Progress in surface enhanced Raman scattering molecular sensing: A review

Surface enhanced Raman scattering (SERS) technique is a very powerful spectroscopic technique that has been used to investigate molecular signature by detecting vibrational bonding information from the Stokes shifted scattered photons. Due to high detection sensitivity, it has been used as a specialized technique, for ultra-sensitive chemical sensing, in food industry, explosive detection, forensic science, microbiology, medicine, medical and biomedical diagnostics. The rapid development of nanofabrication techniques and sensitive SERS spectroscopy leads to molecular detection limit down to single molecule. Plasmonic substrates have been the major concern for such a development. Huge literature reports are available with focused objectives of manipulating plasmonic near-field hot-spots and high SERS. Various nanofabrication techniques such as electron beam lithography, focused ion beam technique, optical lithography, nanosphere lithography, soft lithography and stamping, and molecular assembly based lithography, colloidal chemical routes are employed to fabricate SERS substrates and achieve high SERS signal. Moreover, achieving reliable and reproducible SERS has been a major challenge; hence, in depth understanding of plasmonic near-field assisted SERS process is essential to realize rapid growth of the field. It is believed that a systematic and comprehensive review on the progress of SERS molecular sensing that has happened in the past decades will provide a solid platform. The present comprehensive review focuses on the progress on SERS in the last 20 years with the major thrust on SERS substrate fabrication techniques and chemical sensing. Further, a brief discussion is presented on the application of SERS in food safety, food and fuel adulteration, forensic science, defense, biology and biomedical diagnostics. The graphical abstract represents an overview of the article where SERS molecular sensing is being considered as a theme for various applications such as ‘SERS in forensic science’ [297] , ‘SERS in defense application’ [328] , ‘SERS in biology’ [397] , ‘SERS in food safety’ [398] , ‘SERS in medical diagnostics’ [399] , and ‘SERS in food/fuel adulteration’ [400] . Photograph of Sir C. V. Raman is adapted from the reference [401] . Graphical abstract image is constructed based on the information and images available in the references [297] , [328] , [397] , [398] , [399] , [400] , [401] (figures or graphical abstract figures that are submerged in the present graphical abstract image are adapted from respective references as mentioned above). Copyright informations of the submerged figures are available as mentioned in the respective references. Authors have no intension to distort the original images of the respective reference.