Fundamentals and Applications of Plasmonic Sensors

Surface plasmons, including Localized Surface Plasmons (LSPs) and Propagating Surface Plasmons (PSPs), with unique optical properties, have been widely used in biology, chemistry, physical optics, information sciences technologies, environmental monitoring, energy catalysis/conversion, and other fields. In recent years, plasmonic sensors based on surface plasmons have attracted increasing attention due to their unique optical properties, which arise from the electromagnetic field enhancement induced by the Localized Surface Plasmon Resonance (LSPR) and the high sensitivity of Surface Plasmon Resonance (SPR) to changes in the surrounding medium. Generally, sensing technologies can be divided into two categories: surface-enhanced spectroscopic sensors and SPR sensors. On the one hand, Surface-Enhanced Raman Scattering (SERS) is a kind of surface-enhanced spectroscopic sensors, that can provide fingerprint information for molecular diagnosis with an extremely high Enhancement Factor (EF). Currently, it is known that SERS originates from two mechanisms: the dominant Electromagnetic Mechanism (EM) induced by the LSPR and the Chemical Mechanism (CM) due to the charge transfer. Owing to electromagnetic action, an amplified electromagnetic field, called “hot spots”, is formed at the nanoscale gaps among metal nanostructures, which can significantly improve the Raman signal of nearby molecules. Usually, the total Raman enhancement is approximated as the fourth power of the electric field enhancement with an EF of 10⁹-10¹⁰. The CM is another important factor based on the charge transfer between the molecule and substrate, which can regulate the electron density distribution of molecules, inducing polarization and thus enhancing the Raman signals. On the other hand, SPR sensors are based on the shift of the resonance peak of surface plasmon caused by the change in the refractive index of the surrounding environment. The molecules adsorbed on the surface of metal nanostructures exhibit a different refractive index compared to the surrounding medium. Despite the small difference, it can still be detected through the shift of SPR peak positions, and the sensitivity of an SPR sensor is typically defined as the change in the amount of peak shift per Refractive Index Unit (RIU).

So far, the research on plasma sensors based on surface plasma has made remarkable achievements. However, more theoretical mechanisms and experimental phenomena need to be further explored. To this end, we are compiling this Research Topic to promote the design and fabrication of plasmonic sensors, deepen the understanding of the mechanism of light-matter interaction based on surface plasmonic enhancement, expand the application areas of surface plasmons, construct surface plasmonic sensors with higher performance, and realize their excellent application advantages and important commercial value.

These subject areas include but are not limited to:
• Mechanism and application of electric regulation of SERS;
• Study on SERS enhancement mechanism and regulation strategy;
• Surface (Tip)-enhanced Raman scattering, Raman spectroscopy, in-situ Raman;
• Wearable SERS sensor, flexible SERS biofilm for detecting food safety as well as monitoring human health;
• Micro nano-graded optical cavity multimode coupled SERS field modulation study;
• Preparation and application of SPR sensors.

Keywords: Surface-Enhanced Raman Scattering, Enhancement Factor, Electromagnetic Mechanism, Chemical Mechanism, Refractive Index Unit, Surface Plasmon Resonance

Important Note: All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review.