LSPR of Nanoparticles Inside Strong Absorbent Medium

Abstract

Localized surface plasmon-based sensors are widely used in various fields, such as biosensing and gas sensing, as well as optical and electrochemical sensing. In such sensors, the attenuation effects of the surrounding medium (absorbent medium AbsM) reduce the actual signal strength of the localized surface plasmon resonance (LSPR). We proposed a reflectance spectral correction method (marked as RSC) to reduce the attenuation effects of the absorbent medium inside the LSPR sensor and an extinction spectral decomposition method (marked as ESD) to examine absorption and scattering spectral components. The RSC method results from the energy conservation of the reflection and absorption components, and the ESD method results from the combination of the Kubelka–Munk–Tauc formula with the physical extinction equation. Due to the interaction of the evanescent field with the nanoparticles (silver nanoparticle AgNPs), by using these methods, the scattering peak decreases and the absorption peak increases. As a result, the scattering effects of the nanoparticles have disappeared, and the remaining part of the resonance process is caused by the absorption effects. The proposed methods (RSC and ESD) enable the accurate extraction of the reflection, absorption, and scattering spectra as individual components ( R cor, K cor, and S ATR ). These methods can be used for LSPR data analysis of various nanoparticles, which are generated by different methods such as surface nanoparticle deposition, embedded nanoparticles by thermal diffusion in a solid substrate, and colloidal solutions of nanoparticles. We investigated the surface and embedded nanoparticles. The resonance wavelengths of both samples red-shift, and the resonance strength increases as the incident angle increases. Our results promise a prospect for further development of localized surface plasmon sensors as a common sensing platform for various applications.

Topics & Concepts