Organic dye concentration monitoring through an optical microfiber enabled by multiwalled carbon nanotubes

Abstract

A tapered microfiber sensor based on multiwalled carbon nanotubes (MWCNTs) for detecting the concentration of alizarin red S dye is proposed and verified by experiments. MWCNTs fixed on the surface of optical fiber can adsorb the alizarin red S dye molecule due to its porous structure. The surface refractive index (RI) change caused by MWCNTs coated with the fiber surface adsorbing of red dye can be captured by optical microfiber, which converted into macroscopic wavelength drift in the interference spectrum. The sensor has a high RI sensitivity of 1942.25 nm/RIU and a temperature sensitivity of − 0.03 n m / ∘ C , which has a low temperature cross-sensitivity. The sensor provides rapid detection of alizarin red S dye in the concentration range of 0–1000 mg/L, and the sensitivity is 0.412 nm/(mg/L) in the low concentration range of 0–25 mg/L. The sensor is expected to be a high-quality platform for safety considerations in environmental protection.

A Microfiber Sensor for the Trace Copper Ions Detection Based on Ternary Sensitive film

“…The sensor itself is insensitive to temperature, [ 36 ] and we study the temperature response with functional film coated on the fiber surface. As shown in Figure 3f, the spectral data are recorded at 10 °C intervals in the experiments selected in the temperature range of 20–70 °C.…”

“…As shown in Figure 3e, the wavelength shift data with a linear fitting in the concentration from 100 to 1000 nM copper ion solution has obtained the sensitivity up to 7.715 × 10 6 nm M −1 and the detection limit of 0.0576 ppm, which is well below the 1 ppm limit of Cu 2+ ions in the World Health Organization drinking water standard. [25] The sensor itself is insensitive to temperature, [36] and we study the temperature response with functional film coated on the fiber surface. As shown in Figure 3f, the spectral data are recorded at 10 °C intervals in the experiments selected in the temperature range of 20-70 °C.…”

Graphene-coated three-twisted-taper and four-twisted-taper for highly sensitive temperature and strain sensing

“…The environmental parameters, including the factors of temperature and humidity, can be fast and intensively responded by these functional materials, and then converted into the parameters that microfiber is sensitive, such as refractive index and tensile strain, finally translated into optical signals via different microfiber structures [15]. Recently, various sensing materials have been applied to functionalize microfiber for highly sensitive sensors, such as graphene [16,17], carbon nanotubes [18,19], and quantum dots [20]. Particularly, graphene, as two-dimensional material, has excellent properties including surface plasmon polariton (spp) effect and fast thermal response, and has been emerged in many optical applications, such as optical polarizers and modulators [21][22][23].…”