Therefore, choosing a suitable bimetallic system is crucial that depending upon their application for which the system is intended. However, as aforementioned, the silver nanoparticles (Ag NPs) are not preferred as much as gold nanoparticles (Au NPs) are preferred though the plasmonic properties are relatively good in Ag NPs compared to Au NPs. Therefore, it would be appropriate to combine silver and gold as a bimetallic system such as alloy or core/shell to make use of their physicochemical properties to probe biomolecules through SERS studies. On the other hand, gold nanostructures are widely preferred for the in vivo studies, but they show only average SERS effects. However, though enhanced Raman signals can be obtained from silver nanostructures, they are not desired for the in vivo investigations in biological systems. Consequently, most of the SERS studies have been carried out by using Ag or Au nanostructures. In the quest of searching such suitable metallic nanostructures for SERS applications, the nanostructures of silver (Ag) and gold (Au) are found to be potential candidates due to their enhanced optical and electronic properties exhibiting distinct localized surface plasmon resonances (LSPR) bands in both UV and visible region of the EM spectrum. Therefore, mostly these molecules are coupled with metallic nanoparticles owing to their excellent surface plasmonic (SP) properties. The mechanism of SERS mainly involves the enhancement of electromagnetic field and chemical signals associated with the molecules. It is reported that, in SERS, the intensity of the Raman signal that comes from a molecule gets enhanced by many orders of magnitude when the molecules adsorbed to the surface of metallic nanostructures exhibiting atomic scale coarseness. Raman scattering (SERS) has become one of the effective emerging spectroscopic tools to explore different biological entities owing to its excellent sensitivity and molecular detection competences.
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