Improving SERS sensitivity via hot spots and control of molecular orientation

Abstract

Surface-enhanced Raman spectroscopy (SERS) is a high-throughput, surface-sensitive and label-free analytical technique that provides the molecular fingerprints of bio/chemical analytes. The quality of SERS signals of analytes mainly relies on the electromagnetic field strength generated by nanostructured platforms. In this regard, this article describes a new strategy for enhancing SERS intensity by the integration of hotspot engineering and parallel orientation of molecules to a nanostructure (NS) surface. We investigate the relationship between the nanostructure geometry and the molecular orientation to enhance the SERS intensity of a few thiol-derivative reporter molecules including 4-mercaptophenol (4-MCP), 4-mercaptobenzoic acid (4-MBA), and 4-mercaptophenyl boronic acid (4-MPBA), using Au nanoflowers (NFs) and nanorods (NRs). This study demonstrates a significant enhancement in the relative SERS intensity of aromatic ring breathing vibrations as well as many other skeleton-based bond vibrations of the reporter molecules, observed from Au NF arrays. This study offers a strategic opportunity for the future development of highly efficient bio/chemical sensors, such as pH sensors, glucose sensors, etc., that require monitoring of selective vibrational bonds in those reporter molecules. This study can be an important experimental illustration for an elaborate understanding of the SERS phenomena as well as for the future development of biosensing technologies.