Single Molecule Detection (SERS)

What is single molecule detection? (utilizing SERS)

In Raman Scattering, differing spectra result from interaction with differing matter samples, and these samples can be identified and classified via analysis of the spectral response. However, the available light signal is tiny, and requires extremely sensitive (and very expensive) instruments to measure.
On the other hand, it has been discovered that using nano-patterned thin layers of gold or aluminum, when the laser light is properly controlled, the Raman scattering signal is greatly amplified and enabling enough resolution to allow single molecule detection.
This phenomenon is referred to as SERS (Surface Enhanced Raman Scattering)
Also, SERS eliminates the need for specimen labelling and enables quick and low cost measurement/detection/diagnosis capability.

Principle of SERS

Physical intensification effects and chemical effects combine to increase the signal intensity by up to eight orders of magnitude.
Enhancement due to physical effects: The electric field surrounding nanostructures dramatically enhances the signal.
Enhancement due to chemical effects: Charge transfer between the metal and measurement sample leads to the enhancement effect.