2 Plasmonics for Enhanced Vibrational Signatures
113
Fig. 2.3 Surface enhanced vibrational spectroscopies and their dependence on field enhancement
factors A(v)
for SEIRA and near infrared, visible or near ultraviolet frequencies for linear and
non-linear (resonance) Raman scattering. For SEHRS, optimum structures should
provide high enhancement in two relatively widely separated ranges of the electromagnetic spectrum. In the Sect. 2.3, we discuss basic requirements for plasmonic
nanostructures suitable for surface enhanced vibrational spectroscopy.
2.3 Plasmonic Nanstructures for Supporting Vibrational
Spectroscopy
The basic property of enhancing plasmonic structures is their capability to generate
spatially confined and enhanced fields due to resonances with the collective oscillations of the free conduction electrons in the metal, so-called surface plasmons.
This requires nanostructures with plasmon resonances in different ranges in the electromagnetic spectrum. Moreover, in order to achieve high enhancement levels, the
plasmonic elements should have high Q-factors. For a modern summary about the
field of nanoplasmonics, see e.g. [19, 52–55]. The existence of surface plasmons
strongly depends on the dielectric constants of the metal ε m and requires negative
113
Fig. 2.3 Surface enhanced vibrational spectroscopies and their dependence on field enhancement
factors A(v)
for SEIRA and near infrared, visible or near ultraviolet frequencies for linear and
non-linear (resonance) Raman scattering. For SEHRS, optimum structures should
provide high enhancement in two relatively widely separated ranges of the electromagnetic spectrum. In the Sect. 2.3, we discuss basic requirements for plasmonic
nanostructures suitable for surface enhanced vibrational spectroscopy.
2.3 Plasmonic Nanstructures for Supporting Vibrational
Spectroscopy
The basic property of enhancing plasmonic structures is their capability to generate
spatially confined and enhanced fields due to resonances with the collective oscillations of the free conduction electrons in the metal, so-called surface plasmons.
This requires nanostructures with plasmon resonances in different ranges in the electromagnetic spectrum. Moreover, in order to achieve high enhancement levels, the
plasmonic elements should have high Q-factors. For a modern summary about the
field of nanoplasmonics, see e.g. [19, 52–55]. The existence of surface plasmons
strongly depends on the dielectric constants of the metal ε m and requires negative