Optical Fiber Sensors Based on Nanoparticle-Embedded Coatings

Abstract

The use of nanoparticles (NPs) in scientific applications has attracted the attention of many researchers in the last few years. The use of NPs can help researchers to tune the physical characteristics of the sensing coating (thickness, roughness, specific area, refractive index, etc.) leading to enhanced sensors with response time or sensitivity better than traditional sensing coatings. Additionally, NPs also offer other special properties that depend on their nanometric size, and this is also a source of new sensing applications. This review focuses on the current status of research in the use of NPs within coatings in optical fiber sensing. Most used sensing principles in fiber optics are briefly described and classified into several groups: absorbance-based sensors, interferometric sensors, fluorescence-based sensors, fiber grating sensors, and resonance-based sensors, among others. For each sensor group, specific examples of the utilization of NP-embedded coatings in their sensing structure are reported.

Combination of polymeric substrates and metal–polymer nanocomposites for optical humidity sensors

“…Most of the work on optical humidity sensors is carried out by using optical fibers, which are used in various application areas . Humidity sensors based on optical fibers are classified according to their detection method: transmission‐ and absorbance‐based sensors, interferometric sensors, fiber grating sensors, fluorescence‐based sensors, and resonance‐based sensors . However, these optical fiber sensors also have some disadvantages.…”

“…The instability is introduced by the bleaching and leaching effects of the dyes used in the sensors . In addition to the above limitations, all of the above sensors show a limited humidity operating range, nonlinear response, less sensitivity, and high cost . These drawbacks have driven researchers to work on an alternative optical‐based method using glass substrates.…”

“…Sometimes hygroscopic (hydrophilic) polymers such as agarose are also used for humidity sensing, where the swelling due to adsorption of humidity is responsible for the change in intensity of the output light . The inclusion of nanoparticles (NP) within the polymer is the latest step in developing improved optical‐based humidity sensors . Coating of such NP‐embedded polymers enhances the sensitivity and sensing range of the sensor.…”

Sensing application of an optical fiber dip coated with L-Cystein ethyl ester hydrochloride capped ZnTe quantum dots

“…When the cladding is intentionally replaced by sensitive coatings, there could be a significant interaction between the external medium and the evanescent field [17] to the guided light. The optical properties of alcohol and ammonia determine the change in this evanescent field interaction.…”

Tailored Aggregate-Free Au Nanoparticle Decorations with Sharp Plasmonic Peaks on a U-Type Optical Fiber Sensor by Nanosecond Laser Irradiation

“…These can be categorized by the type (e.g., plastic, single mode, multi-mode, photonic crystal fibers), geometry (e.g., straight, U-shaped, tapered fibers), the sensing mechanism (e.g., evanescence wave absorption, reflection measurement), the area where the MNPs have been immobilized (e.g., tip, side core deposition, cladding deposition), the MNP material (e.g., gold, silver), shape (e.g., spheres, rods, cubes), coatings (e.g., citrate, SiO 2 , polymers), and finally the immobilization method [10][11][12][13][14][15][16][17][18][19][20][21][22]. The selection of the immobilization method, in particular, is essential as it affects the physical characteristics of the immobilized MNPs and, inadvertently, the spectral characteristics of their LSPR extinction spectrum, which, for sensing applications, should be as narrow band as possible.…”