What is the difference between Raman Spectroscopy and Surface Enhanced Raman Spectroscopy?

150 views

[ad_1]

What is the difference between Raman Spectroscopy and Surface Enhanced Raman Spectroscopy?

In: Physics
[ad_2]

Hard to ELI**5** SERS, so this is more like ELI**undergrad**:

You can, to a rough approximation, think of a molecule as being a bunch of little masses (the atoms) attached to each other by little springs (the bonds). Just like collections of masses on springs, molecules have lots of different ways they can vibrate and what, exactly, those “vibrational modes” are is very dependent on what the masses and springs are and how they are connected to each other.

Raman spectroscopy uses the inelastic scattering of light off molecules to tell us about how they vibrate. As the specific vibrational modes are highly dependent on the structure of the molecule, Raman spectroscopy can very quickly give us a lot of information about its structure!

Surface-enhanced Raman spectroscopy (SERS) first places our molecules of interest onto a surface of some sort (usually a metal or silica). The surface will either absorb energy from other modes (say, fluorescence) and/or enhance the response from Raman. This means that a weak Raman signal can be radically enhanced, while potentially interfering (and less informative) fluorescent (et al) signals are suppressed. Putting the molecule on a surface can also change how it vibrates a bit, so you have to be aware that the SERS spectrum usually isn’t *exactly* like the free Raman spectrum.

There’s also SM-SERS, in which the Raman signal is so enhanced that a spectrum can be obtained from a *single molecule* (“SM”). This is usually accomplished by putting the molecule between two metal nanoparticles that act kind of like antennas for the signal and alter the local electromagnetic properties around the molecule.