Raman Technology

What is Surface-enhanced Raman Scattering (SERS)?

Surface-enhanced Raman Scattering explained in a few words

Schematization of the Surface-enhanced Raman Scattering (SERS) mechanism

Schematization of the Surface-enhanced Raman Scattering (SERS) mechanism

Surface-enhanced Raman Scattering (SERS) is a phenomenon that enhances the Raman scattering signals of molecules close to nanostructured metallic surfaces, typically gold or silver. Indeed, these surfaces create intense local electromagnetic fields, amplifying the Raman signals of nearby molecules.

SERS provides all the advantages of Raman spectroscopy with the advantage of higher sensitivity. Raman spectroscopy is an effective method for examining molecules’ vibrations mode. Yet, it struggles with weak signals from the analyte (the analyzed sample). SERS emerged to address this limitation and as a result, various fields, such as chemistry and materials science, have been able to explore molecular structures and interactions at the nanoscale.

To provide you with more information about that topic, we have prepared a webinar with details about the SERS principle, additional resources on the topic, and how our solutions can help your research.

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How does Surface-enhanced Raman Spectroscopy (SERS) work?

The principle of Surface-enhanced Raman Spectroscopy (SERS) revolves around the enhancement of Raman scattering signals from molecules adhered to nanostructured metallic surfaces, often made of gold or silver, via plasmon resonance.

Surface plasmons are free electrons on the surface which are oscillating collectively. When light of a specific wavelength matches the frequency of the oscillations, localized surface plasmons resonate, creating "hot spots."

These hot spots enhance the local electric field near the metal surface, significantly increasing the Raman scattering of nearby molecules and thus amplifying the Raman spectroscopy signals.

What does SERS measure?

SERS provides detailed information about the molecular composition, structure, and environment of the analyzed molecules or analyte. Additionally, SERS can detect molecules at very low concentrations, often down to single molecule levels.

How is SERS different from standard Raman spectroscopy?

SERS differs from Raman spectroscopy in its ability to significantly enhance the Raman signals of molecules.

While both techniques use the Raman scattering phenomenon to provide molecular information, Raman spectroscopy sometimes cannot measure the signals of analytes, which are in very low concentrations. Indeed, when a molecule is present in only trace amounts, the chances of scattering Raman photons on the molecule are low. Furthermore, background interference (such as solvent or matrixes) can overshadow the Raman signal of interest.

However, by using nanostructured metallic surfaces, such as gold or silver, SERS boosts sensitivity and signal enhancement, sometimes to the point of detecting individual molecules.

Furthermore, the organization of molecules on the metallic surface in SERS can lead to distinct spectral results compared to standard Raman spectroscopy. Indeed, interactions between molecules and the metal surface alter vibrational modes, which cause shifts in peak positions and the appearance of new peaks.

How is SERS different from TERS?

Surface-enhanced Raman spectroscopy (SERS) and Tip-enhanced Raman spectroscopy (TERS) differ in their approaches to enhancing Raman signals.

  • SERS utilizes nanostructured metal surfaces to amplify Raman signals when molecules adhere to them.
  • In TERS, a sharp metal tip focuses light onto a small area, intensifying Raman signals.

In summary, TERS employs a tip to concentrate light, while SERS utilizes metal surfaces to enhance signals. Both techniques contribute to improved microscopic analysis. To learn more about TERS, visit this page.

Why does SERS use metal to enhance signals?

Surface-enhanced Raman Spectroscopy (SERS) uses metals because metals do not produce strong Raman signals, and their unique properties facilitate strong interactions with light and molecules.

Specifically, metals like gold and silver exhibit surface plasmon resonance, which involves collective oscillations of electrons on their surfaces when illuminated with light. This phenomenon generates intense local electromagnetic fields near the metal surface, significantly amplifying the Raman signals of molecules adsorbed onto or near it. Additionally, these metals have a property known as negative real permittivity, which means they can support surface plasmon resonance effectively, further enhancing local electromagnetic fields.

Furthermore, metals have high electrical conductivity, allowing for efficient charge transfer processes that contribute to signal enhancement in SERS. They can also be easily nanostructured to create large surface areas with high surface-to-volume ratios, enhancing the interaction between molecules and the metal surface.

These collective properties make metals an ideal substrate for SERS, enabling sensitive molecular detection and analysis of various applications.

What applications use SERS?

SERS achieves high sensitivity, with the capability of detecting even single molecules, making it invaluable in various applications, including, but not limited to, bioanalysis (such as detecting biomolecules like DNA and proteins), environmental monitoring, food safety (for detecting contaminants), and materials science (for analyzing surface properties and molecular compositions).

Additional resources about SERS

You may want to go deeper in SERS applications with these resources:

Application notes

Application webinar

SERS Nanosensors for Biomedical Applications - from Cancer Diagnoses to Characterizing Drug Delivery Nanocarriers
Presented by Claudia Fasolato, Ph.D., Researcher at The Department of Physics and Geology at University of Perugia, in partnership with Spectroscopy:
"In this presentation, I will illustrate how surface enhanced Raman scattering (SERS) and Raman micro-spectroscopy can be successfully applied to different types of biomedical analysis. Among these, I will focus on the diagnosis and therapy of cancer at the single cell level using folate-based SERS-active nanosensors. I will discuss how the sensitivity of SERS can be employed not only for quantifying the interaction of the nanosensor with cancer and normal cells, but also for precisely characterizing nanocarriers for drug delivery applications."

Additional information from our Raman technology pages

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