Abstract
This mini-review presents recent trends in the field of surface-enhanced spectroscopies, which are increasingly gaining ground for biomolecule detection. The paper discusses the role of electromagnetic and chemical bonding mechanisms for an explanation of Raman scattering and fluorescence enhancement. The charge transfer (CT) effect, which is involved in the chemical mechanism, plays an important role in changing the polarizability and is decisive in enhancing certain Raman scattering bands and fluorescence emission. The CT effect is determined by the band structure and the energy of the excitation radiation by which photoelectrons and holes with different energies are generated. Here we analyze the changes in the band structure of silver by adding p-block metals as well as the possibility to control CT and to enhance specific Raman bands through their engineering.