www.wjpls.org 74 Shaista et al. World Journal of Pharmaceutical and Life Science SURFACE-ENHANCED RAMAN SPECTROSCOPY: A REVIEW Shaista Firdous* and S. H. Rizwan Department of Pharmaceutical Analysis, Deccan School of Pharmacy, Hyderabad, Telangana, India. Article Received on 16/08/2020 Article Revised on 06/09/2020 Article Accepted on 27/09/2020 INTRODUCTION Raman Spectroscopy Raman Spectroscopy is an analytical technique which is used to measure vibrational energy levels of sample via scattered light. Raman spectroscopy furnishes unique Raman fingerprint for the identification of substances; provides chemical, structural information as well. The Raman spectroscopic study is governed by Raman scattering. When a beam of light is incident on a system/sample, it absorbs the electromagnetic radiation which causes either an increase in the internal energy of the system or its electrons get activated which leaves it in a higher energy state. This leads to the formation of a short-lived complex between the photon and molecule which is generally called the virtual state of the molecule. This state is unstable and the photon is re-emitted spontaneously as scattered light. However, approximately 1 in 10 million photons undergo Raman scattering. Raman scattering is an inelastic scattering process where a transfer of energy between the molecule and scattered photon is observed. It is explained in terms of Stokes Raman Scattering and Anti-Stokes Raman Scattering. Fig. 1: Three types of scattering processes that can occur when light interacts with a molecule. If the molecule gains energy from the photon during the scattering (the electrons get excited to a higher vibrational level) then the scattered photon loses energy and its wavelength increases; which is called Stokes Raman scattering. Likewise, if the molecule loses energy by relaxing to a lower vibrational level, the Review Article ISSN 2454-2229 wjpls, 2020, Vol. 6, Issue 10, 74-80 World Journal of Pharmaceutical and Life Sciences WJPLS www.wjpls.org SJIF Impact Factor: 6.129 Corresponding Author: Shaista Firdous Department of Pharmaceutical Analysis, Deccan School of Pharmacy, Hyderabad, Telangana, India. ABSTRACT Surface Enhanced Raman Spectroscopy is an offshoot of Raman Spectroscopy offering improved characteristics like compound specific Raman fingerprint for the identification of substances, rendering information on chemical and physical characteristics. Further the technique is non-destructive, highly sensitive and has expanded scope in research fields of analytical, bioanalytical, biophysical and life sciences. This review presents the basics of SERS theory, the prevalent Raman principles, and the mechanisms of SERS enhancement. In any SERS application, SERS substrate plays a pivotal role. A brief description of different SERS substrates, their fabrication method has been presented. Lastly, the related enhanced techniques like Tip-enhanced Raman scattering (TERS), Shell-isolated NP-enhanced Raman scattering (SHINERS), etc., have been mentioned. KEYWORDS: SERS, SERS enhancement, TERS, SHINERS.