Interferometric and localized surface plasmon based fiber optic sensor

Abstract

We demonstrate a novel single point, multi-parameter, fiber optic sensor concept based on a combination of interferometric and plasmonic sensor modalities on an optical fiber end face. The sensor consists of a micro-Fabry-Perot interferometer in the form of a hemispherical stimuli-responsive hydrogel with immobilized gold nanoparticles. We present results of proof-of-concept experiments demonstrating local surface plasmon resonance (LSPR) sensing of refractive index (RI) in the visible range and interferometric measurements of volumetric changes of the pH stimuli-responsive hydrogel in near infrared range. The response of LSPR to RI ( ∆λr ∆RI ∼ 877nm/RI) and the free spectral range (FSR) to pH ( ∆pH ∆FSR = 0.09624/nm) were measured with LSPR relatively constant for hydrogel swelling degree and FSR relatively constant for RI. We expect this novel sensor concept to be of great value for biosensors for medical applications.

A Single-Point, Multiparameter, Fiber Optic Sensor Based on a Combination of Interferometry and LSPR

“…The change in optical length for the change in n gel in (5) should be negligibly small when adding GNPs to the hydrogel. However, the polymerization process could be influenced by the GNP citrate buffer solution in the pregel and change the physical length l in (5). It is important to note that the variation in the FSR with GNP density is not important for a sensor application, since it is the change in FSR that contains information about the measurand.…”

“…Immobilizing the GNPs in a 3-dimensional polymer network (hydrogel) have two distinct advantages; (i) it enables immobilization of very large number of particles giving a strong LSPR signal, and (ii) it will reduce negative effects on analyte diffusion and binding to functionalized nanoplasmonic surfaces. In addition, the method for immobilizing GNP in the hydrogels is flexible with the possibility of exchanging the GNPs with other NMNPs to obtain high refractive index (RI) sensitivity and LSPR amplitude [5].…”

Composite‐Scattering Plasmonic Nanoprobes for Label‐Free, Quantitative Biomolecular Sensing

“…While it is challenging to home in on a specific mechanism for this discrepancy between experimental and numerical findings, literature reports hint at two possible explanations that focus on the effect of molecular adsorption on the nanoparticle surfaces, and alteration of the surface electronic structure of the plasmonic nanoprobes induced by the media, respectively. Van Duyne and co‐workers' studies detail differential blue/redshifting of LSPR peaks based on how analytes adsorb on nanoparticle surfaces, while Muri et al have postulated that the latter could explain the nonlinear blueshifting with increasing bulk RI, as they observed for gold nanorods in glycerol and sucrose solutions . As these mechanisms have not been accounted for in our simulation model, uncovering the basis of this unexpected observation will be a major focus of our ongoing investigations.…”

Optical Fiber Sensors Based on Polymeric Sensitive Coatings

“…Another different approach for the immobilization of the gold nanoparticles is using a stimuli-responsive hydrogel material which can be employed for measuring volumetric changes or well the binding to receptors on the nanoparticles surface [89,90,91]. A schematic representation of this stimuli responsive hydrogel can be found in Figure 14.…”

“…This work evaluates the LSPR coupling and distribution of inter-particle distances between nanoparticles in the hydrogel on optical fiber end face as a function of polymer density of hydrogel which is controlled by a swelling/deswelling of the induced by pH changes. In works [90,91] is also used this same methodology for the design of multi-parameter fiber optic sensors. Work [90] demonstrates LSPR sensing of refractive index in the visible range and interferometric measurements of volumetric changes of the pH stimuli-responsive hydrogel in the infrared region.…”