This study presents design and development of evanescent wave absorbance based U-bent plastic optical fiber (POF) probe with high sensitivity and its applications to refractive index (RI) sensing. The probes were fabricated by a controlled decladding procedure to remove the fluorinated polymer without damaging the poly methyl methacrylate (PMMA) core and a simple and scalable fabrication technique to obtain POF U-bent probes of desired geometry. U-bent probes of fiber diameter from 250 to 1000 μm were fabricated and optimum bend diameter for each fiber diameter was investigated. The sensitivity was found to be maximum when the bend diameter of the probe varies from 2 to 3 times the fiber diameter. Probes with 500 μm core and 1.25 mm bend diameter showed highest sensitivity (5.57ΔA560 nm/ΔRIU) in the visible region to RI changes from 1.33 to 1.47 with a resolution better than 1 milli RI units. Furthermore, U-bent probes were amine functionalized and coated with gold nanoparticles to obtain a localized surface plasmon resonance (LSPR) based RI sensor that has an 8-fold improvement in RI sensitivity, hence extending their applicability to plasmonic biosensing. © 2016 Elsevier B.V. All rights reserved.

Sai V V Raghavendra

Department of Applied Mechanics

Electromagnetic wave reflection

Esters

Fabrication

Fiber optic sensors

Fibers

OPTICAL FIBER FABRICATION

Optical fibers

Plasmons

Plastics

Probes

Refractive index

Surface plasmon resonance

ABSORBANCES

BEND DIAMETER

Design and Development

Fabrication technique

FLUORINATED POLYMERS

Localized surface plasmon resonance

PLASMONIC SENSORS

PLASTIC OPTICAL FIBER (POF)

PLASTIC OPTICAL FIBERS

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Sensors and Actuators, B: Chemical

We report a novel one-step polyamidoamine (PAMAM) dendrimer based polymethyl methacrylate (PMMA) surface functionalization strategy for the development of polymeric optical fiber (POF) based plasmonic sensors utilizing gold nanoparticles (AuNP). Simple contact angle measurements over PMMA sheets reveal the ability of the dendrimers to strongly bind to PMMA surface without additional acid/alkali pretreatment, unlike the conventional hexamethylene diamine (HMDA) based surface modification. Subsequently, U-bent POF probes with high evanescent wave absorbance sensitivity were exploited for relative quantification of the surface amine groups using fluorescein isothiocyanate (FITC) binding and efficient chemisorption of gold nanoparticles (AuNP) in order to identify the optimum conditions viz. dendrimer concentration, incubation time and dendrimer generation. While FITC binding showed a proportional increase in amine functional density with PAMAM concentration and time, interestingly the AuNP (40 nm) binding studies revealed the formation of loose PAMAM multilayers and their desorption. PAMAM (G4) concentration as low as 5 mM and incubation time of 24 h provide faster binding rate with densely packed AuNP and the RI sensitivity of ∼15 (A546 nm/RIU). This simpler and inexpensive strategy could also be exploited for the development of functional PMMA substrates for various applications including nanotechnology, bio-imaging, drug delivery and analytical separations. © 2019 Wiley-VCH Verlag GmbH &amp; Co. KGaA, Weinheim

Fulltext

ChemNanoMat

Self-Assembled Polyamidoamine Dendrimer on Poly (methyl meth- acrylate) for Plasmonic Fiber Optic Sensors

The study demonstrates the development of a novel low-cost plastic optical fiber (POF) based sensor for liquid level measurement. The sensor works on the principle of reduction in scattering-based optical losses (in contrast to the increase in optical losses for evanescent wave-based sensing) in a straight decladded fiber with an increase in the liquid level due to refractive index changes in the medium surrounding the fiber. A compact optical setup is developed in-house consisting of two U-bent fiber probes coupled to a single LED on one end and two photodetectors on the other ends to measure the optical intensity changes. One of the U-bent probes is decladded over the length of the fiber to act as a test probe to measure the liquid level, while the other probe acts as a reference to compensate for the light intensity fluctuations due to light source instability and ambient conditions. The difference in voltage responses of the two photodetectors gives a measure for liquid level. We have investigated the fiber optic level sensor response to rising and falling liquid levels over 55 cm in presence of aqueous liquids of different refractive index values (1.33 to 1.38) and 95% ethanol as well as DI water at various temperatures from 16 °C up to 70 °C. A level sensitivity of 1.4 and 3.3 mV/mm for water level changes was obtained for the liquid level below and above 45 cm respectively. In addition, the fiber optic level sensor shows a stable and reproducible response over several cycles of 30 min duration at different liquid levels. The results demonstrate that this fiber optic level sensor is not only easy-to-make, cost-effective and robust but also offers sensitive, stable and reproducible instantaneous level measurements. © 2019 Elsevier B.V.

Sensors and Actuators, A: Physical

Plastic fiber optic sensor for continuous liquid level monitoring

This study demonstrates the effect of size and concentration of the gold nanoparticles (AuNP) labels on the sensitivity of evanescent wave absorbance (EWA) based fiber optic sandwich immunobiosensor. A plasmonic sandwich immunoassay using human Immunoglobulin G (HIgG) and goat anti-HIgG (GaHIgG) was performed on aU-bent polymethyl methacrylate (PMMA) based plastic optical fiber (POF) probe (core diameter \pmb{500\ \mu} \mathbf{m} and bend diameter 1.4 mm). Enhanced EWA response was observed with 60 nm AuNP labels for the analyte concentration \pmb{1\ \mu} \mathbf{g}/\mathbf{ml} in comparison to 20, 40 and 80 nm AuNP labels. Furthermore, on optimizing the GAbs concentration the sensitivity of the sensor enhanced significantly with \pmb{20\times 60} nm labels with a LOD of 100 fg/ml. The advantages such as ease in fiber probe handling and simple instrumentation are highly promising for development of fiberoptic biosensors for various applications. © 2018 IEEE.

Proceedings of IEEE Sensors

Fiber Optic Plasmonic Sandwich Immunosensor: Influence of AuNP Label Size and Concentration

This study describes the development of a refractive index (RI) based fiber optic chemical sensor using a U-bent plastic optical fiber (BPOF) probe made of 0.5 mm polymethylmethacrylate (PMMA) core and optimum bend diameter of 1.4 mm coated with graphene oxide (GO) film. GO film on BPOF sensor surface significantly enhance the RI sensitivity of the sensor as well as its chemical resistance due to improved refractive index contrast and (PMMA) surface passivation by GO respectively. GO was chemisorbed to hexamethylenediamine (HMDA) functionalized BPOF probe surface by identifying the optimum GO concentration (100 μg/ml) and incubation time (24 h). An enhanced RI sensitivity of 9.42 ± 0.37 (ΔA845nm/ΔRIU) was achieved using GO coating of thickness 3.3 μm, which is 3.6 times higher than that of the bare BPOF probe. The RI sensitivities in presence of organic solvents including methanol, ethanol and isopropyl alcohol are found to be 12.75 ± 1.19, 9.97 ± 0.66 and 13.93 ± 0.92 (ΔA845nm/ΔRIU) respectively. GO film over BPOF was stable even after incubation of the probes in the alcohols over 12 h. In addition, GO-BPOF probes were able to tolerate acetone environment for a prolonged duration of 30 min as opposed to 10 min in case of the bare probes due to improved chemical resistance. Hence, the GO-BPOF could potentially be utilized as a sensitive RI sensor not only for aqueous solutions but also for reactive organic solvents such as alcohols and acetone which are known to damage the PMMA surface. © 2018 Elsevier B.V.

Graphene oxide coated U-bent plastic optical fiber based chemical sensor for organic solvents

Evanescent wave-based excitation of noble metal nanostructures on fiber core surface allows simultaneous excitation over a larger area in comparison with free space coupling, and hence highly suitable for development of surface-enhanced Raman scattering (SERS)-based sensor applications. This study describes the development of plasmonically active U-bent plastic optical fiber (POF) probes for SERS-based sensing. The SERS activity of gold nanostructures on the fiber probe surface obtained by means of electroless deposition, sputtering, and chemisorption of nanoparticles are thoroughly characterized using a confocal microscopic setup. Influence of excitation wavelength and laser excitation power on SERS activity and stability of the plasmonic U-bent probes is evaluated. Gold-sputtered POF probes and gold nanoparticle immobilized POF probes show higher enhancement factor in the order to ~108. A biosensor application of these POF-based SERS sensors is demonstrated by realizing a sandwich immunoassay with 4-MBA as Raman label. © 2018 John Wiley &amp; Sons, Ltd.

Journal of Raman Spectroscopy

Development of plasmonic U-bent plastic optical fiber probes for surface enhanced Raman scattering based biosensing

The refractive index (RI) sensitivity of a localized surface plasmon resonance (LSPR)-based fiber-optic probes is dependent on surface coverage of gold nanoparticles (GNP), fiber core diameter, and probe geometry. For U-bent LSPR fiber-optic probes, which demonstrated an order higher absorption sensitivity over straight probes, bend diameter and probe length may also have a significant influence on the sensitivity. This study on U-bent fiber-optic LSPR probes is aimed at optimizing these parameters to obtain highest possible RI sensitivity. RI sensitivity increases linearly as a function of surface coverage of GNP in the range of 2–22%. U-bent fiber-optic probes made of 200-, 400-, and 600-μm fiber core diameter show optimum bend diameter value as ∼1.4 mm. In addition, RI sensitivity is almost the same irrespective of fiber core diameter demonstrating flexibility in choice of the fiber and ease in optical coupling. The length of the probe preceding and succeeding the bend region has significantly less influence on RI sensitivity allowing miniaturization of these probes. In addition to these experimental studies, we present a theoretical analysis to understand the relative contribution of evanescent wave absorbance of GNP and refractive losses in the fiber due to GNP, towards the RI sensitivity. © Springer Science+Business Media New York 2013.

Plasmonics

Optimal design for U-bent fiber-optic LSPR sensor probes

Hollow bimetallic nanostructures have recently emerged as attractive plasmonic materials due to the ease of optical tunability by changing their size/composition.

RSC Advances

Facile synthesis of size and wavelength tunable hollow gold nanostructures for the development of a LSPR based label-free fiber-optic biosensor

Applied Optics

Refractive index sensor based on plastic optical fiber with tapered structure

Sensors and Actuators B: Chemical

Unprecedented high plasmonic sensitivity of substrates based on gold nanoparticles

Optik

Microbend fiber optic detection of continuously varying refractive index of chlorinated water

Development of LSPR based U-bent plastic optical fiber sensors

Journal	Data powered by TypesetSensors and Actuators, B: Chemical
Publisher	Data powered by TypesetElsevier
ISSN	09254005
Open Access	No