* RRS effect (Resonance Raman Scaterring)
The Raman resonance effect produces an increase in Raman intensity up to 10 times. In this phenomenon, the monochromatic light interaction with the sample produces the transition of the molecules from the fundamental state to an excited electronic state, instead of a virtual state as in normal Raman spectroscopy. This phenomenon of increased intensity could be observed in materials such as carbon nanotubes.
* SERS (Surface-Enhanced Raman Scattering)
Surface-Enhanced Raman Scattering (SERS) is a technique capable of increasing Raman signal intensity up to 10 times. This phenomenon is based on the interaction of monochromatic light with materials that exhibit plasmonic properties. The most common metals used in SERS are nanostructured metals with plasmonic band (gold, silver or copper). Nanostructured electrode surfaces can be generated by depositing metallic nanostructures of these materials. A disadvantage of this phenomenon is, sometimes, the lack of reproducibility of the spectra due to the difficulty of obtaining identical nanostructured surfaces in each experiment. 
* SOERS (Surface-Oxidation-Enhanced Raman Scattering)
Surface-oxidation enhanced Raman scattering (SOERS) is a process similar to SERS, which allows the Raman signal to be enhanced when a silver electrode is oxidized in a particular electrolyte composition. This process is carried out at sufficiently positive potentials to ensure the oxidation of the electrode surface. There are significant differences with the SERS effect, but it is a phenomenon that also enhances the Raman signal. 
* SHINERS (Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy)
In SHINERS, metallic nanoparticles with plasmonic properties are coated with ultra-thin homogeneous silica or alumina layers, forming isolated nanoparticles. The metallic nucleus (Au or Ag) is responsible of the enhancement of the Raman signals of the nearby molecules, while the coating layers eliminate the influence of the metallic nucleus on the Raman and electrochemical signals by preventing the molecules from being directly adsorbed onto them. Silica and alumina coating can improve the chemical and thermal stability of nanoparticles. This fact has great importance in the in-situ study of catalytic reactions. The high sensitivity of the SHINERS surfaces makes these nanostructures a promising tool for the study of liquid-solid interfaces, especially in spectroelectrochemistry. 
* TERS (Tip-Enhanced Raman Scattering)
Tip-enhanced Raman scattering (TERS) is a technique that provides molecular information at nanoscale. In these experiments, metal nanostructures are replaced by a sharp metal tip of nanometric size, concentrating the roughness directly on a small region that improves the spatial resolution of scanning techniques in Raman spectroscopy. 
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