4.1 Molecular and biomolecular SERS detection in liquid environment

This chapter gives a review of SERS molecular and biomolecular sensors in liquid environment with metal NPs aggregates. For full comprehension of the chapter the reader is expected to have a good knowledge of SERS, which involves both surface plasmon resonance (SPR) and Raman scattering (see Volume 1, Sections 2 and 3). In addition, notions regarding the synthesis (Volume 2, Section 6) and localized SPR (LSPR) (Volume 1, Section 1) of metal NPs and nanoantennas are required. Opti- cal spectroscopy is largely employed to establish the plasmonic properties of the NPs; the concept can be found in Volume 1, Section 2. Finally notions of optical microscopy, microspectroscopy, and related instrumentation are required to understand the experimental implementation of optical and Raman/SERS tweezers (Volume 1, Section 1 and Volume 2, Section 4). In the following, some fundamental optical properties of metal NPs are recapitulated.