Metal Oxides-Based SERS Substrates

Abstract

Surface-enhanced Raman scattering (SERS) spectroscopy provides molecular fingerprint information with high sensitivity as low as single-molecule detection limit and offers advantages such as narrow spectral bandwidths, ability for fluorescence quenching and capacity to be used with or without optical labels. Henceforth, SERS is a good choice for cellular imaging and biosensing, detection of chemical and bioanalytes, explosives, etc. In SERS, the Raman active molecule is adsorbed to a metallic substrate in which very large electric field is generated during localized surface plasmon resonance that enhances the Raman activity of adsorbed Raman active molecule and is termed as electromagnetic enhancement mechanism (EM). The traditional SERS substrates include roughened metal electrode, metal thin film, metal nanocolloids, patterned substrates, etc. The advancements in the fabrication of efficient SERS substrate led to the development of metal oxide-based SERS substrate which is discussed in this chapter. Good stability, biocompatibility and sensitivity of semiconductors make 3D metal-semiconductor-based SERS substrates competent with traditional coinage metal-based SERS substrates. This chapter describes the development of recyclable SERS substrate using TiO2 nanorods decorated with silver nanoparticles. This helps to overcome single-use problem of traditional SERS substrates. The SERS chemical enhancement mechanism (CM), due to the chemical bond formation between molecules, also contributes to the total SERS enhancement. The surface defect-mediated chemical enhancement observed in metal oxide followed by various applications of metal oxides-based SERS substrate is also discussed in this chapter.