Optimization and characterization of self-assembled monolayer multilayer surface-enhanced Raman scattering substrate for immuno-nanosensors

Surface-enhanced Raman scattering (SERS) is a powerful analytical tool and the recent expansion of substrates for SERS measurement broadens its field of applications, including SERS-based immuno-nanosensing. This dissertation describes the optimization and characterization of self-assembled monolayer (SAM) multilayer SERS substrates for improving performance of different types of substrates. SERS substrates derived from metal film on nanostructures were modified with multiple metal films interspaced with SAM dielectric spacers to achieve multilayered SERS substrates. The fundamental concept of this substrate geometry exploited the cumulative effect of the multiple electromagnetic fields and various properties of SAMs to optimize SERS enhancement of multilayer SERS substrates to about 20-fold compared to conventional substrates. SAMs of less bulky terminal groups of alkylthiols with relatively small dielectric constant, strong attractive interaction, and good electron donating ability enhanced multilayer SERS. Compared to SFON SERS substrates, alkyl-terminated SAM substrates exhibited about 7-fold SERS enhancement. SAM formation conditions that enhanced strong intermolecular interactions improved SERS enhancement. Thus, -COOH-terminated SAM multilayer substrates fabricated in acidic conditions exhibited SERS enhancement up to 10-fold compared to similar substrates fabricated in basic conditions. It was observed that the distance of separation of the adjacent metal films (