Novel localized surface plasmon resonance based optical fiber sensor

Abstract

Over the last decade various optical fiber sensing schemes have been proposed based on local surface plasmon resonance (LSPR). LSPR are interacting with the evanescent field from light propagating in the fiber core or by interacting with the light at the fiber end face. Sensor designs utilizing the fiber end face is strongly preferred from a manufacturing point of view. However, the different techniques available to immobilize metallic nanostructures on the fiber end face for LSPR sensing is limited to essentially a monolayer, either by photolithographic structuring of metal film, thermal nucleation of metal film, or by random immobilization of nanoparticles (NP). In this paper, we report on a novel LSPR based optical fiber sensor architecture. The sensor is prepared by immobilizing gold NP's in a hydrogel droplet polymerized on the fiber end face. This design has several advantages over earlier designs. It dramatically increase the number of NP's available for sensing, it offers precise control over the NP density, and the NPs are position in a true 3D aqueous environment. The sensor design is also compatible with low cost manufacturing. The sensor design 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 demonstrating a pH sensor based on LSPR sensing in a poly(acrylamide-co-acrylic acid) hydrogel embedding gold nanoparticles.

First step towards an interferometric and localized surface plasmon fiber optic sensor

“…The fiber optic sensor have been fabricated as described from previous work. 5 In this paper 100nm citrate stabilized GNP (Absorption max: 600nm, Sigma Aldrich) with density of 2 • 10 10 to 17 • 10 10 particles/ml were used to make pregel solutions of 10 wt% acrylamide (AAM) and 2 mol% N,N-methylenebisacrylamide (BIS). Ethanol (VWR) and milliq water solutions were used to stimulate a change in volume of the hydrogel.…”

Interferometric and localized surface plasmon based fiber optic sensor

“…The fiber optic sensor have been fabricated as described from previous work. 4 In this paper citrate stabilized 670nm resonant GNR (50OD, 1.14·10 13 particles/mL, nanoCompix) were used to make pregel solutions of 10wt% Acrylamide (AAM)-Acrylic acid (AAC) (molar ratio 1/2 AAM/AAC) and 2 mol% N,N-methylenebisacrylamide (BIS). Hydrochloric acid (HCL) (1.0M, Sigma Aldrich) and sodium hydroxide (NaOH) (1.0M, Sigma Aldrich) were added to mq water to prepare pH solutions to stimulate a change in volume of the hydrogel.…”

“…Previous work shows that the LSPR of 100nm spherical GNP can redshift with deswelling of pAAMAAC hydrogel as a result of an increase of RI in the gel or an electromagnetic interaction between the localized modes. 4 However, the LSPR measurements in figure 7 have a wavelength resonance that is changing between 688 and 687nm meaning that there is a negligible change of local RI or an electromagnetic interaction between the localized modes occurring between the individual GNR. The relatively constant wavelength resonance as a function of hydrogel swelling degree shows that there is potential for utilizing the GNR for label free sensing that is independent of the FSR measurements from a stimuli responsive hydrogel.…”

“…Previous work from our group demonstrated a proof-of-concept fiber optic pH sensor based on the reflection of spherical gold nanoparticles (GNP) embedded in acrylamide hydrogel at the fiber end-face. 4 In this paper, we are combining the LSPR of gold nanorods (GNR) in visible (VIS) range with the interferometric measurements of pH stimuli responsive hydrogel volume in infrared range (IR) in an effort to utilize two label free sensing parameters in one single point. The use of GNR have several advantages over spherical GNP such as increased stability, high response to refractive index and two LSPR peaks that can be used for sensing.…”

Localized Surface Plasmon Resonance for Optical Fiber-Sensing Applications

“…Other interesting approach based on the swelling/deswelling phenomenon related to a polymeric matrix is presented by Muri and Hjelme [68] for pH-sensing applications. In this work, a pH optical fiber sensor is fabricated based on LSPR sensing in a poly(acrylamide-co-acrylic acid) hydrogel embedding gold nanoparticles (GNP).…”