Determining the Interfacial Refractive Index via Ultrasensitive Plasmonic Sensors

Abstract

Plasmonic sensors are promising for ultrasensitive chemical and biological analysis. However, there are increasing experimental findings that cannot be well addressed by theoretical calculations, including the nonlinear dependence of the plasmonic peak wavelength on the refractive index (RI) and the ultrahigh sensitivity beyond the theoretical limit. The gap between experiments and theoretical calculations is that the bulk RI (BRI) used for calculation could be different from the interfacial RI (IRI) determining the electromagnetic response as a result of the interaction of molecules with the surface. But there is still no method to determine the IRI. Herein, we quantitatively determine the IRI by disentangling the surface RI (SRI) from the BRI. The obtained IRI can be directly applied in theoretical calculations to reliably reflect the experimental response and rigorously guide the design of plasmonic sensors. Moreover, it can be a fundamental dimensionless number to describe the light–matter interaction at the interface.

Photonic Fractal Metamaterials: A Metal–Semiconductor Platform with Enhanced Volatile‐Compound Sensing Performance

“…This definition no longer requires an estimation of the environmental refractive indices, which could lead to misleading results. [ 60 ] Our 3D Au–TiO 2 fractals display a sensitivity of 0.5, 1.5, and 1.9 nm vol% −1 for acetone, ethanol, and toluene, respectively (Figure 3j). Notably, the sensitivity of our 3D Au–TiO 2 fractals is about 13 times that of 2D Au metasurfaces, having a sensitivity of 0.11 nm vol% −1 for ethanol, and 2–3 times that of 2D Au metasurfaces enhanced with a top fractal coating of TiO 2 nanoparticles ( S EtOH = 0.4 nm vol% −1 ).…”

In-Situ Plasmonic Tracking Oxygen Evolution Revealing Multistage Oxygen Diffusion and Accumulating Inhibition

“…Therefore, the rapid increase in extinction intensity could be reasonably attributed to the oxygen evolution. 39 Notably, when comparing extinction voltammetry with the linear potential scan from 0 to 0.90 V, a significant lower onset potential for oxygen evolution was observed in extinction measurements (ca. 0.40 V).…”

Plasmonic Sensors for Monitoring Biological and Chemical Threat Agents

“…So, they are promising for ultrasensitive detection and have received increasing applications in biological and chemical analysis, food control, clinical diagnostics, biomedical research, etc. [ 52 ]. Plasmonic sensors also focus on the analysis of a change of intensity in the optical characteristics of the transducer metal surface when the target analyte is captured by the recognition element ( Figure 2 ).…”

“…So, they are promising for ultrasensitive detection and have received increasing applications in biological and chemical analysis, food control, clinical diagnostics, biomedical research, etc. [52]. Plasmonic sensors Sensors have numerous advantages, including user-friendly operation, exceptional performance, rapid response, minimum sample preparation and processing, portability, high sensitivity and specificity, relatively compact size, and real-time analysis that provide many advantages compared to standard analytical methods [41][42][43][44][45].…”