LSPR Coupling and Distribution of Interparticle Distances between Nanoparticles in Hydrogel on Optical Fiber End Face

Harald Muri,Dag Hjelme

doi:10.3390/s17122723

Abstract

We report on a new localized surface plasmon resonance (LSPR)-based optical fiber (OF) architecture with a potential in sensor applications. The LSPR-OF system is fabricated by immobilizing gold nanoparticles (GNPs) in a hydrogel droplet polymerized on the fiber end face. This design has several advantages over earlier designs. It dramatically increase the number nanoparticles (NP) available for sensing, it offers precise control over the NP density, and the NPs are positioned in a true 3D aqueous environment. The OF-hydrogel design is also compatible with low-cost manufacturing. The LSPR-OF platform can measure volumetric changes in a stimuli-responsive hydrogel or measure binding to receptors on the NP surface. It can also be used as a two-parameter sensor by utilizing both effects. We present results from proof-of-concept experiments exploring the properties of LSPR and interparticle distances of the GNP-hydrogel OF design by characterizing the distribution of distances between NPs in the hydrogel, the refractive index of the hydrogel and the LSPR attributes of peak position, amplitude and linewidth for hydrogel deswelling controlled with pH solutions.

Highlights

Fiber optic (FO) sensors based on local surface plasmon resonance (LSPR) have been proposed in various configurations over the last decade [1,2,3,4]
The LSPR response was demonstrated by measuring its peak positions as a function of gold nanoparticles (GNPs)-hydrogel contraction controlled with pH solutions and as a function of increasing ND0
Proof-of-concept experiments have been presented where we explore the LSPR and interparticle distance distribution attributes of the GNP-hydrogel

Summary

Introduction

Fiber optic (FO) sensors based on local surface plasmon resonance (LSPR) have been proposed in various configurations over the last decade [1,2,3,4]. The most important features of LSPR FO sensors are label-free sensing, fast response time, high sensitivity, high selectivity, simplified optical design and remote sensing capabilities. The label-free sensing can be multi-parametric by spectrally resolving different LSPR observed for noble metal nanostructures (NMNS) of different sizes and shapes [5]. LSPR-based FO sensors usually utilize NMNS interacting with the evanescent field at the optical fiber (OF) core-cladding interface or with the light at the OF end face [2,4]. The use of the OF end face offers simpler manufacturing methods compared to utilizing the evanescent field since there is no need for cladding removal. The techniques available for immobilization of NMNS on an OF end face are limited to essentially a monolayer manufactured by photolithographic structuring of metal film, thermal nucleation of metal film or random immobilization of nanoparticles (NP)

Methods

Results

Conclusion