Surface-Enhanced Raman Spectroscopy: Methods, Analysis and Research

In the last decade, we have seen spurring growth in academic and industrial interest in Raman spectroscopy and its modifications, in particular, Surface-Enhanced Raman Spectroscopy (SERS). This is evident by the number of SERS publications in the last decade, from 580 in 2005 to almost 2000 in 2014. There are now companies worldwide that are dedicated to manufacturing SERS substrate, sensors, and other SERS-based products. The miniaturization of Raman instrumentation from bulky and expensive bench-top designs to inexpensive handheld spectrometers has allowed SERS to be employed as an in situ detection technique. Some examples of the industrial success of Raman and SERS are rapid raw material identification (RMID), Process Analytical Technology (PAT) and drug screening in pharma and biotech industries, continuous surveillance of food, water, and environmental safety, and the diagnosis and continuous monitoring of diseases like cancer, diabetes, etc. This progress in translating Raman and SERS techniques into commercial use and commercial products is possible because of the close collaboration between scientists and engineers. However, the weak signals of Raman spectroscopy is an inherent limitation of the spontaneous Raman spectroscopy technique. Therefore, several modifications have been made, including but not limited to, surface-enhanced Raman spectroscopy (SERS), spatially offset Raman spectroscopy (SORS), transmission Raman spectroscopy (TRS), coherent anti-Stoke's Raman spectroscopy (CARS), and tip-enhanced Raman spectroscopy (TERS). Spontaneous Raman spectroscopy has become a one-of-a kind, portable, and affordable technology for in-situ detection and continuous monitoring in resource-limited-settings. The primary focus of this textbook is to try to cover the fundamentals in SERS methods of preparing substrates and sensors, and efficient spectral analysis approaches like chemometrics for diverse applications, listed in the paragraph above. However, with a goal to give a true picture to the audience when assessing the scope of spontaneous Raman and Surface-enhanced Raman for specific applications, we have briefly introduced industrially successful examples of other types of Raman spectroscopy techniques, such as SORS, TRS, and CARS.