monolayer coverage of an analyte on a surface, even in a complex mixture.

Image Credit: Nikalyte Ltd

Surface-enhanced Raman is non-destructive and non-invasive. Its comparatively low water sensitivity makes it ideal for all in-situ and in-vitro applications for biological specimens. Surface-enhanced Raman also functions under various pressure and temperature conditions; and usually delivers results within seconds, if not faster.

The flexibility and power of surface-enhanced Raman make it ideal for widespread surface/interface chemistry, catalysis, biology, food science, environment monitoring, nanotechnology, and pharmaceuticals. Despite the clear benefits of surface-enhanced Raman, the method has been underutilized due to the high cost of appropriate substrates and weak measurement reproducibility.

Nikalyte strives to solve the affordability issue in surface-enhanced Raman spectroscopy. Using its signature nanoparticle deposition platform, Nikalyte has created versatile and economical gold nanoparticle substrates to ensure the affordability of surface-enhanced Raman and render it practical for all laboratories.

In contrast to chemically-produced nanoparticles, Nikalyte’s vacuum nanoparticles are ultra-pure and free from ligands or hydrocarbons. Nikalyte’s “naked” gold nanoparticle SERS substrate provides a very high Raman signal-to-noise ratio and improved detection sensitivity.

This information has been sourced, reviewed and adapted from materials provided by Nikalyte Ltd.

For more information on this source, please visit Nikalyte Ltd.

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