Tapered Optical Fiber Sensor Coated with Single-Walled Carbon Nanotubes for Dye Sensing Application

Abstract

The present study aimed to improve the optical sensing performance of tapered optical fiber sensors toward aqueous Rhodamine B solution of different concentrations by applying single-walled carbon nanotubes (SWCNTs). The functional coating was formed on the surface of the tapered optical fiber sensor using an aerosol layer-by-layer deposition method. Before deposition, the SWCNTs were processed with multistage liquid-phase treatment in order to form a stable dispersion. The effect of SWCNT treatment was investigated through Raman spectroscopy. The deposition of 220 layers caused a reduction of up to 60% of the initial optical power of radiation propagating through the optical fiber core. The optical fiber sensor coated with SWCNTs demonstrated significantly higher sensitivity compared to a non-coated sensor in the range of 2–32 mg/L of Rhodamine B concentration in an aqueous solution. The experimental results demonstrated that the sensitivity was increased 10 times from 32 (mg/L)−1, for the non-coated sensor, up to 317 (mg/L)−1 after SWCNT coating deposition. Moreover, the SWCNT-coated sensor demonstrated high repeatability that allowed for the evaluation of the concentration regardless of the previously analyzed dye concentration.

Advances in Tapered Optical Fiber Sensor Structures: From Conventional to Novel and Emerging

“…Furthermore, the TOF sensor design is flexible and can realize different functions of the sensor by changing its angular structure, sensing medium, and sensing layer. The optical fiber processed by pulling the taper expands the abrupt field when light is transmitted in the fiber, increases the contact area with the external environment, significantly improves the sensitivity and response speed of the fiber optic sensors, and shortens the size of the fiber-optic sensor [ 41 , 42 ]. The preparation methods of TOF probes include arc discharge technology [ 43 ], laser processing technology [ 44 ], chemical etching technology [ 45 ], etc.…”