raman scattering explanation
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Raman scattering is an optical process where incoming excitation light interacting with a sample produces scattered light that is lessened in energy by the vibrational modes of the chemical bonds of the specimen.
Raman scattering is the phenomenon of inelastic scattering of photons where the frequency of the scattered photon is different from the incident photon. The surface enhancement of Raman scattering can be achieved by immobilising the biological moieties on the surface of metal nanoparticles and the phenomenon is known as surface enhanced Raman scattering (Nie & Emory, 1997).
Gold and silver nanoparticles are better than other metal nanoparticles because they are less prone to oxidation (Jain, Huang, El-Sayed, & El-Sayed, 2008). The SERS technique is used to identify biological interactions by monitoring the shift in SERS spectra (Kumar et al, 2015). Mungroo et al have developed a SERS based technique for the detection of eight pathogens—Escherichia coli, Salmonella typhimurium, Staphylococcal enteritis, Pseudomonas aeruginosa, Listeria monocytogenes, Listeria innocua, Methicillin resistant Staphylococcus aureus (MRSA) (Mungroo, Oliveira, & Neethirajan, 2016). They have reported a microfluidic sensor for detecting the aforementioned bacteria using silver nanoparticles. Chemometric analysis (using principle component analysis and linear discriminant analysis) was used to discriminate the bacteria. A unique peak fingerprint was assigned to each bacterium and used for the detection. They were able to detect 2–100 CFU/mL in 30 min.
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